In examining patients with oral sensory or motor complaints, it is important to know if there is any objective evidence of abnormality of cranial nerve function that might relate to the patient’s oral symptoms. A definitive answer to this question usually comes from specific testing of cranial nerve function as part of a general physical examination carried out by either the patient’s physician, an internist, or a neurologist. When the results of a neurologist’s examination are not readily available, a cranial nerve examination carried out by the dentist may help direct diagnostic efforts in the interim. The following schema (summarized in Table 2-7) is provided with such circumstances in mind and not as a substitute for a thorough neurologic examination carried out by a skilled specialist. On the other hand, dentists and oral surgeons in hospitals are often responsible for the admitting history and physical examination of their patients. In view of the focus of dentistry, it is logical that the physical examination carried out by a dentist should be complete as far as the head and neck are concerned and should include an assessment of cranial nerve function. The dentist’s professional training and experience give him or her a specialized knowledge of the range of normal oral function, providing a level of accuracy usually not available to one less experienced in the examination of the mouth. For these reasons, instruction and experience in the evaluation of cranial nerve function, particularly as it relates to the oral cavity (eg, cranial nerves V, VII, IX, and XII), are fully justified as part of a dentist’s education.
The routine cranial nerve examination is carried out systematically according to the sequence of nerves (from I to XII). Each examiner will develop a personal routine, but it should always be standardized so that the results of repeated examinations will be comparable. In addition to the standard evaluation described here, there are a number of other techniques of special interest in particular clinical situations.
Cranial Nerve I (Olfactory Nerve). Olfactory nerve function is traditionally tested by closing one of the patient’s nostrils with a finger and asking if the patient can smell a strongly scented volatile substance such as coffee or lemon extract. The test is then repeated for the other nostril. The patient should sniff strongly to draw the volatile molecules well into the nose. This procedure tests for olfactory nerve function only when the nasal airway is patent to the olfactory receptors and when the substance being tested does not produce a response solely on the basis of chemical irritation of nonspecific somatic sensory receptors in the nasal mucosa. Such responses are due to stimulation of branches of the trigeminal nerve. For this reason, substances such as ammonia, perfumes (because of alcoholic content), and onions, although strongly scented, cannot be used to test for olfactory function. A compact “scratch-and-sniff ” test (suitable for clinical use) that uses 50 different microencapsulated olfactory stimulants (the University of Pennsylvania Smell Identification Test [UP-SIT], Sensonics, Inc., Haddon Heights, N.J.) has been developed by the University of Pennsylvania Clinical SmellCRANIAL NERVE FUNCTION
In examining patients with oral sensory or motor complaints, it is important to know if there is any objective evidence of abnormality of cranial nerve function that might relate to the patient’s oral symptoms. A definitive answer to this question usually comes from specific testing of cranial nerve function as part of a general physical examination carried out by either the patient’s physician, an internist, or a neurologist. When the results of a neurologist’s examination are not readily available, a cranial nerve examination carried out by the dentist may help direct diagnostic efforts in the interim. The following schema (summarized in Table 2-7) is provided with such circumstances in mind and not as a substitute for a thorough neurologic examination carried out by a skilled specialist. On the other hand, dentists and oral surgeons in hospitals are often responsible for the admitting history and physical examination of their patients. In view of the focus of dentistry, it is logical that the physical examination carried out by a dentist should be complete as far as the head and neck are concerned and should include an assessment of cranial nerve function. The dentist’s professional training and experience give him or her a specialized knowledge of the range of normal oral function, providing a level of accuracy usually not available to one less experienced in the examination of the mouth. For these reasons, instruction and experience in the evaluation of cranial nerve function, particularly as it relates to the oral cavity (eg, cranial nerves V, VII, IX, and XII), are fully justified as part of a dentist’s education.
