Ces radiol. 2007, 61(3):255-263

Noninvasive diagnosis of subarachnoid haemorrhageReview article

Miroslav Heřman

Radiologická klinika LF UP a FN, Olomouc

Present knowledge of non-invasive diagnosis of traumatic, as well as spontaneous subarachnoid haemorrhage, is summarised in this review. Unenhanced CT represents the method of choice for investigation of both types of subarachnoid haemorrhage. Fresh blood is depicted as a hyperdense filling of subarachnoid spaces, where it replaces the hypodense cerebro-spinal fluid. The subarachnoid haemorrhage caused by trauma is usually found in association with other intracranial traumatic changes and signals an unfavourable prognosis. When a subarachnoid haemorrhage is detected on CT early after an accident, there is a high probability that a worsened finding will appear on follow-up examination. The unenhanced CT is also used to detect spontaneous subarachnoid haemorrhage. Where the CT finding is negative and there is a high probability of subarachnoid haemorrhage, a delayed lumbar puncture is recommended. It should be performed at least six hours after problems have arisen, and a delay of as much as twelve hours is preferable. When CT or the lumbar puncture provide evidence of a subarachnoid haemorrhage, the cause of this haemorrhage needs to be investigated. The most frequent cause is a ruptured aneurysm (75 %), while in 10 % of patients a non-aneurysmal perimesencephalic subarachnoid haemorrhage is proven, in 10 % no cause is found at all and the remaining 5 % stem from other haemorrhages with a different aetiology, such as arteriovenous malformation (AVM), arterial dissection, tumour, vasculitis, coagulopathy etc. The cause of a subarachnoid haemorrhage can be predicted from the distribution of blood on unenhanced CT images. In all cases (with the exception of perimencephalic haemorrhage) a variable amount of blood may also occur intracerebrally, in the ventricles, or within the subdural space. Non-invasive imaging methods - CT angiography (CTA) and less frequently MR angiography (MRA) - are preferred to provide confirmation of the cause of the haemorrhage. Angiography (DSA) is nowadays only performed for diagnostic reasons when CTA or MRA findings are negative or directly before interventional radiological treatment.

Keywords: CT, CTA, subarachnoid haemorrhage, brain, MRA

Accepted: July 10, 2007; Published: September 1, 2007  Show citation