Cavernous-type venous lesions in the central nervous system are conventionally called cavernomas, cavernous angiomas, or cerebral cavernous malformations. Given the typical absence of neoplastic features, the terms “cavernoma” and “angioma” are being phased out, and all cavernous-type malformations can be called “cavernous venous malformations” (CavVMs).
In a two-part article in the Journal of Neurosurgery, Brigham and Women’s Hospital surgeons discuss the epidemiology, clinical and radiologic features, and surgical management of this group of pathologies. This summary covers part 1, dural and extradural CavVMs.
The authors are Walid Ibn Essayed, MD, formerly a resident in the Department of Neurosurgery at the Brigham, Joshua D. Bernstock, MD, PhD, a resident in the Department, Rose Du, MD, PhD, director of Cerebrovascular Surgery in the Department, and colleagues.
Dural CavVMs are histologically similar to intra-axial CavVMs, but they have distinctive features:
- Neoplastic-like behavior (patients classically present with symptoms related to local mass effect)
- Low propensity for hemorrhagic events
- No signs of peri-malformation hemorrhage on imaging and histology
Cavernous sinus, middle fossa, and sella CavVMs are the dural CavVMs most frequently discussed in medical literature.
Cavernous sinus CavVMs
Cavernous sinus CavVMs present like benign neoplasms with progressive cranial nerve palsies and headaches. Hemorrhage is rare and usually localized. These CavVMs are most frequent in middle-aged females and the Japanese population.
Certain radiologic features differentiate CavVMs from cavernous sinus meningiomas, including a well-demarcated T2-hyperintense signal and normal caliber of the cavernous carotid artery despite circumferential encasement. Angiographic findings are often nonspecific. When MRI findings are concerning, scintigraphy-based imaging can be helpful because an accumulation of 99mTc pertechnetate–labeled red blood cells within the cavernous sinus is specific for CavVMs.
Resection is recommended for patients with progressively worsening neurological findings and/or large lesions. Surgery allows diagnostic confirmation and is potentially curative after gross-total resection.
Other dural CavVMs
Dural CavVMs developing outside the middle fossa and cavernous sinus are particularly rare. There is a slight male predilection (56%). Most cases display benign expansile growth, but about 15% are aggressive, exhibiting aggressive nodular sheet-like growth and regional infiltration, including bony involvement. Young age seems to be associated with more aggressive behavior. Curative gross-total resection is achievable in most cases.
The authors also discuss orbital and spinal epidural CavVMs.
Once termed “cavernous hemangiomas,” orbital CavVMs are now understood to be low-flow malformations. A significant female predilection has been noted (7:3 ratio). These lesions frequently progress slowly, but when symptomatic, they present with retrobulbar or periorbital pain, vision loss, and proptosis. In rare cases, intraconal hemorrhage is observed.
On imaging, orbital CavVMs are T2-hyperintense without the classic “popcorn appearance.” On angiography, they are occult in one-third of cases and present with capillary blush in two-thirds of cases, consistent with a low-flow malformation.
In symptomatic patients, early resection is the best option to prevent further visual deterioration. Visual acuity frequently improves. Careful evaluation of orbital anatomy is essential to choose the best route. The transcranial route is ideal for medially located malformations, CavVMs in the orbital apex, diffuse malformations, and CavVMs with intracranial extension. Orbital reconstruction is critical to avoid enophthalmos.
Intraoperatively, these lesions have a firm capsule that can be dissected progressively from the surrounding orbital fat; occasionally, peripheral hemosiderin staining is noted.
Spinal epidural CavVMs
Purely epidural CavVMs are distinct entities within the spectrum of spinal cavernous malformations and should be distinguished from those within the vertebral body with epidural extension. They are most common at thoracic levels but can develop at any level of the epidural space. Their features are:
- Symptoms are usually slowly progressive with spinal cord and/or nerve root compression
- Angiography is typically negative
- Intraoperative findings are consistent with those of low-flow lesions
Spinal epidural CavVMs are usually well encapsulated and resected via peeling the lesion from the dura, allowing for en bloc gross-total resection without significant hemorrhage. As with other spinal lesions, the extent of bony removal should be tailored to the craniocaudal and transversal extension of the malformation and requires various degrees of spinal fusion.
The authors present illustrative cases for each type of CavVM and examine the physiopathological and genetic features that link dural and extradural CavVMs to intradural CavVMs (classic intra-axial CavVMs, CavVMs growing on nerve roots and intradural extramedullary spinal malformations). Intradural CavVMs are discussed in a separate article in the same journal issue.