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Images in Neurology
Nov 2012

Schwannoma of the Palmar Cutaneous Nerve: Electrodiagnosis With Radiologic and Pathologic Correlations

Arch Neurol. 2012;69(11):1512. doi:10.1001/archneurol.2012.168

A 61-year-old otherwise healthy man presented with pain and altered sensation in his right wrist and palm. Physical examination revealed painful and lightening Tinel sign at the base of the thenar eminence as the only abnormal sign. Electrodiagnostic studies showed a 30% reduction in the sensory action potential amplitude of the palmar cutaneous nerve as compared with the left, without any change in the usual transcarpal parameters of the median and ulnar nerve conduction studies. Magnetic resonance imaging of the wrist demonstrated a subcutaneous mass on the palmar aspect of the wrist, suggestive of a peripheral nerve sheath tumor1 (Figure 1). At surgery, the tumor was found to be an encapsulated mass of the thenar branch of the median nerve, in contrast with the invasive, nonencapsulated characteristics encountered in neurofibromatomas.2 Histopathologic examination was compatible with a schwannoma (Figure 2). The operation was reported to be without complications, and at 12 months' follow-up, the patient was asymptomatic, underlying the good prognosis of some median nerve tumors.3

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