Cerebral aneurysm

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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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