We report the case of a 31-year-old man with a finger drop variant of Guillain-Barré syndrome (GBS). The patient visited a neurological clinic with complaints of difficulty in extending the fingers, which occurred seven days after he had fever and diarrhea. The physician who first saw the patient suspected posterior interosseous nerve palsy and referred him to our hospital. Neurological examination 35 days after the onset revealed distal weakness of the upper extremities, particularly in the bilateral extensor digitorum (Medical Research Council [MRC] scale 1/1 [right/left]). The left triceps surae muscle was also weak (MRC scale 5/4). Bilateral Achilles tendon reflexes were absent, but other neurological findings were normal. Cerebrospinal fluid examination showed albuminocytologic dissociation. Serum immunoglobulin G antibodies against GM1 were positive. Nerve conduction studies revealed reduced amplitude of compound muscle action potentials (CMAPs) without evidence of demyelination in the median, ulnar, radial, and tibial nerves. CMAP amplitude was most severely reduced in the radial nerve among the upper extremity nerves. We diagnosed the patient with acute motor axonal neuropathy. His symptoms gradually improved after treatment with intravenous immunoglobulin. When encountering acute finger drop, neurologists should consider the finger drop variant of GBS as a differential diagnosis.
Keywords: Guillain–Barré syndrome; acute motor axonal neuropathy; anti-GM1 antibodies; drop finger; finger drop variant.