This article details a method for inducing controlled cortical traumatic brain injury in anesthetized mice. The procedure involves precise surgical techniques to expose the dura mater and apply an impact to simulate brain injury.
Take an anesthetized mouse with an exposed skull.
Identify the sagittal and coronal sutures, which are skull joints, to locate the target site for injury.
Drill through the skull and remove the bone flap to expose the dura mater, the protective layer over the brain's cortex.
Secure the mouse in a stereotaxic frame with an attached impact device.
Position the impactor tip over the exposed area to inflict traumatic brain injury.
Lower the tip to contact the dura mater, retract it to set an impact depth, and apply the injury.
Withdraw the impactor and remove the mouse from the frame.
Control bleeding from the injury site, then close the scalp using surgical adhesive.
Administer an analgesic subcutaneously to alleviate pain and allow the mouse to recover.
The injury causes progressive damage to the cortex and underlying hippocampus and thalamus regions, along with fluid accumulation, impairing cognitive functions and motor coordination.
To induce a controlled cortical traumatic brain injury, first, use a scalpel to make a 1 centimeter incision along the midline of the scalp to expose the skull. Retract the scalp from the operative site, and identify the sagittal and coronal sutures on the exposed skull.
To perform a craniectomy, equip a micro drill with a 5 millimeter trephine drill bit, to activate the drill at maximum speed and apply the bit perpendicular to the skull, 2 millimeters to the left of the sagittal suture and 2 millimeters rostral to the coronal suture with gentle, even pressure. A slight give will be felt when the drill penetrates the skull.
Use forceps and a small-gauge hypodermic needle to remove the bone flap, fully exposing the underlying dura mater, and rotate the impactor tip into the operative field. Secure the bilateral temporal bones between the miniature ear bars of the stereotaxic frame, and lock the incisors within the incisor clamp to create a stable three-point hold on the mouse head. Lower the tip until it makes contact with the exposed dura mater. The contact sensor of the instrument will make an audible tone to alert that contact has been made.
Retract the impacting tip from the zero point, and lower the impactor position on the stereotaxic frame to set the desired impact depth. Then activate the impactor on the actuating device before rotating the device back out of the field to allow the animal to be removed from the frame.
Immediately after the injury, apply direct pressure from a sterile cotton tipped applicator to the skull and injured cortical surface to control any bleeding, and use a fresh applicator to dry the skull. Close the scalp over the craniectomy according to standard techniques, and administer postoperative analgesia. Then, place the animal in the lateral decubitus recovery position in a clean, pre-warmed cage with monitoring until full recumbency, and measure the body weight every three days throughout the course of the experiment.
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