FINAL DIAGNOSIS: -- Cryptic arteriovenous malformation (AVM) with severe hemosiderosis of left frontal lobe of brain.
Arteriovenous malformations usually involve the lateral aspects of the cerebrum and are seen as a tangle of vessels involving the leptomeninges over the surface of the brain. Abnormal vessels penetrating the underlying brain substance are usually demonstrated by arteriography. The main lesion is usually superficial.
Sometimes the main lesion is small and buried deep in the brain parenchyma. The have been called "cryptic" (hidden). These "cryptic" AVM are seen most often in the first two decades of life and are have an high risk of intracerebral hemorrhage.
In a retrospective study of 12 angiographically negative cases of AVM, it was found that all except one case were composed of abnormal vessels, predominantly hyalinized and arterialized venous channels extending deep into adjacent brain parenchyma (cryptic component). There was gliosis in all cases. A capillary component (telangiectatic) buried in the brain substance was found in eight cases. Various degrees of old and recent thromboses, seen predominately in venous channels, were encountered in 11. Eight cases showed evidence of old intraparenchymal or subarachnoid bleeding with focal hemosiderosis. Three cases demonstrated calcifications.
Clinically, factual or subjective evidence of weakness in one extremity was found in ten cases. Nine patients had sudden onset of headache. Nine patients had positive CAT scans although not diagnostic for AVM.
The case presented is the largest and most "siderotic", "cryptic" AVM seen by the author to date!.
Contributed by Mariano Alvira, MD