Cavernous Malformations of the Brain
Cavernous malformations (aka: cavernomas, cavernous hemangiomas) can be thought of as vascular tumors. They are composed of a capillary-like network of endothelial cells (the cells that normally line blood vessels). However, unlike normal capillaries throughout the body the capillaries of cavernomas are prone to leak.
Interestingly, cavernous malformations do not have any brain tissue within them. This helps distinguish them from another related vascular abnormality known as an arteriovenous malformation.
The genetics of cavernous malformations have been elucidated by studying familial forms of the disorder. There are at least three known genetic defects that predispose patients to develop cavernomas. These genes appear to be important in the formation of blood vessels (a process known as "angiogenesis") and the blood brain barrier. Therefore, mutations in these genes can cause the abnormal growth of vascular tissue.
Cavernomas can cause numerous signs and symptoms depending on their location within the brain. Seizures are the most common symptom. However, progressive neurological impairment such as worsening weakness can also occur.
Sometimes cavernomas can block the flow of cerebrospinal fluid leading to hydrocephalus (increased fluid in the ventricles of the brain). Hydrocephalus can cause increased intracranial pressure leading to headaches, nausea, and vomiting. However, it is important to realize that many patients with cavernomas have no symptoms at all!
If symptoms are present, they tend to progress over time. This is because cavernous malformations bleed and re-bleed resulting in an expansion of its size over time. As the malformation increases in size it can push on adjacent brain tissue causing worsening symptoms.
Unlike arteriovenous malformations, life threatening and severe hemorrhages are rare. Cavernomas bleed at an initial yearly rate of anywhere between 1% to 5%. After the first bleed, the risk of re-bleeding increases to as high as 10% per year. In other words, if a cavernoma bleeds, it is more likely to re-bleed at a later date.
The diagnosis of cavernous malformations are made via imaging studies. They are usually detected via MRIs that are ordered for evaluation of neurological symptoms. Cavernomas are seen best on T2 and gradient echo MRI sequences. They typically look like a piece of popcorn.
Select patients undergo a more invasive imaging procedure known as angiography. Angiography is used to rule out another similar lesion known as an arteriovenous malformation. Since cavernomas are venous malformations they are not seen on angiograms.
Depending on the location, most cavernous malformations in the brain and spinal cord are removed surgically. However, in some areas such as the brainstem where surgical resection may be difficult, or impossible, patients may be offered radiation therapy.
Cavernous malformations of the brain are abnormal vascular growths composed of capillary networks. They are likely the result of genetic mutations in genes responsible for blood vessel growth. Depending on their location they can cause numerous neurological symptoms such as seizures and weakness. MRI often shows the characteristic "popcorn" lesion. Treatment is usually with surgical resection, although some cavernomas may be radiated depending on their location.
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