The Clinical Anatomy of the Cranial Nerves - Joel A. Vilensky - E-Book

The Clinical Anatomy of the Cranial Nerves E-Book

Joel A. Vilensky

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Beschreibung

The cranial nerves are an endlessly fascinating family of twelve nerves that have a dramatic impact on our daily lives. A dysfunction of the cranial nerves can cause loss of vision or double vision, loss of smell, poor balance, or loss of muscle function, and can also be an indicator of underlying neurological disorders. The Clinical Anatomy of the Cranial Nerves: The Nerves of "On Old Olympus Towering Top" is an engaging and accessible book on the anatomy and clinical importance of these unique nerves. The text opens with a brief introduction of key neuroanatomical concepts that relate the clinical and anatomical sections that follow. Additionally, this book uniquely provides a detailed description of the bones of the head and face in order for the reader to understand the routes taken by the cranial nerves through the skull. Chapters then detail each nerve and its unique impact in relationship to our senses, motor function, and health. Vividly illustrated and supported by real-life clinical cases, the book will appeal to anyone wishing to gain a better understanding of the cranial nerves. Merging anatomical and clinical information with intriguing clinical cases, The Clinical Anatomy of the Cranial Nerves: The Nerves of "On Old Olympus Towering Top" introduces readers to the anatomy and diverse function of this intriguing family of nerves.

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CONTENTS

Cover

Title page

Preface

Contributors

Acknowledgments

Introduction

THE CRANIAL NERVES AND THIS BOOK

THE CENTRAL NERVOUS SYSTEM

OSTEOLOGY OF THE SKULL

REFERENCES

1 The Olfactory Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

2 The Optic Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

3 The Oculomotor Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

4 The Trochlear Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

5 The Trigeminal Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

6 The Abducent Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

7 The Facial Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

8 The Vestibulocochlear (Acoustic) Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

9 The Glossopharyngeal Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

10 The Vagus Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

11 The Accessory Nerve

ANATOMY/FUNCTION SUMMARY

ANATOMY/FUNCTION

CLINICAL ASPECTS

REFERENCES

12 The Hypoglossal Nerve

ANATOMY / FUNCTION SUMMARY

ANATOMY / FUNCTION

CLINICAL ASPECTS

REFERENCES

13 Nervus Terminalis (Cranial Nerve N)

ANATOMY/FUNCTION

REFERENCES

14 Concluding Remarks: The Past and Future and Magic of the Cranial Nerves

CRANIAL NERVE II: TAKE CARE OF YOUR SIGHT

CRANIAL NERVES II, III, IV, AND VI: VISUAL ABNORMALITIES IN CHILDREN IN A DEVELOPING COUNTRY

CRANIAL NERVES III, IV, AND VI: NOT ALL IS AS IT SEEMS WITH EYE MOVEMENTS

CRANIAL NERVE V: BE CAREFUL WHAT YOU ASK FOR!

CRANIAL NERVE V: THE BEST LAID PLANS …

CRANIAL NERVE VII: SOMETIMES IT IS HIT OR MISS

CRANIAL NERVE VII: TRAGEDY BEHIND A FACIAL NERVE PARALYSIS

CRANIAL NERVE VII: FACIAL NERVE AND FACIAL FUNCTION

CRANIAL NERVE VIII: SPINNING WHEELS

CRANIAL NERVE X: SPEAK UP, PLEASE, I CANNOT HEAR YOU

CRANIAL NERVE X: VEXING VOCALS

CRANIAL NERVE X: VAGOTOMY – FOND MEMORIES OF AN OBSOLETE OPERATION

CRANIAL NERVE XII: SOMETIMES THE BAD NEWS IS REALLY BAD

REFERENCES

End User License Agreement

List of Tables

Introduction

Table I.1 Commonly used terms of relationship and comparison

Chapter 03

Table 3.1 The actions of each of the six eye muscles around each axis.

List of Illustrations

Introduction

Figure I.1 Schematic illustration depicting the origin and functional aspects of the 12 CNs. The central image is a human brain as viewed from its base with the origins of the CNs highlighted in yellow. The small surrounding images are shown in larger versions with labels in the individual chapters of this book.

Figure I.2 Terms of orientation for the brain and spinal cord displayed on a side view of a human brain.

Figure I.3 This three-dimensional image shows the components of a spinal nerve, with the spinal cord shown within a vertebra of the vertebral column. The small upper inset shows how the vertebra fits into the vertebral column.

Figure I.4 A flowchart showing the features and characteristics of the ANS, with examples of function.

Figure I.5 Generalized autonomic pre- and postganglionic neurons with a ganglion (note that the pre- and postganglionic neuron synapse in the ganglion). In general, the ganglia of sympathetic fibers are visible to the naked eye and are located close to the spinal cord, whereas the ganglia of parasympathetic fibers in the head are located near their target structures. In contrast, parasympathetic ganglia in the rest of the body are microscopic and tend to be located in the walls of the target organs. For this figure, we show a sympathetic fiber providing innervation to a part of the colon.

Figure I.6 Components of a nerve. The right side of the illustration shows a drawing of the cross-section of a nerve containing numerous fascicles. The drawing is paired on the left to a histological microphotograph of a nerve. Note the blood vessels within the nerve, the connective tissue sheaths surrounding the nerve, the fascicle and the single nerve fiber, and the myelin sheath.

Figure I.7 Mary King with Bell palsy.

Figure I.8 Schematic illustration of a neuron and synapse.

Figure I.9 (a) Lateral view of the brain and brainstem. (b) Lateral view of the brain and brainstem with the latter shown as if you were looking through the left half of the brain.

Figure I.10 Inferior view of the brain and brainstem showing the origin of the CNs on the left and the bony canals into which they travel on the right, which is a superior view of the cranial floor. The orange structure is the pons, the pink is the medulla, and the yellow is the spinal cord.

Figure I.11 Axial MRI scan of the brain. This specific type of MR scan intensifies the difference between the white and gray matter but has the white matter appearing as almost black whereas the gray matter does look gray.

Figure I.12 Drawing of a lateral view of the brainstem showing the location of the CN nuclei.

Figure I.13 The figure on the lower left shows an inferior view of the brain with the origins of CNs digitally enhanced in yellow (same image as in Figure I.1). The larger figure on the right shows a drawing of the brainstem and the origin of the CNs.

Figure I.14 Axial (transverse ) CT of skull and brain (imagine looking down at the skull and brain from the top after it had been cut open but the image produced shows the right side of the brain on the left side of the image). Note that a CT shows much less brain tissue detail than the MRI shown in Figure I.11. CT scans take much less time to obtain than MRI scans and are also less expensive.

