Neuronal and Glial Changes in the Brain Tissue Adjacent to the Arteriovenous Malformations

Publisher Website
Google Scholar
Abstract
There has been a common belief that arteriovenous malformation (AVM) has a zone of gliosis between the nidus and the surrounding brain tissue, and that the AVM can be removed at this line without additional neurological deficits. To assess the propriety of this theory, gliosis, axonal changes, and demyelination were examined with immunohistochemical techniques at the brain tissue adjacent to the AVM.Of 82 histologically verified AVMs, 18 were large AVMs with a diameter of more than 4cm, and 36 were medium-sized AVMs with a diameter of 2 to 4cm. Another 28 were small AVMs, with a diameter of less than 2cm. Formalin of ethanol fixed, paraffin embedded surgical specimens of these AVMs were thin sliced and used for immunohistochemical staining. We used anti-glial fibrillary acidic protein (GFAP) antibody for detection of gliosis, anti-myelin basic protein (MBP) antibody for demyelination and anti-200kD neurofilament antibody for neuronal changes.In the brain tissue facing the small AVM, no definite changes or reactions were identified. The axons abruptly ended at the wall of the AVM, and these axons were myelinated well as shown by MBP immunostaining. There were no reactive astrocytes detectable by GFAP immunostaining in the brain tissue facing the small AVM. This staining clearly indicated that the brain tissue facing the small AVM was normal. The brain tissue adjacent to the medium-sized AVM had similar properties to those facing the small AVM. The only difference between small and medium-sized AVMs was a few reactive astrocytes detectable in the brain tissue close to the AVM. However, this reaction was mild, and axons and myelin appeared normal. In the large AVMs, however, several reactive changes were observed. The axonal density was reduced in the brain tissue within 500μm from the edge of the AVM.The axons were thick and tortuous in this zone. These axonal changes were observed typically at the brain tissue facing the large draining veins. In some neurons, soma and dendrites were also stained by the anti-NF antibody, which normally stains only axons. The MBP staining was correlated to the NF staining, i. e., demyelination was especially observed at the tissue adjacent to the large draining veins. There was a zone of gliosis in the issue facing the large AVMs. The reactive astrocytes and glial fibers were observed in this zone. However, this zone was not more than 1mm from the edge of the AVM in the non-hemorrhagic cases.In cases presenting intracerebral hemorrhage, a definite zone of gliosis was observed in the tissue facing the hematoma in even small or medium-sized AVMs. The brain tissue obtained from patients who underwent multi-staged surgery showed a gliotic layer at the surgical site. In those hemorrhagic cases and multi-staged surgical cases, a useful dissecting plane could be present and might be useful in surgery.In summary, the brain tissue facing the small or medium-sized AVMs was histologically normal, whereas brain tissue facing the large AVMs had a small zone of gliosis. The zone was however, not more than 1mm. Therefore, surgery for AVMs located in functionally important areas must be based on the present data.

This publication has 0 references indexed in Scilit: