MRI characteristics of midbrain tumours

We diagnosed 60 cases of midbrain tumours by MRI between 1993 to 1997. Ther e were 39 males and 21 females, aged 2-64 years, mean 25.6 years. We found 38 patients with true intramedullary midbrain tumours, 11 predominantly in the tectum, 20 in the tegmentum and 7 with a downward extension to the pens ; there were 7 within the cerebral aqueduct. There were 22 patients with in filtrating midbrain tumours extending from adjacent structures, 11 cases ea ch from the thalamus and pineal region. All patients received surgical trea tment. Gross total resection was achieved in 42 cases. subtotal (> 75 %) re section in 18. Pathological diagnoses included 16 low-grade and 15 high-gra de astrocytomas; 5 oligodendro-astrocytomas; 2 ependymomas; 11 glioblastoma s; and 11 pineal parenchymal or germ-cell tumours. Midbrain tumours are a h eterogeneous group of neoplasms, with wide variation in clinical and MRI fe atures, related to the site and type of tumour. MRI not only allows precise analysis of their growth pattern, but also can lead to a correct preoperat ive diagnosis in the majority of cases.