Figure I.15 Meninges of the brain. The dura is a heavy outer covering of the brain and spinal cord whereas the arachnoid is a delicate, translucent layer underneath the dura. The pia is a very thin membrane that is totally adherent to the surface of the brain (not labeled). Image courtesy of Dr. Pamela Gregory, Tyler Junior College, Tyler, Texas.

Figure I.16 Blood supply to the brain. The upper image shows the position of the major vessels supplying the brain. The lower image shows how the vessels lie relative to the brainstem.

Figure I.17 Coronal MRI image (imagine the patient looking at you) of a patient with an ischemic stroke on the left at the border between the pons and medulla in the brainstem. The darkened area within the red circle indicates an area of brain tissue necrosis (tissue death).

Figure I.18 Axial MRI showing left herniation of the part of the brain known as the uncus compressing the brainstem (it is on the left because you are looking at a slice of the brain as if you were standing at the patient’s feet). This patient presented with double vision. The MRI examination confirmed the cause of the double vision as compression of CN III by the uncus of the temporal lobe of the brain (see Chapter 3).

Figure I.19 Sir Laurence Olivier playing Hamlet, contemplating Yorick’s skull in Scene 1 of the Shakespearean play.

Figure I.20 Anterior view of the skull.

Figure I.21 The bones of the orbit.

Figure I.22 The foramina and openings associated with the bony orbit.

Figure I.23 Proposed mechanisms for inducing a blowout fracture of the inferior orbital wall.

Figure I.24 Alignment of the supraorbital, infraorbital, and mental foramina.

Figure I.25 Bones of the lateral view.

Figure I.26 Lateral and inferior views of the infratemporal fossa.

Figure I.27 Medial view of the side of the mandible showing the mandibular foramen.

Figure I.28 Foramina of the lateral view of the skull.

Figure I.29 Posterior view of the skull.

Figure I.30 Posterior (left) and anterior (right) views showing the attachment points of the trapezius muscle. Also, on right, the thyroid cartilage containing the laryngeal prominence and the hyoid bone of the neck are shown.

Figure I.31 Basal view of the skull – The external surface.

Figure I.32 Foramina that can be seen from the basal view.

Figure I.33 The cranial fossae – the Internal surface of the skull.

Figure I.34 The foramina (openings) of the cranial fossae.

Figure I.35 The sella turcica, which is part of the sphenoid bone.

Figure I.36 Bisected skull. The medial and lateral walls of the nasal cavity and associated structures are illustrated. Compare this image with Figures I.31 and I.33, which exhibit the external and internal views of the skull base, respectively.

Chapter 01

Figure 1.1 Helen Adams Keller (1880–1968) was an American author, political activist, and lecturer. She was the first deaf–blind person to earn a Bachelor of Arts degree. The story of how Keller’s teacher, Anne Sullivan, penetrated the isolation imposed by Keller’s absence of language ability has become widely known through the dramatic depictions of the play and film,

The Miracle Worker

. Here, Keller is shown using one of her remaining senses, olfaction, to smell roses.

Figure 1.2 Schematic illustration of the olfactory nerve.

Figure 1.3 Bisected view of the head of a cadaver showing the interior of the nasal cavity and the location of the olfactory epithelium (yellow shading).

Figure 1.4 Paired images showing the location of the olfactory bulb in the skull and on the brain. The inside surface of the base of the skull is shown on the lower left of the image. The surface of the brain that rests on the skull is shown on the upper right side of the image. An olfactory bulb was digitally inserted into the skull to demonstrate how it rests on the cribriform plate.

Figure 1.5 The four booklets of the Smell Identification Test

TM

.

Figure 1.6 Coronal view of a CT scan of a patient with a massive neuroesthesioblastoma. The arrows outline the tumor, which has greatly distorted the normal nasal anatomy in this patient.

Figure 1.7 MRI of the brain of a patient with a meningioma (tumor of meninges). Note how the tumor (circled in red) is located immediately above the cribriform plate and is therefore in a perfect location to compress the olfactory bulb and thereby interfere with olfaction.

Chapter 02

Figure 2.1 This painting is by Jacques Blanchard (or Blanchart) (1600–1638), who was a French Baroque painter. It is titled,

Tobias Healing the Blindness of his Father

. The painting depicts the Catholic Bible story of Tobias using fish gallbladder to cure the blindness of his father, which was caused by bird droppings entering his eyes.

Figure 2.2 Schematic illustration of the optic nerve and visual pathway in the brain. Note that some information from both eyes normally crosses over to the opposite side of the brain. Each eye thus transmits the information it receives to both sides of the brain.

Figure 2.3 Anatomy of the eye. The macula lutea is a yellow depression surrounding the fovea centralis. Modified from an image copyrighted by Dreamstime Images (Used with permission).

Figure 2.4 The layers of the retina and the formation of the optic nerve.

Figure 2.5 Detailed anatomy of the parts of the optic nerve as viewed from above (see text for explanation).

Figure 2.6 Normal optic disc as viewed from an ophthalmoscope.

Figure 2.7 Illustration of the mechanism underlying papilledema. Increased CSF pressure compresses the optic nerve and caused a swollen optic disc, as seen on the right. The drawing is superimposed on an axial MRI of the anterior part of the brain and orbits. The optic nerve is purposely drawn excessively large to demonstrate the condition and is not therefore anatomically correct relative to the MRI.

Figure 2.8 Swollen optic disc (papilledema) as seen through an ophthalmoscope. Compare with the normal disc shown in Figure 2.6.

Figure 2.9 Coronal MRI of a 20-year-old patient who showed progressive loss of vision in the right eye over the last several weeks. The patient was eventually diagnosed with MS. The white area within the red circle represents inflammation of the optic disc/nerve. The swollen right optic nerve (circled) is quite obvious compared to the invisibility of the left nerve on the image.

Figure 2.10 The two halves of the image show how a patient with optic neuritis might see an object (right side) compared to how a normal person sees the same image (left side). The patient sees much less contrast and color than a normal person.

Figure 2.11 Schematic illustration showing where the pituitary gland is located in the sella turcica and in the skull (inset). The image also shows the venous filled spaces, called the

cavernous sinuses

, which are located along the sides of the sella turcica. This important space is discussed in subsequent chapters, especially Chapter 3. See also Figure I.35.

Figure 2.12 Paris views showing normal vision and loss of the temporal visual fields.

Figure 2.13 The light reflex. A light shone into either eye results in bilateral pupillary constriction.

