Elements of cranio-facial neurologic semeiology

Introduction.
A thorough neurologic examination of the cranial nerves is a procedure of the utmost semeiologic (diagnostic) value that, if correctly carried out, can highlight several hidden pathologic conditions of odontostomatologic, neurologic and otorhinolaryngologic significance.
We suggest keeping a medical record for a thorough assessment of the cranial nerves (sensory and motor components) potentially involved in a neuroalgologic problem.
Understanding cranial nerve semiology is not possible without a summary knowledge of some elementary concepts of functional anatomy hereafter briefly illustrated (biblio 25).
 

The cranial nerves

The cranial nerves are composed of 12 pairs of nerves that vary both in their morphology and their function, such variety depending on the fact that specialized sensory organs have been developed in the head.
 
1)meddean.luc.edu
2)tna-support.org

Pair I: olfactory nerve

Functional neuroanatomy: sensory nerve whose task is to carry the olfactive stimuli to the brain.
Semeiology: with eyes closed, the patient is invited to identify some familiar smells like, for example, tobacco, coffee or soap. Some non-irritating aromatic substances, such as pine, rose or cinnamon oil, can also be used. The test shoud be carried out on one nostril at a time, so that each nerve can be examined separately (side fig.).	Olfactory nerve examination
Examination form for the olfactory nerve (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair II: Optic nerve

Functional neuroanatomy: pure special sensory nerve that carries the visual stimuli. It cannot be regarded as a peripheral nerve, but it should be considered part of the central nervous system as much for its structure as for its embryonal origin.
Semeiology: there are two noninstrumental clinical tests that can be carried out in a routine examination: checking visual acuity with a Snellen Eye Chart and evaluating visual fields. The visual field of each eye stretches for about 60° from the side of the nose, for about 120° from the temporal side and for 130° vertically. The patient, who is invited to sit in front of the examiner, is asked to stare forward and to cover one eye. The examiner, standing 3 feet (90 cm) in front of the patient, raises his arms and alternately moves his/her forefingers (side fig.). The patient is asked to say when he/ she is able to detect, with every single eye, both the right and the left forefingers of the examiner. The physician keeps drawing his/ her forefingers closer to the mid-line until the patient is able to see them. Since sensitivity to red usually diminishes in the areas where there is a reduction of the visual field, the test can be completed by slowly moving a red object through the field, starting from the normal side towards the one where the deficit is suspected. The patient will have to point out when he cannot see the red object anymore or when he sees it faded.	Visual field test
Examination form for the optic nerve (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair III: Oculomotor nerve – Pair IV: trochlear nerve – Pair VI: abducens nerve

Pair III: oculomotor nerve   Functional neuroanatomy: It is a pure motor nerve. It innervates the extrinsic eye muscles for the movement of the eyeball and the upper lid (levator palpebrae superioris, superior, medial and inferior rectus and inferior oblique). It also innervates the intrinsic smooth muscles for accomodation and focus reactions. Pair IV: trochlear nerve  Functional neuroanatomy: motor nerve intended for innervation of the superior oblique muscle. Its excitement determines outward and downward eyeball rotation. Pair VI: abducens nerve  Functional neuroanatomy: It is solely a somatomotor nerve that together with cranial nerves III and IV is part of the oculomotor group. It is intended for the innervation of the lateral rectus muscle. It owes its name to the fact that it allows the eyeball to move laterally.
Semiology of CN III – IV – VI: a lesion of the oculomotor nerves will result in a paresis of the oculomotor muscles, producing the symptom of diplopia. The semiologic procedures must allow the physician to understand which one is the paretic muscle in order to identify the related nerve. Diagnosis of the paretic muscle: the lateral rectus muscle, innervated by cranial nerve VI, rotates the eye horizontally outward; it acts in synergy with the medial rectus muscle of the contralateral eye in the horizontal gaze. The pure action of the medial rectus muscle, innervated by cranial nerve III, is to rotate the eye horizontally inward. Likewise, the superior rectus muscle that is innervated by nerve III and rotates the abducted eye upward, forms a couple of agonistic muscles together with the inferior oblique, also innervated by nerve III and whose task is to rotate the adducted eye upward. The two muscles act together to allow to look up. Eventually, the last couple of agonistic muscles, whose function is to allow to look down, is made up of the inferior rectus muscle, which is innervated by cranial nerve III and rotates the abducted eye downward, and the superior oblique muscle that is innervated by nerve IV and rotates the adducted eye downward. In case of extraocular palsy, the following phenomena occurs:  1) because of the prevalence of the antagonistic muscle, the sick eye deviates in the opposite direction to the action field of the paretic muscle (medial rectus palsy: outward eye rotation = divergent strabismus; lateral rectus palsy: inward eye rotation = convergent strabismus). Such phenomenon is easily observed by asking the patient to look straight forward; 2) diplopia; 3) the eye cannot carry out the pure movement for which the muscle affected by paresis should be intended. Any possible paresis of the extraocular muscles will be highlighted by a test of the oculomotor group. We must start by observing the relationship between eyelid and cornea, both from a static and a dynamic point of view. It is necessary to observe for ptosis and verify whether the eyelids follow the vertical and lateral movements of the eyeballs. In order to test parallelism of the visual axes in the forward gaze and in the horizontal and vertical conjugate gaze, the patient is asked to track the finger that the examiner moves on a horizontal and vertical level, far enough to avoid eye convergence (Side fig.). Convergence is tested by having the patient stare at his own forefinger that he/she will have to keep at a distance of about 2 feet (60 cm) from his nose. The examiner will then move the passive patient’s hand on the mid-line toward the bridge of the patient’s nose. In a normal situation, eyes will converge and pupils will constrict.	Test of the parallelism of the visual axes and of rotation defects in the vertical gaze upward
Examination form for the oculomotor, trochlear and abducens nerves (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair V: Trigeminal nerve

