Facial Palsy, Pain, and Numbness

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[edit] Facial Palsy, Pain, and Numbness

T. Jock Murray

William Pryse-Phillips

Of the many ills that may affect us, disorders involving the face are of particular importance. One can sometimes be dispassionate about pain, numbness, or weakness of a limb—a seemingly distant portion of our bodies—but the face has strong significance in our concept of “self.” It is a mirror to the world and a sounding board for ourselves. Disorders in the face have much greater personal significance than disorders occurring elsewhere.

[edit] FACIAL PALSY

The muscles of the upper part of the face obtain innervation from the motor cortex on each side. Thus the right frontalis and orbicularis oculi in the upper quadrant of the face are supplied by motor fibers running in the right VII nerve, whose nuclear cell bodies receive corticopontine fibers from both the left and the right cortical motor areas. The nerve supply to the muscles of the lower face on the right, however, comes from other cells in the VII nerve nucleus that only receive impulses from the opposite (left) cerebral cortex.

With a unilateral left cortical lesion, therefore, the frontalis and orbicularis oculi on the right will still function but the orbicularis oris and platysma will not. A unilateral upper motor neuron lesion produces only a lower quadrant facial weakness. If the nerve is damaged at the nucleus, in the cerebellopontine angle, within the facial canal, or immediately after leaving the canal, all of the muscles on that side of the face will be paralyzed. Therefore one can decide whether the cause of weakness is an upper or lower motor neuron lesion by seeing whether the frontalis and orbicularis oculi muscles are involved (lower motor neuron lesion) or not (upper motor neuron lesion). In the latter case, weakness of the hand and arm on the same side are also likely to be found.

[edit] Localization of Lesions

[edit] Supranuclear

[edit] Cortical Lesions.

Paresis of the lower half of the face can result from a contralateral cortical lesion in the motor area controlling facial movement. Usually, such a lesion will give rise to typical upper motor neuron weakness in the arm as well.

[edit] Corticospinal Tract Lesions.

Corticospinal tract lesions may occur anywhere between the cortex and the facial nuclei and although cerebral infarction is the most common cause, this type of paresis can result from a tumor or other compressive lesions, from multiple sclerosis, or from motor neuron disease.

[edit] Nuclear.

If the lesion involves the facial nucleus in the pons, other signs may be found, indicating involvement of nearby brainstem structures, including the medial lemniscus and the nuclei and fibers of the V, VI, or VIII (vestibular) nerves. Possible lesions within the pons include a tumor, multiple sclerosis, and infarction. Congenital absence of the facial nuclei or nerves is also possible (Mobius syndrome) and is characterized by bilateral facial paralysis from birth, palsy of the VI nerves, and sometimes deafness.

[edit] Infranuclear

[edit] In the Subarachnoid Space.

When the VII nerve leaves the brainstem it crosses the subarachnoid space at the cerebellopontine angle and enters the internal auditory meatus in close company with the VIII nerve and the nervus intermedius and lies adjacent to the middle cerebellar peduncle. Lesions here may affect all or any of these structures. Complaints of vertigo, tinnitus, or deafness, reduction in facial sensation, loss or diminution of the corneal reflex, VI nerve palsy, facial weakness, and/or cerebellar signs on the same side may be found.

[edit] In the Meatus.

A lesion of the nerve in the internal auditory meatus and its continuation, the facial canal, may be determined by the presence of associated damage to the following (Fig. 162-1):

• Greater superficial petrosal nerve (loss of tear formation in that eye)
  
• VIII nerve (tinnitus, deafness, vertigo)
  
• Nerve to the stapedius (hyperacusis in that ear)
  
• Chorda tympani (diminution of taste in the anterior two thirds of the tongue)
  

Figure 162-1 Schematic representation of the facial nerve and its branches.

The most common lesion here is a tumor, infection, or fracture of the petrous temporal bone after trauma.

[edit] At the Genu.

With the lesion at the genu, there will be associated damage to the VIII nerve fibers and also to the nerves to the stapedius and chorda tympani. Signs will be as suggested above for lesions in the meatus. The most common causes here are trauma, mastoiditis, the presence of a neoplasm (usually benign), and herpes zoster. Facial pain is common with this latter disorder (Ramsay Hunt syndrome), and a herpetic vesicular eruption on the fauces or in the external auditory meatus will be visible. Patients sometimes complain of deafness or vertigo related to involvement of the VIII nerve as well.

