TRIGEMINAL NEURALGIA AND OTHER FACIAL PAIN

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CHAPTER 64 TRIGEMINAL NEURALGIA AND OTHER FACIAL PAIN

Alan Stiles, James Evans

HISTORICAL CONSIDERATIONS

Trigeminal neuralgia has been identified in the medical literature as the classic neuropathic pain syndrome. The first known description was made in the first century A.D. by Aretaeus. Many physicians have penned descriptions of this affliction; the first to comprehensively describe it was John Locke in 1677. He described the condition of one such patient:

“…such violent and exquisite torment, that it forced her to such cries and shrieks as you would expect from one upon the rack, to which I believe hers was an equal torment, which extended itself all over the right side of her face and mouth. When the fit came there was, to My Lady’s own expression of it, as it were a flash of fire all of a sudden shot into all of those parts, and at every one of those twitches which made her shriek out, her mouth was constantly drawn to the right side towards the right ear by repeated convulsive motions, which were constantly accompanied by her cries…. These violent fits terminated on a sudden and then My Lady seemed to be perfectly well….” (John Locke and Kenneth Dewhurst)1,2

John Hunter (1728-1793), an English physiologist and surgeon, described trigeminal neuralgia in his A Practical Treatise on the Diseases of the Teeth in 1778 as follows:

“This pain is seated in some one part of the Jaws. As simple pain demonstrates nothing, a Tooth is often suspected, and is perhaps drawn out; but still the pain continues, with this difference however, that it now seems to be in the root of the next Tooth: it is then supposed either by the patient or the operator, that the wrong Tooth was extracted; wherefore, that in which the pain now seems to be, is drawn, but with as little benefit. I have known cases of this kind, where all the Teeth of the affected side of the Jaw, have been drawn out, and the pain has continued in the Jaw; in others, it has had a different effect, the sensation of pain has become more diffused, and has at last, attacked the corresponding side of the tongue. In the first case, I have known it recommended to cut down upon the Jaw, and even to perforate and cauterize it, but all without effect.

Hence it should appear, that the pain, in question, does not arise from any disease in the part, but entirely a nervous affection.”2a

William Osler (1849-1919) eloquently captured the clinical essence of trigeminal neuralgia in his own words:

“In advanced cases the paroxysms follow one another rapidly and without assignable cause, and in the intervals the patient may never be quite free from pain. They are inaugurated by almost any form of external stimulus, by a draught of air, by movement of the facial muscles or of the tongue in speaking, by touching the skin, particularly over those points from which the pain seems to take its origin, by the act of swallowing, especially when the pain involves the mucous membrane field of distribution of the nerve. It is not a self-limited disease. In some instances the neuralgia reaches such a frightful intensity that it renders the patient’s life insupportable. In former years suicide was not an uncommon consequence.”3

THE CLINICAL SYNDROME

Trigeminal neuralgia is a severe, almost exclusively unilateral, neuropathic pain located within the distribution of the trigeminal nerve, manifesting as paroxysmal, high-intensity, stabbing pain lasting seconds. Each attack may be followed by a refractory period, a period of relief that lasts seconds, minutes, or even hours. The burst of pain can occur spontaneously or can be triggered by stimulating a specific area of the face, known as a trigger zone. Trigger zones can be difficult to locate: They exist anywhere within the trigeminal distribution, including intraorally. The trigger zone is located in the same division of the trigeminal nerve as the pain. For this reason, patients characteristically avoid touching the face, washing, shaving, biting, chewing, or any other maneuver that stimulates the trigger zones and produces the pain.4 This avoidance is an invaluable clue to the diagnosis. With almost every other facial pain syndrome, patients massage, abrade, or apply heat and cold to the painful area; however, in trigeminal neuralgia, exactly the opposite occurs: Patients avoid any stimulation of the face or mouth. The pain is often characterized as an “electric shock” and is typically accompanied by a unilateral grimace; hence the designation tic douloureux. The pain may occur daily for weeks or months and then cease, sometimes for years, before returning; these intervals are known as periods of remission.

Although this pain has been clinically described for centuries, the etiology of trigeminal neuralgia and the other cranial neuralgias is not fully understood. For years, the integrity of the myelin sheath has been the focal point of investigation; however, the only agreement is that there is a dysfunction of the trigeminal sensory system.5 Trigeminal neuralgia is classified as primary (idiopathic or type 1) or secondary (type 2), which is caused by compression or irritation, tumor, or disease, such as multiple sclerosis.

Intermittent trigeminal neuralgia is uncommon in multiple sclerosis, with an incidence of between 1% and 2%.6,7 Conversely, the incidence of multiple sclerosis among patients with trigeminal neuralgia is approximately 3%. Patients with multiple sclerosis and trigeminal neuralgia typically have a history of classic trigeminal neuralgia, except that the trigeminal neuralgia appears at a younger age when patients have multiple sclerosis than when the disease occurs in its idiopathic form. Some patients with multiple sclerosis present with recurrent episodes of face pain that are generally long lasting, not stabbing or lancinating, and without associated trigger zones. These patients are assumed to not have true trigeminal neuralgia but a form of atypical facial pain.

