The value of magnetic resonance imaging in carpal tunnel syndrome

We examined 62 patients (72 hands) with carpal tunnel syndrome (CTS) by magnetic resonance imaging (MRI) of the carpal tunnel and latency measurements of the median nerve. In 32 of 72 hands a probable causative lesion of the CTS was identified by MRI, for example tenosynovitis, a cyst-like structure, or an aberrant muscle. The MRI findings were confirmed by surgery in 16 of 24 hands, slightly corrected in 5, and not substantiated in 3. In 65 of 72 hands, MRI disclosed pathology of the median nerve, most prominently an enlargement of the nerve at the level of the os pisiforme, a finding not seen during surgery. Oedema of the nerve was found in 14 of 72 hands. The distal latencies were prolonged in 62 of 72 hands. The sensory latencies correlated significantly with the MRI-determined cross-sectional area of the nerve at the level of the distal radius. The lack of other correlations suggests that partly independent features of the nerve lesion are demonstrated in each method or that the sensitivity and specificity of both methods are limited. Further experience with MRI in CTS is desirable. At present, the practical use of MRI in CTS should be restricted to special diagnostic problems such as carpal tunnel syndromes which do not respond adequately to conservative or surgical treatment.