The routine cranial nerve examination is carried out systematically according to the sequence of nerves (from I to XII). Each examiner will develop a personal routine, but it should always be standardized so that the results of repeated examinations will be comparable. In addition to the standard evaluation described here, there are a number of other techniques of special interest in particular clinical situations.
Cranial Nerve I (Olfactory Nerve). Olfactory nerve function is traditionally tested by closing one of the patient’s nostrils with a finger and asking if the patient can smell a strongly scented volatile substance such as coffee or lemon extract. The test is then repeated for the other nostril. The patient should sniff strongly to draw the volatile molecules well into the nose. This procedure tests for olfactory nerve function only when the nasal airway is patent to the olfactory receptors and when the substance being tested does not produce a response solely on the basis of chemical irritation of nonspecific somatic sensory receptors in the nasal mucosa. Such responses are due to stimulation of branches of the trigeminal nerve. For this reason, substances such as ammonia, perfumes (because of alcoholic content), and onions, although strongly scented, cannot be used to test for olfactory function. A compact “scratch-and-sniff ” test (suitable for clinical use) that uses 50 different microencapsulated olfactory stimulants (the University of Pennsylvania Smell Identification Test [UP-SIT], Sensonics, Inc., Haddon Heights, N.J.) has been developed by the University of Pennsylvania Clinical Smell
The routine cranial nerve examination is carried out systematically according to the sequence of nerves (from I to XII). Each examiner will develop a personal routine, but it should always be standardized so that the results of repeated examinations will be comparable. In addition to the standard evaluation described here, there are a number of other techniques of special interest in particular clinical situations.
Cranial Nerve I (Olfactory Nerve). Olfactory nerve function is traditionally tested by closing one of the patient’s nostrils with a finger and asking if the patient can smell a strongly scented volatile substance such as coffee or lemon extract. The test is then repeated for the other nostril. The patient should sniff strongly to draw the volatile molecules well into the nose. This procedure tests for olfactory nerve function only when the nasal airway is patent to the olfactory receptors and when the substance being tested does not produce a response solely on the basis of chemical irritation of nonspecific somatic sensory receptors in the nasal mucosa. Such responses are due to stimulation of branches of the trigeminal nerve. For this reason, substances such as ammonia, perfumes (because of alcoholic content), and onions, although strongly scented, cannot be used to test for olfactory function. A compact “scratch-and-sniff ” test (suitable for clinical use) that uses 50 different microencapsulated olfactory stimulants (the University of Pennsylvania Smell Identification Test [UP-SIT], Sensonics, Inc., Haddon Heights, N.J.) has been developed by the University of Pennsylvania Clinical SmellCRANIAL NERVE FUNCTION
In examining patients with oral sensory or motor complaints, it is important to know if there is any objective evidence of abnormality of cranial nerve function that might relate to the patient’s oral symptoms. A definitive answer to this question usually comes from specific testing of cranial nerve function as part of a general physical examination carried out by either the patient’s physician, an internist, or a neurologist. When the results of a neurologist’s examination are not readily available, a cranial nerve examination carried out by the dentist may help direct diagnostic efforts in the interim. The following schema (summarized in Table 2-7) is provided with such circumstances in mind and not as a substitute for a thorough neurologic examination carried out by a skilled specialist. On the other hand, dentists and oral surgeons in hospitals are often responsible for the admitting history and physical examination of their patients. In view of the focus of dentistry, it is logical that the physical examination carried out by a dentist should be complete as far as the head and neck are concerned and should include an assessment of cranial nerve function. The dentist’s professional training and experience give him or her a specialized knowledge of the range of normal oral function, providing a level of accuracy usually not available to one less experienced in the examination of the mouth. For these reasons, instruction and experience in the evaluation of cranial nerve function, particularly as it relates to the oral cavity (eg, cranial nerves V, VII, IX, and XII), are fully justified as part of a dentist’s education.
The routine cranial nerve examination is carried out systematically according to the sequence of nerves (from I to XII). Each examiner will develop a personal routine, but it should always be standardized so that the results of repeated examinations will be comparable. In addition to the standard evaluation described here, there are a number of other techniques of special interest in particular clinical situations.
Cranial Nerve I (Olfactory Nerve). Olfactory nerve function is traditionally tested by closing one of the patient’s nostrils with a finger and asking if the patient can smell a strongly scented volatile substance such as coffee or lemon extract. The test is then repeated for the other nostril. The patient should sniff strongly to draw the volatile molecules well into the nose. This procedure tests for olfactory nerve function only when the nasal airway is patent to the olfactory receptors and when the substance being tested does not produce a response solely on the basis of chemical irritation of nonspecific somatic sensory receptors in the nasal mucosa. Such responses are due to stimulation of branches of the trigeminal nerve. For this reason, substances such as ammonia, perfumes (because of alcoholic content), and onions, although strongly scented, cannot be used to test for olfactory function. A compact “scratch-and-sniff ” test (suitable for clinical use) that uses 50 different microencapsulated olfactory stimulants (the University of Pennsylvania Smell Identification Test [UP-SIT], Sensonics, Inc., Haddon Heights, N.J.) has been developed by the University of Pennsylvania Clinical Smell
and Taste Research Center, for more accurate and comprehensive testing of olfactory function.
Cranial Nerve II (Optic Nerve). Optic nerve function is tested by the investigation of visual acuity and the visual fields. In addition, clinicians who are trained in the use of the ophthalmoscope can use this instrument to examine the ocular fundus directly for lesions. Visual acuity is tested with the familiar wall chart, but it can also be evaluated by asking the patient to read print of various sizes in a book or newspaper held at various distances from the patient’s eyes.
Gross defects in the field of vision can be detected by having the patient indicate how close to the midline a pencil held in the observer’s hand must be brought before it can be seen. For this test (known as the confrontation test), hold the pencil 2 to 3 feet to one side of the patient’s face while the patient covers the other eye. Move the pencil in turn along the main axes of the field of vision until the patient can see it.
Cranial Nerves III, IV, and VI (Ocular Nerves). The three ocular nerves are concerned with the pupillary reflex (III), accommodations (III), and eye movements (III, IV, and VI). These nerves are tested simultaneously by examining the size, outline, and reaction of each pupil to light and dark and to accommodation for near and far vision. Conjugate eye movements, individual eye movements, and convergent vision (all under the control of bilateral extraocular eye muscles) are tested by having the patient follow the path of a pencil held both at a distance and close up as it traverses right to left and up and down.
Cranial Nerve V (Trigeminal Nerve). The trigeminal nerve is tested for both motor and sensory function. The small motor branch of this nerve supplies the muscles of mastication, and the strength of these muscles is used as a measure of the intactness of their motor supply. The force of contraction and muscle bulk (motor loss leads to laxity and muscle atrophy) of the masseter and temporal muscles are noted by external palpation of these muscles bilaterally while the patient clenches. Lateral movement of the jaw against the examiner’s finger is one test of pterygoid function. Weakness of the temporalis, masseter, and pterygoid muscles may also manifest itself by deviation of the jaw when the patient opens the mouth. (Disorders of the temporomandibular joint may produce similar signs, however, with the instability of the jaw to passive displacement at the temporomandibular joint resulting in easy subluxation of the joint.)
Another useful indicator of the motor power of the masticatory muscles is their ability to carry out voluntary displacement of the jaw against the imposed resistance of the examiner’s hand, tested as follows: place the thumb on the lower molar table, with fingers externally about the body and ramus; the patient moves the jaw forward, sideways, and upward, with his or her head steadied by your other hand.
Abnormalities of the jaw jerk may indicate muscular weakness or an abnormality of the proprioceptive reflex arc controlling jaw movements. Press your index finger downward and posteriorly above the mental eminence, and lightly strike the finger with a percussion hammer or with one or two fingers of the other hand. In normal subjects, a single reflex response can usually be discerned by palpation. The principle is the same as that of the more familiar knee jerk test.
Sensory function of the trigeminal nerve should logically be tested for all three divisions (ophthalmic, maxillary, and mandibular), but testing is often focused on the corneal reflex to touch (ophthalmic division), with rather cursory testing of touch and pinprick sensation on the facial skin and often with no testing of the intraoral mucosa. The dentist’s interest in orofacial problems will often require more detailed evaluation of intraoral sensitivity and skin sensitivity for the lower half of the face; however, a complete evaluation of all sensory modalities subserved by branches of cranial nerve V—pain, touch, temperature, two-point discrimination, and taste (ie, gustatory fibers of cranial nerve VII traveling with the lingual branch of cranial nerve V)—is rarely possible and is usually attempted only as part of a thorough research investigation.
The following instruments, many of which can be adapted for the testing of trigeminal sensory function, are available as aids in sensory evaluation:
1. Graded Frey’s hairs (a series of fine hairs or nylon fibers calibrated according to the force required to bend the filament when it is placed against skin, mucosa, or tooth)
2. Two-point esthesiometers, often designed with a pistol grip to facilitate the placement of the points of the instrument on the oral mucosa (similar testing can be carried out with a simple caliper)
3. Calibrated thermal devices for the application of hot and cold
4. Discs of various grades of sandpaper for the evaluation of textural differences
5. Stereognostic forms for the evaluation of oral stereotactic ability
6. Two-dimensional maps of the oral mucosa on which sensory response about a lesion or area of paresthesia can be accurately recorded.
7. Taste testing Abnormalities in any of these various modalities of trigem-
inal sensory function may be taken as evidence of an abnormality of the affected branch of cranial nerve V and provide additional evidence of the diagnosis of neuropathy that may be suggested by the patient’s subjective report of paresthesia, numbness, or other unusual sensations.
Cranial Nerve VII (Facial Nerve). The facial nerve is tested for abnormalities of motor function involving the “mimetic” muscles of facial expression and also for gustatory disorders. A gustatory salivary reflex involves facial nerve gustatory stimuli and increased salivary function, and affections of the chorda tympani may be associated with failure of the salivary flow to increase following the application of lemon juice or citric acid to the affected side of the mouth.
Motor function of cranial nerve VII is tested by observing facial muscle function in response to requests to wrinkle the forehead, frown, close the eyelids tightly, wink, open the mouth, retract the mouth, blow out the cheeks, pucker the lips, “screw up” the nose, whistle, and speak. Close observation and comparison of the right and left sides may be necessary to detect minor degrees of facial paralysis in some patients; in other patients, the defect will be obvious and disfiguring.
Cranial Nerve VIII (Acoustic Nerve). Acoustic nerve function includes both cochlear (hearing) and vestibular (balance) components, which are physiologically distinct and which are tested separately. Hearing may be tested at three levels of sophistication in the following ways:
1. By observing the patient’s ability to hear (a) normal speech and a whisper or (b) the ticking of a watch held at varying distances from each ear
2. By holding one or more tuning forks near each ear, on the mastoid process, and on the forehead (allowing separation of nerve and conduction deafness as well as identification of unilateral defects)
3. By audiometric testing (the most precise method) Simple tests for vestibular function include the past-point-
ing test and assessment for the eye movements that are characteristic of nystagmus when the patient is asked to look to one side and then upward (nystagmus will cause a fast jerk to the direction indicated, followed by a slow return to the midline, with or without rotary movements of the eyeball). More elaborate studies of vestibular function involve tests for the occurrence of past-pointing, nystagmus, and vertigo and nausea when cold water or a blast of cold air is injected into the external auditory canal of the upright patient.