Trigeminal neuralgia can be the first manifestation of multiple sclerosis, but this is rare. Most patients who have trigeminal neuralgia in association with multiple sclerosis have significant physical signs of multiple sclerosis for many years before the facial pain begins. Most, for example, have paraparesis or paraplegia, which are disorders of sensory function. Bilateral trigeminal neuralgia occurs more often than expected in patients with multiple sclerosis.

On rare occasions, trigeminal neuralgia may be a manifestation of brainstem disease and has been reported to result from pontine infarction.8 Neoplasms involving the trigeminal nerve generally produce constant neuropathic pain associated with sensory loss. Animal models have not been able to reproduce the pain of trigeminal neuralgia, and this limits clinicians’ ability to study the condition on a basic science level.

TESTING

The diagnosis of trigeminal neuralgia is made from the clinical history. No medical testing is available to confirm the diagnosis; however, some authorities have mentioned a response to carbamazepine as being “diagnostic.” When the condition is found, magnetic resonance imaging is recommended, to rule out secondary causes. Typically, the neurologic examination findings are normal. Clinically, the onset of trigeminal neuralgia is generally after age 50, although it can occur at any age. Twice as many women as men are affected. There is usually no sensory loss in “idiopathic” trigeminal neuralgia as measured by ordinary sensory testing, although some clinicians refer to occasional sensory findings.9–12 In contrast, sensory disturbances in the distribution of the trigeminal nerve are relatively common when patients have multiple sclerosis or a structural lesion involving the trigeminal nerve or roots. Such sensory loss may even involve the inside of the mouth. Some clinicians have postulated that trigeminal neuralgia left untreated may become more atypical, accompanied by sensory disturbances and constant pain.13

Fromm and colleagues described 18 patients whose initial trigeminal pain was not characteristic of neuralgia but suggestive of a toothache or sinus pain and frequently lasted several hours.14 Often this pain was set off by jaw movements or by drinking hot or cold liquids. Then, at a later time, ranging from several days to 12 years, more typical trigeminal neuralgia developed in the same general area as the initial pain. Six of these patients became pain free while taking carbamazepine or baclofen. The authors designated the problem pretrigeminal neuralgia. This neuralgia must be differentiated from trigeminal tumors, atypical facial pain, atypical odontalgia, and facial migraine, among other entities. A magnetic resonance imaging scan emphasizing the middle and posterior fossae is recommended as a diagnostic study in this situation.

In rare instances, trigeminal neuralgia is accompanied by hemifacial spasm. The combination has been designated tic convulsif.15 Tic convulsif is characterized by periodic contractions of one side of the face, accompanied by great pain. It may be confused with the facial contortions on the involved side that can accompany the paroxysms of true trigeminal neuralgia.15 Painful tic convulsif is reported to be more severe in women than in men. It may begin in or around the orbicularis oculi as fine intermittent myokymia, with some spread thereafter into the muscles of the lower part of the face. On occasion, strong spasms involve all of the facial muscles on one side almost continuously. In rare cases, the face becomes weak, and some of the facial muscles atrophy. Tic convulsif is usually indicative of a tumor, ectatic dilation of the basilar artery, or a vascular malformation compressing the trigeminal and facial nerves.16

DIFFERENTIAL DIAGNOSIS

Cluster-Tic Syndrome

Both trigeminal neuralgia and cluster headache in the same individual have been termed “clustertic syndrome.”17–23 In these cases, the entities are treated separately, and each is controlled with different medications.17,24 In some cases, surgical decompression of the trigeminal nerve has been successful in alleviating the pain.25,26 Secondary causes must be considered in all of these cases.27,28

Glossopharyngeal Neuralgia

Glossopharyngeal neuralgia is even rarer than trigeminal neuralgia. Clinically, the pain is similar to that of trigeminal neuralgia except that the distribution includes cranial nerve IX, the glossopharyngeal nerve, and the auricular (otic variety) and pharyngeal (cervical variety) branches of the vagus nerve. The pain is described as severe, transient, stabbing, or burning and is felt in the ear, the base of the tongue, the tonsillar fossa, or the area beneath the angle of the jaw, where it can be mistaken for trigeminal neuralgia affecting the third division of the trigeminal nerve. Rotation of the head, chewing, and swallowing may be triggers. The attacks of pain generally come in paroxysms and are lightning-like, but some patients have a more constant sore-throat sensation. Severe bradycardia, hypotension, or transient asystole, resulting in syncope or convulsions, may occur in some patients with glossopharyngeal neuralgia.29,30 Secondary causes must be ruled out with magnetic resonance imaging, and similar medications used for trigeminal neuralgia may work for this disorder as well.31–34

Geniculate Neuralgia

Geniculate neuralgia is an extremely painful disorder affecting the sensory part of the seventh cranial nerve, described as trigeminal neuralgia of the nervus intermedius.35 The pain is described as a severe stabbing pain deep within the ear.