Functional neuroanatomy: It is composed of a very large somatosensory component and a small somatomotor portion. The trigeminal lacks completely the visceral component either sensory or motor. The trigeminal is a mixed nerve; the sensory component of the three branches affects respectively: 1) the ophthalmic branch: upper eyelid, lateral eyebrows, forehead, mucous membrane of nose and paranasal sinuses, cornea, eyeball, scalp; 2) the maxillary branch: upper lip, side of nose, lower eyelid, cheeks, teeth and maxillary gum, mucous membrane of hard and soft palates and tonsils; 3) the mandibular branch: lower lip, mouth floor, tongue, teeth and mandibular gum, temporal region including TMJ and excluding mandibular angle. The motor component (belonging to the mandibular branch) innervates the masticatory muscles: temporal and masseter, outer and inner pterygoids, mylohyoid and digastric.
Sensory component analysis: sensory trigeminal is tested by touching with a proper needle both sides of the patient’s face simultaneously and simmetrically. The patient is invited to report if there is any difference among the stimuli he perceives (Side fig.). The patient should first observe the equipment used for the test. Besides this static test, a dynamic test is also necessary; moreover it would be proper to verify sensitivity to thermal stimuli (cold metal / hot water). The patient can just present a sensitivity deficit (esthesia) of the face (hypoesthesia, anesthesia), or else he/ she can present some positive signs like: - pain - paresthesia: spontaneous, painless, sensory disorder (quality must be specified) - dysesthesia: provoked sensory disorder (quality must be specified, e.g. numbness caused by cotton rubbing) - allodynia: pain produced by painless stimuli (quality of pain and type of stimulus used must be specified) Anesthesia: sensitivity defects can roughly be subdivided into: - total anesthesia of the whole sensory component; it occurs when ganglion and nerve root are involved; - total anesthesia in the territory of distribution of one or two of the peripheral branches: it generally indicates a lesion that is peripheral to the ganglion; - pure tactile anesthesia: it shows that there is a lesion of the trigeminal main nucleus; - thermoanesthesia: it is the sign of a lesion of the trigeminal bulbospinal nucleus. Pain: Pain can roughly be subdivided into two big families: paroxysmal pain and continuous pain. The first ones is a stinging pain of short duration but severe intensity; usually the patient is asked to try to compare the pain he feels with one of the following sensations: - an electric shock (striking pain) - a deep cut (stabbing pain) - a deep prick (sharp pain). Paroxysmal pain is usually the symptom of a dysfunction of the first sensory neuron (of the nerve. posterior root ganglion or spinal ganglion). Continuous pains is generally less severe than the paroxysmal one; it is often liken to hot or cold painful sensations (thermalgia). This pains, often not localized, can be exacerbated by slight local stimuli or, in most serious cases, even by sensory stimuli (light or intense noises) or emotional stimuli (hyperpathia). If paroxysmal or continuous pain is produced by external stimuli, it is called allodynia. In case of trigeminal essential neuralgia, for instance, an ordinary stimulus to a particular skin area called “trigger point” is able to trigger paroxysmal pains. During the exam of the sensory component, of course, the examiner must gather as much information as possible about quality, intensity and duration of the pain felt by the patient. In case of allodynia (that is, if pain is provoked), it is necessary to specify the nature of the stimulus able