Surgical intervention can be quite effective for treating certain types of medically intractable neurological disease. Currently available surgical modalities while effective, generally involve invasive procedures that can result in surgical injury to non-target tissues. Consequently, it would be a value to expand the range of surgical approaches to include a technique that is noninvasive and produces neuronal lesions.
This video presents a method for producing focal neuronal lesions in the brain in a noninvasive manner. This method is termed precise interest cerebral noninvasive guided surgery and will be referred to here by its acronym Ping. The general approach for this method is to open the blood-brain barrier focally and trenchantly using MR-guided focused ultrasound.
Then to administer a blood-brain barrier impermeable neurotoxin systemically. The neurotoxin, then gains access to the brain parenchyma only where the blood-brain barrier has been opened. This producer neuronal loss that is restricted to the target region of the blood-brain barrier opening.
The key steps of the method are animal preparation, the ping procedure, and post-mortem cellular analyses. The anesthetized animal is placed on a surgical drape over a heating pad. 2%ISO flooring is delivered through a nose cone for the maintenance phase of anesthesia.
A scavenging line is positioned for of the anesthetic. The scalp is shaved in preparation for the later application of acoustic gel. A line is then placed in the tail vein.
This line will be used for the administration of micro bubbles and contrast agent during the sonication phase of the ping procedure and will be used for the infusion of quinolinic acid during the post sonication phase. The line is secured with tape. This photograph shows key features of the sled in which the animal is placed for the focused ultrasound procedure.
In preparation for placing the animal in the sled. A beaker of water, a syringe containing acoustic gel, and a small screwdriver are required. This view from above the sled shows the procedure for positioning the animal.
The transducer is removed and placed to the side of the sled. The animal is then placed in the sled and the head is positioned. An incisor bar and ear bars are used to secure the head.
When the ear bars are positioned, they are secured by tightening using a small screwdriver. Water is applied to the surface of the scalp. This is followed by application of acoustic gel with the syringe on the scalp.
Additional water is placed on the acoustic gel and on the base of the transducer. The transducer is then lowered onto the acoustic gel and secured. A pneumatic sensor is then taped to the body of the animal for monitoring respiration.
The control room for the MRI and focused ultrasound equipment is comprised of two primary stations. The station to the left, where the investigator is sitting, is the planning area for targeting focused ultrasound. The station to the right is the control area for the MRI system.
The copper reinforced window B on the MRI station looks into the room housing the seven Tesla magnet. Looking through the window. The magnet can be seen with a sled leading into the aperture of the magnet.
Specialized software is used for planning the target of the focused ultrasound. This software controls a combination of electronic and mechanical movement of the targeting system. The trajectory planner defines the target and chose the target area.
In this case, the sample target is the striatum and the target site is mapped onto a T2-weighted coronal MRI section. After establishing the targeting, the animal receives an injection of microbubbles via the tail vein line. This process has not visible through the window because it takes place on the far side of the magnet were filming is not possible.
Focused ultrasound is delivered 30 seconds after the injection of micro bubbles. Immediately after delivering focused ultrasound, get a dynamite is injected via the tail vein line. And the opening of the blood-brain barrier is confirmed using contrast-enhanced T1-weighted imaging.
After receiving sonication, the animal is returned to the surgical hood where 2%ISO fluorine anesthesia is maintained through a nose cone. A syringe filled with quinolinic acid is attached to an infusion pump and the output is connected to the tail vein line for a one-hour infusion into the animal. Cortical malformations are surgical targets in certain neurological disorders, such as drug-resistant epilepsy.
The tish rat is a genetic neurological mutant with a cortical malformation characterized by bilateral heterotopia. In this experiment, the heterotopia in a tish rat were targeted on both sides of the brain. Frames A and B showed the same T2-MRI of a tish brain taken one-day post ping.
Frame A depicts the location of the normally position neocortex and the underlying heterotopia H the positions of the lateral ventricles are also shown in frame B areas of hyperintensity indicated by arrows correspond to the targets of sonication in the heterotopia. The white arrow indicates a medial target in the heterotopia on the left side of the image, and the yellow arrow indicates a lateral target in the heterotopia and on the right side of the image. Five days post ping the animal was euthanized, and the brain prepared for histological analysis.
Fluoro Jade staining was performed to identify degenerating neurons in the brain. The rectangle in the T2 section indicates the fluoro Jaden stained area of the brain shown at the right. The bright yellowish-green stained area contains numerous degenerating neurons.
At higher magnification individual degenerating neurons can be seen. The ping method provides a noninvasive approach for destroying neurons in a targeted area of the brain. Trenchant vocal opening of the blood-brain barrier allows a systemically administered neurotoxin to gain access to the brain parenchyma in a precisely targeted manner.
This method has been used successfully in rats and mice. Importantly, ping has been used to disconnect neurocircuitry in brain regions that are commonly the target of surgical intervention for treating neurological disorders such as epilepsy.
