The diagnosis and management of patients with facial pain can be daunting even to experienced physicians. The causes are myriad, ranging from the mundane (sinus and dental disease) to the exotic (short-lasting unilateral neuralgiform headache with conjunctival injection and tearing, or SUNCT). Misdiagnosis and mismanagement are common. The goal of this chapter is to discuss some of the more important causes of facial pain and to guide proper identification and treatment.

Simply because pain is felt in the face does not imply that it necessarily originates in facial structures. As elsewhere in the body, pain may be local in origin, or referred. The role of the trigeminovascular system and the spinal trigeminal nucleus as a point of anatomic and physiologic convergence is discussed in Chapter 19. Suffice it to say that the location of the pain may not be so important diagnostically as other features.

The approach to the evaluation of facial pain requires careful attention to detail. In the patient history, it is essential to obtain an accurate description of the nature of the pain, or pains, what may have incited it, and what currently provokes and ameliorates it. Are there associated phenomena, such as autonomic changes? Past medical history, including trauma and surgical or dental procedures, may provide essential clues. Is there associated depression or any other psychiatric problem? What therapies have been tried, and with what outcomes?

After obtaining a detailed history, a thorough examination is necessary. In addition to the general physical examination, a thorough neurologic examination is essential. The examiner looks for signs of raised intracranial pressure (papilledema, diminished up gaze, sixth cranial nerve palsies) and cranial nerve dysfunction (particularly oculosympathetic paresis). The head and neck require careful attention. Are there trigger points? Is there dental or sinus tenderness? Auscultation for bruits and palpation of the carotid artery are sometimes informative maneuvers.

Finally, the results of prior diagnostic studies are reviewed, noting the timing of the studies. Were the appropriate studies performed? If the situation has changed, perhaps an imaging study should be repeated. Sometimes a diagnosis may become apparent only after serial clinical examinations or diagnostic studies, or both.

After a careful history, examination, and review of the data, a tentative diagnosis may be rendered. Often, further consultation is required. Treatment is offered based on the tentative diagnosis and may, in itself, sometimes be diagnostic. The thoughtful physician should always be willing to reconsider the diagnosis.

Facial pain clearly represents a diagnostic challenge. With attention to the fundamental approach outlined in the preceding paragraphs, the vast majority of patients may achieve a satisfying outcome.

Neuralgias are paroxysmal pain in the distribution of a particular nerve. The pain is typically maximal at onset and lancinating and may be described as “electric shocks” or “jabbing.” There may be a single, sharp pain or repetitive pains in succession. The pain may be so brief as to last but an instant, or it may last several seconds. There is usually a refractory period after the severe pain, during which pain does not occur. Some neuralgic conditions have trigger zones (areas that, when stimulated, provoke an attack) or other triggers. Careful history taking often reveals other pain occurring as well, such as continuous aching, burning, or throbbing. Inquiry must be made about all the sensations that occur because some patients mention only the severe exacerbations. Response to treatment may provide a clue to diagnosis but can also be misleading. “Diagnostic blocks” in the setting of facial pain do not necessarily define the site from which the pain arises because of overlap of cranial nerves V, IX, and X (which converge on the spinal trigeminal nucleus and the tractus solitarius). Facial and cranial neuralgias are classified in the International Classification of Headache Disorders, 2nd edition (ICHD-II) by the presumed nerve of origin (Table 35-1).

The best-known facial neuralgia is trigeminal neuralgia, which is discussed in detail in this chapter and, in many ways, serves as a model for understanding other neuralgias causing facial pain.

TRIGEMINAL NEURALGIA

Trigeminal neuralgia is a severe, (usually) unilateral facial pain, characterized by lancinating pains in the distribution of one or more divisions of the trigeminal nerve. Although onset may occur in the second and third decades, the majority of cases begin in middle and old age. With an annual incidence rate of 4 to 5 per 100,000, it is one of the most frequently seen neuralgias in the elderly.¹ The pain may be so excruciating that facial muscle spasms can be seen—hence, the older term, tic douloureux. Hemifacial spasm, which can be seen with trigeminal neuralgia, can look similar to these spasms and, while rapid and involuntary—as opposed to the reactive spasms of tic douloureux—can be difficult to differentiate.

