Recurrent cerebral abscess in association with pulmonary arteriovenous fistulae.

pressure on the third nerve by the basilar aneurysm. The oculomotor nerve is closely related to the bifurcation of the basilar artery, and such aneurysms may cause third nerve palsy.1 Isolated internal ophthalmoplegia with basilar aneurysm, however, has not been described. Oculomotor palsy characteristically occurs with aneurysms of the posterior communicating artery at the time of rupture or rapid enlargement.2 Pupillary dilatation without external ophthalmoplegia was reported in a case of Payne and Adamkiewicz3 in which the mydriasis was present for two weeks before surgery and persisted after operation. Pupillary dilatation may precede other signs in third nerve compression due to uncal herniation as the pupillomotor fibres are situated in an arc superficially on the superior surface of the nerve.4 Acute hydrocephalus was present in our patient, but there was no coincidental deterioration in his conscious level, neurological state, heart rate or blood pressure. However, oculomotor nerve compression at the tentorial hiatus may have been the cause of the transient mydriasis in the patient reported here, as ventricular dilatation is a known complication following subarachnoid haemorrhage and is caused by blockage of arachnoid villi by blood and breakdown products.@ Unilateral pupillary dilatation may occur with seizures,6 but in such cases the mydriasis is accompanied by conjugate deviation of the eyes and occurs during or immediately following the seizure. In our case it occurred 16 hours after the ictus. Transient unilateral pupillary dilatation associated with a clinical picture of subarachnoid haemorrhage therefore may be of some diagnostic value and has not been reported hitherto in association with basilar aneurysm. The present case serves to emphasise the importance of proceeding to vertebral angiography as many aneurysms in the posterior cerebral circulation can now be treated surgically with excellent results.