Thymoma-Associated Progressive Encephalomyelitis with Rigidity and Myoclonus Successfully Treated with Thymectomy and Intravenous Immunoglobulin

cle spasms were frequently experienced. Her neck, trunk and extremities showed rigido-spasticity. Painful spasms were easily elicited by auditory, visual and tactile stimuli. Reflex myoclonus was also observed. Hyper-reflexia was seen in 4 limbs and pathological reflexes were bilaterally positive. Sensation was normal. Blood cell counts and serum chemistry revealed no abnormalities. The anti-glutamic acid decarboxylase (GAD) antibody level was 9,020 U/ml in serum and 109 U/ml in cerebrospinal fluid (normal 1.5). Anti-acetylcholine receptor antibody was positive at a titer of 11.9 nmol/l (normal 0.2). Serum anti-amphiphysin antibody was negative. Cerebrospinal fluid analysis showed no abnormality. Head and spinal cord MRI was normal. There was no slowing in electroencephalography. Nerve conduction study was normal. There was no decrease in compound muscle action po tential on repetitive stimulation of the median nerve. Needle electromyography revealed continuous contraction of both agonist and antagonist muscles in the extremities ( fig. 1 A). Thoracic CT depicted the presence of thymoma in the anterior mediastinum ( fig. 1 B).