The facial pain tends to occur in paroxysms and is maximal at or near onset. The severe exacerbations tend to last from one to several seconds but may occur in volleys. There may also be a coexisting continual deep or dull pain. Patients may or may not, therefore, have pain-free periods.

Trigeminal neuralgia most often involves the second and third divisions of the trigeminal nerve (V₂ and V₃) but can include or be limited to the first division as well. Trigger zones may be present. Often, lightly touching these areas will trigger a paroxysm, and patients tend to protect these areas. Other triggers may include chewing, talking, brushing teeth, cold air, or smiling and grimacing. A refractory period of several minutes typically follows an episode, during which a paroxysm cannot be provoked. In occasional patients, the pain may be bilateral, but not on both sides simultaneously.

This condition may be idiopathic (primary) or symptomatic (secondary). Idiopathic implies no known underlying condition, but many idiopathic cases are probably the result of vascular compression of the trigeminal nerve near its entry into the pons. Symptomatic causes include multiple sclerosis, tumors, and basilar artery aneurysm or ectasia.^2–4

Unlike some other facial pain conditions, trigeminal neuralgia typically does not awaken patients at night. Some patients have a history of so-called pretrigeminal neuralgia, which is said to be dull, continuous, aching pain in the jaw, evolving eventually into trigeminal neuralgia. This brief, milder pain is sometimes wrongly suspected to have a dental origin, and dental procedures are performed. Because trigeminal neuralgia is sometimes precipitated by dental procedures (e.g., dental extraction), confusion about etiology has resulted.⁵

The pathophysiology of trigeminal neuralgia is not fully elucidated. Demyelinative lesions of trigeminal fibers appear to set up ectopic impulses and ephapses. This alteration of afferent input may disinhibit pain pathways in the spinal trigeminal nucleus. Evidence for a role of central pain mechanisms includes the presence of refractory periods after a triggered episode, trains of painful sensations after a single stimulus, and some latency from the time of stimulation to the onset of pain.⁶

Clinically, certain features of the history help in making the diagnosis. Paroxysms of pain in the distribution of the trigeminal nerve, especially if trigger points are present, are typical. The examination may reveal these trigger zones, which often are near the midline. If sensory loss is present, a mass lesion is more likely. In younger patients (20 to 40 years old) with trigeminal neuralgia, multiple sclerosis should be considered. A demyelinative lesion in the pons would explain bilateral symptoms.

Once the diagnosis is suspected on clinical grounds, a careful search for ipsilateral dental pathology should be undertaken (oral surgery consultation should be considered). Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) should be performed to look for evidence of demyelinating lesions, a mass lesion in the cerebellopontine angle, or an ectatic blood vessel (rarely seen with MRA). The differential diagnosis includes SUNCT/SUNA (discussed later in the section, “SUNCT/SUNA”), cluster-tic syndrome, jabs and jolts syndrome, and other neuralgias—all of which are discussed later in this chapter.

Trigeminal neuralgia is usually successfully treated with medication (Table 35-2). The American Academy of Neurology has published evidence-based guidelines.⁷ Carbamazepine is felt to be the most effective medication. Oxcarbazepine has somewhat less evidence but is the second choice. Baclofen, phenytoin, valproate, pimozide, and clonazepam may have utility as well, alone or in various combinations, but this is anecdotal information and does not have the same level of evidence-based support. Baclofen may be synergistic with carbamzepaine.⁸ Misoprostol, a prostaglandin E analogue, has been reported as effective in trigeminal neuralgia caused by multiple sclerosis.⁹ Gabapentin and lamotrigine have also been reported to be useful, although there is less clinical experience with these agent.^10,11

Neuroleptic medications, including chlorpromazine and perphenazine, have been used successfully in intractable cases, and novel neuroleptics such as olanzapine and quetiapine have been tried as well. Tizanidine has been used in selected cases. Topiramate has been suggested, because other anticonvulsant medication has been effective.