[edit] In the Facial Canal.

At the facial canal, only the chorda tympani will be involved with the facial nerve because everything else has branched off at a higher level. If the lesion is very low down in the canal, even the chorda tympani will be spared. The most common causes here include infections of the middle ear and mastoid area that involve the nerve because of local extension of the inflammation. Facial paralysis is probably often caused by herpesvirus infections and sometimes occurs in diphtheria, mumps, measles, chickenpox, Epstein-Barr virus infection, and tetanus. Sarcoidosis causes facial paralysis, often bilaterally, because of involvement of the nerve in the canal and not in the parotid gland (although this may also be affected). Guillain-Barré syndrome may produce bilateral facial weakness, and in these cases the lesion probably affects all or any part of the nerve.

Trauma (e.g., skull fracture) may damage the nerve either as it runs in the petrous bone or facial canal, or after the nerve has left the stylomastoid foramen. Direct stab, surgical, or gunshot wounds to the face, ear, or parotid gland may produce facial paralysis. Less common causes of facial paralysis include lead poisoning, thiamine deficiency, and polyarteritis nodosa, but the most common cause of all (3 in 4) is Bell's palsy.

During assessment of the patient with apparent facial palsy, the first question to ask is whether both the upper and the lower face are involved. If they are, then the cause is a lower motor neuron lesion. If the pathology involves the VII nerve nucleus, full examination will almost always show other signs of a brainstem lesion, but usually the site of damage is distal. Assessment of tear formation, hearing, and taste, as well as general neurologic examination and blood pressure recording, should allow accurate localization.

[edit] BELL'S PALSY

Bell's palsy is a common peripheral facial paralysis of unknown cause that affects perhaps 20 out of 100,000 persons per year. The onset is always sudden, never progressive, and the paralysis is almost always unilateral. Although most causes will recover spontaneously, the severity of the cosmetic effects, the complications during the course of the illness, and the dangers of incomplete recovery warrant some form of therapy. Many patients relate the onset to exposure to cold temperatures or wind. It has been suggested that it is more common in taxi drivers, and during World War II it was seen in Army personnel driving trucks with the windows open. Hereditary factors may play a role because one third of the patients have a positive family history of Bell's palsy. Because the disease sometimes occurs in epidemics, a viral etiology has been suggested; the herpes group of viruses has been implicated in some cases (herpes simplex, Epstein-Barr), suggesting that Bell's palsy is only part of a generalized viral inflammatory disease. Whatever the initiating cause, the nerve becomes further damaged by edema and ischemia because it is entrapped within the bony facial canal at a site usually below the geniculate ganglion.

[edit] Clinical Features.

At the onset, the acute, unilateral, lower motor neuron flaccid paralysis of the face is accompanied, or preceded in half of the cases, by pain behind the ear that reaches a peak within 2 or 3 hours. There may be associated fever, dizziness, tinnitus, decreased hearing, or a mildly stiff neck. All of the functions of the facial nerve will probably be affected, producing motor weakness of all facial muscles on that side and frequently loss of taste on the anterior two thirds of the tongue. There will be inability to wrinkle the forehead and close the eye related to weakness of the frontalis and orbicularis oculi. Eversion of the lower eyelid, loss of the nasolabial fold, and dropping of the corner of the mouth, with drooling of saliva, are common effects. In some cases, there is only partial palsy, which may make the diagnosis more difficult. Hyperacusis caused by paralysis of the stapedius muscle and reduced lacrimation and salivation indicate a lesion proximal to the end of the canal, sometimes even proximal to the geniculate ganglion, but these are less common in Bell's palsy.

Bell's palsy usually involves the VII nerve only; evidence of other neurologic deficits suggests some other disorder such as a stroke, tumor, infection, or multiple sclerosis. Occasionally the V and other cranial nerves are involved too, usually subclinically, and the disorder can be a manifestation of a more generalized but mild peripheral neuropathy. It is a good rule, however, to suspect a more sinister central nervous system (CNS) disorder if more than the VII lesion is evident.

