Saccular cerebral aneurysm
Saccular cerebral aneurysms, also known as berry aneurysms, are intracranial aneurysms with a characteristic rounded shape. They account for the vast majority of intracranial aneurysms and are the most common cause of non-traumatic subarachnoid hemorrhage.
On this page:
Terminology
Those larger than 25 mm in the maximal dimension are called giant cerebral aneurysms.
Charcot-Bouchard aneurysms are minute aneurysms which develop as a result of chronic hypertension and appear most commonly in the basal ganglia and other areas such as the thalamus, pons, and cerebellum, where there are small penetrating vessels (diameter <300 micrometers).
Epidemiology
Prevalence of saccular cerebral aneurysms in the asymptomatic general population has been reported over a wide range (0.2-8.9%) when examined angiographically, and in 15-30% of these patients, multiple aneurysms are found 4.
A familial tendency to aneurysms is also well recognized, with patients who have more than one first-degree relative affected, having a ~30% (range 17-44%) chance of themselves having an aneurysm 4.
Pathology
Macroscopically, aneurysms are rounded lobulated focal outpouchings, usually arising at arterial bifurcations.
Most intracranial aneurysms are true aneurysms. The aneurysmal pouch is composed of thickened hyalinised intima with the muscular wall and internal elastic lamina being absent as the normal muscularis and elastic lamina terminate at the neck of an aneurysm. As an aneurysm grows it may become irregular in outline, and may have mural thrombus. Typically rupture occurs from dome 4.
Associations
Numerous associations have been identified, most relating to abnormal connective tissue. Associations include:
- Ehlers-Danlos syndrome (type IV)
- Marfan syndrome (controversial 3)
- autosomal dominant polycystic kidney disease 1
- coarctation of aorta 2
- bicuspid aortic valve
- neurofibromatosis type 1 3
- hereditary hemorrhagic telangiectasia
- alpha 1 antitrypsin deficiency 3
- cerebral arteriovenous malformation: a flow related aneurysm
- fibromuscular dysplasia
- thoracic and abdominal aortic aneurysms 7
Location
Cerebral aneurysms typically occur at branch points of larger vessels but can occur at the origin of small perforators which may not be seen on imaging. Approximately 90% of such aneurysms arise from the anterior circulation, and 15-30% of these patients have multiple aneurysms 4.
- anterior circulation: ~90%
- ACA/ACoA complex: 30-40%
- supraclinoid ICA and ICA/PCoA junction: ~30%
- MCA (M1/M2 junction) bi/trifurcation: 20-30%
- posterior circulation: ~10%
- basilar tip
- SCA
- PICA
Radiographic features
Berry aneurysms can be imaged in a variety of methods:
Each of these confers certain advantages and disadvantages, although in general digital subtraction catheter angiography, especially with 3D acquisitions, is considered the gold standard in most institutions.
CT
The appearance depends upon the presence of thrombosis within an aneurysm. An aneurysm appears as a well-defined round, slightly hyperattenuating lesion, most apparent on maximum intensity projection reformatted images.
- calcification can be present
- post contrast
- patent aneurysm: bright and uniform enhancement
- thrombosed aneurysm: rim enhancement due to filling defect
MRI
On MRI also the patent and thrombosed aneurysm display different imaging features:
-
T1
- most of the patent aneurysms appear as flow void, or they may show heterogeneous signal intensity
- in thrombosed aneurysms, the appearance depends on the age of clot within the lumen
-
T2
- typically hypointense
- laminated thrombus may show a hyperintense rim
Digital subtraction angiography (DSA)
It has been reported more sensitivity in 3D DSA over 2D DSA when regarding the detection of small aneurysms 6. Attention must be given when measuring the aneurysm neck size as it can be overestimated by the 3D reconstructions.
Treatment and prognosis
Treatment of large or symptomatic aneurysms should be considered, with either endovascular coiling or surgical clipping.
Management of small aneurysms is controversial. Less than 7 mm in maximal diameter aneurysms are statistically unlikely to rupture, however, due to their prevalence, anyone working in the area has seen numerous patients with small aneurysms which have ruptured resulting in subarachnoid hemorrhage, often with devastating consequences.
Five-year cumulative risk of rupture of anterior circulation aneurysms 5:
- <7 mm: 0%
- 7-12 mm: 2.6%
- 13-24 mm: 14.5%
- >25 mm: 40%
Five-year cumulative risk of rupture of posterior circulation aneurysms 5:
- <7 mm: 2.5%
- 7-12 mm: 14.5%
- 13-24 mm: 18.4%
- >25 mm: 50%
As such management will vary according to local experience, the location and appearance of an aneurysm, patient demographics, etc.
Endovascular coiling is graded with the Raymond–Roy Occlusion Classification (RROC) scheme.