Figure 2.14 The accommodation reflex. Focusing on a near object results in pupillary constriction, movement of the eyes toward the nose (adduction), and thickening (swelling) of the lens of both eyes.

Chapter 03

Figure 3.1 Child with congenital absence of left oculomotor nerve trying to look up. Note that the eyelid is more prominent on the left because the oculomotor nerve controls the muscle that raises the eyelid.

Figure 3.2 Schematic drawing of the oculomotor nerve showing its innervation of four of the extraocular muscles.

Figure 3.3 Photograph and drawing highlighting the origin of the oculomotor nerve from the brainstem.

Figure 3.4 Close-up photograph showing the origin of the oculomotor nerve (III) between the superior cerebellar artery (SCA) and posterior cerebral artery (PCA), and adjacent to the posterior communicating artery (PCoA). The basilar artery (BA) is also in the view. The inset shows the location on the brainstem of the larger image.

Figure 3.5 The path of the right oculomotor nerve. Illustrative drawings superimposed on a partially dissected head showing the path of the oculomotor nerve from the oculomotor nucleus in the brainstem to the orbit. The right and left nerves pass through two brainstem regions, the red nucleus (colored red) and also the substantia nigra (colored black). Each nerve, upon exiting the brainstem, then enters the subarachnoid space, the cavernous sinus, and, finally, the superior orbital fissure to enter the orbit.

Figure 3.6 Coronal cross-sectional view of the cavernous sinus highlighting the position of the oculomotor nerve vis-à-vis the other cranial nerves and blood vessels located within the sinus.

Figure 3.7 Components of the oculomotor nerve. The nerve contains somatic efferent fibers from the oculomotor nucleus in the midbrain. These are joined by preganglionic parasympathetic fibers from the Edinger–Westphal nucleus, also in the midbrain. As the nerve travels through the cavernous sinus it is joined by postganglionic sympathetic fibers. In the orbit the preganglionic parasympathetic fibers reach the ciliary ganglion (CG) where they synapse and then reach the eye via the short ciliary nerves.

Figure 3.8 The main upper image shows an enhanced radiographic image in which the nerves entering the orbit through the superior orbital fissure and optic canal (optic nerve) are identified. The lower image shows these canals on a frontal view of the bony orbit.

Figure 3.9 The extraocular muscles and their attachments on the eye.

Figure 3.10 Diplopia. Double “exposure” image showing how a person with oculomotor palsy might see a single image.

Figure 3.11 Eye movements.

Figure 3.12 Computer-generated illustration of the nerves and muscles of the orbit. The inset is a magnified view showing the ciliary ganglion and related structures.

Figure 3.13 Cadaver dissection of the orbit showing the ciliary ganglion and short ciliary nerves.

Figure 3.14 Patient with right oculomotor palsy. Note the down-and-out position of the right eye.

Figure 3.15 Photographs of the woman described in the case trying to look in various directions after having an eye injury caused by penetration by a stiletto heel.

Chapter 04

Figure 4.1 Doll with large eyes showing how the eyes of a patient with left trochlear nerve palsy might appear (note slightly elevated left eye).

Figure 4.2 The complete path of the trochlear nerve is shown in the drawing. Note that it is the only cranial nerve that originates from the back of the brainstem. Because the examination of the brain is most frequently done from a frontal view, the origin of the trochlear nerve helps explain why this nerve is difficult to discern from standard views of the base of the brain.

Figure 4.3 Brainstem photograph and drawing highlighting the origin of the trochlear nerve. There is some asymmetry between the idealized drawing on the right and the photograph on the left.

Figure 4.4 Cadaver-based photograph of the skull base and an inset showing a magnified view of a highlighted trochlear nerve piercing the dura and entering the cavernous sinus.

Figure 4.5 Coronal cross-sectional view of the cavernous sinus highlighting the position of the trochlear nerve vis-à-vis the other cranial nerves and blood vessels located within the sinus.

Figure 4.6 A superficial (left) and deep dissection of the orbit (from above) highlighting the position of the trochlear nerve and superior oblique muscle.

Figure 4.7 High-resolution MRI showing the right and left trochlear nerves (yellow arrow) arising from the dorsal midbrain.

Figure 4.8 Photographs of a patient demonstrating left trochlear nerve palsy. The upper image shows the patient’s eyes in a neutral position and the lower image shows the patient looking to the left (adducted left eye).

Figure 4.9 Boy with a left trochlear nerve palsy showing head tilt to the opposite side.

Figure 4.10 Child with congenital left superior trochlear nerve palsy at 3 weeks (a), 3 months (b), and 6 months (c).

Chapter 05

Figure 5.1 Photograph of a patient undergoing an episode of trigeminal neuralgia.

Figure 5.2 Schematic drawing of the anatomy of the trigeminal nerve.

Figure 5.3 Brainstem photograph (right) and schematized drawing (left) highlighting the origin of the trigeminal nerve.

Figure 5.4 Image showing the origin of the right trigeminal nerve and its divisions.

Figure 5.5 Photograph showing the root of the trigeminal nerve, the ganglion, the three divisions, and the foramina (opening) each passes through.

Figure 5.6 The major muscles of mastication shown on a drawing (top) and on a dissection (bottom).

Figure 5.7 Sagittal dissection showing the tensor and levator veli palatini muscles. Inset shows how the tensor uses the medial pterygoid plate as a pulley so that it can tense the soft palate (uvula).

Figure 5.8 Coronal cross-sectional view of the cavernous sinus highlighting the location of V

1

and V

2

vis-à-vis the other cranial nerves and blood vessels located within the sinus.

Figure 5.9 Orbital dissection showing the branches of the ophthalmic division of the trigeminal nerve and some additional orbital nerves superimposed (white circle) on a view of the bony anterior and middle cranial fossae.

Figure 5.10 Branches of the ophthalmic and maxillary divisions of the trigeminal nerve within the orbit. Abbreviations: AE, anterior ethmoidal; CG, ciliary ganglion; F, frontal; IF, infratrochlear; IO, infraorbital; L, lacrimal; LC, long ciliary; LG, lacrimal gland; NS, nasociliary; PE, posterior ethmoidal; SC, short ciliary; ST, supratrochlear; SO, supraorbital; Z, zygomatic; ZC, zygomatic communicating branch; ZF, zygomaticofacial; ZT, zygomaticotemporal.

Figure 5.11 The major cutaneous nerves of the face (branches of the trigeminal nerve) superimposed on a photograph of Albert Einstein. Abbreviations: AT, auriculotemporal; B, buccal; IO, infraorbital; IT, infratrochlear; L, lacrimal; M, mental; SO, supraorbitial; ST, supratrochlear; ZF, zygomaticofacial; ZT, zygomaticotemporal.

