subarachnoid hemorrhage - ct angiograph

7/28/2019 Subarachnoid Hemorrhage - CT Angiograph

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Subarachnoid Hemorrhage

Intracranial saccular aneurysms represent the most common etiology of

nontraumatic subarachnoid hemorrhage (SAH), with about 80% of SAH resulting

from ruptured aneurysms.

Pathophysiology

Aneurysms are acquired lesions related to hemodynamic stress on the arterial

walls at bifurcation points and bends. Saccular or berry aneurysms are specific to the

intracranial arteries because their walls lack an external elastic lamina and contain a

very thin adventitiafactors that may predispose to the formation of aneurysms. An

additional feature is that they lie unsupported in the subarachnoid space.

Aneurysms mostly arise from the terminal portion of the internal carotid artery

(ICA) and from the major branches of the anterior portion of the circle of Willis. In a

25-year autopsy study of 125 patients with ruptured or unruptured aneurysmsconducted at Johns Hopkins, hypertension, cerebral atherosclerosis, vascular

asymmetry in the circle of Willis, persistent headache, pregnancy-induced

hypertension, long-term analgesic use, and family history of stroke all were correlated

positively with the formation of saccular aneurysms.

The occurrence of aneurysms in children indicates the role of intrinsic

vascular factors. A number of disease states resulting in weakness of the arterial wall

are associated with an increased incidence of berry aneurysms.

Hypertension (previously documented acute severe hypertension with diastolic

value over 110 mm Hg), smoking, alcohol, multiple aneurysms, increasing aneurysmsize, fatty metamorphosis of the liver, long-term analgesic use, and oral

contraceptives have been linked to aneurysmal subarachnoid hemorrhage.

Disease states associated with higher incidence of berry aneurysms include the

following:

Increased blood pressure - Fibromuscular dysplasia, polycystic kidney disease, andaortic coarctation

Increased blood flow - Cerebral arteriovenous malformation (AVM); persistentcarotid-basilar anastomosis; ligated, aplastic, or hypoplastic contralateral vessel

Blood vessel disorders

Systemic lupus erythematosus (SLE), Moyamoyadisease[1] , and granulomatous angiitis

Genetic - Marfan syndrome, Ehlers-Danlos syndrome, Osler-Weber-Rendusyndrome, pseudoxanthoma elasticum, and Klippel-Trenaunay-Weber syndrome

Congenital - Persistent fetal circulation and hypoplastic/absent arterial circulation Metastatic tumors to cerebral arteries -Atrial myxoma, choriocarcinoma, and

undifferentiated carcinoma

Infectious - Bacterial, fungalCT without contrast

CT is the most sensitive imaging study in subarachnoid hemorrhage.
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CT scan reveals subarachnoid hemorrhage in the right sylvian fissure; no evidence

of hydrocephalus is apparent.

CT scan reveals subarachnoid hemorrhage in the sylvian fissure, right more thanleft.

A 47-year-old woman presented with headache and vomiting; her CT scan in theemergency department revealed subarachnoid hemorrhage.
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Findings may be negative in 10-15% of patients with SAH. Maximum sensitivity

is within 24 hours after the event; sensitivity is 80% at 3 days, 50% at 1 week. When

carried out within 6 hours of headache onset, CT has 100% sensitivity and specificity.

Look for evidence of hydrocephalus (trapped temporal horns and "Mickey Mouse"

appearance of ventricular system). Look for intraparenchymal clot, intraventricularhematoma, and interhemispheric hematoma. Degree and location of SAH are

significant prognostic factors.

The Fisher grading system is used to classify SAH, as follows:

- Grade I - No subarachnoid blood seen on CT scan

- Grade II - Diffuse or vertical layers of SAH less than 1 mm thick

- Grade III - Diffuse clot and/or vertical layer greater than 1 mm thick

- Grade IV - Intracerebral or intraventricular clot with diffuse or no subarachnoid

blood

Cerebral angiography

To assess the following:

Vascular anatomy

Cerebral angiogram reveals a middle cerebral artery aneurysm.

Cerebral angiogram reveals a middle cerebral artery aneurysm.

Cerebral angiogram (lateral view) reveals a large aneurysm arising from the leftanterior choroidal artery.
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Cerebral angiogram (anteroposterior view) reveals a large aneurysm arising from

the left anterior choroidal artery. Site of bleed (location of aneurysm that bled this time) Presence of other aneurysms (about 20% have multiple aneurysms) Operative planning Negative angiographic findings do not rule out aneurysm. Approximately 10-

20% of patients with clinically diagnosed SAH (CT and/orlumbar puncture) havenegative angiographic findings. A repeat angiogram is usually required in 10-21

days.
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subarachnoid hemorrhage - ct angiograph

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