Idiopathic Stabbing Headache

Idiopathic stabbing headache was first described as a “jabs and jolts syndrome” by Sjaastad and associates in 1979.36 Clinically, the pain is ultrashort, lasting less than one second; it can be located anywhere in the head but usually not in the facial region. It occurs as a stabbing pain or a series of recurring stabs. The frequency at which this occurs is extremely erratic, and there are no triggers. Idiopathic stabbing headache is a primary benign headache that is clinically relevant to the diagnosis of trigeminal neuralgia because nearly two thirds of patients find indomethacin to be helpful.37

Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing (SUNCT)

SUNCT is characterized as unilateral moderate to severe orbital stabbing pain that lasts for 5 to 250 seconds and may occur up to 40 or more times a day.38 The pain is accompanied by autonomic features, the most significant of which are the tearing and conjunctival injection. Attacks have been known to be precipitated by chewing, by swallowing, by touching of the nose or eyelids, or by certain neck movements. SUNCT is refractory to medical management and does not respond to indomethacin or traditional treatments for trigeminal neuralgia.

Atypical Facial Pain

Atypical facial pain or facial pain of unknown cause is characterized by a deep burning or aching sensation that is continuous and poorly localized. The pain may be unilateral or bilateral and does not necessarily follow the distribution of the peripheral nerves. It may be accompanied by sensory changes, such as allodynia, dysesthesia, and paresthesia.39 The usual sufferers are middle-aged women. Sleep and facial functions, such as eating and talking, are rarely affected, except when pain is intraoral. Some patients have a history of trauma or a dental or surgical procedure before the onset of pain.

In 1993, Pfaffenrath and colleagues suggested modifying the International Headache Society diagnostic criteria for atypical facial pain (Fig. 64-1).40 Because Pfaffenrath and colleagues’ criteria could apply to pain symptoms of separate etiologies, clinicians further categorize these pains according to their specialty in hopes of a better understanding of the condition, as well as in directing treatment toward correcting the cause of the pain. Facial pain of unknown cause was also categorized by Graff-Radford, who proposed an outline to help clinicians compartmentalize their clinical findings and to create a more uniform approach to treating these disorders with limited knowledge of the etiology (Fig. 64-2).41

image

Figure 64-1 Pfaffenrath and colleagues’40 suggested modifications of the International Headache Society diagnostic criteria for atypical facial pain.

image

Figure 64-2 Graff-Radford’s proposed classification for features of facial pain of unknown cause.41

TREATMENT

Medical Management

Initial management of trigeminal neuralgia is medical, and surgical therapy should be considered if medical treatment fails or cannot be tolerated and if secondary causes are found during the initial workup.42,43 It is important to discuss all treatment options with the patient early in the treatment process. A neurosurgical consultation early in the medical management of the patient allows the patient time to understand the multiple treatment options. It is impossible to predict which patients may not respond to medications, and so it is imperative that they understand treatment options before desperately seeking surgery after months of failed medication trials. Patient preference for either medical or surgical treatment as first-line therapy must be a part of the decision making as well, and this can be facilitated by having an early consultation with a neurosurgeon.

The medical treatment of trigeminal and other cranial neuralgias is based on the capacity of the drugs employed to decrease nerve hyperexcitability either peripherally or centrally. Clinically pharmacological therapies are aimed at providing rapid and sustainable pain relief with a minimum of side effects. Unfortunately, the clinical trials in trigeminal neuralgia are not adequate to enable clinicians to fully understand each medication’s effect on this disease. Each patient is evaluated individually, with age, other systemic illnesses, and previous tried medications taken into account, and then medication choices can be made.

Treatment is usually begun with an antiepileptic medication that has proved antineuralgic properties. The initial dose should be low and titrated up gradually, with close clinical monitoring, until either the maximum tolerated or pain-free dose is attained. For years, the “gold standard” has been carbamazepine, 100 mg to 200 mg two or three times daily, which provides benefit in more than 75% of patients. Today there are multiple medications from which to choose, but a response to carbamazepine has been described as being almost diagnostic.

If, because of side effects, the initial medication is not tolerated, then an alternative medication is employed. For example, if carbamazepine is not tolerated, other medications, including baclofen,44–50 sodium valproate,51 gabapentin,52–56 lamotrigine,58,54–61 oxcarbazepine,62–66 topiramate,62,67,68 felbamate,69 zonisamide, vigabatrin, pregabalin, and clonazepam,70,71 are sometimes effective, but the therapeutic efficacy of most of these agents has not been adequately studied formally. There is a continuing need for new antineuralgic medications because of the limited tolerance and limited efficacy of the agents already available.5

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