Stereotaxic Cisterna Magna Approach for Therapeutic Delivery in a Mouse Model

Begin with an anesthetized mouse on a stereotaxic frame with its head tilted.

A scalp incision in the mouse exposes the dura mater covering the cisterna magna, a cerebrospinal fluid or CSF-filled space between the cerebellum and brainstem.

Using forceps, grasp the dura and create a small opening in it to access the cisterna magna.

Use a sterile swab to remove excess CSF.

Identify the anatomical reference point where the spinal cord connects to the brainstem, then determine the stereotaxic coordinates.

Lower the stereotaxic arm holding the micropipette, which contains the therapeutic solution.

Advance the micropipette through the cisterna magna into the brainstem at the predetermined coordinates.

Inject the solution slowly, and hold the pipette briefly to prevent backflow.

The therapeutic solution directly reaches the brainstem and upper spinal cord regions, which are difficult to reach using standard stereotaxic methods.

View the dorsal surface of the brainstem with detailed landmarks through the open dura.

Use the angled forceps to grab the dura extending from the occipital bone to the atlas, then use the spring scissors to make a small opening of approximately 0.5 to 1.5 millimeters in the dura. Once the dura is opened, drain excess cerebrospinal fluid with a sterile Q-tip. The obex, the point where the central canal opens into the fourth ventricle, is the standard anterior-posterior and mediolateral zero point.

Position the pipette or syringe to the target using the stereotaxic arm. Lower the arm of the dorsal onto the dorsal surface which forms from the dorsoventral zero point. Then lower the pipette onto the brainstem and inject the solution.

Leave the needle in place for one to five minutes after injection to avoid a needle track when using volumes between 3 to 50 nanoliters. Then lift the pipette or syringe using the stereotaxic arm and repeat this for multiple targets.