[edit] Treatment

General supportive measures, such as mild analgesics and warm coverings for the face and ear, can be started immediately. The eyelid should be taped shut if blinking is not possible; artificial tears may be instilled twice daily to prevent drying of the conjunctiva. Medical therapy for Bell's palsy has in the past included a variety of treatments, from reassurance to vasodilators. Most are useless; only steroids started early reduce the chance of some residual paralysis. A suggested course of therapy for an adult consists of 60 mg of prednisone per day for 5 days, tapering to zero over a further 6 days. The patient should be evaluated weekly for the first 2 weeks and then again in 4 weeks.

If the symptoms worsen when the steroids are reduced, or if the postauricular pain returns, then the treatment course may be repeated once. Surgical decompression of the nerve is not indicated; the only surgical procedure that may be of benefit in these patients is late surgical autografting of the hypoglossal to the VII nerve if spontaneous recovery has not taken place.

[edit] Complications and Prognosis

Although at least 85% of patients with Bell's palsy will recover spontaneously in 2 months, the physical and social disability of those who do not warrants the use of immediate prednisone therapy in all cases seen before the third day. Patients more likely to be left with some paresis are those with complete paralysis of the nerve initially, those with pain other than that in the ear, those with diabetes or hypertension, and those over 60 years of age. In most cases, however, recovery starts within 2 weeks of onset, with the upper facial muscles recovering first. Complete restoration of function may not be achieved over a year. If there is no improvement by the eighteenth day, some permanent disfigurement may be expected.

The occurrence of crocodile tears (shedding of tears when salivating) from a month or so after the initial palsy is caused by aberrant regeneration of some fibers that grow out to the lacrimal gland instead of the salivary gland. If other regenerating fibers reach the wrong muscles, then abnormal movements may be seen, such as winking when the jaw is opened. If recovery is slow, contractures of the facial muscles can occur, and incomplete recovery may lead to the condition of clonic hemifacial spasm.

[edit] HEMIFACIAL SPASM

Hemifacial spasm is an abnormal movement disorder characterized by repetitive jerky contractions of the face on one side so that the eye closes and the mouth is drawn up toward the ear. The most common cause is the presence of a long loop of the anterior inferior cerebellar artery that impinges on the VII nerve in the posterior fossa, producing electrical “chatter.” This results in the involuntary contraction of the muscles of one side of the face, which is both uncomfortable and socially embarrassing. The condition may be treated by injection of botulinum toxin into the motor end points of the affected facial muscles, or more radically (but permanently) by exposure of the VIII nerve roots in the posterior fossa and dissection of the nerve from the impinging artery, very much in the same way as the V nerve is decompressed in some patients with trigeminal neuralgia.

[edit] FACIAL MYOKYMIA

Discontinuous but repetitive involuntary twitching or writhing of the periorbital muscles is common in everyone when tired or otherwise stressed, and it presumably occurs as a result of excessive activity in some generator within the brainstem. The movements are small, usually unilateral, and brief, with each set of contractions lasting only a few seconds. Rarely, brainstem lesions as seen in multiple sclerosis or tumors cause the same thing.

[edit] FACIAL PAIN

The pain-sensitive structures in the face and the anterior part of the head are mostly innervated by the V or IX cranial nerves, although referred pain from other areas may also be felt in the lower part of the face. The major causes of facial pain may be conveniently subdivided under four headings:

• Local structural changes in craniofacial tissues
  
• Irritation of nerves (the neuralgias)
  
• Referred pain
  
• Atypical facial pain
  

[edit] Clinical Approach

[edit] Quality of the Pain.

The pains in facial neuralgias are brief, knifelike, or lancinating in character, whereas the postherpetic neuralgias are classically described as burning. Pain described with an exuberance of phraseology, marked anguish, and great intensity may be associated with depression (“atypical facial pain”). Severe boring pain felt unilaterally behind the eye and radiating into the face occurs in cluster headache. Toothache, ocular disease, and sinusitis produce crescendos of pain or continuous aching, frequently with a throbbing component. Constant pains may also be felt in association with an infiltrating carcinoma at the base of the skull, usually arising in the nasopharynx, and also with brainstem vascular disease. Central irritation of the V nerve fibers by demyelination, for example, produces a pain indistinguishable from that of trigeminal neuralgia, but other neurologic signs should be present.

[edit] Site.

