A CLOSED LOOP SYSTEM FOR PARTIAL RESTORATION OF SPINAL CORD REFLEX FUNCTION
Fathy Badran, Mohamed
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Current spinal cord injury treatments focus on compensating for the loss of speciﬁc motor control capability or sensory input. They can be categorized as rehabilitation methodologies designed to help patients cope with their injury rather than restoring them to their pre-injury state. In this thesis, a diﬀerent approach is investigated on how to use an implanted system, which will function in a biomimetic manner, to replace information transmission across a spinal nerve lesion. A proof of concept case study on a dorsal root lesion was performed. In this study, a designed closed loop system was tested both in vitro and in vivo in an animal study that involved one dog. The thesis hypothesis is that following the transection or tight ligature of the L5 dorsal root proximal to the root ganglion, the lost patellar tendon reﬂex would be partially restored by capturing the volley created by tapping the tendon and transmitting it across the lesion. This volley would be captured by the recording electrode distal to the lesion and be transmitted accordingly to the stimulating electrode either on the dorsal root proximal to the lesion or on the L5 ventral root. The lost patellar tendon reﬂex was regained using the closed loop system under the condition of maintaining a close contact between the electrodes and the nerves. The validation of this concept in an animal study is an important step towards the long-term goal of limb function restoration, following the occurrence of spinal root lesion, using a closed loop system. But serious challenges remain to achieve this objective. In this context, the thesis addressed the neurological challenges toward the generalized application of the closed loop system to various spinal root lesions. Furthermore, a prototype shape memory microelectrode was fabricated to address the issue of maintaining a close contact of the electrode with the nerve. Several fabrication issues were recognized and a new proposed microelectrode is proposed for large ﬁbers. The long-term application of the closed loop system was evaluated concerning acute and chronic studies. Finally, the lessons learned from this study and their impacts on future animal testing were addressed.