Diagnosis of carpal tunnel syndrome: electrodiagnostic and magnetic resonance imaging evaluation.

In clinically diagnosed CTS without symptoms or signs to suggest other disorders that can mimic CTS, it is unclear whether performing nerve conduction studies are cost-effective. An outcome study to determine whether nerve conduction studies are necessary for the diagnosis may help to clarify this issue. Even less evidence exists regarding the cost-effectiveness of imaging for CTS. MR imaging reliably depicts normal carpal tunnel anatomic details, including the median and ulnar nerves as well as their intraneural fascicular structure. It can also identify pathologic nerve compression and mass lesions that compress nerves such as ganglion cysts. Currently, MR imaging is probably most commonly used to image patients with ambiguous electrodiagnostic studies and clinical examinations. In the near future, MR diffusion-weighted imaging should be possible for peripheral nerves. As is the case with brain imaging, diffusion-weighted imaging of peripheral nerves is likely to be the most sensitive imaging modality for the detection of early nerve dysfunction. Electrodiagnostic studies are likely to remain the pivotal diagnostic examination in patients with suspected CTS for the foreseeable future. With advances in software and hardware, however, high-resolution MR imaging of peripheral nerves should become faster, less expensive, and probably more accurate, possibly paving the way for an expanded role in the diagnosis of this common syndrome.