Lacertus notch as a sign of lacertus syndrome

Objective Many clinicians are unfamiliar with a diagnosis of lacertus syndrome (LS). We investigated the value of the lacertus notch sign in diagnosing LS. Methods We included 56 consecutive patients (112 upper extremities) who had neuropathic pain and neurological symptoms of the hand. The presence of LS and the lacertus notch sign in each upper extremity was assessed. Results Of the 83 upper extremities with LS, 54 (65.1%) had a lacertus notch sign, whereas 29 (34.9%) did not. Of the 29 upper extremities without LS, 9 (31.0%) and 20 (69.0%) had and did not have a lacertus notch sign, respectively. The rates of lacertus notch presence in upper extremities with and without LS were significantly different. Of the 63 upper extremities with a lacertus notch sign, 54 (85.7%) were diagnosed with LS, whereas 9 (14.3%) were not. Of the 49 upper extremities without a lacertus notch sign, 20 (40.8%) were diagnosed with LS, and 29 (59.2%) were not. We observed significant differences in the rates of LS in upper extremities with and without lacertus notch. Conclusions The presence of the lacertus notch sign is useful for diagnosing LS. When patients with neuropathic pain and neurological symptoms present with a lacertus notch sign, clinicians should consider the possibility of LS.