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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