E. Cavernous malformation
Cavernous malformations, otherwise known as cavernous hemangiomas or cavernomas, are rare intracranial vascular malformations; they occur in 0.4% to 0.5% of the general population. On CT, lesions are typically well-circumscribed, moderately hyperintense with contrast, and can have calcifications. MRI imaging characteristics (best seen on T2-weighted gradient echo sequences) include a stereotypic dark hemosiderin ring visible at the periphery of the lesion, suggestive of an old hemorrhage. Biopsy can be difficult due to these lesions’ common location in eloquent regions of the brain. There is a “popcorn ball”–like appearance on FLAIR sequence with perilesional edema, and the cavernous malformation faintly enhances on the T1 post-contrast sequence (compared to the non-contrast T1 sequence, not shown). This “popcorn ball” with the dark hemosiderin ring on T2-weighted sequences is diagnostic for a cavernous malformation.
A brain metastasis typically looks more solidly enhancing than a cavernous malformation, and often lacks the hemosiderin ring. Glioblastoma multiforme is often more irregular in appearance, with necrotic portions. Wegener granulomatosis often involves dural thickening and a more gradual onset of symptoms. Intracerebral granulomatous lesions can show peripheral enhancement and typically have high intensity on T2-weighted images. Meningiomas are dural-based lesions that are typically uniformly enhancing.
Cavernous malformations typically present in the third or fourth decade of life, although a quarter of cases present in infancy or childhood. Presenting symptoms include headache, seizure, and progressive neurologic deficits. While it was once believed that cavernous malformations were congenital, this is being reevaluated; it is now hypothesized that cavernous malformations may form throughout a person’s lifetime.
Surgical resection of a cavernous malformation is sometimes possible. The role of radiosurgery remains controversial. If neither surgery nor radiosurgery is possible, conservative management with MRI surveillance is an option, particularly for lesions that have not bled or that are asymptomatic and in critical locations in the brain.