gms | German Medical Science

Many experimental studies for cerebrovascular accidents such as stroke, infarction or subarachnoid hemorrhage take advantage of a rat model. Among the techniques to monitor cerebral blood flow are angiography, repeated MRI or laser doppler flowmetry. None of these allows for continued online measurement of blood flow velocity in the major cerebral arteries. In the present study we describe an extended craniotomy that enables direct doppler sonographic examination of rat cerebral vessels.

Female Wistar rats were anesthetized and immobilized in a stereotactic frame. The scalp was shaved and the incision performed from behind the left eye to the interauricular line. Under microscopical view the bone was removed by drilling from the sutura frontonasalis to the bregma and both orbital rims. The flap was elevated with a dissector and after opening of the dura hemostasis of bridging veins was achieved by coagulation. Ultrasonographic examination was performed using a triplex window displaying simultaneously B-mode, colour coded vessel rendering and doppler assessment of blood flow velocity. The animals were anesthetized for the measurements and flow assessments were repeated several times in each animal.

The extended craniotomy and repeated anesthesias were well tolerated by the animals. Brain structures, ventricular system and the major arteries were visible. Averaged mean flow velocities were: A. cerebri anterior: 11.8 cm/s, A. carotis: 13.1 cm/s, A. cerebri media: 9.4 cm/s, A. cerebri posterior: 6.3 cm/s, A. basilaris: 7.1 cm/s.

The presented method allows for direct visualization of brain structures, ventricular system and cerebral blood flow velocity. It might help in developing a reliable animal model of subarachnoid hemorrhage or in verifying the occlusion of the middle cerebral artery in rodent stroke models. Ongoing research focuses on determining normal values of blood flow velocities in cerebral arteries of the rat.