Cranial Nerve IX (Glossopharyngeal Nerve). The glossopharyngeal nerve provides taste fibers to the posterior aspect of the tongue, somatic sensory fibers to the same area of the tongue as well as to the pharynx and soft palate (tested along with sensory function of cranial nerve X, below), and motor fibers to the stylopharyngeus muscle, which plays only a minor role in palatal function. Thus, any accurate testing of cranial nerve IX motor function is impossible.
Cranial Nerve X (Vagus Nerve). The vagus nerve is the chief motor nerve of the pharynx and larynx; it also provides sensory fibers to the pharyngeal and faucial mucous membrane. Routine testing is carried out by observation of pharyngeal movements (eg, symmetric elevation of the soft palate and shortening of the uvula when the patient says “ah”) and the pharyngeal (gag) reflex (ie, contraction of the palate and faucial muscles in response to the examiner’s touching the mucosa of the posterior pharynx). The gag reflex may be temporarily eliminated with a topical analgesic spray so that the soft palate and pharynx can be palpated manually for masses and muscular tonus. Since the major clinical problem associated with cranial nerve X dysfunction is dysphagia, a more detailed evaluation of this nerve’s function can include the careful observation of swallowing. The laryngeal component of the vagus nerve is studied by inspection of laryngeal function with indirect laryngoscopy (using a headlamp and a dental mirror, with the patient’s tongue extended) and by various vocal tests of phonation. Pulse and respiratory rates are measures of the visceral component of the vagus nerve although a variety of other factors also affect these rates.
Cranial Nerve XI (Accessory Nerve). The spinal accessory nerve is tested through its motor supply to the trapezius and sternomastoid muscles. For the trapezius, ask the patient to shrug his or her shoulders against the resistance of your hands; for the sternomastoid, have the patient turn and flex the head against the same resistance.
Cranial Nerve XII (Hypoglossal Nerve). The hypoglossal nerve provides the motor supply to the tongue; hypoglossal paralysis causes deviation of the tongue when the patient extrudes it. Atrophy of the tongue’s musculature may be noted on oral examination, and its muscular tonus can be ascertained by the force with which the patient can push the tongue against either cheek or by evaluation of the tongue jerk. Dyskinesia (such as may occur in parkinsonism and amyotrophic lateral sclerosis) is observed on the dorsal surface of the tongue, particularly when the tongue comes to the resting position after vigorous or forceful activity. Crenation of the margin of the tongue caused by forceful and persistent molding of the organ against irregular lingual surfaces of the dental arch is frequently seen in neurologically normal patients and is difficult to evaluate as a sign of lingual atrophy. More often than not, crenation is the result of muscle tension that may also be manifest in other parts of the body or that may accompany severe malocclusion. Occasionally, it may be due to true macroglossia.
Cranial Nerve II (Optic Nerve). Optic nerve function is tested by the investigation of visual acuity and the visual fields. In addition, clinicians who are trained in the use of the ophthalmoscope can use this instrument to examine the ocular fundus directly for lesions. Visual acuity is tested with the familiar wall chart, but it can also be evaluated by asking the patient to read print of various sizes in a book or newspaper held at various distances from the patient’s eyes.
Gross defects in the field of vision can be detected by having the patient indicate how close to the midline a pencil held in the observer’s hand must be brought before it can be seen. For this test (known as the confrontation test), hold the pencil 2 to 3 feet to one side of the patient’s face while the patient covers the other eye. Move the pencil in turn along the main axes of the field of vision until the patient can see it.
Cranial Nerves III, IV, and VI (Ocular Nerves). The three ocular nerves are concerned with the pupillary reflex (III), accommodations (III), and eye movements (III, IV, and VI). These nerves are tested simultaneously by examining the size, outline, and reaction of each pupil to light and dark and to accommodation for near and far vision. Conjugate eye movements, individual eye movements, and convergent vision (all under the control of bilateral extraocular eye muscles) are tested by having the patient follow the path of a pencil held both at a distance and close up as it traverses right to left and up and down.
