1. What is a cavernous malformation/cavernoma?
A cavernous malformation,
also known as a cavernous hemangioma or cavernoma,
is an abnormal vascular entity (or "lesion") made
up of many small compartments (lobules) like a bunch of small
berries, or a mulberry (see Cavernoma Page 2 for images). These microcomparments contain blood (hemorrhagic)
products in different stages of evolution. The "sinusoidal"
compartments are enclosed by abnormally thin and quite fragile
endothelialized walls. Unlike an arteriovenous malformation
(AVM; 
take me to the AVM section now), there
is no large feeding artery and no large draining vein in a
cavernoma. However, there frequently is a venous
angioma associated with the cavernoma! (
take me to the Venous Angioma section
now ).
Most cavernomas
are found in the larger (supratentorial) parts of the
brain hemispheres, but up to 1 in 4 or 5 (i.e., 20-25% of all cavernomas) are found
in the hindbrain (posterior fossa; infratentorial),
especially in the pons region of the brainstem. Much
less commonly a cavernoma may be found in the spinal
cord (but this may be more likely to occur in patients
with a family history of cavernous malformations).
2. How common are cavernous
malformations/cavernomas?
They are not very common.
Their prevalence (presence at any given time) in the
population is probably somewhere between 0.1 - 0.5% (i.e., 1 in 200 to 1 in 1000 people in the general population);
they are about as common as brain arteriovenous malformations
(AVM), and far less common than brain aneurysms.
3. Why does a cavernous malformation develop?
Cavernomas occur sporadically
(spontaneously in a noninherited manner) in the majority
of cases, but in some cases may demonstrate inheritance
(familial; i.e., a positive or strong family history
of cavernous malformations). In familial cases, a specific
chromosome 7 gene abnormality has been demonstrated,
and familial cavernous malformation has been reported
to be more common in hispanic (especially Mexican-American)
people. In familial cases, cavernous malformations are
more commonly multiple (i.e., two or more cavernomas
present at the time of diagnosis), and may certainly also involve the spinal cord.
On chromosome 7, the specific two genes involved are refered to as CCM1 (band 7q11.2-q21; aka KRIT 1 because of its role in creating the KRIT 1 protein, or Krev interaction-trapped 1 protein), and CCM 2 (band 7p15-p13; controls production of the protein malcavernin). A third gene referred to as CCM 3 (on chromosome 3q) has been identified and is being investigated further.
4. What are the symptoms
of a cavernous malformation?
Cavernomas may be asymptomatic,
or may present with seizures (60%) or with progressive
neurological impairment or "deficits"
(50%). Some can present with hydrocephalus or raised
intracranial pressure (headache, nausea, vomiting, visual
disturbance, sleepiness) depending on their size and location.
It is uncommon for cavernomas to cause sudden catastrophic
or devastating neurological injury, but the progressive brain
(or spinal cord) injury associated with cavernomas may be
severely disabling as time goes on.
Why do these symptoms
occur? The reason is repeated bouts of hemorrhage in
the cavernoma. Different cavities of the cavernoma may have
different ages of blood products. The walls are fragile, and
the growth of micro blood vessels into these lesions results
in blood product (hemosiderin) leeching around
the cavernoma, and cycles of cavernoma growth through hemorrhage
and rehemorrhage. The hemorrhage is rarely a large
devastating hemorrhage.
Top of page
5. More about cavernous
malformation hemorrhage and rehemorrhage.
The risk of hemorrhage
from a cavernoma is somewhere between 0.5-1% per year.
It may be greater (or at least easier felt symptomatically)
in cavernomas located in more "eloquent" brain such
as the basal ganglia, thalamus, brainstem, and spinal cord.
The rehemorrhage rate varies in the literature, but
is probably somewhere between 4-10% per year (some
reports indicate an even higher rate in the first year or
two following the first diagnosed cavernoma hemorrhage).
6. What are the complications
of a cavernous malformation?
The major complications
are seizures and progressive neurological impairment,
and the type of "deficit" varies according to the
size and location of the cavernoma, and the extent and multiplicity/frequency of the hemorrhage(s).
7. How is a cavernous
malformation detected (investigations)?
Cavernomas are
detected best through MRI. They can enhance with contrast,
but frequently do not. They are not detectable on a cerebral
angiogram (i.e., are referred to as angiographically occult
vascular malformations or AOVMs; however, an associated venous
angioma may be detected on the angiogram!). The best two
MRI sequences used to detect cavernomas are regular
T2 ("popcorn" appearance) and gradient
echo (GRE; "India ink" blotch
appearance). These are shown below. A CAT scan can also show
a cavernoma, but the resolution is better with an MRI.
Note that in familial
or multiple cavernoma patients, it is worthwhile screening
the cervicothoracic spinal cord via MRI to exclude the
presence of an occult cavernoma there.