Figure 5.12 Path of the maxillary nerve. The nerve exits the brainstem as part of the main trigeminal root (yellow) and passes through the cavernous sinus and foramen rotundum; it then enters the orbit as the infraorbital nerve (orange) through the inferior orbital fissure and traverses the floor of the orbit, becoming cutaneous on the face through the infraorbital foramen (green).

Figure 5.13 Sagittal section of the head showing some of the branches of the maxillary nerve. Abbreviations: GPN, greater palatine nerve; ION, infraorbital nerve; LPN, lesser palatine nerve; SAN, superior alveolar nerve; SG, sphenopalatine (pterygopalatine) ganglion; TVPM, tensor veli palatini.

Figure 5.14 The nasopalatine nerve is highlighted as it traverses the nasal septum and the incisive foramen to innervate part of the septum and the anterior part of the maxilla.

Figure 5.15 Image showing where dental injections are made to anesthetize the upper teeth and hard palate.

Figure 5.16 The main figure shows a dissection of the infratemporal fossa, highlighting the chorda tympani nerve and the lingual (LN) and inferior alveolar (IAN) branches of the mandibular nerve. The inset (circled in white) shows these same nerves, as well as the deep temporal nerves, which innervate the temporalis muscle. The inset diagram is courtesy of http://what-when-how.com/dental-anatomy-physiology-and-occlusion/dento-osseous-structures-blood-vessels-and-nerves-dental-anatomy-physiology-and-occlusion-part-5/.

Figure 5.17 Illustration showing the path of the lingual nerve and inferior alveolar nerves. The inferior alveolar (dental) nerve is shown entering the mandibular canal and exiting the mental foramen to appear on the chin (see Figure I.24).

Figure 5.18 Illustration showing the chorda tympani nerve joining the lingual nerve and traveling with the nerve to the submandibular ganglion, where its postganglionic parasympathetic fibers innervate the submandibular and sublingual salivary glands. The lingual nerve provides sensation to the tongue as shown. The inferior alveolar nerve is shown as it traverses the mandibular canal and exits the mental foramen.

Figure 5.19 Illustrations show the path of the inferior alveolar nerve as it traverses the mandibular canal and innervates the lower teeth before exiting the canal as the mental nerve. The inset in the upper image left shows how an impacted lower molar can compress the nerve.

Figure 5.20 The pathway of the corneal (blink) reflex.

Figure 5.21 Illustration showing the cutaneous distribution of the three branches of the trigeminal nerve.

Figure 5.22 Patient about to undergo bilateral alcohol injections to treat her TN.

Figure 5.23 Photograph of a patient with herpes zoster ophthalmicus on her right side. Note the confinement of the lesions to the cutaneous distribution of V

1

. .

Figure 5.24 Patient with Sturge–Weber syndrome.

Figure 5.25 Images showing compression of the inferior alveolar nerve by a dental instrument that was inadvertently left in the patient.

Figure 5.26 Photograph showing the osteology involved in an inferior alveolar nerve injection and an inset showing an actual injection.

Chapter 06

Figure 6.1 Photograph of a boy with a left abducent nerve palsy (left image) due to a bullet located in his brain, as shown in the 1914 radiographic image (right image). He also has ptosis on the right, which is not from the CN VI injury.

Figure 6.2 Schematic illustration showing the abducent nerve passing into the orbit and innervating the lateral rectus muscle.

Figure 6.3 Photograph and drawing highlighting the origin of the abducent nerve from the brainstem.

Figure 6.4 Schematic illustration showing the path of the abducent nerve passing from the brainstem to the orbit.

Figure 6.5 Coronal cross-sectional view of the cavernous sinus highlighting the position of the abducent nerve vis-à-vis the other cranial nerves and blood vessels located within the sinus.

Figure 6.6 Superior view showing the abducent nerve entering the orbit (roof of orbit removed) and innervating the lateral rectus muscle. Note that the superior rectus and levator palpebrae muscles are cut and reflected and that the lateral rectus muscle is cut. Note also how the abducent nerve enters the medial surface of the muscle. CG, ciliary ganglion.

Figure 6.7 A closer superior view than that shown in Figure 6.6 in which the abducent nerve is shown entering and innervating the lateral rectus muscle.

Figure 6.8 Eye movement in a patient with bilateral abducent nerve palsy. In (a), the patient is asked to look straight, in (b) the patient is asked to look to the right, and in (c) the patient is asked to look to the left.

Chapter 07

Figure 7.1 Drawing from 1869 showing a patient with bilateral facial weakness.

Figure 7.2 Schematic illustration of the anatomy of the branches of the facial nerve.

Figure 7.3 Brainstem photograph and illustration highlighting the origin of the facial nerve from the brainstem (note the differentiation of the nerve into two elements; the lateral element is the intermediate nerve).

Figure 7.4 The intermediate (IN), facial (VII), and vestibulocochlear (VIII) nerves entering the internal auditory canal (IAC).

Figure 7.5 Upper left: a drawing of the junction between the right anterior and middle cranial fossae with the bone overlying the petrous portion of the temporal bone “cut away” to show the intrinsic structures including the internal auditory canal (IAC) and the geniculate ganglion. Upper right: a superior view of the cranial fossae showing the location from which the drawing on the left is derived (black oval); CN VII is drawn in on the image. Lower left: a drawing of the nerves entering the IAC (from the image directly above with CN VII labeled). (The drawing shows nerve VII including the intermediate nerve; the other nerves entering the IAC are all components of CN VIII; see Chapter 8.) Lower right: an actual dissection of the area circled in the above images with most of the petrous portion of the temporal bone removed. Abbreviations: VIIp, CN VII proximal to IAC; IAM, internal auditory meatus (canal); VIId, CN VII distal to IAC; GPN, greater petrosal nerve; GG, geniculate ganglion, VIIdg, CN VII distal to the geniculate ganglion. The image on the upper left is reprinted from Tubbs

et al

. (2009). The lower right image is modified with permission from Liu, Arnold, and Robinson (2012).

Figure 7.6 Illustration showing the parts of the facial nerve, with the inset showing the stylomastoid foramen for orientation.

Figure 7.7 Flowchart showing the muscular branches of the facial nerve.