to produce, or exacerbate, pain. Paresthesia: it consists of abnormal sensations not provoked by external stimuli. They can qualify as: - thermal sensations; - numbness; - pinpricks; - ‘dead flesh’ sensation; - ‘tightening’ sensation; - ‘spiderweb’ sensation on the skin. If such sensations are triggered by external stimuli, they are called dysesthesias; in this case they can be regarded as objective sensitivity disorders. If the examiners observe a painless sensitivity disorder, he / she must must specify whether the sensation is episodic or continuous and define its quality and intensity. If it is a provoked disorder, the examiner must specify the nature of the stimulus determining the sensation.	Trigeminal sensory component test.
Corneal reflex: a further test that can be carried out in order to find a possible deficit of the trigeminal ophtalmic branch consists in eliciting a corneal reflex. The reflex arc is made up of a sensory path and a motor path. The sensory path is the trigeminal first branch, whereas the motor path is the facial nerve that innervates the orbicular eye muscle. Patient’s inability to perceive the corneal stimulus or his/her failure to blink are, respectively, the result of a damage of the sensory component or of the motor component of the reflex arc; in both cases the corneal reflex is subdued or even absent. When there is a trigeminal unilateral lesion, the corneal stimulus to the same side of the lesion does not produce any response of the two eyelids, whereas a stimulus to the cornea of the healthy side elicits a bilateral response. In cases of facial unilateral lesions, instead, no matter where the corneal stimulus is applied, there is never a contraction of the orbicular muscle of the eye that is on the same side of the lesion. Stimulation of the healthy side elicits only an ipsilateral response. Corneal sensitivity is in both eyes. Ulceration, keratitis and blindness can occur owing to corneal anesthesia. The corneal reflex is induced by touching the cornea with a fine wisp of cotton while the patient is asked to look away from the examiner (side fig.). Responses of the two eyes must be compared by both the examiner and the patient. Motor component analysis: a unilateral lesion of the trigeminal motor component determines hypotrophy of the ipsilateral masticatory muscles. This can be easily observed by asking the patient to clench arches, while the examiner palpates the masseter muscles simultaneously. During mouth opening movements, it is possible to observe a deviation of the mandible toward the side of the lesion, due to the prevailing action of the contralateral pterygoid muscles. The patient is not able to properly move the jaw laterally keeping his / her mouth open.	Corneal reflex assessment
Mandibular reflex or “tension” reflex of the masticatory muscles: the mandibular reflex consists of an afferent pathway and an efferent one, both located in the mandibular branch and leading to the trigeminal motor nucleus located in the pons. A brisk masseteric reflex is the sign of a bilateral pyramidal dysfunction above the pontine nucleus, whereas a benumbed closing reflex occurs in case of deficit. In order to carry out such test, the patient must keep a rest position (mouth close with teeth not touching). The examiner, who is at the back of the patient, places a finger on the patient’s chin and then strikes quickly his / her fingers with a reflex hammer (side fig.); in a physiological condition, this will elicit a weak contraction of the masseter, temporal and mandibular levator muscles.	Mandibular reflex assessment
Examination form for the trigeminal nerve (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair VII: Facial nerve