Trigeminal neuralgia is felt in the V nerve territory, usually in the second or third divisions and very seldom in the first. Glossopharyngeal neuralgia is felt in the back of the throat, lower jaw, gums, and neck on the involved side. Postherpetic neuralgia is usually in the first division of the nerve, whereas cluster headache is felt largely in or just posterior to the eye. The pain may also extend up into the frontotemporal area and occasionally more diffusely below the eye. Referred pain is usually felt in the lower part of the face, often bilaterally, and the same is true of atypical facial pain. Trigger zones on the cheek or in the mouth are characteristic of the classic neuralgias.

[edit] Timing.

The classic neuralgias are brief, repeated, knifelike stabs of pain described as “lancinating” and each lasting seconds, with no pain between the jabs; pain of much longer duration, perhaps even continuous, occurs in all of the other types of facial pain. With cluster headache, 40 to 60 minutes of acute pain often occurs at night, waking the patient from sleep, unlike the classic neuralgias, which hardly ever do so. Constant or long-lasting pains occur with infiltration or irritation of the V nerve by, for example, nasopharyngeal tumors, aneurysm of the posterior communicating artery, or chronic basal meningitis. Atypical facial pain tends to be constant.

Cluster headache occurs in bouts lasting a few weeks (hence the name) with months of freedom in between. There is also a periodicity with the classic neuralgias: repeated paroxysms of pain over the space of 1 or 2 weeks, often followed by a remission lasting up to months. Postherpetic pain usually goes away within 2 years but is almost constant while it is present and is accompanied by excessive pain reaction with simple touch. Spontaneous complete remission seldom occurs with the classic neuralgias.

Chewing and recent dental work may produce pain from the temporomandibular joint (TMJ) that is usually associated with over-closure of the bite, which is susceptible to orthodontic treatment. Chewing and the presence of hot or cold fluids in the mouth may produce glossopharyngeal neuralgia and accentuate the pain of toothache. Touching the skin may intensify the continuous background pain of postherpetic neuralgia and may trigger neuralgia.

[edit] Associated Symptoms.

Associated symptoms of facial pain are of great importance. Mucosal and periosteal lesions producing primary facial pain may be associated with symptoms of sinusitis (nasal discharge, sometimes bloody; postnasal discharge; a history of recent upper respiratory infection). Cluster headaches are often associated with a small pupil, conjunctival engorgement, and severe lacrimation and nasal congestion, with an outpouring of sweat on the same side of the face and of clear fluid from the nostril. The whole episode looks rather like an intense, localized parasympathetic discharge.

Central (brainstem) lesions producing “symptomatic trigeminal neuralgia” include vascular disease, neoplasm, syringobulbia, and multiple sclerosis. Other clinical signs of these conditions will probably be found and almost always will be associated with a loss of the corneal reflex and perhaps subjective or objective alteration in sensation in the territory of the affected nerve. Peripheral infiltrating or compressive lesions of the nerve are also associated with sensory change, which rules out the diagnosis of trigeminal neuralgia. Posterior communicating artery aneurysm, nasopharyngeal carcinoma, cerebellopontine angle tumor, and chronic basal meningitis may all be expected to produce at least some signs in other cranial nerve territories. Evidence of depressive illness should be sought in patients with atypical facial pain.

In the classic neuralgias (trigeminal and glossopharyngeal), in cluster headache, and in atypical facial pain there are no physical signs on examination of the cranial nerves (although unilateral ptosis and miosis are seen in some cases of cluster headache). With dental, sinus, or jaw lesions, at least local signs will be detected, whereas with irritation of the V or IX nerves, postherpetic neuralgia, and brainstem disease, neurologic signs are likely.

In the absence of physical signs, referred pain from the heart, jaw, or other structures; atypical or depressive pain; and classic neuralgias will be most likely. In the presence of any physical signs, however, full investigation is required, perhaps including radiographic studies of the nasopharynx and of the skull, including the internal auditory meatus; lumbar puncture; and in many cases, contrast radiography and computed tomography (CT) or magnetic resonance imaging (MRI).

[edit] Clinical Presentations

[edit] Local Facial Pain Syndromes

[edit] Facial Pain Caused by Local Pathology.

