"Nidus sparing sign" on computerized tomography in intracerebral haemorrhage due to a rupture of arteriovenous malformation.

The authors investigated the validity of noncontrast computerized tomography (NCCT) to predict the presence of arteriovenous malformations (AVM) as a cause of intracerebral haemorrhage (ICH) in the acute stage. They found a small iso- or slightly hyperdense nodular or tubular defect devoid of haematoma in its periphery on NCCT in 8 of the 13 AVM cases that underwent both NCCT and contrast CT. This CT finding was named "nidus sparing sign" (NSS). This haematoma-free notch was enhanced on contrast infusion and confirmed to correspond to the AVM nidus surgically and pathologically. In one case with negative angiograms, a small AVM was verified histologically within the tissue corresponding to the NSS. The NSS noted on the NCCT could be of great value in case emergency surgery is needed for comatose patients with ICH, particularly lobar ICH, without enough time left to undergo angiography and/or magnetic resonance imaging. Neurosurgeons are able to safely perform an evacuation of the haematoma keeping in mind the possibility of a ruptured AVM and if so, the spatial relationship between the AVM nidus and the haematoma. This might also be a valuable CT sign in deciding whether or not angiography should be undertaken in ICH cases.