Trigeminal neuralgia is pain in the distribution of the trigeminal dermatomes. The pain is described as an electric shock–like, stabbing, unilateral pain having abrupt onset and termination. Intervals between attacks are pain free. Non-noxious triggers occur in the same or different sensory areas of the face, and there is minimal or no sensory loss in the region of pain [1–7]. Trigeminal neuralgia has an incidence of 4 or 5 per 100,000 people up to 20 per 100,000 per year after the age of 60 years [7–9] and a prevalence of 0.1 to 0.2 per 1000. The female-to-male ratio is about 3:2 [8].

The trigeminal nerve (cranial nerve V) is the largest of the cranial nerves. It begins in the brainstem at the trigeminal nucleus and travels along the ventrolateral surface of the pons and through the subarachnoid space until it enters the temporal bone, where it forms into the gasserian ganglion located in the Meckel cave [10]. The divisions are the ophthalmic or V1 branch, the maxillary or V2 branch, and the mandibular or V3 branch (Figs. 117.1 and 117.2). The relative distribution of pain in trigeminal neuralgia is as follows: V1, 20%; V2, 44%; V3, 36% [10].

f117-01-9781455775774 — FIGURE 117.1 Dermatomes for trigeminal nerve. V1, ophthalmic nerve. V2, maxillary nerve. V3, mandibular nerve. (From Waldman SD. Trigeminal nerve block: coronoid approach. In Waldman SD, ed. Atlas of Interventional Pain Management, 2nd ed. Philadelphia, WB Saunders, 2004.)

f117-02-9781455775774 — FIGURE 117.2 Anatomy of trigeminal nerve. The gasserian ganglion is formed from two roots that exit the ventral surface of the brainstem at the midpontine level. These roots pass in a forward and lateral direction in the posterior cranial fossa across the border of the petrous bone. They then enter the Meckel cave. The gasserian ganglion has three sensory divisions, the ophthalmic (V1), the maxillary (V2), and the mandibular (V3). (From Waldman SD. Gasserian ganglion block. In Waldman SD, ed. Atlas of Interventional Pain Management, 2nd ed. Philadelphia, WB Saunders, 2004.)

Most patients with classic symptoms have mechanical compression of the trigeminal nerve as it leaves the pons and travels in the subarachnoid space toward the Meckel cave [10–12]. Most commonly, there is cross-compression by a major vessel. Other proposed causes include demyelinating plaques from multiple sclerosis, neoplastic disease, and abscess formation with bone resorption and irritation of the trigeminal nerve in the maxilla or mandible. Trigeminal neuralgia occurs in about 1% of patients with multiple sclerosis, and approximately 2% to 8% of patients with trigeminal neuralgia have multiple sclerosis [7,8,13].

Regardless of the etiology, it is likely that both peripheral and central mechanisms play a role in the pathogenesis of this syndrome.

Symptoms

Typical trigeminal neuralgia symptoms involve electric shock–like pain in the distribution of one or more branches of the trigeminal nerve. Pain is often intermittent, with pain-free intervals of months or even years [10]. The pain may last a few seconds to less than 2 minutes. The pain has at least four of the following five characteristics: distribution along one or more divisions of the trigeminal nerve; sudden intense, sharp, superficial, stabbing, or burning quality; severe intensity; precipitation from trigger areas or by certain daily activities, such as eating, talking, washing the face, or cleaning the teeth; and between paroxysms, the patient is completely asymptomatic [6,14]. In general, patients do not report any other neurologic deficit.

Physical Examination

The diagnosis of trigeminal neuralgia is made primarily by history. The Sweet criteria for this diagnosis are five pain descriptors. The diagnosis must be questioned if these criteria are not met [5], as follows: the pain is paroxysmal; the pain may be provoked by light touch to the face (trigger zones); the pain is confined to the trigeminal distribution; the pain is unilateral; and the findings on clinical sensory examination are normal [5,15]. When possible, physical examination of the oral cavity, dentition, and trigeminal nerve distribution should be performed to rule out other diseases. A complete cranial nerve examination should be performed. In general, no sensory or motor deficits are present, but serial examinations may detect a change and identify a secondary cause of trigeminal neuralgia [6].

