Visualization of intraneural edema using gadolinium-enhanced magnetic resonance imaging of carpal tunnel syndrome

Background: In general, carpal tunnel syndrome (CTS) is diagnosed based mainly on clinical findings and electrophysiology. However, the pathological state of the compressed median nerve could not be shown on imaging. Gadoliniumenhanced magnetic resonance (MR) imaging may give us an idea about the status of the blood-nerve barrier of peripheral nerves. Therefore, detecting intraneural edema may be a way of diagnosing entrapment neuropathy. The present study investigated the diagnostic role of gadolinium-enhanced MR imaging of CTS. Methods: The subjects were 23 patients (34 hands) with idiopathic CTS. To serve as control subjects, 12 wrists of asymptomatic volunteers were studied. Using the spin-echo method, T1- and T2-weighted axial MR images were obtained. Intravenously injected gadolinium was used to obtain enhanced images. We studied the relation between nerve enhancement and the symptomatology. Results: After intravenous injection of gadolinium, there was no enhancement of the unaffected nerves in the carpal tunnels of the control group. Gadolinium enhancement was found in only 87% of patients with CTS who visited the hospital at an early stage and therefore had no nerve deficiency on electrophysiological studies (39%). Based on this finding, during the early stages when the nerve is in a state of neuropraxia, gadolinium-enhanced MR imaging of the median nerve might prove to be the most sensitive modality for detecting early nerve dysfunction. MR imaging also revealed a higher frequency of enhancement in the advanced stage of CTS with muscle atrophy. Conclusions: We conclude that gadolinium-enhanced MR imaging can detect not only morphological changes but also pathological changes of the median nerve in patients with CTS. Currently, gadolinium-enhanced-MR imaging is probably most commonly used to image patients who have ambiguous electrodiagnostic studies and clinical examination in an early stage of CTS. © 2009 The Japanese Orthopaedic Association.