Cranial Nerve V (Trigeminal Nerve). The trigeminal nerve is tested for both motor and sensory function. The small motor branch of this nerve supplies the muscles of mastication, and the strength of these muscles is used as a measure of the intactness of their motor supply. The force of contraction and muscle bulk (motor loss leads to laxity and muscle atrophy) of the masseter and temporal muscles are noted by external palpation of these muscles bilaterally while the patient clenches. Lateral movement of the jaw against the examiner’s finger is one test of pterygoid function. Weakness of the temporalis, masseter, and pterygoid muscles may also manifest itself by deviation of the jaw when the patient opens the mouth. (Disorders of the temporomandibular joint may produce similar signs, however, with the instability of the jaw to passive displacement at the temporomandibular joint resulting in easy subluxation of the joint.)
Another useful indicator of the motor power of the masticatory muscles is their ability to carry out voluntary displacement of the jaw against the imposed resistance of the examiner’s hand, tested as follows: place the thumb on the lower molar table, with fingers externally about the body and ramus; the patient moves the jaw forward, sideways, and upward, with his or her head steadied by your other hand.
Abnormalities of the jaw jerk may indicate muscular weakness or an abnormality of the proprioceptive reflex arc controlling jaw movements. Press your index finger downward and posteriorly above the mental eminence, and lightly strike the finger with a percussion hammer or with one or two fingers of the other hand. In normal subjects, a single reflex response can usually be discerned by palpation. The principle is the same as that of the more familiar knee jerk test.
Sensory function of the trigeminal nerve should logically be tested for all three divisions (ophthalmic, maxillary, and mandibular), but testing is often focused on the corneal reflex to touch (ophthalmic division), with rather cursory testing of touch and pinprick sensation on the facial skin and often with no testing of the intraoral mucosa. The dentist’s interest in orofacial problems will often require more detailed evaluation of intraoral sensitivity and skin sensitivity for the lower half of the face; however, a complete evaluation of all sensory modalities subserved by branches of cranial nerve V—pain, touch, temperature, two-point discrimination, and taste (ie, gustatory fibers of cranial nerve VII traveling with the lingual branch of cranial nerve V)—is rarely possible and is usually attempted only as part of a thorough research investigation.
The following instruments, many of which can be adapted for the testing of trigeminal sensory function, are available as aids in sensory evaluation:
1. Graded Frey’s hairs (a series of fine hairs or nylon fibers calibrated according to the force required to bend the filament when it is placed against skin, mucosa, or tooth)
2. Two-point esthesiometers, often designed with a pistol grip to facilitate the placement of the points of the instrument on the oral mucosa (similar testing can be carried out with a simple caliper)
3. Calibrated thermal devices for the application of hot and cold
4. Discs of various grades of sandpaper for the evaluation of textural differences
5. Stereognostic forms for the evaluation of oral stereotactic ability
6. Two-dimensional maps of the oral mucosa on which sensory response about a lesion or area of paresthesia can be accurately recorded.
7. Taste testing Abnormalities in any of these various modalities of trigem-
inal sensory function may be taken as evidence of an abnormality of the affected branch of cranial nerve V and provide additional evidence of the diagnosis of neuropathy that may be suggested by the patient’s subjective report of paresthesia, numbness, or other unusual sensations.
Cranial Nerve VII (Facial Nerve). The facial nerve is tested for abnormalities of motor function involving the “mimetic” muscles of facial expression and also for gustatory disorders. A gustatory salivary reflex involves facial nerve gustatory stimuli and increased salivary function, and affections of the chorda tympani may be associated with failure of the salivary flow to increase following the application of lemon juice or citric acid to the affected side of the mouth.
Motor function of cranial nerve VII is tested by observing facial muscle function in response to requests to wrinkle the forehead, frown, close the eyelids tightly, wink, open the mouth, retract the mouth, blow out the cheeks, pucker the lips, “screw up” the nose, whistle, and speak. Close observation and comparison of the right and left sides may be necessary to detect minor degrees of facial paralysis in some patients; in other patients, the defect will be obvious and disfiguring.
