Recurrence of carpal tunnel syndrome in isolated non-syndromic macrodactyly: DTI examination of a giant median nerve.

Macrodystrophia lipomatosa, a hamartomatous enlargement of soft tissues leading to gigantism of a part or a whole extremity, generally affects the territory of distribution of a single nerve. In some cases, this condition may cause an entrapment neuropathy. We report the clinical, radiological, and surgical findings of a patient with isolated non-syndromic macrodactyly and giant median nerve presenting recurrent carpal tunnel syndrome (CTS). In this case, conventional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) supported the presence of fibrohamartomatous infiltration, determining an enlargement of the median nerve and consequently an increased susceptibility to compression damage. A 57-year-old man presenting macrodactyly of the second and third finger of the right hand showed recent onset of severe hypoesthesia of the first three fingers of the right hand. He also underwent surgery for right CTS 23 years before. The electromyography/electroneurography confirmed the diagnosis of CTS. The ultrasonography showed a massive enlargement of the median nerve within the carpal tunnel, while MRI confirmed the enlargement of the median nerve with thickened hypointense bundles and interposed tissue, with increased mean diffusivity and decreased fractional anisotropy at DTI. We discuss about the use of a relatively novel imaging technique, investigating for the first time an uncommon cause of a very common entrapment neuropathy.