We have found carbamazepine to be the most useful of all the available drugs. If doses are started low, especially in the elderly (e.g., 50 mg b.i.d. or less) and advanced gradually, the drug is highly efficacious with few side effects, and few patients develop tolerance. If pain control is insufficient, baclofen may be added. With both carbamazepine and oxcarbazepine, the occasional development of hyponatremia needs to be monitored by laboratory evaluation. If the patient is desperate for immediate pain relief, intravenous infusion of phenytoin or fosphenytoin (250 to 500 mg at no more than 50 mg/min, monitoring pulse and blood pressure) may be rapidly effective, although many patients quickly develop tolerance to the drug. Nonetheless, intravenous phenytoin may afford immediate temporary relief while oral carbamazepine therapy is begun. This maneuver may also enable the physician to better examine the patient with a sensitive face.¹² Details of the use of these medications may be found elsewhere in this book (see Chapters 62, 63, and 64). Rarely, there are spontaneous permanent remissions of trigeminal neuralgia. More often, the illness tends to wax and wane in terms of severity and frequency of exacerbations. Therefore, in patients achieving good relief of pain with medications, periodic attempts to gradually withdraw these drugs are warranted.

For patients refractory to therapy with drugs, various surgical procedures may have efficacy. Janetta has popularized microvascular decompression, the dissection away from the trigeminal nerve of various vascular structures, often an ectatic superior cerebellar artery.¹³ Long-term outcome is good (more than 80% pain-free), but this procedure does involve an intracranial approach with some morbidity and mortality risk. Other procedures directed against the trigeminal nerve include percutaneous radiofrequency rhizotomy, glycerol rhizolysis, and balloon compression. Complications include anesthesia dolorosa (a central pain disorder resulting from hypersensitization of the second-order spinal trigeminal nucleus neuron) and keratitis, as well as facial weakness caused by injury of the facial nerve. More recently, excellent results with minimal morbidity have been reported with gamma knife therapy.¹⁴ For patients unable or unwilling to tolerate more aggressive surgical procedures, peripheral nerve root avulsion may provide relief. Although often temporarily effective, nerves often regenerate and pain recurs.

Tenser has noted that, after surgery for trigeminal neuralgia, herpes simplex virus reactivation occurs in 17% to 94% of patients. The speculation is that altered function of cranial nerve V (CNV) underlies the beneficial response to the various surgical manipulations (injury to the trigeminal root ganglion).¹⁵

In summary, patients suffering from trigeminal neuralgia deserve a careful evaluation, especially to exclude symptomatic causes such as multiple sclerosis or a cerebellopontine angle mass. Ipsilateral dental pathology should be sought. Pain relief can usually be achieved through aggressive pharmacologic therapy, surgery, or both.

CLUSTER-TIC SYNDROME

It has been reported that the pains of trigeminal neuralgia and cluster headache may coexist.¹⁶ In the cluster-tic syndrome, there are three types of pain. One component of the pain resembles trigeminal neuralgia—paroxysmal, extremely brief, and severe. The second component is more similar to cluster headache, although of variable length, with autonomic phenomena (lacrimation, rhinorrhea). The third type of pain is a mixture of the first two. This pain may be provoked by trigger points or moving the neck.

Cluster-tic syndrome usually afflicts patients between 20 and 70 years old. It may exist in chronic or episodic forms (remissions and recurrences). Medical therapy is usually unsuccessful, although when surgery (microvascular decompression or trigeminal rhizotomy) relieves the neuralgia, the clusterlike pain may be lessened and become more responsive to therapy.

The differential diagnosis includes SUNCT/SUNA, which is discussed later in this chapter. Secondary (symptomatic) SUNCT has been reported as a result of arteriovenous malformation in the cerebellopontine angle, and secondary cluster-tic syndrome has been associated with an ectatic basilar artery running deep into the cerebellopontine cistern.^17,18 We feel it is possible that so-called cluster-tic syndrome and SUNCT may actually be the same condition, at least in some cases.