Differential diagnosis
When the abnormality has been confirmed to be vascular, the differential includes:
- fusiform aneurysm
- infundibulum: usually triangular dilatation with the vessel arising from the apex
- dissecting aneurysm
- mycotic aneurysm
- variant arterial anatomy (see imaging differential diagnosis case)
Practical points
Regardless of the modality used, a number of features need to be assessed to allow a decision in relation to treatment to be made:
- size: ideally three axis maximum size measurements
- neck: maximal width of the neck of an aneurysm
- the shape and lobulation
- orientation: the direction in which the aneurysm points is often important in both endovascular and surgical planning
- any smaller branches in the vicinity of an aneurysm
- any branch taking off from the aneurysm
- the presence of other aneurysms or vascular malformations
- relevant arterial variant anatomy (that may complicate or exclude endovascular treatment)
See also
Related Radiopaedia articles
Stroke and intracranial haemorrhage
-
stroke and intracranial hemorrhage
- code stroke CT (an approach)
-
ischemic stroke
- general discussions
- scoring and classification systems
- signs
- by region
- hemispheric infarcts
- frontal lobe infarct
- parietal lobe infarct
- temporal lobe infarct
- occipital lobe infarct
- alexia without agraphia syndrome: PCA
- cortical blindness syndrome (Anton syndrome): top of basilar or bilateral PCA
- Balint syndrome: bilateral PCA
- lacunar infarct
-
thalamic infarct
- Déjerine-Roussy syndrome (thalamic pain syndrome): thalamoperforators of PCA
- top of the basilar syndrome
- striatocapsular infarct
- cerebellar infarct
-
brainstem infarct
- midbrain infarct
- Benedikt syndrome: PCA
- Claude syndrome: PCA
- Nothnagel syndrome: PCA
- Weber syndrome: PCA
- pontine infarct
- Brissaud-Sicard syndrome
- facial colliculus syndrome
- Gasperini syndrome: basilar artery or AICA
- inferior medial pontine syndrome (Foville syndrome): basilar artery
- lateral pontine syndrome (Marie-Foix syndrome): basilar artery or AICA
- locked-in syndrome: basilar artery
- Millard-Gubler syndrome: basilar artery
- Raymond syndrome: basilar artery
- medullary infarct
- Babinski-Nageotte syndrome
- hemimedullary syndrome (Reinhold syndrome)
- lateral medullary stroke syndrome (Wallenberg syndrome)
- medial medullary syndrome (Déjerine syndrome)
- midbrain infarct
- acute spinal cord ischemia syndrome
- hemispheric infarcts
- by vascular territory
- treatment options
- complications
-
intracranial hemorrhage
-
intra-axial hemorrhage
- signs and formulas
- ABC/2 (volume estimation)
- CTA spot sign
- swirl sign
- by region or type
- signs and formulas
- extra-axial hemorrhage
-
intra-axial hemorrhage
Inspired signs
-
inanimate object inspired
- astronomical inspired
- ball of wool sign
- chain of lakes sign
- champagne glass pelvis
- Coca-Cola bottle sign
- coin lesion
- corduroy artifact
- corduroy sign
-
corkscrew sign (disambiguation)
- corkscrew sign (midgut volvulus)
- corkscrew sign (diffuse esophageal spasm)
- corkscrew sign (inner ear)
- dinner fork deformity
- fishhook ureters
- ghost triad (gallbladder)
- goblet sign
- ground glass opacity
- hatchet sign
- hockey stick sign (disambiguation)
- horseshoe (disambiguation)
- hourglass sign
- keyhole sign (disambiguation)
- leather bottle stomach
- Lincoln log vertebra
- mosaic appearance (disambiguation)
- napkin ring sign
- open book fracture
- pearl necklace sign
- polka-dot sign
- rachitic rosary
- ring shadow
- rugger jersey spine
- sack of marbles sign
- sail sign (disambiguation)
- scalpel sign
- spilled teacup sign
- stepladder sign (disambiguation)
-
string of pearls sign (disambiguation)
- string of pearls sign (abdominal radiograph of small bowel)
- string of pearls sign (polycystic ovarian syndrome)
- string of pearls sign (fibromuscular dysplasia)
- Tam o' Shanter sign
- telephone receiver deformity
- tombstone iliac wings
- Venetian blind sign
- water bottle sign
-
weapon and munition inspired signs
- bayonet deformity
- boomerang sign (disambiguation)
- bullet-shaped vertebra
- cannonball metastases
- Cupid bow contour
- dagger sign
- double barrel sign
- halberd pelvis
- panzerherz
- pistol grip deformity
- saber-sheath trachea
- scimitar syndrome
-
target sign (disambiguation)
- double target sign (hepatic abscess)
- eccentric target sign (cerebral toxoplasmosis)
- reverse target sign (cirrhotic nodules)
- target sign (choledocholithiasis)
- target sign (hepatic metastases)
- target sign (intussusception)
- target sign (neurofibromas)
- target sign (pyloric stenosis)
- target sign (tuberculosis)
- trident appearance
- Viking helmet sign
- white pyramid sign
