Radiology Resident Case of the Week
Bao Nguyen, M.D.
Peer Review Status: Internally Reviewed by Daniel
Crosby, M.D.
Imaging:
The spin echo images demonstrate a well circumscibed berrylike lesion in the posterior midpons which is characterized by mixed signal intensity, rim of hemosiderin, inhomogenous gadolinium enhancement, and absence of surrounding edema.
The 3-vessel cerebral angiogram shows normal filling and morphology of the right internal carotid, left internal carotid and vertebrobasilar artery distributions, with no evidence of shunt vascularity or abnormal tumor blush.
Incidental note was made on the MR of a region containing enhancing linear structures suggestive of the prominent intramedullary veins in the deep right frontal lobe. The diagnosis of a venous angioma was confirmed on the cerebral angiogram (arrowheads).
Diagnosis:
Angiographically occult pontine cavernous angioma with associated
right frontal venous angioma.
Etiology/Epidemiology/Pathology:
Cavernous angiomas represent a subset of hamartomatous
intracranial vascular anomalies, which include arteriovenous
malformations (AVM), venous malformations, capillary telangiectasia
and varices. Cavernous angiomas are characterized by a well
circumscribed mulberry-like collection of sinusoids lined by
endothelium, which unlike AVMs and capillary telangiectasias, are not
associated with arteriovenous shunting or intervening brain
parenchyma.
Cavernous angiomas occur sporadically with no sex predilection, but may be familial in a small number of cases with autosomal inheritance and variable penetrance, particularly in patients with multiple concurrent lesions. Cavernous angiomas may occur anywhere in the CNS, including the spinal cord, but are predominantly supratentorial in location. Pontine lesions represent the most common infratentorial location.
Most cavernous angiomas are asymptomatic and found incidentally on MRI, but when symptomatic, they may present with seizure, hemorrhage, or focal mass effect (as in this case where the lesion resulted in gradual progressive nystagmus). Hemorrhage, though infrequent may occur with devastating consequence. The annual risk of hemorrhage from a cavernous angioma is reportedly 0.25% per year, a risk significantly less than hemorrhage from an arteriovenous malformation, which is reportedly 2-3%..
Cavernous angiomas typically present between the third and fifth decades of life and are usually solitary. The classic MRI appearance is a well-defined heterogenous lesion with a dark hemosiderin rim staining the surrounding parenchyma. The hemosiderin deposition is believed to result from a gradual oozing of blood through the thin-walled sinusoids of the cavernous angioma over time. The lesion may be angiographically occult in 30-40% of cases, but a faint contrast blush may sometimes occur during the late capillary or venous phases of the arteriogram.
Miscellaneous:
Cerebral vascular malformations reportedly occur in 1-4% of the
general population.
DDx:
AVM, hemorrhagic tumor
(primary or metastatic), hypertensive hemorrhage or hemorrhagic
infarct.
Key References:
Awad, I & Barrow, D. Cavernous Malformations. 1993. American
Association of Neurological Surgeons. Park Ridge, Illinois.
Osborn, Ann. Diagnostic Neuroradiology. 1994. Mosby. St. Louis.
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