Functional neuroanatomy: the facial nerve is a pure motor nerve that supplies the facial muscles. Strictly connected with the facial nerve is the Wrisberg intermediate nerve, that conveys the sensation of taste from the anterior 2/3 of the tongue and carries the visceral motor component for the lacrimal, sublingual and submandibular glands. The afferent fibers that convey taste sensation from the anterior 2/3 of the tongue to the nervus intermedius belong, in the most peripheral tract, to the lingual nerve (trigeminal branch), then to the chorda tympani (lingual-facial anastomosis). The nervus intermedius joins the facial nerve in the fallopian canal.
Motor component analysis: Assessing the motor component of cranial nerve VII implies observing facial espressions carefully, already from anamnesis, looking for any changes in the symmetry or intensity of movements, tics, tremors, grimaces. The patient is then asked to do the following movements: - protrude both lips as if “sulking”, in order to assess the efficiency of the mouth orbicular muscle (Side fig). - look up. This movement causes the patient to frown; trying to smooth such wrinkles with the fingers, the examiner can appreciate the efficiency of the frontal muscles (Side fig.) - draw the angles of the mouth downwards, to assess the efficiency of the platysma muscle (Side fig.); - close eyes tight. The examiner will attempt to open eyelids, assessing the ability of the eye orbicular muscles to resist to such movement (Side fig.);  - smile showing teeth so as to allow assessment of the efficiency of the upper lip levator muscles (Side fig.);  - hold air in the mouth puffing out cheeks. The examiner will compress the patient’s cheeks to force air ejection (Side fig.). It is useful to remember two typical medical histories that can help recognizing involvement of nerve VII. Peripheral facial paralysis: the peripheral facial paralysis involves muscles of both the upper and lower face and is, therefore, quite serious; it affects the facial nucleus located on the pons level. Observing the face at rest, one notes an asymmetry between the hemifaces: on the injured side, due to frontal muscle palsy, there will be a drooping of the eyebrow and a smoothing of the forehead wrinkles, whereas, due to eye orbicular palsy, there will be lagophthalmos. Because of lagophthalmos, a keratitis may be established, with danger of corneal ulceration. Involvement of the orbicularis oris and the levator labii superioris determines nasolabial fold flattening and drooping of the corner of the mouth respectively, resulting, as a consequence, in the difficulty to pronounce labial consonants. The mouth looks bent, because of the prevalence of the platysma muscle contralateral to the injured side. The patient’s inability to frown or close the eyes looks clear just by asking him / her to do some movements. As the eyelids keep open, it is possible to observe Bell’s phenomenon, that is, the rotation upward of the globe of the side of the paralysis. Moreover, the patient is not able to show teeth symmetrically. Secretion of saliva and tears and taste sensation from the anterior 2/3 of the tongue may be damaged, if the nerve is injured before the separation of the surface greater petrosal and of the chorda tympani. Central facial paralysis: it is less serious than the one above, as it affects only the muscles of the lower face; the patient closes the eyes normally and does not present Bell’s phenomenon; the corner of the mouth is drooping and cannot be drawn when attempting to show the teeth. The central facial paralysis is due to a lesion of the contralateral motor cortex and of the pyramidal fasciculus that leaves from it to reach the face nucleus. This paralysis does not involve all the facial muscles as the facial nucleus is divided into two parts: the upper part, innervating the upper face muscles, receives a contingent of pyramidal fibers from both the ipsilateral and contralateral cerebral hemispheres, whereas the lower part, innervating the lower face muscles, receives fibers coming from the only contralateral cerebral hemisphere.	Orbicular m. of mouth Frontal m. Platysma m. Orbicular m. of eye Levator m. of upper lip (smile) Levator m. of upper lip (puff out cheeks)
Sensory component analysis: the sensation of taste from the anterior two-thirds of the tongue is conveyed by the facial nerve and, in a lesser part, by the lingual nerve, a branch of the mandibular division of the trigeminal. Taste from the posterior one-third of the tongue, instead, is carried by the glossopharyngeal nerve. The most important clinical component is the one leading to the facial nerve. Since the sense of taste and smell are strictly connected, a loss of the sense of smell will often seriously damage taste, too. According to De Jong, taste is tested using: - sweet (4% glucose solution) - sour (1% citric acid solution) - salty (2.5% sodium chloride solution) - bitter (0.75 % quinine chloride or anesthetic) Bitter is always used last. The test is carried out by dipping a cotton swab into the solution and touching one side of the protruding tongue (side fig.). The patient should always be able to identify taste before withdrawing the tongue in the oral cavity. This test is done on one side of the tongue at a time.	Taste examination
Examination form for the facial nerve (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair VII: Vestibulocochlear nerve