Any infection or tumor in the facial region or in the nose, pharynx, or ear may cause pain in the face. Common causes are toothache, nasopharyngeal tumors, trauma to the face, and vascular lesions, probably the most important of which is cranial arteritis, the inflammation of the scalp vessels being felt as a pain over the temporal region and posterior facial area, especially with chewing (so-called jaw claudication). The arteries are typically reddened, pulseless, and tender. These patients may go blind if the diagnosis is not made and the condition is not immediately treated with steroids.

[edit] Vascular Causes of Facial Pain.

Cluster headache is a very severe eye and head pain that originates in the ocular, frontal, or frontotemporal regions and often spreads over the side of the head and face. The pain is associated with watering of the eye and nasal discharge on the same side, conjunctival suffusion, and sometimes ptosis and miosis (Horner's syndrome), which often remains after the acute pain has gone. The condition is most commonly seen in males and its timing is peculiar, frequently waking the patient from sleep in the early hours of the morning. The pain recurs daily over the course of a few weeks before disappearing, only to return weeks or months later in another bout (or “cluster”). Whether this is a neuralgia or a form of migraine is not clear.

Migraine headaches are usually experienced in the side of the head but sometimes patients feel pain in the face as well. The differential diagnosis should not be difficult because migraines usually have a throbbing, aching quality, as opposed to the sharp, lancinating, or burning sensation characteristic of most types of neuralgia.

[edit] The Neuralgias

[edit] Major Neuralgias

[edit] Trigeminal neuralgia.

Trigeminal neuralgia is characterized by recurrent paroxysms of sharp, stabbing pain in one or more branches of the nerve on one side of the face, occurring in persons over age 50 who show no physical signs of V nerve dysfunction. The cause is uncertain; the disorder has often been referred to as “idiopathic trigeminal neuralgia” or “tic doloureux,” but examination of the trigeminal nerve has disclosed microneuromas and vascular compression in some cases. Other V nerve lesions that may result in pain include compression by an aneurysm or tumor, trauma, and multiple sclerosis, but these are often accompanied by physical signs and are regarded as symptomatic rather than idiopathic trigeminal neuralgia. Because the latter occurs only in the older age group (patients are almost always over the age of 50), one should suspect multiple sclerosis if it develops in a younger person. There is a reported association between trigeminal neuralgia and diabetes.

Trigeminal neuralgia is the commonest of the classic neuralgias. It is more common in women and, for some reason, on the right side of the face. The pain comes on in paroxysms; individual jabs of pain last only seconds, but a paroxysm may last for up to 15 or 20 minutes. These attacks of “lightning” pain may recur daily or several times a month. Patients are pain-free between the paroxysms. Over half of the cases will have remissions of 6 months or longer during the course of the disorder.

The term tic doloureux refers to the grimace that is often made with each jab of pain. Patients usually recognize trigger points, stimulation of which will precipitate the pain. These are commonly over the malar area, at the base of the nose, or along the gums. Because of aggravation of the pain with eating or chewing, many patients fast when a bout develops. The facial pain rarely occurs on both sides and never affects both sides at the same time, a useful point in differentiating it from other types of pain that may spread to the other side of the face; any pain that crosses the midline warrants a different diagnosis.

The differential diagnosis includes a number of disorders that cause sudden jabbing pain in the side of the face, but these can usually be eliminated by a careful history and examination. There may be confusion over pain from dental problems or from those arising from the nasal sinuses. Costen's syndrome, caused by a disorder of the TMJ, can cause jabbing pain that radiates into the face; however, this can be differentiated by tenderness in the TMJ and by the dull aching pain remaining in the background when the jabs have gone. In trigeminal neuralgia there is no pain at all between the paroxysms. Another confusing disorder is cluster headache, not because it is very similar but because this very severe, localized eye and head pain is often unrecognized, whereas everybody knows about trigeminal neuralgia and physicians tend to make the more familiar diagnosis. Herpes zoster will eventually show the typical skin vesicles, and one can establish the diagnosis of glossopharyngeal neuralgia by spraying the tonsillar region with local anesthetic, which should abolish the pain for a period. If one does find neurologic signs, such as loss of sensation over the face or weakness of the masseter or temporalis muscles, one must consider a compressive lesion of the trigeminal nerve. The muscle contraction headaches that refer from the occipital region are often felt as a pressing ache behind the eyes, which draws attention away from the cervical muscles where the problem originates. The distribution of atypical facial pain is often over the central part of the face, quite unlike that seen with trigeminal neuralgia.

