[Real-time ultrasonography in neurosurgery. Puncture of an intracranial hypoechogenic cavity].

The authors have been using real time echography in neurosurgical procedures since 1981: either for detection of a small sub-cortical tumor during a surgical operation, either for biopsy-guidance, or for puncturing a cavity (abscess, cyst or hematoma). The imaging is performed with a CGR SONEL 100 apparatus and two different frequency transducer elements: 3.5 MHz and 5 MHz. 56 patients underwent this technique; 22 times the lesion was hypoechoic: abscess give homogeneous, round hypoechoic image, often surrounded by a fine hyperechoic line; intracerebral hematoma produces an hypoechoic image after a 10 to 15 days evolution: compared to an abscess it then has a more hyperechoic irregular wave-like limit; tumoral-cyst echogenicity is very low; it can even be anechoic. If a stereotaxic structure exists, indication of real time echography must be limited to such stereotaxy contraindications: threatening intracranial hypertension, suppurated lesion, fragile patient. The technique has its limit: that is the small volume of the target-lesion (inferior to 10 mm); advantages must be emphasized: light procedure, satisfying confidence when considering the probe progression, sometimes better information than that of a CT-Scan examination especially for tumoral and cystic lesions.