Differentials
Non-aneurysmal perimesencephalic SAH
SIGNS / SYMPTOMS
There are no features in the history or on examination that differentiate this condition from subarachnoid haemorrhage (SAH).
INVESTIGATIONS
No aneurysms are found on angiography. CT usually reveals subarachnoid blood in front and around the pons (perimesencephalic or pontine cistern). Caution is required when this blood distribution pattern is seen, as it may also be seen with a ruptured aneurysm located in the posterior circulation.[91] Overall, it has a better outcome than SAH.
Arterial dissection
SIGNS / SYMPTOMS
Pain is less severe and is frequently felt behind the eye or localised to anterior or posterior neck region. Dull neck pain might precede a more severe pain, occurring at the time of SAH. Examination findings might include a Horner’s sign and/or neurological deficits related to stroke secondary to dissection.
INVESTIGATIONS
Dissected arteries are visualised on cerebral angiography, magnetic resonance angiography (MRA), or computed tomography angiography (CTA). Axial T1 and T2 fat-suppressed neck MRI images might visualise the characteristic intramural haemorrhage associated with dissection.
Cerebral and cervical arteriovenous malformation (AVM)
SIGNS / SYMPTOMS
Symptoms and signs are similar to SAH. Subarachnoid haemorrhage could be preceded or accompanied by findings related to mass effect caused by the AVM.
INVESTIGATIONS
Arteriovenous malformations visualised on cerebral angiography, MRA, or CTA.
Dural arteriovenous fistulae (AVF)
SIGNS / SYMPTOMS
Symptoms and signs are similar to SAH.
INVESTIGATIONS
Arteriovenous fistulae visualised on cerebral angiography, MRA, or CTA.
Vasculitis
SIGNS / SYMPTOMS
A subacute to chronic history of recurrent neurological deficits, with corresponding abnormalities on examination. Headache is usually less severe.
INVESTIGATIONS
Cerebrospinal fluid pleocytosis may be present. Angiography might disclose beading of medium and small intracranial arteries. Brain and meningeal biopsy is, however, the diagnostic standard for this condition.
Saccular aneurysms of spinal arteries
SIGNS / SYMPTOMS
Pain localised to posterior neck/occipital area. Meningismus might be more prominent. A sciatica-like picture due to blood in the lumbar thecal sac can be seen.
INVESTIGATIONS
Spinal angiography visualises the aneurysm(s).
Cardiac myxoma
SIGNS / SYMPTOMS
Age between 30 and 60 years. Cardiac, obstructive, or constitutional symptoms precede SAH.
INVESTIGATIONS
Echocardiography is method of choice for diagnosis.
Septic (mycotic) aneurysm
SIGNS / SYMPTOMS
On physical examination there may be a fever, heart murmur, skin petechiae, Osler's nodes, Janeway lesions, splinter haemorrhages under the nails, and Roth spots in optic fundi. Ischaemia may occur in the bowel and spleen.
INVESTIGATIONS
Subarachnoid blood is usually focal, not widely distributed in cisterns, fissures, and sulci as in SAH. Blood cultures may be positive. Blood tests may show an elevated erythrocyte sedimentation rate and peripheral leukocytosis. Cerebral angiography reveals aneurysms located distally, typically in the distribution of the middle cerebral artery. Intracerebral haematomas are likely to be seen on CT. Echocardiography might reveal valvular vegetations.
Pituitary apoplexy
SIGNS / SYMPTOMS
Patients have a known history of pituitary adenoma. Visual loss is seen in up to half of patients with pituitary apoplexy (not a feature of SAH). Acute adrenal insufficiency develops in two-thirds of patients.
INVESTIGATIONS
MRI with contrast shows pituitary haemorrhage or infarction. Subarachnoid blood is minimal and confined to the region around the pituitary gland.
Cocaine abuse
SIGNS / SYMPTOMS
There is a history of drug abuse preceding the event. The headache is usually less severe.
INVESTIGATIONS
Urine drug screen is positive for cocaine. Subarachnoid blood is usually minimal and focal in sulci. CT might also reveal intracerebral haematomas.
Anticoagulant-associated intracranial haemorrhage
SIGNS / SYMPTOMS
There is a history of anticoagulant use. The headache is less severe.
INVESTIGATIONS
A CT shows minimal subarachnoid blood and possible intracerebral haematomas. Coagulation studies are abnormal (prolonged PTT and/or elevated INR).
Sickle cell disease
SIGNS / SYMPTOMS
There is a history of sickle cell disease, previous strokes, or sickling episodes.
INVESTIGATIONS
Computed angiography might reveal intracerebral haematomas associated with subarachnoid blood. Haemoglobin S is identified upon testing.
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