Treatment of all of the classic neuralgias is started with oral carbamazepine, a drug that gives excellent results in most patients in a dosage slowly increasing from 100 mg twice a day to a maximum of 1 gm daily.^[1] In most patients the result is so dramatic within hours that it almost serves as a diagnostic test. However, about 20% of the elderly have side effects such as ataxia, drowsiness, and confusion and cannot tolerate the drug. Marrow depression has also been recorded, although rarely. Before carbamazepine was available, about half of the patients responded to oral diphenylhydantoin. If the patient does not respond to these agents, then baclofen or clonazepam are often helpful in controlling the pain. Recent publications have suggested some newer agents may also be beneficial, including misoprostol, gabapentin, and lamotrigine.

The pain may also be relieved by radiofrequency heating, glycerol injection, or ultrasonic lesions of the trigeminal rootlets in the posterior fossa. These techniques are about 90% effective, although they may have to be repeated. A few patients still complain of pain in a totally anesthetic area even after nerve block or surgical section (anesthesia dolorosa). Trigeminal root section was once performed, but now more selective lesions can be placed and such an approach can be considered only in patients who do not respond to drugs.

Based on the observation that many patients have V nerve irritation from the pulsation of an artery abutting the nerve, a very successful surgical treatment has been to separate the two using a small sponge during open operation. The drawback is that this involves a major operation. Although it provides excellent relief with less sensory loss than the radiofrequency or injection techniques, most patients prefer to try the latter first.

[edit] Glossopharyngeal neuralgia.

Glossopharyngeal neuralgia is characterized by paroxysmal bursts of sharp, stabbing pain localized to the region of the ear, throat, tongue, and jaw. It is much less common than trigeminal neuralgia and may be bilateral. The trigger zones are usually in the tonsillar area, tongue, or external auditory meatus so the patient may precipitate the pain by swallowing, talking, yawning, or placing a finger in his ear. There is no neurologic deficit on examination.

This is the only neuralgia that is a significant hazard to the life of the patient. Because the glossopharyngeal nerve innervates the carotid sinus, syncope, convulsions, or even cardiac arrest can occur as a result of the paroxysmal discharge. Atropine prevents bradycardia and hypotension but does not affect the pain. Dehydration and wasting are also significant problems in the patient who is unwilling to swallow because he or she knows that it may lead to agony.

Spraying local anesthetic onto the tonsillar region and the posterior pharynx is a useful way of differentiating this disorder from trigeminal neuralgia. Glossopharyngeal neuralgia occasionally results from tumors, aneurysms, or systemic inflammatory disease affecting the nerve. The drug treatment is the same as that for trigeminal neuralgia; if it fails, intracranial section of the nerve proximal to the ganglion is required.

[edit] Minor Neuralgias

[edit] Occipital neuralgia.

There is some confusion between occipital neuralgia and muscle contraction headache caused by tension or cervical spondylosis as both can produce long-lasting pain over the back of the neck and occiput with radiation bifrontally. In the more usual presentations of occipital neuralgia, however, sharp lancinating pains occur in the occipital region only, and tapping over the nerve (exactly half way between the mastoid process and the cervical spinous processes) causes a paroxysm of pain. Relief can be obtained by injecting the nerve with procaine and hydrocortisone; if this is only effective for a short time, than an alcohol block can be done, or the nerve can be sectioned.

[edit] Geniculate neuralgia.

Geniculate neuralgia, a neuralgia of the sensory portion of the VII nerve, results in lancinating pain around the ear, sometimes radiating to the external ear, the mastoid region, the soft palate, or the neck. The explanation for these areas of radiation is probably based on central connections between the V, VI, and IX nerves in the spinal nucleus and tract. The cause is seldom determined; the pain usually responds to carbamazepine.

[edit] Vagal neuralgia.

Vagal neuralgia may occur in the territory of the superior laryngeal nerve, causing unilateral neck pain aggravated by movements of the neck and by swallowing or speaking. The paroxysmal pain radiates from the side of the larynx up behind the ear to the gums, or even down over the shoulder and breast. Most patients are female and middle-aged or older. Many have a trigger point near the pyriform fossa. Massage of the neck may relieve the neuralgia temporarily, but carbamazepine is of more lasting value.

