[Intraoperative ultrasound imaging in neurosurgery]

Intraoperative sector scanning enables routine imaging of the entire anatomy of intracranial and spinal spaces. Almost all of the pathological processes are exactly localised. It is an essential preliminary condition that fully sterilizable, handy ultrasound probes of 6 to 10 MHz including an accurate instrument- and puncture guide are available. Initial orientation projections similar to CT- or MRI scans are chosen using defined anatomical "landmarks". Cavities filled with aqueous fluids like ventricles, arachnoidal cysts, cystic low-grade gliomas are shown as regions of low echo intensity. Other pathological processes are usually imaged by their hyperecho-characteristics: brain oedema has an increased reflexion compared to normal brain tissue; all brain tumors are diffusely echogenic, the image allows preliminary grading e.g. of gliomas. Vascular processes like aneurysms and angiomas are well defined by wall- and perfusion characteristics. Ultrasound guiding enables even the most minutely detailed microsurgical approach; cysts and disorders of CSF circulation can be treated by simple ultrasound-monitored catheterization. Even stereotactic biopsy can often be replaced. Complications, such as hemorrhages, are recognised immediately.