Functional Limitations

In general, there are no impairments associated with trigeminal neuralgia. However, the pain from this entity may result in significant limitation in several activities of daily living. During exacerbations, patients may be functionally incapacitated because of pain and may be unable to perform activities such as comb hair, chew food, or shave. Talking on the telephone may be painful. Wearing glasses or makeup may not be possible. The pain from trigeminal neuralgia is not continuous but paroxysmal, suggesting spontaneous discharges from specific neurons, and it frequently occurs by innocuous tactile stimuli [4]. Therefore any activity that involves contact with the face may become difficult or impossible.

Diagnostic Studies

When a diagnosis of trigeminal neuralgia is suspected, patients should have diagnostic brain imaging with magnetic resonance imaging. Magnetic resonance imaging with gadolinium contrast can aid in diagnosis of multiple sclerosis plaques, neoplasm, and any neurovascular compressive relationship to the trigeminal root [5]. Electromyography, nerve conduction studies, and quantitative sensory testing may provide sensitive, quantitative, and objective results for the diagnosis, localization, and accuracy of damage to the trigeminal nerve [16]. Other studies that may have a role in diagnosis include intraoral, skull, and sinus radiographs and daily diaries of pain.

Differential Diagnosis

See Table 117.1.

Table 117.1

Differential Diagnosis of Trigeminal Neuralgia or Facial Pain

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Condition	Prevalence	Major Location and Radiation	Timing	Character and Severity	Provoking Factors	Associated Factors
Dental
Pulpal	Very common	Well localized to a tooth	Can last 10-20 minutes after sugary stimulus	Sharp, stabbing, throbbing, dull, moderate to severe	Hot, cold, or sweet foods provoke it, rarely spontaneous	Immediate relief on removal of stimulus
Fractured or cracked tooth	Fairly common	Localized to one or two teeth, but may be poorly localized, difficult to visualize	Very short lasting, seconds, intermittent	Sharp, moderate	Biting, never spontaneous, may be sensitive to heat	Rebound pain, worse after force removed, opposing natural tooth normally present
Pulpal—chronic pulpitis	Common	Poorly localized intraorally	Intermittent, hours	Mild, dull, throbbing	Occasionally heat	Often large restoration
Periodontal—chronic apical periodontitis	Common	Poorly localized, intraoral	Intermittent, minutes to hours	Mild, dull, throbbing	Large restoration	Sinus may be visible, bad taste
Bone pain– osteomyelitis	Rare	Most often mandible, widespread	Continuous	Throbbing, severe	Biting on mobile teeth	Pyrexia, malaise, trismus, swelling, may be paresthesia, pus, mobile teeth, sequestra
Denture pain, pressure on mental nerve, secondary trigeminal neuralgia	Rare	Localized intraoral	Intermittent, daily	Aching, may be sharp if over mental nerve	Eating with denture	Often redness, ulceration in area of pressure
Neurologic Trigeminal Neuralgia
Classic, typical [14]	Rare	Intraoral or extraoral in trigeminal region	Each episode of pain lasts for seconds to minutes; refractory periods and long periods of no pain	Sharp, shooting, moderate to very severe	Light touch provoked (e.g., eating, washing, talking)	Discrete trigger zones
Atypical trigeminal neuralgia [17]	Rare	Intraoral or extraoral in trigeminal region	Sharp attacks lasting seconds to minutes, more continuous-type background pain, less likely to have complete pain remission	Sharp, shooting, moderate to severe but also dull, burning, continuous mild background pain	Light touch provoked, but continuous-type pain not so clearly provoked	May have small trigger areas, variable pattern
Trigeminal neuropathy [18]	Very rare	Trigeminal area, but may radiate beyond	Continuous	Dull with sharp exacerbation	Areas of allodynia, light touch	Sensory loss, subjective- objective, progressive, vasodilation and swelling may occur
Glossopharyngeal neuralgia	Very rare	Intraoral in distribution of glossopharyngeal	Each episode lasts for seconds up to 2 minutes	Sharp, stabbing, burning, severe	Swallowing, chewing, talking	No neurologic deficit
Postherpetic neuralgia [19]	Rare