Subacute Upper Motor Neuron Dysfunction Possibly Associated with the Anti-GM1 Autoantibody: A Case Report

Anti-GM1 antibodies are associated with Guillain-Barré syndrome (GBS), primarily peripheral neuropathy. However, there are cases of anti-GM1 IgG antibody-positive GBS with upper motor neuron (UMN) signs. We herein report a case of gastrointestinal infection followed by subacute gait disturbance with predominant signs of UMN on a neurological examination. The serum and cerebrospinal fluid tests were positive for anti-GM1 and anti-asialo-GM1 IgG antibodies. An electrophysiological evaluation revealed normal nerve conduction and prolonged central motor conduction times. No MRI abnormalities were observed. The symptoms improved with treatment, which was accompanied by decreased antibody titers. This case highlights the fact that anti-GM1 IgG-associated disorders may present with predominant UMN involvement.