Unilateral carpal tunnel syndrome caused by an occult ganglion in the carpal tunnel: a report of two cases.

Carpal tunnel syndrome (CTS) usually presents bilaterally and a secondary nature should be suspected in patients with unilateral symptoms, especially those with a long-standing history, and when the symptomatic hand shows severe neurophysiologic impairment, while the contralateral hand is neurophysiologically intact. Space-occupying lesions are known to cause CTS and the incidence of space-occupying lesions in unilateral CTS is higher than that of bilateral CTS. It is easy to detect a mass when it is palpable; however, occult lesions are usually overlooked. Whenever a patient presents with unilateral symptoms and unilateral neurophysiologic impairment, the possibility of a space-occupying lesion compressing the median nerve should be kept in mind in the differential diagnosis. This study presents two cases with an occult ganglion in the carpal tunnel compressing the median nerve and causing unilateral symptoms of CTS. We stress on the importance of imaging studies in patients with unilateral symptoms that are usually not used in CTS. The reported patients were evaluated and magnetic resonance images revealed an intratunnel space-occupying lesion.