Clinical Reasoning: A case of unilateral facial pain

Abstract

A 62-year-old man admitted with B cell chronic lymphocytic leukemia (CLL) reported 2 weeks of progressive left-sided jaw and facial pain. He first noticed the pain occurring during prolonged chewing. It was exacerbated by teeth clenching and resolved with jaw rest. The patient described the pain as dull and gnawing without radiation. He also described a "knot" within his left "jaw muscles" at the mandibular angle. He had decreased range of motion, could not fully open his mouth, and felt that his jaw was misaligned. He was therefore placed on a soft mechanical diet. He denied a temporal headache or transient loss of vision. He was on his second day of obinutuzumab chemotherapy but was not on any other new medications. He had no history of trauma to his face, head, or neck.The most notable abnormalities on examination were that his left masseter and temporalis muscles were more prominent than the right, both at rest and when clenching. His left masseter was tender, and his jaw's range of motion was reduced and limited by pain. On general head and neck examination, there was no temporal artery tortuosity. There was no tenderness of either of the temporomandibular joints (TMJs) and no parotid gland swelling. There was no lateral mandibular deviation or clicking sounds from the TMJ, and there was no neck dystonia. Oral examination did not reveal abscesses or other signs of inflammation.Cranial nerve examination revealed normal visual acuity, visual fields, and extraocular movements. The patient had normal perception of pain, light touch, and temperature sensation in V1-V3 bilaterally, without hyperesthesia or allodynia. Lateral pterygoid function was preserved. Frontalis activation, eye closure, lip pursing, and smile were symmetrical and normal. Hearing was normal. Tongue and pharyngeal muscle movements were normal. The remainder of the neurologic examination revealed no other pathologic or lateralizing features. Questions to consider:1. What is the localization of the lesion? 2. What is the differential diagnosis? GO TO SECTION 2From the Department of Neurology, Mayo Clinic, Jacksonville, FL.Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article. e170© 2015 American Academy of Neurology ª 2015 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. SECTION 2: LOCALIZATION AND DIFFERENTIAL DIAGNOSISLocalization. The localization most likely involves a lesion of the peripheral nervous system or masticatory muscle. The isolated masseter muscle tenderness and lack of sensory symptoms or other cranial nerve findings make spinal trigeminal tract, brainstem, and thalamic lesions much less likely. The masticatory muscle asymmetry could represent either left muscle hypertrophy or right muscle atrophy. While a lesion of the right trigeminal motor nucleus could cause right-sided atrophy, cortico-trigeminal tracts project bilaterally, making this sort of lesion unlikely. However, ischemic or co...