Cranial Nerve VIII (Acoustic Nerve). Acoustic nerve function includes both cochlear (hearing) and vestibular (balance) components, which are physiologically distinct and which are tested separately. Hearing may be tested at three levels of sophistication in the following ways:
1. By observing the patient’s ability to hear (a) normal speech and a whisper or (b) the ticking of a watch held at varying distances from each ear
2. By holding one or more tuning forks near each ear, on the mastoid process, and on the forehead (allowing separation of nerve and conduction deafness as well as identification of unilateral defects)
3. By audiometric testing (the most precise method) Simple tests for vestibular function include the past-point-
ing test and assessment for the eye movements that are characteristic of nystagmus when the patient is asked to look to one side and then upward (nystagmus will cause a fast jerk to the direction indicated, followed by a slow return to the midline, with or without rotary movements of the eyeball). More elaborate studies of vestibular function involve tests for the occurrence of past-pointing, nystagmus, and vertigo and nausea when cold water or a blast of cold air is injected into the external auditory canal of the upright patient.
Cranial Nerve IX (Glossopharyngeal Nerve). The glossopharyngeal nerve provides taste fibers to the posterior aspect of the tongue, somatic sensory fibers to the same area of the tongue as well as to the pharynx and soft palate (tested along with sensory function of cranial nerve X, below), and motor fibers to the stylopharyngeus muscle, which plays only a minor role in palatal function. Thus, any accurate testing of cranial nerve IX motor function is impossible.
Cranial Nerve X (Vagus Nerve). The vagus nerve is the chief motor nerve of the pharynx and larynx; it also provides sensory fibers to the pharyngeal and faucial mucous membrane. Routine testing is carried out by observation of pharyngeal movements (eg, symmetric elevation of the soft palate and shortening of the uvula when the patient says “ah”) and the pharyngeal (gag) reflex (ie, contraction of the palate and faucial muscles in response to the examiner’s touching the mucosa of the posterior pharynx). The gag reflex may be temporarily eliminated with a topical analgesic spray so that the soft palate and pharynx can be palpated manually for masses and muscular tonus. Since the major clinical problem associated with cranial nerve X dysfunction is dysphagia, a more detailed evaluation of this nerve’s function can include the careful observation of swallowing. The laryngeal component of the vagus nerve is studied by inspection of laryngeal function with indirect laryngoscopy (using a headlamp and a dental mirror, with the patient’s tongue extended) and by various vocal tests of phonation. Pulse and respiratory rates are measures of the visceral component of the vagus nerve although a variety of other factors also affect these rates.
Cranial Nerve XI (Accessory Nerve). The spinal accessory nerve is tested through its motor supply to the trapezius and sternomastoid muscles. For the trapezius, ask the patient to shrug his or her shoulders against the resistance of your hands; for the sternomastoid, have the patient turn and flex the head against the same resistance.
Cranial Nerve XII (Hypoglossal Nerve). The hypoglossal nerve provides the motor supply to the tongue; hypoglossal paralysis causes deviation of the tongue when the patient extrudes it. Atrophy of the tongue’s musculature may be noted on oral examination, and its muscular tonus can be ascertained by the force with which the patient can push the tongue against either cheek or by evaluation of the tongue jerk. Dyskinesia (such as may occur in parkinsonism and amyotrophic lateral sclerosis) is observed on the dorsal surface of the tongue, particularly when the tongue comes to the resting position after vigorous or forceful activity. Crenation of the margin of the tongue caused by forceful and persistent molding of the organ against irregular lingual surfaces of the dental arch is frequently seen in neurologically normal patients and is difficult to evaluate as a sign of lingual atrophy. More often than not, crenation is the result of muscle tension that may also be manifest in other parts of the body or that may accompany severe malocclusion. Occasionally, it may be due to true macroglossia.