Stereotaxic Impactor for Traumatic Brain Injury (TBI) Induction

Traumatic brain injury is one of the leading causes of morbidity and mortality among young people around the world. [15] 

Animal models are commonly used to study brain trauma and test new treatments. The Controlled Cortical Impact (CCI) model is the most popular and accepted method for researching the physical, mental, and behavioral problems that result from brain injury. CCI is favored because it allows precise control over how the brain tissue is damaged. [16]

Here’s a step by step guide for TBI induction:

1. Set Up the Stereotaxic Instrument: Prepare all necessary materials, ensuring the area and instruments are thoroughly cleaned and sterilized. [17]
2. Shave the Fur: Use an electric razor to shave the fur from the ears to just between the eyes, moving in different directions to clean the area effectively. Apply povidone-iodine to the shaved area, avoiding the eyes. [17]
3. Mount the Animal: Secure the animal onto the stereotaxic apparatus by inserting the ear bars into the ear canal and tightening them. Ensure the head is immobile and level with a ruler. Confirm the 90° angle between the ruler and the animal’s scalp using the stereotaxic instrument. [17]
4. Make the Incision: Using a sterile scalpel, make an anterior/posterior incision on the scalp from the lambda (a point at the back of the skull) to between the eyes. Pinch the skin with sterilized hemostats to keep the incision open and dry the exposed skull surface with sterile cotton swabs. [17]
5. Position the Guide Cannula: Mount the guide cannula and locate bregma on the skull. Record the anterior/posterior and lateral coordinates, then find the correct coordinates for probe placement using a stereotaxic atlas. Adjust the guide cannula to the correct coordinates and record the ventral coordinate. Mark the drilling spot on the skull with a sterile pencil. [17]
6. Drill the Hole: Sterilize the drill bit and carefully drill a hole at the marked location until you penetrate the skull. Ensure the guide cannula can pass through the hole without touching the sides. Use a sterile needle to puncture the meninges for unobstructed cannula insertion. [17]
7. Prepare for Skull Screws: Using a hand drill, create six holes for skull screws: two anterior, two lateral, and two posterior to the cannula hole. Sterilize the screws and anchor them tightly onto the skull. [17]
8. Insert the Guide Cannula: Clean the guide cannula with ethanol and saline, then mount and lower it to the proper ventral coordinate, ensuring a perfect vertical insertion without touching the sides. [17]
9. Secure with Dental Cement: Place an anchor screw medially behind the posterior skull screws. Mix a thin batch of liquid dental cement to cover the guide cannula, screws, and skull. Apply a thicker batch to secure the area, ensuring smoothness to prevent skin irritation. [17]
10. Finish the Cement Application: As the cement thickens but before it solidifies, separate the skin from the cement cap and mold it to ensure smoothness. [17]
11. Allow Cement to Dry: Let the dental cement dry completely before removing the animal from the apparatus. Remove the hemostats and apply bacitracin around the cement cap. [17]
12. Fit the monoinjector to the stereotaxic frame: Lower the needle into the hole to the target DV coordinate and inject. Leave the injection needle in place for at least 30 sec after completion of the injection and before removal of the needle. [18]
13. Remove the monoinjector and seal the hole with bone wax. Suture the incision and remove the animal from the stereotaxic frame. [18]
14. Post-Procedure Injections: Administer 0.25 ml of penicillin intramuscularly, followed by 1 ml of saline subcutaneously. [17]
15. Monitor Recovery: Place the animal in its cage and monitor it until consciousness is regained. Return it to its room for recovery. [17]
16. Post-Op Monitoring: Check animals daily for signs of infection, pain, or distress until the end of the experiment. Look for low movement, distress vocalization, hunched posture, diarrhea, swelling, discharge, and lack of feeding/drinking. Administer buprenorphine for pain and antibiotics for infections as needed. Euthanize the animal if symptoms persist despite treatment. [17]