[Intraoperative ultrasonography in brain surgery]

Intraoperative ultrasound was used in 33 patients. 19 lesions were primary malignant brain tumours, including 12 gliomas, three astrocytomas and four oligodendrogliomas. There were five metastases, three meningeomas, two dysembryoplastic neuroepithelial tumours and two angiomas. One patient had an arachnoid cyst, and another an infarct. The main advantage of carrying out intraoperative ultrasound examination is that it helps to localize the tumour, particularly in small subcortical lesions where the brain surface may appear normal. Ultrasound is less useful for characterizing the tumour, although the various tumours do show some differences. As a rule, the glioblastomas are inhomogeneous and poorly marginated, while low grade gliomas are more homogeneous and well marginated. Also meningeomas and metastases tend to be homogeneous and well marginated. Periofocal oedema is hyperechogenic compared with brain tissue, with an intensity between that of normal brain tissue and tumour mass. Cyst, calcification and haemorrhage are easily demonstrated.