A 70 year old male presented in February 2000 with persistent cough. Chest radiograph revealed a mediastinal abnormality. A computed tomography (CT) scan of the thorax confirmed an anterior mediastinal mass. CT guided mediastinal biopsy was performed but proved inconclusive. The patient declined further invasive investigation for 2 years. After follow up CT showed significant enlargement he underwent surgery in September 2002. An excellent post operative recovery was made. Histology confirmed a minimally invasive thymoma.

However, 6 weeks later he developed progressive proximal leg weakness, lethargy, and night sweats. He described a sensation like “someone touching his legs” and became agitated and restless at night. He was readmitted in November 2002 and on the first night became acutely confused and markedly disorientated with visual hallucinations.

On examination he was agitated and confused. His eyes opened spontaneously, there was no coherent verbalisation, and he withdrew to pain. He was apyrexial although there was marked hyperhidrosis and hypersalivation. Blood pressure was 120/70 mm Hg, and pulse was 98 bpm and regular. He had profuse diarrhoea although his abdomen was soft and non-tender. There were irregular myoclonic jerks of all four limbs predominating in his upper limbs as elbow flexion jerks. There was no startle reaction. Cranial nerve examination was unremarkable. Power and deep tendon reflexes were normal and plantar responses flexor. Intravenous phenytoin was administered with resolution of the myoclonic movements.

Laboratory investigations including electrolytes, auto-antibody screen, and anti-neuronal antibodies were unremarkable. Cerebral spinal fluid (CSF) was clear, colourless, and acellular, CSF glucose was 4.0 mmol/l …