Figure 7.8 Upper left: dissection of the lateral aspect of the face showing the parotid gland and major branches of the facial nerve. Lower right: deeper dissection showing the stem of the facial nerve as it emerges from the stylomastoid foramen and splits into its many branches within the parotid gland, which is reflected. The lower image is provided with the courtesy of Drs. M. Robinson and L. Liu, the University of Sydney, Australia.

Figure 7.9 Illustration showing the stapedial branch of the facial nerve innervating the stapedius muscle. This muscle dampens the movements of the stapes in response to loud sounds so that the vibrations transmitted to the oval window are reduced. The stapes is about 0.1 in. in length and is located within the middle ear cavity.

Figure 7.10 Muscles of facial expression. Original image used with permission of Dreamstime.com.

Figure 7.11 Flowchart showing the branches and functions of the intermediate nerve.

Figure 7.12 The path of the greater petrosal nerve is shown in green. The top image (1) shows a superior view of the cranial base (cranial fossae) in which the path of the nerve is shown as it exits the petrous portion of the temporal bone and crosses over the foramen lacerum to reach the pterygoid canal. The middle image (2) shows a posterior view of the sphenoid bone (yellow in top figure) and the nerve (green) entering the pterygoid canal. The lower image (3) shows an anterior view of the sphenoid bone and the nerve exiting the canal to enter the pterygopalatine fossa.

Figure 7.13 This illustration is based on one in the 1918 edition of

Gray’s Anatomy of the Human Body

. Note the location and nerves leading to the sphenopalatine (pterygopalatine) ganglion. Also in this illustration, the greater petrosal nerve (greater superficial petrosal nerve) is shown joining with the deep petrosal nerve to form the Vidian nerve (nerve of the pterygoid canal). This nerve brings sympathetic and parasympathetic inputs to the ganglion for distribution.

Figure 7.14 Schematic illustration of the course of the chorda tympani from the facial nerve to the lingual nerve and tongue. Inset shows an oblique vertical slice through the petrous portion of the temporal bone. The anterior two-thirds of the tongue are drawn in a lighter shade than the posterior one-third to indicate the area innervated by the chorda tympani nerve.

Figure 7.15 Illustration of the right middle ear, viewed from the tympanic membrane laterally. The chorda tympani traverses across the tympanic membrane from posterior to anterior.

Figure 7.16 A phenomenon known as crocodile tears sometimes occurs as a sequela of Bell palsy. In this condition, thinking about food results in tearing.

Figure 7.17 Photograph of the ear of a patient with Ramsey Hunt syndrome. The sores are typical of herpes zoster lesions.

Figure 7.18 The Bell phenomenon. This sign is characterized by an upward movement of the eye when an attempt is made to close the eyelids. The space in the image is there to protect patient identify.

Figure 7.19 Infant with right-sided facial paralysis due to injury during birth. Note the absence of a smile on his right side.

Figure 7.20 A woman with injury to the right marginal mandibular branch of her facial nerve. Note how while trying to smile her right lower lip remains in a neutral position as a result of the nerve injury.

Chapter 08

Figure 8.1 Vincent Van Gogh,

Self Portrait, 1889

– the year before he died. Although he was not diagnosed in life, Van Gogh may well have suffered vertigo due to Ménière’s disease. This depiction of the swirling vortex, spinning, turning, and moving world is familiar to many patients suffering from this vestibular disturbance.

Figure 8.2 Schematic illustration of the distal portion of CN VIII (also showing some of CN VII). VIIIv is the vestibular portion of the CN VIII, whereas VIIIc is the cochlear portion. NI is the intermediate nerve (see Chapter 7).

Figure 8.3 Dissection (left) and drawing (right) showing origin of cranial nerves III to XII from the brainstem, highlighting the origin of CN VIII.

Figure 8.4 Cadaver dissection (white circle) inserted on to photograph of the petrous portion of the temporal bone (see Figure I.33) showing the path of CN VIII from the brainstem through the subarachnoid space into the IAC. Abbreviations: I, incus; IAM, internal auditory meatus (canal); M, malleus; VIIIc, cochlear portion of nerve; VIIIv, vestibular portion of nerve. The dissection inset is used with permission from Liu, Arnold, and Robinson (2012).

Figure 8.5 Drawing of the vestibular and cochlear apparatuses. The expanded ends of the semicircular canals (ampulla) contain the sensory organs of the canals (crista ampullaris; not labeled in this illustration) whereas the sensory organs of the utricle and saccule are within these two structures. Note that within the bony labyrinth is a much smaller membranous labyrinth that contains endolymph. The organ of corti is found within the cochlea. VIIIc is the cochlear portion of the VIIIth nerve and VIIIv is the vestibular portion. Inset showing location of the vestibular and cochlear apparati in the head is courtesy of Wikimedia (http://commons.wikimedia.org/wiki/File:Anatomy_of_Human_Ear_with_Cochlear_Frequency_ Mapping.svg). See also Figure 8.7.

Figure 8.6 Central vestibular pathways. The afferent neurons from the vestibular apparatus project via fibers in CN VIII to the four vestibular nuclei (superior, inferior, medial, and lateral nuclei) located in the rostral medulla and the caudal pons. The MLF (medial longitudinal fasciculus) is a fiber bundle that conducts this information to the cranial nerve nuclei of the oculomotor, trochlear, and abducent nerves. Information from the vestibular nuclei also projects to the spinal cord via the medial and lateral vestibulospinal tracts (VST) (important for balance and posture), to the cerebellum (also for balance and posture), and to the cerebral cortex via the thalamus (for awareness of head position).

Figure 8.7 A sectional drawing of the cochlea showing the spiral ganglion. The other labeled structures are the modiolus, which is the central bony element in the cochlea, and the scalae vestbuli, media (cochlear duct), and tympani, which are canals within the cochlea. The inset in the upper left shows the cochlea situated in the temporal bone.

Figure 8.8 Flowchart depicting the mechanism of hearing.

Figure 8.9 Caloric testing of the vestibular ocular reflex in a comatose patient with intact brainstem.

Figure 8.10 A coronal MRI image of a patient with a left acoustic neuroma (vestibular schwannoma) (circled).

Chapter 09

Figure 9.1 Radiograph of Mr. Brad Byers “swallowing” a sword.

Figure 9.2 Schematic diagram of the glossopharyngeal nerve. This diagram also shows the many connections between the autonomic and somatic nervous systems associated with the glossopharyngeal and vagus (CN X) nerves, which are not generally discussed but which are very prevalent, especially in the head and neck.

Figure 9.3 Axial section CT image of the upper neck of a patient in which a tumor (circled) encloses the glossopharyngeal nerve (this is not the CT scan of the patient in the case but a patient with an identical tumor on his left side; the published CT was not as clear as this one because it was done with an old CT scanner).

