Over an 18-month period (June 1994-December 1994), all patients presen
ting with a subarachnoid haemorrhage (SAH) were considered for magneti
c resonance angiography (MRA) as part of their investigation. Our expe
rience to date leads us to believe that anterior midline aneurysms can
be confidently and rapidly diagnosed with MRA alone without recourse
to invasive intra-arterial digital subtraction angiography. This assum
es, of course, that images can be obtained; some patients cannot be in
vestigated by MR because of the presence of metallic foreign bodies; i
n a small proportion without anaesthesia the images will be so degrade
d as to be valueless and some patients will be judged unsuitable from
the outset because of their clinical state. In 30 patients, a diagnosi
s of an anterior midline aneurysm was made on MRA and 21 of these pati
ents underwent surgery on the MR images alone. Surgery, undertaken via
a midline approach in these 21 patients, confirmed the MR findings.