[edit] Postherpetic neuralgia.

Herpes zoster may cause two painful facial syndromes. The first is the Ramsay Hunt syndrome, characterized by pain in or behind the ear associated with herpetic vesicles in the external auditory meatus or throat. There may be weakness or paralysis of the masseter or facial muscles and decreased salivation on that side. Sometimes vesicles can also be seen over the eardrum, tongue, uvula, or external ear, or in the auditory canal.

The second syndrome is herpes zoster ophthalmicus with supraorbital neuralgia. This results in a severe, burning, aching, or stabbing pain around and above the eye; often it becomes a long-lasting pain syndrome. One often sees cutaneous scarring, redness, or edema around the eye and there is often hyperesthesia in that area. Corneal ulceration with infection can result in blindness.

Only 2% of patients with ophthalmic herpes get this type of neuralgia, but the incidence increases with age. Treatment is unsatisfactory, but the pain spontaneously improves after 2 years. Acyclovir has been found effective for treatment of the acute-stage pain; it hastens healing but has no effect on the incidence of postherpetic neuralgia. Famciclovir may also be beneficial. Some patients respond to massage of the area, to the use of a vibrator, or to spraying ethyl chloride locally, particularly if done frequently to start with and then daily, protecting the eye while spraying. Tricyclic drugs such as amitriptyline are the most helpful agents of all. Nortriptyline has the same analgesic action as amitriptyline but with less sedative effect. Avulsion of the supraorbital nerve or undercutting of the skin of the area may give relief if all else fails.

[edit] Referred Facial Pain.

Pain felt in the face may originate from the eye, ear, nose, throat, teeth, sinuses, TMJs, heart, or muscles of the head and neck. Patients often feel that any pain in the face originates in their teeth or sinuses. If it is around their eyes, they will initially have their eyes tested, and it is all too common for patients presenting with specific facial pain syndromes to have bought an expensive pair of glasses, had their sinuses drained and a few teeth removed, and invested in a new set of dentures. The cosmetic results are excellent but the analgesic results poor.

One common form of referred facial pain is that resulting from TMJ disorders. Pain from the joint caused by excessive biting, malocclusion, or arthritis is referred to the frontal and parietal areas of the skull or to the face. The patient may relate the pain to the ear and often experiences sharp pains radiating toward the jaw and tongue. The mechanism in most cases is that of chronic jaw clenching caused by tension and anxiety, and often a self-perpetuating spasm of the muscles of mastication occurs. Many of these patients have bruxism (nocturnal tooth-grinding), suggesting an underlying chronic tension state.

On examination, there is tenderness anterior to the ear over the TMJ, and one may feel crepitus on mouth opening. Jaw opening is often limited and closure is asymmetric. The discomfort can be relieved by putting a tongue depressor between the back teeth and asking the patient to bite gently on it, which removes pressure from the joint. The existence of this syndrome has been questioned; it has been suggested that it represents a watered-down version of atypical facial pain (see below), and it often responds to tricyclic drugs.

The eyes are not a common source of pain in the face despite common opinion. An exception is probably glaucoma, which can cause severe pain around the eye. Sinusitis as a cause of facial pain is attested to by television commercials, but it is rare. Otitis is another cause, particularly in the young. Angina pectoris is an unusual cause of facial pain. Cardiac pain is usually referred from the chest to the jaw region but we have seen some patients with angina complaining of pain in the anterior face or posteriorly as far as the ear.

[edit] Atypical Facial Pain.

Atypical facial pain syndrome is characterized by a constant aching, throbbing, or burning in the facial region. It may be mild or severe and is often experienced bilaterally. The pain may spread over the scalp, neck, and even to the shoulder or arm. It is often worse at night. There are usually no trigger zones, and examination shows no sensory loss nor any other neurologic abnormalities.

The syndrome is usually seen in middle-aged women and is aggravated or precipitated by illness, surgical procedures, social problems, or depression of mood. By the time such patients reach the neurologist, they are usually truly depressed and it is important to recognize this emotional component of the disease. Psychiatric evaluation and social assessment are both important.

Treatment consists of tricyclic drugs and supportive psychotherapy. Carbamazepine is not of value, and surgery is unhelpful.