Figure 9.4 Photographic (left) and schematic drawing (right) showing the origin of the cranial nerves from the brainstem with the glossopharyngeal nerve highlighted.

Figure 9.5 High-magnification view of CNs IX, X, and XI exiting the brainstem and entering the jugular foramen. The grid shows 1 mm squares.

Figure 9.6 Frontally cut skull section that extends inferiorly to include the neck showing the back muscular wall of the pharynx and esophagus, the glossopharyngeal nerve, and the stylopharyngeus muscle. This view is looking at the back of the pharynx with the vertebral column removed (see Figure 9.7).

Figure 9.7 Top: sagittal midline section photograph of a cadaver showing the parts of the pharynx. Bottom: illustration showing the same features. Lower illustration reprinted with permission from Mayo Foundation for Medical Education and Research.

Figure 9.8 The large illustration shows the complex of nerves within the wall of the pharynx that comprise the pharyngeal plexus. The nerves are derived from CNs IX and X, and also include some sympathetic fibers (not shown). The inset shows the anatomical location of the region of the main image.

Figure 9.9 The main afferent and efferent functions of the glossopharyngeal nerve.

Figure 9.10 Flowchart showing all the functions of the glossopharyngeal nerve. The orange arrows indicate motor pathways (general and visceral) and the blue indicate sensory pathways (general and special).

Figure 9.11 Illustrative drawing set upon a cadaver image to show the innervation of the parotid gland. This gland resides along the ramus of the mandible and is the largest of the salivary glands. The pathway from the glossopharyngeal nerve trunk to this gland is very complex and explained here as well as in the text. A branch of the glossopharyngeal nerve, the tympanic nerve, leaves the nerve as it exits the jugular foramen (not shown). This nerve traverses the middle ear cavity and emerges in the cranial cavity as the lesser petrosal nerve. It then exits the cranial cavity near the foramen ovale and enters the infratemporal fossa (Figure I.26). The nerve, which is carrying preganglionic parasympathetic fibers, reaches the otic ganglion and the fibers synapse there. Then the postganglionic fibers join a sensory branch of the mandibular nerve, the auriculotemporal nerve (Figure 5.2), and from this nerve terminal branches enter and innervate the parotid gland.

Figure 9.12 Drawing showing the carotid sinus and body at the bifurcation in the neck of the common carotid artery. The branches of the glossopharyngeal and vagus nerves that innervate these structures are also shown.

Figure 9.13 A patient with gustatory sweating (Frey syndrome). This 69-year-old patient had her parotid gland removed when she was 18. Salivation was stimulated with sour candy. Note how the tissue paper sticks to the side of the face due to her gustatory sweating.

Figure 9.14 The main image shows a coronal view CT scan (it is as if you are looking at the patient’s face) of a disproportionately long, right styloid process; note specifically that it extends beyond the lower border of the mandible, which is not normally the case as shown by the inset, which depicts a lateral view of the middle of a normal skull in which leaders point to both normal styloid processes (see Figure I.25). The CT also shows that the patient’s left styloid process is similarly enlarged, although to a lesser extent than on the right.

Figure 9.15 Injection to anesthetize the glossopharyngeal nerve.

Chapter 10

Figure 10.1 Plate 18 from

Osteopathy Complete

by E.D. Barber, D.O., published in 1898. This illustration,

Freeing and Stimulating the Pneumogastric Nerve

, shows a typical osteopathic treatment intended to influence the Xth cranial nerve (pneumogastric/vagus). Regulation of physiological processes was a major goal of early osteopathic treatment for a wide range of disorders. Osteopathic physicians during this period believed that they could modify both the peripheral and central nervous system by manipulative techniques that affected nerve centers throughout the body.

Figure 10.2 Schematic illustration of the long path of the vagus nerve.

Figure 10.3 Photographic (left) and schematic drawing (right) showing the origin of the cranial nerves from the brainstem, with the vagus nerve highlighted.

Figure 10.4 High-magnification view of CNs IX, X, and XI exiting the brainstem and entering the jugular foramen. The grid shows 1-mm squares.

Figure 10.5 The vagus nerve is shown in the neck along with its ganglion and the internal carotid artery.

Figure 10.6 Recurrent laryngeal nerve. (a) Cadaver dissection photograph showing both the left and right RLNs along the trachea in the neck. (b) Illustration showing how the left RLN arises from the left vagus nerve and passes around the arch of the aorta. (c) Cadaver photograph showing similar relationships to (b) but also the relationship between the left RLN and the ligamentum arteriosum. Part (b) is reprinted with permission from Van Melle, Meyens, and Budts (2010).

Figure 10.7 Drawing of the aorta with celiac and other abdominal autonomic ganglia superimposed on a cadaver dissection of the posterior (back) abdominal wall (as seen from a front view). IVC, inferior vena cava.

Figure 10.8 Illustration showing the branches of the vagus nerve in the neck.

Figure 10.9 Illustration drawn upon a cadaver photograph showing the cardiac nerves arising from the left and right vagus (and left and right recurrent laryngeal) nerves and streaming to plexuses located near the heart. Vagal impulses to these plexuses act to slow the heart whereas sympathetic inputs (not shown) act to speed up the heart.

Figure 10.10 Axial (transverse) CT image of the patient described in the case of Ortner’s syndrome. Note how the left RLN is compressed by the aneurysm.

Figure 10.11 Laryngoscopic views of a patient with a paralyzed vocal cord (black arrow).

Figure 10.12 Schematic illustration of the hypothesized connections between the brain and the immune system based on the vagal nerve connections (see inset).

Figure 10.13 Illustration of a how a vagal nerve stimulator is attached to the nerve and the heart to regulate (rest) the heart after heart failure.

Figure 10.14 Left-sided lesion of the vagus nerve being demonstrated by asking the patient to say “ah.” The uvula is deviated to the right because there is no contralateral force being supplied by the damaged left levator veli palatini muscle (normal side pulls the uvula to the right).

Figure 10.15 Illustration showing placement of a vagal nerve stimulator for epilepsy.

Figure 10.16 Illustration showing how a commercial stimulator may work with the vagus nerve to improve immune health.

Chapter 11

Figure 11.1 Photographs from a patient with bilateral accessory nerve paralysis. (a) Clear droopy position of the shoulders as seen from the back. (b) Shoulders forced backward; note prominent scapulae. (c) Natural position of the shoulders from the front. (d) A “trick” the patient could perform because of the paralysis of the trapezius muscles. The little fingers were locked together and then the arms pulled together so that the elbows completely crossed to the opposite side. The head was then put through the space between the forearms (see text).

