The Gilliatt-Sumner hand: a diagnostic clue of neurogenic thoracic outlet syndrome

An 18-year-old, right-handed woman presented with a two-year history of progressive weakness and wasting of her right thenar muscles. She had no history of significant illness or trauma. Physical examination revealed predominant weakness and atrophy in her abductor pollicis brevis (APB) muscle (Figure 1A). She complained of paraesthesia over her medial forearm. Nerve conduction study (NCS) revealed unrecordable medial antebrachial cutaneous sensory potentials, and low-amplitude median motor potentials, findings that were consistent with disturbance at the lower trunk of the brachial plexus. Magnetic resonance image (MRI) detected a fibrous band causing distortion of the lower trunk of the right brachial plexus (Figure 1B and C). Based on these findings, the patient received a diagnosis of neurogenic thoracic outlet syndrome (NTOS). NTOS is a common form of thoracic outlet syndrome, which is a group of disorders involving the compression of neurovascular structures in the region above the first rib and behind the clavicle.1,2 NTOS is typically caused by a lesion affecting the lower trunk of the brachial plexus. Gilliatt-Sumner hand,3 a constellation of symptoms that includes predominant atrophy of the APB muscle, additional atrophy of the interosseous and abductor digiti minimi muscles, and normal sensation within the region innervated by the median nerve (including the thenar eminence), is a diagnostic indicator of NTOS. If a sensory abnormality exists, it primarily involves the medial forearm, not the area innervated by the median nerve. These are the points that distinguish NTOS from other conditions that include atrophy of the thenar muscles, such as carpal tunnel syndrome, amyotrophic lateral sclerosis, and Hirayama disease. Electrodiagnostic and imaging studies can aid in confirmation of the diagnosis. NCS can distinguish plexopathy from distal neuropathy4 and MRI can detect compression of the lower trunk of the brachial plexus.2,5 NTOS remains underdiagnosed despite being a treatable condition. Therefore, when patients present with Gilliatt-Sumner hand, clinicians should consider NTOS and confirm the diagnosis with electrodiagnostic and imaging studies. (A) Severe atrophy of the APB muscle (arrowhead) and mild atrophy of the abductor digiti minimi muscle (arrow) on the right side. Mild atrophy of the first dorsal interosseous muscle (arrow) on the right side. (B) Coronal 3D short-tau inversion recovery (STIR) MRI showing distortion of the lower trunk of the brachial plexus on the right side (arrowhead). (C) In contrast to the 3D STIR image, the oblique sagittal reconstructed 3D T2-weighted image more clearly revealed a fibrous band (arrows) compressing the lower trunk of the right brachial plexus (arrowhead). The authors would like to thank the members of the Electrodiagnostic Medicine Group of Hiroshima University (especially Dr Nakamori, Dr Dohi, Dr Shinozaki, Dr Naito and Ms. Hironaka) for helpful discussions. Conflict of interest: None declared.