- windswept knees
- wine bottle sign
-
vegetable and plant inspired
- aubergine sign
- celery stalk appearance
- coconut left atrium
- coffee bean sign
- cotton wool appearance
- drooping lily sign
- ginkgo leaf sign (disambiguation)
- holly leaf sign
- ivy sign
- miliary opacities
- mistletoe sign
- onion skin periosteal reaction
- pine cone bladder
- popcorn calcification
- potato nodes
- rice bodies
- rice grain calcification
- salt and pepper skull
- tree-in-bud
- water lily sign
-
fruit inspired
- apple core sign (disambiguation)
- apple-peel intestinal atresia
- banana and egg sign
- banana fracture
- banana sign
- berry aneurysm
- bowl of grapes sign
-
bunch of grapes sign (disambiguation)
- bunch of grapes sign (hydatidiform mole)
- bunch of grapes sign (bronchiectasis)
- bunch of grapes sign (IPMN)
- bunch of grapes sign (botryoid rhabdomyosarcoma)
- bunch of grapes sign (intracranial tuberculoma)
- bunch of grapes sign (multicystic dysplastic kidney)
- bunch of grapes sign (intraosseous hemangiomas)
- lemon sign
- pear-shaped bladder
- strawberry gallbladder
- strawberry skull
- watermelon skin sign
-
animal and animal produce inspired
- human
- fish and marine life
- birds
- mammals
- anteater nose sign
- antler sign
- bat wing opacities
- bear paw sign
- beaver tail liver
- Brahma bull sign
- buffalo chest
- bull's eye sign (disambiguation)
- bunny waveform sign
- claw sign
- dog ear sign
- dog leg sign
- ears of the lynx sign
- eye of tiger sign
- feline esophagus
- giraffe pattern
- hide-bound sign
- ivory vertebra sign
- leaping dolphin sign
- leopard skin sign
- moose head appearance
- panda sign
- pleural mouse
- raccoon eyes sign
- rat bite erosions
- rat-tail sign
- Scottie dog sign
- Snoopy sign
- stag's antler sign
- staghorn calculus
- tiger stripe sign
- zebra sign
- zebra stripe sign
- arthropods
- reptiles
- micro-organisms
- mythical creatures
-
food inspired
- Cheerio sign (disambiguation)
- chocolate cyst
- cottage loaf sign
- double Oreo cookie (glenoid labrum)
-
doughnut sign (disambiguation)
- crescent in a doughnut sign (bowel)
- doughnut sign (bone)
- doughnut sign (bowel)
- doughnut sign (chest)
- doughnut sign (orbit)
- hamburger sign (spine)
- head cheese sign (lungs)
- honeycombing (lungs)
- ice cream cone sign (middle ear ossicles)
- ice cream cone sign (vestibular schwannoma)
- licked candy stick appearance (bones)
- linguine sign (breast implants)
- macaroni sign
- omental cake
- Oreo cookie (heart)
- pancake adrenal
- pancake brain
- pancake vertebra
- Polo mint sign
- salad oil sign (breast implants)
- sandwich sign (disambiguation)
- sandwich vertebra
- sausage digit
- spaghetti sign
- Swiss cheese sign
-
alphabet inspired
- C sign (MSK)
- delta sign
- E sign
- H-shaped vertebra
- H sign
- J-shaped sella
- J sign (shoulder)
- L sign (brain)
- lambda sign
- M sign
- omega epiglottis
- S sign of Golden
- tau sign
- T sign
- U fibers
- U-figure (pelvis)
- U sign (brain)
- V (inverted) sign
- W hernia
- X-marks-the-spot sign
- Y sign (epidural lipomatosis)
- Z deformity
-
Christmas inspired
- Christmas tree bladder in neurogenic bladder
- holly leaf sign in calcified pleural plaques
- ivy sign in leptomeningeal enhancement
- nutcracker esophagus in esophageal dysmotility
- shepherd's crook deformity of the femur in fibrous dysplasia
- snowcap sign in avascular necrosis
- snowman sign
- snowstorm appearance in complete hydatidiform mole and testicular microlithiasis
- miscellaneous
Pituitary region masses
-
general reading
- pituitary gland anatomy
- pituitary MRI - an approach
-
pituitary region masses
- most common pituitary region masses
- solid and enhancing pituitary region mass
- mixed cystic and solid pituitary region mass
- mostly/purely cystic pituitary region masses
- purely intrasellar pituitary mass
- pituitary region mass with intrinsic high T1 signal
- abnormal enhancement/bulkiness of the pituitary infundibulum
- enlarged sella turcica
- mnemonic: SATCHMO
- history of imaging the pituitary region
-
pathology
-
pituitary tumors
- pituitary adenoma (commonest in the adult population)
- pituitary carcinoma
- pituitary lymphoma
- meningioma
- craniopharyngioma
- optic pathway glioma
- germinoma
- chordoma
- dermoid (CNS) / epidermoid / intracranial teratoma
- pituicytoma
- spindle cell oncocytomas
- pituitary metastases
- granular cell tumor of the pituitary (pituitary choristoma)
- pilocytic astrocytoma of the neurohypophysis (infundibuloma)
- cellular infiltrates
- other lesions
- anterior circulation berry aneurysm
- hamartoma (tuber cinereum hamartoma)
- Rathke cleft cyst
- intracranial lipoma
- sphenoid sinus mucocoele
- pituitary abscess
- pituitary stone
-
pituitary tumors