OBJECTIVETo address the several disadvantages of currently available ultrasonic aspirators used in microsurgery, new instruments were designed for neurosurgical use under a microscope.DESCRIPTION OF INSTRUMENTATIONThe weight of the handpiece was reduced to 90 g. Two types of angled probes were constructed. Keyhole-type probes have 93- and 112-mm lengths, a 2.2-mm tip diameter, and 9.5- and 11.2-mm sheath diameters at the most proximal site and produce a tip amplitude of 300 &mgr;m (supplied by 23.5-kHz ultrasonic power). Needle-type probes have 89- and 171-mm lengths, a 1.9-mm tip diameter, and 3.5- and 3.3-mm sheath diameters at the proximal site and produce a tip amplitude of 70 &mgr;m. All of these instruments are compatible with magnetic resonance imaging.METHODSThe newly developed handpiece and probes were used in an experimental model. The 119 mass lesions treated included giant thrombosed aneurysms, various gliomas, vestibular schwannomas, deep-seated meningiomas, clival tumors, and suprasellar tumors.EXPERIENCE AND RESULTSThe handpiece and probes were safely used in regions that are difficult to access, such as the third ventricle and the cerebellopontine angle. It was possible to manipulate the needle-type probe in the suprasellar region through the transsphenoidal route, and the probe was very efficient for thrombectomy in giant aneurysms. The ultrasonic power of keyhole-type probes was sufficient to remove meningiomas.CONCLUSIONThis newly developed neurosurgical handpiece with angled probes has great utility for microscopic dissections, because of its small size and light weight.