[A case of angiographically occult arteriovenous malformation with metaplasia (so-called brain stone)]

The patient was a 69-year-old female. Right hemiparesis occurred on April 25, 1996, and then was relieved a day later. Because headache (dull pain in the left) persisted subsequently, she consulted our department on April 26. Head CT showed, without enhancement effect, osseous high density on the surface of the left frontal area. MRI showed high intensity on T1 and low intensity on T2 with flow-void like findings. Cerebral angiography showed a pooling of contrast medium in the same region. 123I-IMP-SPECT revealed reduced cerebral blood flow in the left frontal and parietal lobes just under the same region. On June 11, the patient underwent surgery during which a tumor with arachnoid hypertrophy was extracted en block. Histopathologically, there were abnormal blood vessels with elastic fibers, expanding to an ossified site, and AVM accompanying ossification was thus diagnosed. Postoperative 123I-IMP-SPECT showed improved cerebral blood flow in the left frontal and parietal lobes. The patient was discharged on June 22. The TIA pathologic condition, a symptom of its onset, was considered attributable to cerebral blood flow steal due to AVM.