Figure 11.2 Schematic illustration of the path of the accessory nerve.

Figure 11.3 Modification of an image originally published in the classic

Gray’s Anatomy

from 1858. The sternocleidomastoid and trapezius muscles are highlighted.

Figure 11.4 (a) Image from Arnold (1838); asterisk and arrows (added): rootlets of accessory nerve depicted as arising from the medulla. (b) Figure from

Gray’s Anatomy

(1858). Asterisk and arrow (added): unlabeled nerve trunk described in the text as the “cranial part” of accessory nerve. (c) The prevailing view of cranial nerve XI. In our view and that of Lachman and colleagues from which this entire image was reprinted (Figure 5 with slight modification; Lachman, Acland, and Rosse, 2002), this prevailing view is not correct and the cranial root of the accessory nerve should be considered part of cranial nerve X. M, medulla; SC, spinal cord.

Figure 11.5 (a) Classic view of the accessory nerve, with a spinal and a cranial root (see also Figure 11.4). (b) Our view, as well as that of other modern anatomists, in which the accessory nerve consists exclusively of the “spinal root.” The previously named “cranial root” is considered part of the vagus (see text).

Figure 11.6 High magnification view of CNs IX, X, and XI exiting the brainstem and entering the jugular foramen. The grid shows 1-mm squares.

Figure 11.7 Top: cadaver photograph showing nerve XI in the posterior triangle of the neck entering the reflected sternocleidomastoid and the trapezius muscles from the side. IJV, internal jugular vein. Bottom: the spinal accessory nerve is shown coursing along the large reflected trapezius muscle.

Chapter 12

Figure 12.1 Patient with gunshot wound to left hypoglossal nerve. The patient exhibits typical lesion (see text for explanation).

Figure 12.2 The pathway of the hypoglossal nerve is illustrated in the image. The name hypoglossal is derived from the fact that the nerve enters the tongue (glossus) from below, as clearly shown in the image.

Figure 12.3 Photograph showing rootlets of the hypoglossal nerve arising from the medulla and entering the hypoglossal canal.

Figure 12.4 Cadaver photograph showing the path of the hypoglossal nerve in the neck. ICA, internal carotid artery.

Figure 12.5 Extrinsic muscles of the tongue. The tongue also has intrinsic muscles that do not attach outside of the tongue.

Figure 12.6 Cadaver photograph showing the infrahyoid or “strap” muscles (sternohyoid, sternothyroid, and omohyoid) that are innervated by the ansa cervicalis. The sternocleidomastoid muscle (SCM) is not a strap muscle. It is innervated by the spinal accessory nerve, CN XI (see Chapter 11).

Figure 12.7 Illustration showing all of the nerves that take part in providing innervation to the tongue.

Figure 12.8 Promotional illustration showing hypoglossal nerve stimulation for sleep apnea. In this condition, the tongue may fall backward and block the upper airway. The mild stimulation provided by the stimulator maintains the tone of the major tongue muscles preventing this backward displacement.

Chapter 13

Figure 13.1 Illustration from Fritsch (1878) showing his drawing of the dogfish shark brain. The terminal nerve is labeled although Fritsch did not name it as such.

Figure 13.2 (a) Semidiagrammatic illustration of the nasal septal view of the NT in a human infant. Dashed lines represent vessels (also in (b)). Modified from Figure 1 in Brookover (1917). (b) Enlargement of the posterior ventral portion of (a) to show a possible sympathetic nerve connection between the NT and the ascending septal branch of the nasopalatine nerve. Modified from Figure 2 in Brookover (1917). (c) Illustration showing a nasal septum view of the NT in a six-month-old human fetus. Modified from Figure 1 in McCotter (1915). (d) Nasal septal view showing the NT in a 45 mm human fetus. Modified from Pearson (1941). All images used with permission. CG, crista galli.

Guide

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The Clinical Anatomy of the Cranial Nerves

The Nerves of “On Old Olympus Towering Top”

Joel A. Vilensky, Ph.D.

Professor of Anatomy and Cell BiologyIndiana University School of MedicineFort Wayne, IN

Wendy M. Robertson, P.A., M.D.

Senior Staff NeurologistDepartment of NeurologyHenry Ford HospitalDetroit, MI

Carlos A. Suárez-Quian, Ph.D.

ProfessorDepartment of Biochemistry and Molecular & Cellular BiologyGeorgetown University Medical CenterWashington, DC

This edition first published 2015 © 2015 by John Wiley & Sons, Inc.

Editorial Offices1606 Golden Aspen Drive, Suites 103 and 104, Ames, Iowa 50010, USAThe Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK9600 Garsington Road, Oxford, OX4 2DQ, UK

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Library of Congress Cataloging-in-Publication Data

The clinical anatomy of the cranial nerves : the nerves of old Olympus towering top / Joel A. Vilensky, Wendy M. Robertson, Carlos A. Suárez-Quian.       p. ; cm.    Includes index.

    ISBN 978-1-118-49201-7 (cloth)    I. Vilensky, Joel A., 1951– , author. II. Robertson, Wendy M., author. III. Suárez-Quian, Carlos Andrés, author.    [DNLM: 1. Cranial Nerves–anatomy & histology. WL 330]    QM471    612.8′19–dc23

2014030763

A catalogue record for this book is available from the British Library.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.

Dedication

This book is dedicated to teacher, mentor, and friend, Dr. Sid Gilman. We thank him most sincerely for being all three and for revealing to us, through his knowledge and actions, the amazing neurological talents of his own mentor, Dr. Derek Denny-Brown.

Preface

This book is about the most interesting nerves in the body. So interesting and also sometimes so frustrating that we repeatedly in this book refer to the cranial nerves as being “magical.” The traditional twelve cranial nerves defy logic by the amazing senses they convey, the convoluted intracranial paths they take and the problems they can cause when they do not function correctly.

The title of our book, The Clinical Anatomy of the Cranial Nerves: The Nerves of “On Old Olympus Towering Top”, is derived from a mnemonic that virtually all clinicians learn to remember the numbers associated with each of the cranial nerves (see Introduction chapter).

In The Clinical Anatomy of the Cranial Nerves: The Nerves of “On Old Olympus Towering Top” we have done our best to describe the anatomy and physiology of these nerves from a clinical perspective, but in a such a way that the reader does not need to be a clinician to understand our text. This is facilitated by general sections in our Introduction on the nervous system and on the osteology (bones) of the skull.

