Anomalous cerebral venous sinus drainage.

The case discussed is a 58 year old female that presented with sudden onset of headache, a Glasgow Coma Score of 15 and no neurological deficit. Computed tomography (CT) scan of the brain did not show any evidence of haemorrhage. CT angiography revealed a left sided cerebellar ateriovenous malformation with the Digital Subtraction Angiography (DSA) also showing anomalous posterior fossa venous sinus anatomy. In this case the occipital sinus provided the only drainage pathway for both the superior sagittal sinus (SSS) and the straight sinus. Of clinical significance is during the routine method of access to midline posterior fossa surgery the occipital sinus is ligated and divided. This would have resulted in massive venous infarction. Highlighting the importance of reviewing the venous anatomy on radiological images prior to neurosurgical procedures.