Functional neuroanatomy: from a functional point of view, the acoustic nerve consists of two clearly separate parts: the cochlear nerve and the vestibular nerve. The task of the first nerve is to transmit hearing sensations (audition) to the brain, whereas the second nerve, coming from the vestibule of inner ear, transmits information about movement and body position in the space, in order to keep muscle strength and tone.
Cochlear semiology: it is necessary to inspect the presence of tinnitus aurium or decreased hearing, both with anamnesis and semiologic tests. Unlike the vestibular examination, the exam of the auditory component is a routine one. The examiner stands at the back of the patient and whisper words. He asks if the patient can hear the ticking of the watch or the snapping of fingers (Side fig.). The Rinne test (side fig.) can also be done. This is performed by placing the vibrating tuning fork against the mastoid of the patient; when the examiner can no longer hear the sound, then he will hold the tuning fork in front of the patient’s ear. Normally, the patient should still be able to perceive some vibrations, but this will not happen in case of deafness originated from the middle ear or in case of deafness from an advanced nervous lesion.	Hearing capacity test Rinne test
Vestibular semiology: lesions of the vestibular system can determine the illusion of movement, that is, vertigo.
Cochlear nerve examination form (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair IX and X : Glossopharyngeal and Vagus nerves

Functional neuroanatomy: nerves IX and X are discussed together, because they are strictly related anatomically and functionally and their lesions present similar medical histories. Glossopharyngeal and vagus are mixed nerves as they have a visceral, somatic and motor component and a visceral, somatic and sensory component. Both nerves provide for the somatomotor component of the muscles of the pharynx and soft palate; whereas the vagus nerve, on its own, carries motor fibers for the striated muscles of larynx. The somatosensory component conveys sensitivity from the posterior one-third of the tongue, the palate, the tonsils and the pharynx. As already mentioned above, the glossopharyngeal nerve also carries the special visceral sensory component, that is, the sensation of taste from the back one-third of the tongue. Eventually, the visceromotor component of the nerve IX controls the secretion of the parotid gland; instead, the very complex visceromotor part of the vagus supplies the heart, bronchi, gastroenteric tube and bile ducts.
Semeiology: the semeiologic process is directed toward the identification of a series of signs and symptoms.  Soft palate palsy can be identified by asking the patient if he / she has difficulty in swallowing; on the other hand, problems swallowing can occur in case of paralysis of the pharynx, too. The examiner must pay attention to the quality and sound of the patient’s voice. If it is nasal, a soft palate palsy can be suspected. Conversely, if it is hoarse and low, the paralysis will affect the larynx. Next, the examiner must have the patient say “Ah”; in case of unilateral lesion, the uvula tends to deviate toward the intact side, the soft palate remains down on the injured side and the pharynx posterior wall makes a curtain-like move. When there is a lesion of nerves IX and X, a sensory loss of the soft palate, the pharynx and the palatine tonsils occurs. Therefore, by touching one of these areas ipsilateral to the lesion with a long cotton swab (Side fig.), no reflex will be provoked, whereas, if the contralateral part is stimulated, there will be muscle contraction only on the intact side.	Gag reflex test
Examination form for the glossopharyngeal and vagus nerve (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair XI : Accessory nerve

Functional neuroanatomy: it is a pure motor nerve that is made up of the combination of two nerves: the vagus accessory nerve and the spinal accessory nerve. The latter is a somatomotor nerve that innervates the sternocleidomastoid and trapezius muscles.
Semeiology: the routine semeiologic process aims at verifying proper contraction of the muscles innervated by the accessory nerve. The examiner must resist the attempt of the patient to turn his / her head to the side and to shrug his / her shoulders (Side figures).	Sternocleidomastoid muscle Trapezius muscle
Accessory nerve examination form (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

Pair XII: Hypoglossal nerve

Functional neuroanatomy: it is almost solely a motor nerve intended for innervation of the intrinsic and extrinsic tongue muscles. It is therefore important for swallowing, phonation and breathing.
Semeiology: any possible changes of tongue motility must be looked for by asking the patient to quickly stick out the tongue. It is also necessary to test the strength of the muscles of the tongue. The examiner must ask the patient to push the tongue against the inner surface of the cheek; the examiner will resist such movement placing his / her hand on the outer surface of the same cheek (Side fig.). After asking the patient to “show the tongue”, the examiner will report any deviation (Side fig.).	Strength of muscles of the tongue Tongue exam
Hypoglossal nerve examination form (from: “Cartella Neuroalgologica Orofacciale” (“Orofacial neuroalgogic chart”) in ‘Riabilitazione Orale’ (‘Oral Rehabilitation’) by R. Ciancaglini, Masson Ed.,1999).

 
1)meddean.luc.edu
2)tna-support.org
 

You are here: Home-Headache-El. neur. semeiol.

Previous topic: Primary Headache Next topic: Craniofacial Neural.