Saccular (berry) aneurysms
• Saccular aneurysms develop within the circle of Willis
and adjacent arteries. Common sites are at arterial
– Between posterior communicating and internal carotid
artery – posterior communicating artery aneurysm
– Between anterior communicating and anterior cerebral
artery – anterior communicating and anterior cerebral
– At the trifurcation or a bifurcation of the middle cerebral
artery – middle cerebral artery aneurysm.
• Aneurysms cause symptoms either by
spontaneous rupture, when there is usually no
preceding history, or by direct pressure on
– For example, an enlarging unruptured posterior
communicating artery aneurysm is the
commonest cause of a painful IIIrd nerve palsy.
Arteriovenous malformation (AVM)
• AVM are vascular developmental malformations, often with a fistula
between arterial and venous system causing high blood flow through the
• Once an AVM has ruptured, the tendency is to rebleed – 10% will then do
• They maybe ablated with endovascular treatment (catheter injection of
glue in the nidus)
Clinical features of SAH
• There is a sudden devastating headache, often occipital.
• Headache is usually followed by vomiting and often by
coma and death.
• Survivors may remain comatose or drowsy for hours, days,
• SAH is a possible diagnosis in any sudden headache.
• Following major SAH there is neck stiffness and a positive
• CT imaging is the immediate investigation
• Subarachnoid and/or intraventricular
blood is usually seen.
• Lumbar puncture is not necessary if SAH is
confirmed by CT, but should be performed if
• CSF becomes yellow (xanthochromic) several hours after SAH.
• Spectrophotometry to estimate bilirubin in the CSF released
from lysed cells is used to define SAH with certainty.
• MR angiography is usually performed in all potentially fit for
surgery, i.e. generally below 65 years and awake.
• In some, no aneurysm or source of bleeding is found, despite
a definite SAH.
• SAH must be differentiated from migraine.
• Thunderclap headache is used (confusingly) to describe either SAH
or a sudden (benign) headache for which no cause is ever found.
• Acute bacterial meningitis occasionally causes a very abrupt
headache, when a meningeal microabscess ruptures.
• SAH also occasionally occurs at the onset of acute bacterial
• Cervical arterial dissection can present with a sudden headache.
• Immediate treatment of SAH is bed rest and
• Hypertension should be controlled.
• Dexamethasone or mannitol is often prescribed
to reduce cerebral oedema.
• Nimodipine, a calcium-channel blocker, reduces
• Nearly half of SAH cases are either dead or moribund before reaching
• Of the remainder, a further 10–20% rebleed and die within several weeks.
• Patients who remain comatose or who have persistent severe deficits have
a poor outlook.
• In others, who are less impaired, and where angiography demonstrates
aneurysm, either a direct approach to clip the aneurysm neck or
intravascular coiling is carried out.
• For AVMs, surgery, and focal radiotherapy (gamma knife) are used, when
• Kumar & Clark's clinical medicine 7th edition