The influence of head position upon head tremor.

A young man, known to have tuberous sclerosis, recently presented to us with tiredness and recurrent seizures after being fit free for fifteen years. Removal of an insulinoma led to complete relief ofsymptoms which had for some time been attributed to the tuberous sclerosis. The patient was a 23 year old man. Diagnosis of tuberous sclerosis was made in childhood. He had adenoma sebaceum and mild mental retardation. He had had generalised seizures up to the age of seven years and had then been fit free until 18 months before presentation. Seizures continued despite therapeutic levels of carbamazepine and primidone. He also complained of sleepiness after exertion and an increased appetite for sweet foods. There was no family history of tuberous sclerosis. Apart from the typical skin changes and retardation there were no abnormal physical findings. His weight was normal for his height and there had been no change in weight. CT scanning of the brain showed the typical intracerebral masses of tuberous sclerosis. He was referred for investigation when a plasma glucose of 1-7 mmol/l (normal range 4 5-10 mmol/l) was noted following a seizure. Excess insulin excretion was demonstrated 9 hours into a fast when he suffered a generalised seizure with plasma glucose 1-2 mmol/l and insulin 55 mIU/l (expected <10 in presence of hypoglycaemia). Whilst CT of the pancreas was unremarkable, coeliac angiography demonstrated a 3 cm blush in the inferior portion of the pancreatic head. A benign islet cell tumour was subsequently removed. He has remained seizure free and maintains a normal blood sugar without excess carbohydrates. There is only one other reported case of insulinoma complicating tuberous sclerosis and as in our patient the diagnosis was delayed.' A second patient has been reported with a non-functioning islet-cell tumour found at necropsy. She also had hyperparathyroidism as part of a multiple endocrine neoplasia. Her mother had a parathyroid adenoma and adenoma sebaceum, probably representing a forme fruste of tuberous sclerosis.2 There may be a more than chance association between these two rare conditions. The incidence of insulinoma is estimated at one case per million per year3" and the point prevalence of tuberous sclerosis at 10-6 per 100 000 persons in a community based study.' Insulinoma should be considered in patients with tuberous sclerosis who present with recurrent or uncontrolled fitting. PM DAVOREN MT EPSTEIN Royal Newcastle Hospital, Newcastle, NSW Australia