User Instructions for FMA Insertion

Introduction:

The Model VPI-002 FMA insertion tool can be used with any commercial micro-drive system. The polished stainless-steel 16-gauge cannula, which is used to pick up the FMA substrate, can be mounted to most microelectrode holders or micro-drive electrode assembly clamping devices. The FMA insertion tool uses a vacuum pump system that provides enough suction to allow slight manipulations of the FMA substrate. It has a white “wand” that allows the FMA substrate to be released without having to turn off the vacuum pump. A stand is provided to hold the wand near the surgical field. The wand, stand, and Tygon tubing leading from the wand to the cannula can be gas sterilized, however, it may be desirable to remove the Tygon tubing from the wand and sterilize it separately and then re-attaching. The Tygon tubing and cannula can also be autoclaved but it is not recommended to autoclave the wand. There is a small round button on the side of the wand that blocks the vacuum and can be left in the open position at all times.

FMA Positioning:

The investigator should manipulate the substrate to ensure it is perpendicular to the tissue into which it will be inserted and is over the intended point of insertion. Optimum placement of either the connector or the titanium pedestal that supports the connector should be completed prior to removing the carbo wax that protects the microelectrodes. This will minimize the possibility of damaging the electrodes. It is not recommended that the substrate be moved more than a couple of millimeters beyond its natural resting place because the array can move as result of the cable being moved. The amount of vacuum the insertion tool provides has been purposely minimized so that it will not allow the user to position the FMA substrate to a point significantly beyond its natural resting place. Ideally the investigator has positioned the FMA where it is to implanted.

Operation:

After the FMA substrate has been positioned over the target area, support the substrate so that it rests above the tissue. Dissolve the carbo wax off the FMA substrate by gently squirting warm (40 to 50 degree centigrade) distilled water over the FMA substrate. Gauze or other sterile material may be placed below the FMA substrate to collect or provide convenient run off. Carbo wax or Polyethylene Glycol is inert and bio compatible. In fact, it has been used to hold microwire arrays together as they are inserted into the brain.

Position the stainless-steel cannula over the FMA substrate. When it is just barely touching the substrate and positioned in the center of the top ceramic cup, turn the vacuum pump on by pressing the green switch. Lower the array slowly until it produces a slight dimpling of the pial surface. Allow the pia to relax for several minutes and then lower the array again, no more than 1 or 2 millimeters, and allow the pia to relax again. The electrodes should “pop” through the pia after several minutes. Repeat this process, never allowing the pial membrane to dimple more than a couple of millimeters. Depending on the length and number of electrodes in the array, it may take from 20 to 50 minutes to totally implant the array. Once the array is implanted so that the bottom ceramic substrate is flush with the surface of the pial surface, push the frosted round button on the wand to release the substrate. Retract the stainless steel cannula and turn off the vacuum pump.