A 32 year old female was admitted to a general district hospital with a 3 day history of aches in the legs, fever (38 °C), urinary retention and leg weakness. Neurological examination revealed a flaccid tetraparesis with abolished abdominal and ankle reflexes, diminished knee reflexes, bilateral extensor plantar responses, and sensory level at T12. The patient was given high dose intravenous prednisone (1 g) for 5 consecutive days. She became bedridden with complete paraplegia of the legs and was referred to our department. Upon admission, in addition to a flaccid tetraparesis (strength 1/5 in the legs and 4/5 to 4±5 in the arms, MRC grade) with abolished abdominal, knee and ankle reflexes, extensor plantar responses, and sensory level at T5, a bilateral gaze evoked nystagmus was detected. Urodynamic examination revealed an atonic bladder. Lumbar puncture revealed a pleocytosis (34/mm3; 84% lymphocytes) and a cerebrospinal fluid (CSF) protein of 132 mg/dl. Neither intrathecal immunoglobulin synthesis nor oligoclonal bands were detected. Complete microbiological and virological investigations on CSF and blood specimens were negative. Further negative findings included serum angiotensin converting enzyme, anti-nuclear antibodies, anti-neutrophil cytoplasmic antibodies, and onconeuronal antibodies. Serological testing for anti-ganglioside antibodies (Ganglio-combi test; Bühlmann Laboratories) showed elevated titres for asialo-GM1 (4283 Bühlmann titre units (BTU); normal<1700), GM1 (2855 BTU; normal<1700) and GQ1b (4117 BTU; normal<1700). Magenetic resonance imaging (MRI) of the spinal cord depicted an extensive cervicothoracic myelopathy (fig 1A–D). On MR images of the brain, multiple dot-like cortical and subcortical lesions were delineated, predominantly located in the frontoparietal gray and white matter (fig 1E–G). Electrodiagnostic studies indicated a severe symmetrical demyelinating neuropathy with reduced motor conduction velocities (right peroneal nerve 12.8 m/s, right tibial nerve 16.0 m/s, and right median 44 m/s), prolonged distal latencies (right peroneal nerve 17.1 ms, right tibial nerve 14.5 ms, and right median 5.3 ms), and prolonged or absent F waves, with MUAP displaying temporal dispersion and diminished amplitudes, and with electromyographic signs of acute denervation. The sensory action potentials and conduction velocities were normal.