Neurosurgical apparatus has a guidance device having a guide tube and a neurosurgical instrument for insertion into the guide tube. The inner surface of the guide tube is arranged, for example profiled, to at least partially engage the outer surface of the neurosurgical instrument when inserted therein. The guide tube thus guides the neurosurgical instrument along a predefined path through the guide tube. At least one of the guidance device and the outer surface of the neurosurgical instrument are configured to provide a fluid return path for carrying any fluid displaced from within the guide tube during insertion of the neurosurgical instrument into the guide tube. A seal may also be provided for sealing the fluid return path.
