Cerebral aneurysm
Cerebral aneurysm
Cerebral aneurysm
· Symptoms – history of migraines, persistent headache with several months duration, different from usual headache
· Imaging
o Computer tomography – CT
§ Fast and readily available
§ Excellent for detection of acute hemorrhage
o Magnetic resonance imaging - MRI
§ Higher soft tissue resolution / contrast
§ Multiplanar capability
o Plain film – not indicated
· Normal Head CT
o Blood, acute
§ High attenuation – bright
o Midline – is symmetry preserved
o Ventricles
o Cisterns
o Sulci
o Grey white matter interface
o Soft tissue
o Bones
o Sinuses
· Precontrast
o Spherical mass, smooth margin, high attenuation, slight mass effect, located just anterior to the circle of Willis. No acute haemorrhage, edema or infarct
o At the level of the midbrain and cerebellum
o Differential diagnosis: Tumour, Hematoma, Abscess, AVM, Aneurysm
o Consider IV contrast and MRI
· Post Contrast CT
o Brightly enhancing round lesions suggestive of cerebral aneurysms
Circle of Willis - http://www.strokecenter.org/education/ais_vessels/ais048.html
· Communicating system of vessels that supplies blood to the brain
· Anterior portion fed by the internal carotid arteries
· Posterior portion fed by the vertebral arteries
Tests for evaluating suspected Cerebral Aneurysms
· CT plus contrast, MRI, MRA, Cerebral angiography
MR – T1 sequence
· T1 Sequence
o Fat has a high signal and appears bright, CSF has a low signal and is dark
o Mass characteristics
§ Low signal emission – flow void, moving blood is dark
§ Position adjacent to ICA
· T2 Sequence
o Round lesions with flow void confirmed
Magnetic Resonance Angiography – MRA
· MR technique for imaging vessels. Uses MR pulse sequence – “Time of Flight” that can turn flowing blood into strong signal – “white blood”
· Does not require contrast, non-invasive
· Can convert a stack of contiguous MR slices into a 3D angiographic model – excellent visualisation of the Circle of Willis and aneurysm characterisation
· Traditional angiography remains the gold standard
· Findings: Internal carotid artery aneurysms
o Giant suprasellar internal carotid artery – ICA – aneurysm
o Supraclinoid internal carotid aneurysm
Treatment options:
· Surgical clipping
· Angiographic embolisation
Cerebral Aneurysms
· Cerebral aneurysms are dilatations or outpouchings of the arterial wall
o Saccular – “berry” or fusiform – dilated and elongated
o Mycotic, neoplastic, traumatic
· Saccular aneurysms form secondary to weakness in the media and elastica of the arterial wall – typically occur at the vessel bifurcations or branching
o Frequency 3.6 to 6.0% of the population and 15 to 20% have multiple aneurysms
o Most common locations – Circle of Willis
§ Anterior communicating artery 30-35%
§ Posterior communicating artery 30-35%
§ Bifurcation of the middle cerebral artery 20%
§ Basilar tip 5%
o Risk factors
§ Female gender, family history, polycystic disease (ADPKD), connective tissue disorders, Smoking (Cardiovascular risk factors?)
o Treatment options – conservative or aggressive?
§ >5 to 9mm increased risk of rapture
o Treatment options
§ Surgical clipping of the neck of the aneurysm, aneurysm occlusion – angiography, proximal vessel occlusion
o Complications
§ Subarachnoid haemorrhage – SAH- 80 % of SAH are due to rapture of saccular aneurysms
§ CT without contrast
· Acute blood is bright – high attenuation
· High attenuation blood presence in dilated ventricles
· Enlarged aneurysm with surrounding edema causing mass effect
· Impression: subarachnoid hemorrhage following rupture of a internal carotid artery aneurysm
o Acute blood in the cisterns and ventricles, dilatation of ventricles (hydrocephalus), mass effect on the lateral ventricles, midline shift
· Recommend interventional radiological treatment
o Pathology: how does a ruptured aneurysm bleeds into the subarachnoid space?
§ Cavities in the brain are filled with CSF. Open to subarachnoid space via the foramen in the 4th ventricle – foramen of Luscka and Foramen of Magendie
o Transcatheter embolisation Guglielmi Coiling
§ Method – wall off the aneurysm from the circulation by filling it with platinum wire coils
§ Benefits – utilises standard angiographic techniques, less invasive then surgical clipping (craniotomy), can reach distal or inaccessible aneurysms
§ Risks – occlusion of parent artery by renegade coils, perforation of aneurysm, little information available on long term outcomes
§ Procedure: Femoral artery catheterisation route to the internal carotid artery. Inject contrast. Continue moving catheter through the internal carotid towards the Circle of Willis. Locate the aneurysm. Estimate volume. Thread a microcatheter through the main catheter to the aneurysm site. Deliver fine wound platinum coils through the microcatheter via a guide wire. Release coils into the aneurysm. Pack until full.
§ Projected outcomes in the absence of carefully randomised trials:
· Guglielmi coil treated cerebral aneurysm
o Best for aneurysms 4-10mm with narrow necks. Best for aneurysms difficult to access using surgical approach. Best for patients for whom surgery is contraindicated. Problems – incomplete occlusion – rebleeding, potential complications – rupture, artery occlusion, coil migration. Long term outcomes still unclear
· Surgically treated cerebral aneurysms
o Classic approach – surgical clipping of the aneurysm neck. Better occlusion of aneurysm.
Take home message:
· Rule out intracranial abnormality – Precontrast CT to identify acute bleed, followed by post contrast. MR to characterise further. Cerebral artery angiography is the gold standard. MRA offers a convenient alternative
· Treat the aneurysm – surgical clipping or thrombosis. Consider aneurysm location, size and neck shape. Patient stability.
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