Shows dilated arteries and veins on the surface, in the subarachnoid space.
Lateral, selective ICA angiogram.
The ICA is dilated, feeding a "ball of vessels" with a short "transit time" and an early draining vein.
Multiple serpentine flow voids.
Multiple serpentine flow voids.
The second kind of vascular malformation is the cavernous malformation (cavernoma or cavernous hemangioma). These lesions come in two different modes, they may be inherited, and, therefore, typically multiple and bilateral. However, there may be solitary and sporadic cavernous hemangiomas as well. There have been numerous articles showing a high incidence of autosomal dominant inheritance for cavernous hemangiomas among Hispanic Americans of Mexican ancestry. A 1996 article from the New England Journal [REF 3]documents that the reported association is not only valid and true, but it may be the result of a "founder mutation". The molecular biology of multiple cavernous hemangiomas suggests that the abnormal chromosome is number 7, and genetic markers suggest that most affected families probably have a single common ancestor - the "founder" of cavernous hemangiomas.
The cavernous hemangioma is basically a "blood sponge". It is a slow flow lesion, and not a shunt. Like the arterial venous malformation, it may present with either hemorrhage or seizures. This "blood sponge" consists of variable sized vascular spaces that vary between capillaries, sinusoids, and larger cavernous spaces. However, unlike the arterial venous malformation, there is no intervening brain tissue between the vascular spaces - hence, the name "blood sponge". Classically, these cavernous malformations, because of their slow flow, were not identified on routine angiographic investigations. They were typically called "occult" or "cryptic" malformations.
On imaging studies,
these lesions oftentimes have remarkably minimal mass effect. They may
be slightly hyperattenuating or calcified on non-contrast CT. Contrast
enhancement may be minimal or marked. They typically have minimal, if any,
mass Effect (if they are not complicated by hemorrhage). In an analogous
fashion, surrounding vasogenic edema does not occur, unless there has been
a complication with hemorrhage. On magnetic resonance imaging, which is
far more sensitive in their detection, they oftentimes have a very characteristic
appearance. The cavernous hemangioma, may have internal areas of thrombosis
and/or hemorrhage. This internal bleeding is typically of multiple different
ages. There may be conversion of hemoglobin to methemoglobin which produces
foci of hyperintensity on the T1 weighted image. Hemosiderin may be cleared
from the central area of the lesion, and can be deposited around the periphery
of the cavernous hemangioma. The peripheral hemosiderin produces significant
T2 shortening, producing a "black halo" surrounding the lesion. The hemosiderin
rim around the outside is usually continuous (rather than discontinuous)
and may be associated with a "blooming" effect with progressively greater
degrees of T2 weighting. Note: Florence
Griffith Joyner (Flo-Jo)
died at age 38 from an epileptic seizure caused by a cavernous angioma.
Multiple vascular spaces of varying size.
Near the left frontal horn, there is a nodular hypointense lesion, without mass effect.
The left frontal lobe has an amorphous calcified lesion, without obvious mass effect.
There is a nodular hypointense lesion adjacent to the right ventricle, without mass effect. Two small lesions are present
Near the right vent
Venous angiomas are the third type of vascular malformation. These may be isolated anomalies, but have reported in association with cavernous malformations. (Some authors have reported that the cavernous hemangioma may be a secondary lesion produced by the venous varix.) The venous angioma is a post-capillary malformation. The classic description of the venous angioma or varix includes a crown of multiple small venules that converge on a larger venous trunk. The venous trunk usually drains into a dural sinus. One theory suggests that the primary problem is a lack of "bridging veins" connecting the cortex to the dural sinuses. Any vein that does make the connection to the dural sinus (the so-called "transcortical vein") will now drain an unusually large volume of brain, and therefore enlarges. The "crown" of veins that converge onto the connecting trunk are "collecting veins" that drain the capillaries from the affected volume. Because a large volume of brain, and a corresponding large volume of blood drain into a single vessel, the venous pressure within the varix can be elevated. This elevated pressure may help produce the secondary cavernous hemangiomas. Hemorrhage from a varix is unusual, and many cases are either incidental findings, or present in association with a cavernous hemangioma.
On CT, the varix is
a tubular structure, often oriented to point toward the cortical surface
and to the nearest dural sinus. The varix has the attenuation of blood
and enhances after contrast infusion. On MR imaging, there is usually a
tubular flow-void in the varix on routine spin-echo sequences. Angiographically,
the varix has been described as a "medusa head". It really looks more like
a hydra or a palm tree - the dominant transcortical vein is the trunk;
and the radiating crown of feeding veins are the leaves.
Lat Vertebral Angiogram.
AP Vert Angio.
Mosaic of Medusa
Gross Photo of Palm Tree
Contrast Enahanced CT.
Vein of Galen malformations (VGM) usually involve combination of lesions. The great vein of Galen receive flow from the internal cerebral veins and the basal veins of Rosenthal. It is a large vein, that in turn drains into the straight sinus. However, unlike the dural sinuses ( and unlike systemic veins elsewhere in the body) the vein of Galen is unsupported by surrounding tissue, lacks a fibrous wall, and is instead free within the fluid of the quadrigeminal plate cistern. Because the vein of Galen is such a large vascular channel, unsupported by surrounding tissue, any increase in venous pressure results in a dilatation of the vein - often converting its normal cylindrical shape into a sphere - hence the nickname "vein of Galen Aneurysm". Increased pressure within the deep venous system also interferes with normal venous development, usually producing persistence of embryologic channels that normally regress (e.g. the "falcine vein"). Thus, VGM is a better name, including both the enlarged central vein, as well as other venous anomalies.
Many etiologies have been suggested for the creation of a VGM. Clinical material is available to support several different mechanisms, all of them are potential causes for increased pressure in the deep central veins of the fetus including:
Dural fistula (high flow)
Parenchymal AVM (high flow)
Choroidal shunts (high flow)
Straight sinus thrombosis (obstruction)
Hypoplasia of the straight sinus (relative obstruction)
The clinical presentation of the VGM is variable, many patients present at birth with high-output cardiac failure, persistent patent ductus arteriosus, an audible cerebral bruit, a palpable thrill, and various degrees of hydrocephalus. Hydrocephalus is caused either by direct mechanical effects (compression of the aqueduct by mass effect from the dilated vein) or secondarily through decreased CSF reabsorption from central venous hypertension.
The radiologic diagnosis
is often straight-forward. A rounded mass is identified in the appropriate
location of the quadrigeminal plate cistern (QP cistern). The mass is usually
hyperdense on plain CT, and enhances brightly. Fetal and even obstetric
US will show the mass is vascular, with pulsatile flow on Doppler. MR may
show a pulsation artifact in the phase-encoding direction, as well as a
flow-void on routine SE pulse sequences. Treatment and outcome are variable.
Significant factors influencing morbidity include clinical status, degree
of shunt (if a high-flow lesion), degree of hydrocephalus, and the nature
of the primary cause of the VGM.
1. Coffey RJ, Nichols DA, Shaw EG, and the Gamma Unit Radiosurgery Study Group. Stereotactic Radiosurgical Treatment of Cerebral Arteriovenous Malformations. Mayo Clinic Proceedings 1995;70(3):214-21.
3. Günel M, Awad IA, Finberg K, Anson JA, Steinberg GK, Batjer HH, Kopitnik TA, Morrison L, Giannotta SL, Nelson-Williams C et al. A founder mutation as a cause of cerebral cavernous malformation in Hispanic Americans. N Engl J med 1996;334:946-51.
8. Murphey MD, Fairbairn KJ, Parman LM, Baxter KG, Parsa MB, Smith WS. From the archives of the AFIP. Musculoskeletal angiomatous lesions: radiologic-pathologic correlation. Radiographics 1995;15:893-917.
10. Segall HD, Ahmadi J, McComb G, Zee C, Becker TS, and Han JS. Computed Tomographic Observations Pertinent to Intracranial Venous Thrombotic and Occlusive Disease in Childhood. State of the Art, Some New Data, and Hypotheses. Radiology 1982;143:441-9.