Median nerve conduction studies and wrist magnetic resonance imaging in acromegalic patients with carpal tunnel syndrome

Purpose: Carpal tunnel syndrome (CTS) often occurs with acromegaly; however, the pathophysiology of CTS in acromegalic patients remains unclear. This study evaluated the median nerve in acromegalic patients with and without CTS. Methods: We examined the median nerves of 21 acromegalic patients (eight patients with CTS and 13 patients without CTS) using electrophysiological nerve conduction studies and wrist magnetic resonance images. They underwent transsphenoidal surgery to resect their growth hormone-secreting pituitary adenomas. The median nerves of the patients with CTS were reassessed by the same studies. Results: The sensory conduction velocity was significantly later in the median nerves of patients with CTS than in patients without CTS (34.9 vs. 45.8 m/s, respectively; P = 0.006). In the wrist magnetic resonance images, the cross-sectional area of the median nerve in CTS patients and non-CTS patients was 18.7 and 10.5 mm², respectively. The median nerve was significantly larger in patients with CTS than in patients without CTS (P < 0.003). The flattering ratio of the median nerve and palmar deviation of the flexor retinaculum were not significantly different between the two patient groups. After tumor resection, the nerve conduction velocities improved in patients with CTS, but the nerve remained enlarged. The CTS symptoms disappeared in all patients, except one. Conclusions: The median nerves of acromegalic patients with CTS were enlarged and had impaired nerve conduction. This finding represents a predominant intrinsic feature in the pathophysiology of the disease rather than an extrinsic feature such as a thickened transverse carpal ligament.