Arteriovenous malformation of the spinal cord. Three-dimensional reconstruction of the intramedullary abnormal vessels.

We report a case of spinal arteriovenous malformation (AVM) in which detailed morphological examination of the intramedullary vascular lesion was carried out employing serial section studies. The relationship of the malformation to parenchymal lesions was evaluated. An abnormal vessel at the spinomedullary transition, whose lamina elastica was partially interrupted, was suggestive of a shunt vessel. The location of the intramedullary abnormal vessels and foci of softening of the spinal cord almost overlapped in distribution. Three-dimensional reconstruction of the intramedullary abnormal vessels demonstrated marked elongation and tortuosity of the original vascular architecture and they ended in the extramedullary abnormal vessels with thickened wall. Thus, our study showed that the intramedullary abnormal vessels were the result of secondary changes subsequent to pressure and volume overload inflicted upon the spinal venous system through AVM. Compression by tortuous elongation of the intramedullary vessels is the apparent cause of the parenchymal softening. A traumatic factor in the aetiology of the AVM was also discussed, since the patient had had two preceding episodes of traffic accidents with cranial and lumbar injury. Trauma seemed to be significant factor as a trigger of symptoms.