Abstract
Trigeminal neuralgia (TN) is a relatively rare chronic, neuropathic, facial pain condition, affecting more women than men, generally after the fourth decade of life (1–3). It is defined by the International Association for the Study of Pain (IASP) as a sudden, usually unilateral, severe, brief, stabbing recurrent pain in the distribution of one or more branches of the fifth cranial nerve (1).
In 35.2% of the cases both the second and third branches of the trigeminal nerve are affected (4). Patients usually describe the pain as sharp, stabbing, lancinating, electric-like, burning and excruciating (1, 2, 5). Paroxysms can be triggered by light mechanical activation of a trigger zone or may occur spontaneously (1, 5). Commonly reported stimuli include light touch of the skin, shaving, washing, chewing and cold wind (1, 3, 5). In most cases the attacks do not occur during sleep (5–7).
The pain is of brief duration, lasting from a few seconds up to 1–2 min (1, 2, 5). This is characteristically followed by a refractory period of up to a few minutes (1, 4, 6). Paroxysms may occur at intervals or many times daily or, in rare instances, succeed one another almost continuously (1, 5–7). The course of TN is variable; patients may report pain-free intervals of months or years before new attacks begin (1, 2, 4). Episodes tend to become more frequent and severe as time passes (7). Routine neurological testing reveals no sensory or reflex deficit (1, 2, 7).
Since the identification of TN is done purely on a clinical basis due to the absence of objective tests to confirm the diagnosis, a careful history and clinical examination are essential in order to avoid misdiagnoses (3, 8). Although the IASP has provided diagnostic criteria for this condition, typical forms of TN may develop atypical signs and atypical presentations may later develop the hallmark signs of TN (8). As a result, a variety of entities should be considered as differential diagnoses for TN. Among these are disorders which affect the sinuses, teeth, temporomandibular joints, eyes, nose and the neck (3, 5, 9). Upon clinical examination most of these can be ruled out; however, conditions such as cluster headache, short lasting, unilateral, neuralgiform pain with conjunctival injection and tearing (SUNCT), chronic paroxysmal hemicrania (CPH), cracked tooth syndrome, jabs and jolts syndrome, giant cell arteritis and post-herpetic neuralgia may be more difficult to exclude if the clinical picture is not typical (1, 3, 8).
Case report
A 56-year-old man was referred to the Tufts Craniofacial Pain Center with a preliminary diagnosis of neuropathic pain suggestive of TN. His complaint was very brief attacks of sharp pain on the left side of the face extending from the jaw to the ear. According to his description, the pain would start in the lower aspect of the jaw as a sharp, burning, aching pain which would shoot up to the ear. Each episode would initiate at an intensity of 4 on the visual analogue scale (VAS) and would become a 10 by the time it reached the ear. The attack lasted from 10 to 15 s and could happen twice during an hour with up to three attacks in a day. The pain presented by the patient was strongly suggestive of TN and, in fact, these attacks fulfilled the criteria of the IASP for TN (1). The attacks had been occurring for a period of 2 months at the time of examination. No events in particular would trigger the paroxysm other than during periods of extreme fatigue.
On initial orofacial evaluation the patient was screened for the presence of any neurological, neurovascular, muscular, osseous or dental disorder. No sensory loss or trigger zones were detected along the distribution of the trigeminal nerve. A panoramic radiograph was utilized as an initial inspection tool for any bony or dental pathology. There were no significant findings. Muscle examination of the head and neck produced a diagnosis of myofascial pain, affecting the lateral pterygoid muscle and temporal tendon on the left side. The diagnosis of myofascial pain was based on tenderness and referred pain on palpation. The referred pain evoked by palpation of trigger points reproduced the patient's pain, according with the diagnosis of active trigger points (10). Due to these findings a brain magnetic resonance imaging was not indicated at this time. On dental examination the patient was found to have an Angle's Class I occlusion with multiple missing posterior teeth on both sides of the arch (numbers 1, 14, 15, 16, 17, 18, 19, 21, 26, 29, 30, 32). The upper missing teeth were replaced by a partial denture. A frenum midline deviation to the left side and a canting of the maxilla to the same side were also present. Mandibular range of motion was within normal limits (protrusion 8 mm, lateral excursion left 12 mm, lateral excursion right 11 mm, maximum opening 42 mm).
The treatment provided was the insertion of a flat lower orthotic appliance with bilateral posterior contacts on premolars and molars. The patient was to wear the appliance day and night except when eating. One week later the patient returned to the clinic for a follow-up and reported that the frequency and intensity of attacks had diminished. VAS rating had dropped to 3.5 and he reported experiencing only slight twinges of pain which remained confined to the jaw. Two weeks later the patient reported no pain (VAS of 0). The same scenario was found 1 month later. Palpation of the lateral pterygoid and temporal tendon showed that they were no longer tender and that palpation no longer elicited referral of pain. At a 3- and 10-month phone follow-up the patient reported he was free of pain. The patient continues to wear his appliance at nighttime only, at this time.
Discussion
Myofascial pain is characterized by a regional, dull, aching muscle pain and the presence of localized tender sites (trigger points) in a muscle, tendon or fascia (11). Although this is found to be the most typical presentation, a limited number of patients may present pain quality and severity similar to that found in TN. Travell has described the severity of symptoms caused by myofascial trigger points as ranging from agonizing, incapacitating pain to painless restriction (12). Patients with myofascial trigger point pain may report VAS ratings as high as or higher than pain conditions of neurological origin. The painfulness of myofascial trigger points can, and often does, negatively impact the quality of life (12).
When palpated, these trigger points may produce a characteristic pattern of regional referred pain on provocation (11). Manual manipulation of trigger points usually reproduces or aggravates the spontaneously occurring pain (10). The temporalis muscle pain pattern extends mainly over the temporal region, to the eyebrow, the upper teeth and occasionally the maxilla and the temporomandibular joint (13). Referred pain from trigger points in the lateral pterygoid muscles is felt strongly in the maxilla and temporomandibular region (14). This referral zone includes the area just anterior to the ear. This is the area in which the patient in our case report experienced his sharp, shooting pain. The patterns of referral of these muscles, along with the other muscles of mastication, include the regions innervated by the maxillary and mandibular divisions of the trigeminal nerve.
Myofascial pain may be aggravated by mandibular function when the muscles of mastication are involved (11). Since episodes of TN may sometimes be triggered by the facial and tongue movements incidental to chewing and swallowing, it must be differentiated from masticatory pain (15).
Our diagnosis and treatment choice were based on our clinical findings of tenderness to palpation and referred pain from muscles, which pointed to a muscular dysfunction related to the loss of posterior teeth. The occlusal contact patterns of the teeth have significant influence on the activity of the masticatory muscles (11). Consequently, in the absence of an adequate maxillomandibular interrelationship, muscle dysfunction may develop. It has been well reported in the literature that intraoral appliances function in reducing muscle tension by re-establishing occlusal balance (16). Therefore this was selected as the initial treatment.
The wide array of diseases that affect the orofacial region make it challenging for the clinician to diagnose them. This is due to the presence of overlapping symptomatology and varying presentations.
The objective of this case report was to emphasize the importance of a thorough craniofacial examination when dealing with patients with signs and symptoms suggesting TN. Occasionally, occlusal disharmony along with musculoskeletal disorders may mimic some characteristics of TN. We suggest that in cases in which all diagnostic criteria of TN are not clearly met, or atypical features are present, the most conservative diagnoses and treatments should be considered initially. Treatment options can later be escalated according to the patient's response.
A diagnostic evaluation of patients with orofacial pain may include laboratory tests, neurological evaluation and imaging of the head, face, jaws and teeth, when appropriate (7). We suggest that physical examination of the myofascial tissues of the head and neck may also be appropriate in these patients.