We liberally sprinkle our chapters with case studies so that the reader can “feel” what patients experience when one or more of their cranial nerves don’t function correctly, as well as understand better intellectually what these nerves do compared to texts without such clinical cases.

As with all anatomy books, this one has many illustrations. We searched many sources or drew our own (or commissioned an artist to draw them) to obtain images that we felt illuminate and simplify the complexity of these nerves in terms of anatomy and function. Further, and we think unique to this book, we present many images from actual anatomical dissections of the cranial nerves. The latter show the reader the real anatomy of these nerves rather than the sometimes simplified version that drawings may present.

We believe this book is suitable for an undergraduate course on the cranial nerves, and is certainly a useful supplement to health professionals learning about these nerves for the first time, including first year medical students, or those wanting to review the anatomy of the cranial nerves for their clinical practice. We also believe interested lay persons and patients with cranial nerve disorders will find this book understandable, informative, and useful.

Joel A. VilenskyCarlos A. Suárez-QuianWendy M. Robertson

Contributors

Howard P. Cupples, M.D.Professor and Chair, EmeritusDepartment of OphthalmologyGeorgetown University School of Medicine Washington, DC

Andrew Frederickson, M.S.Researcher Center for Cranial Nerve and Brainstem DisordersUniversity of Pittsburgh School of Medicine Pittsburgh, Pennsylvania

Lucille Hess, Ph.D., CCC-SLPProfessor Emeritus Communication Sciences and Disorders Indiana-Purdue University-FW Fort Wayne, Indiana

Peter J. Koehler, M.D., Ph.D., FAANStaff Neurologist Department of Neurology Atrium Medical Centre Heerlen, The Netherlands

Mortimer Lorber, D.M.D., M.D.Professor Emeritus Department of Pharmacology and Physiology Georgetown University School of MedicineWashington, D.C.

M. Anthony Pogrel, D.D.S., M.D. William Ware Endowed Professor and Chairman Associate Dean for Hospital Affairs Department of Oral and Maxillofacial Surgery University of CaliforniaSan Francisco, California

Mohan K. Rao, M.D.Staff Otolaryngologist Ear, Nose, & Throat Associates PC Dupont Medical Park Fort Wayne, Indiana

Carol E.H. Scott-Conner, M.D., Ph.D. Professor of SurgeryDepartment of Surgery University of Iowa Carver College of Medicine Iowa City, Iowa

Raymond Sekula, M.D.Professor of NeurosurgeryDepartment of NeurosurgeryUniversity of Pittsburgh School of Medicine Pittsburgh, Pennsylvania

Alex Senchenkov, M.D.Staff SurgeonMayo ClinicRochester, Minnesota

Ujjowala D. Shrestha, M.D.Consultant Pediatric OphthalmologistTilganga Institute of OphthalmologyKathmandu, Nepal

Laurie Swan, P.T., Ph.D., DPTInstructor, Pierce CollegeOwner and CEO, Synaptic SeminarsPuyallup, Washington

Jonathan Trobe, M.D.Professor of Neurology and OphthalmologyDepartment of OphthalmologyUniversity of Michigan School of MedicineAnn Arbor, Michigan

John E. Woods, M.D.Emeritus Professor of SurgeryMayo ClinicRochester, Minnesota

Acknowledgments

This book has many illustrations based on cadaver dissections. We will never know the names of the many people who donated the bodies that we (or others) photographed to convey the anatomy of the cranial nerves, but we are most grateful to these individuals for their generous donation.

Haley Moon was a research/technical assistant for this book and helped in all ways including obtaining permissions to use illustrations and doing some of the artwork. We thank her very much. Lowene Stipp and Joanne Summers are thanked for the secretarial assistance they provided to develop this book.

Steven Fraser drew all of the illustrations that appear as the second figure in all of the chapters and we are grateful to him for his beautiful work and for his patience with our many revisions.

We thank Dr. Edward Weber for graciously providing radiologic images for us.

At Wiley we thank our editor and editorial assistant, Justin Jeffryes and Stephanie Dollan, for assisting us with development and producing this book.

The concluding chapter of this book contains essays from clinicians (Contributors) about their experience with the cranial nerves and we are grateful to them for the time they spent writing these amazing stories for us.

Our families are much thanked for allowing us the two years we spent writing and editing this book.

We are grateful to Dr. Fen-Li Chang and the Indiana University School of Medicine – Fort Wayne for hosting our meeting in Fort Wayne.

We would like to thank the students we have taught and the teachers we have had for all they have done for our careers and for making us cherish learning and teaching human anatomy and its clinical relevance.

Donald Black is thanked for his review of some of the initial chapters of this book. We would also like to thank Drs. Mark Hofmeyer, Blair Marshall, and David Pearle, MedStar Washington Hospital Center, who helped us appreciate the changes that the heart and esophagus undergo following transplantation in Chapter 10. Dr. Susan Stoddard provided some initial guidance in the development of this book and we appreciate her assistance.

Drs. R. Shane Tubbs and Stephen W. Carmichael are thanked for discussions about the methodology involved in writing a textbook. We appreciate the help of Amy Finch with checking our text for inadvertent use of material from other sources.

We are also incredibly grateful to our British copyeditor, Patricia Bateson, for improving this book way beyond our expectations.Finally, we thank our very capable and immensely helpful typesetter Revathy Kaliyamoorthy, SPi Global.

Introduction

THE CRANIAL NERVES AND THIS BOOK

The cranial nerves (CNs) are magical. These nerves play an essential role in the processes that allow you to experience the wonder of the world around you – that is, to experience smell, taste, sight, and hearing, to maintain your balance and also to feel the wind on your face, a kiss on your lips, and to express feelings using the muscles of your face without even being consciously aware that you are doing so. Similarly, speaking, singing (good or bad), and eating are all directly controlled by the CNs. In fact, one CN, the tenth nerve or vagus, is responsible for controlling digestion from your lips to almost the end of your digestive tract and this same nerve regulates heart rate, breathing, and speech. In contrast, the nerves of the rest of your body (spinal nerves) primarily control voluntary muscle movement and convey simple sensations, for example, touch, but do not have the finesse of the CNs. In other words, we think spinal nerves are rather mundane and cranial nerves are, well, as we said at the beginning, magical.

Despite being able to conduct unique sensations, cranial nerves are constructed similarly to spinal nerves. They are in essence cables composed of many individual wires (fibers). However, whereas all spinal nerves contain both afferent and efferent fibers, that is, fibers entering and leaving the central nervous system (CNS), this is not necessarily the case for a CN.