[edit] FACIAL NUMBNESS

Any complaint of continuous numbness of the face should raise concern. Although patients who are depressed may have this symptom and it may occur in migraine, most cases of persisting facial numbness are due to an underlying structural disease process, usually situated in the brainstem or in the V nerve itself and seldom cortical. The major differentiation between brainstem and V nerve lesions is difficult, but if all three modalities (pain, temperature, and touch) are involved, this suggests a nerve lesion, whereas if there is dissociation of sensation a brainstem lesion may be suspected. If all three divisions of the nerve are involved, again the lesion is likely to be either in the cranial cavity as the nerve leaves the brainstem and runs toward the gasserian ganglion or in the ganglion itself. A lesion that is more distal will affect only one of its three divisions. Such a lesion is usually at the cerebellopontine angle but may be a primary or secondary tumor at the base of the skull or, rarely, a pontine glioma. In the case of basal skull tumors, the mandibular division may also be involved, causing weakness of the masseter, temporalis, and pterygoids on that side. Complaints of numbness of the chin mandate a search for malignancy.

Cerebellopontine angle tumors usually cause complaints of sensorineural hearing loss and tinnitus. Headache, vertigo, balance and gait disturbance, facial numbness, pain, and weakness are less common symptoms. Examination reveals involvement of the auditory or cochlear branches of the VIII nerve and a decreased corneal reflex. Other evidence of V or VII damage occurs in about half of the cases seen, and cerebellar signs occur in over half. Evidence of raised intracranial pressure, corticospinal tract involvement, and VI cranial nerve involvement is less commonly found. It is interesting that facial pain is an unusual finding with compression of the V nerve by a tumor or aneurysm.

In perhaps a fifth of the patients no cause is ever found. Such patients are described as having trigeminal sensory neuropathy of benign type because it may clear spontaneously. Pain is sometimes felt by these patients but it is seldom, if ever, an initial symptom. The corneal reflex is frequently retained and there is no motor weakness.

About 10% of patients with facial numbness have multiple sclerosis, diagnosed on the basis of the later appearance of signs of involvement of other areas of the nervous system. Other conditions, accounting for some 20% of cases, include viral encephalitis of the brainstem, presenting as an acute illness with involvement of the V and often also of the VI and VII nerves and signs of meningeal irritation; dental and facial trauma; chronic pansinusitis; and, rarely, such conditions as basal meningitis, syringobulbia, peripheral neuropathy, collagen-vascular disease, and the rare neuroma of the gasserian ganglion.

Therefore a patient who is seen with clinical evidence of V nerve sensory involvement must be examined carefully to see whether he or she has dissociated sensory loss, and whether one, two, or three divisions of the nerve are involved (with or without additional motor involvement). The corneal reflex must be tested with great care.

Investigation should include radiographs of the skull base, nasopharynx, and internal auditory meatus, and CT or MRI scans of the posterior fossa. Serologic tests for syphilis and lumbar puncture may be necessary because demonstration of a raised level of protein, IgG, or cells in the cerebrospinal fluid will assist diagnosis. An electromyographic (EMG) study of brainstem reflexes may confirm involvement of the ophthalmic division of the V nerve and may also indicate damage to the VII nerve. Brainstem evoked potentials will be of value in cerebellopontine angle tumors, and if there is any doubt about the diagnosis an ear, nose, and throat specialist should be asked to examine the posterior nasal space. Only if all of these investigations are negative can an exclusion diagnosis of benign trigeminal neuropathy be made and the patient observed for recovery over the course of the ensuing months or years.

[edit] REFERENCES

[edit] ADDITIONAL READINGS

• GH Fromm, BJ Sessle: Trigeminal neuralgia London: Butterworth-Heinemann; 1990:
• FS Mamdani: Pharmacologic management of herpes zoster and postherpetic neuralgia. Can Fam Phys 1994; 40:321 - 332.
• SL Spruance: Bell's palsy and herpes simplex virus. Ann Int Med 1994; 120:1045 - 1046.
• JM Taha, JM Tew: Treatment of trigeminal neuralgia by percutaneous radiofrequency rhizotomy. Neurosurg Clin North Am 1997; 8:31 - 39.
• CPN Watson: Nortriptyline versus amitriptyline in postherpetic neuralgia: a randomized trial. Neurology 1998; 51:1166 - 1171.