IP Requirement: Industry IP

Experience Requirement:

– Mechanical Design

– Electronics

– Rapid Prototyping

A peripheral nerve, one that has exited the spinal cord into the upper or lower limb, can be injured through different mechanisms: stretch, crush, or penetrating laceration. Nerve recovery and regeneration is dependent on the type, location and severity of injury. Mild stretch or crush injuries usually recover within 6-12 weeks, however, severe injuries may never recover, leading to permanent sensory or motor deficit. Penetrating lacerations usually require surgical repair with or without nerve graft reconstruction. After a 4 week period of ‘rest’, a surgically repaired nerve typically regenerates at a rate up to 1 millimeter per day. Sensory nerves are more resilient than motor nerves and may recover several years after injury. Motor nerves, however, have a limited time for healing as the ‘motor endplates’ (where the muscle receives the nerve signal) die off without innervation from the injured nerve. If a threshold of motor endplates does not achieve sufficient reinnervation by 18-24 months, clinical motor recovery is no longer possible as the muscle atrophies and, therefore, prompt surgical repair or release is often indicated. 

The quiescent phase, that before motor or sensory response is achieved, may last several months up to a year and is dependent on the length of nerve recovery to the sensory receptor or motor endplate. The closer the nerve injury is to its target, the faster the recovery after repair. For example, digital nerve repair in the finger returns sensation to the tip of the finger within 3 months, however, common sensory nerve repair in the forearm returns sensation to the tip of the finger within 6-12 months. 

Once a nerve has been surgically repaired or released, motor and sensory recovery is measured periodically in the clinic. An ‘advancing Tinel’s test’ is performed by the clinician through tapping on the nerve distal to the repair site. Shock-like sensations felt by the patient in response to the tapping of the nerve may indicate distal nerve regeneration, however, this test is merely subjective and unreliable. Postoperative electromyography and nerve conduction velocities are objective studies that can detect distal response, but only until a threshold of nerve regeneration has been achieved and are therefore limited by time and recovery length. Unfortunately, there are no reliable objective measures to accurately confirm and monitor nerve regeneration in the quiescent phase. The patient and surgeon would greatly benefit from an implantable device that confirms, tracks and monitors the nerve regeneration process. 

A small grain-sized piezoelectric sensor, called neural dust mote [1,2], can be surgically implanted distal to a repaired nerve in order to detect and record electrical activity. Crystals within the piezoelectric sensor vibrate with ultrasound waves, generating electricity to power a tiny transistor aboard the mote, thus the sensor requires no batteries or external power supply. Action potentials through a regenerating nerve alter crystal vibrations creating backscatter. Such alterations in the sensor readout signal can be detected outside the body through an ultrasound wavefront which can be processed through a software algorithm within an external device to confirm, monitor, and track nerve regeneration en vivo and in real time.

A hand-held tracking device is needed to detect and process responses from the implanted sensor. This device must be lightweight, hand-held and ergonomically designed for ease of use within a busy clinic or physical therapy office setting. Confirmation, tracking and monitoring information must be accessible to both the patient and treatment team. First and foremost, detection of action potentials from the distally placed sensor confirms that the nerve is, in fact, regenerating towards its target. This is the most important piece of postoperative information, providing reassurance that the surgery was successful.  

The sponsor will requires assignment of generated intellectual property and NDA’s from all team members before starting the project. 

References 

1. Seo, Dongjin, Jose M. Carmena, Jan M. Rabaey, Elad Alon, and Michel M. Maharbiz. “Neural dust: An ultrasonic, low power solution for chronic brain-machine interfaces.” arXiv preprint arXiv:1307.2196 (2013). 
2. Seo, Dongjin, Ryan M. Neely, Konlin Shen, Utkarsh Singhal, Elad Alon, Jan M. Rabaey, Jose M. Carmena, and Michel M. Maharbiz. “Wireless recording in the peripheral nervous system with ultrasonic neural dust.” Neuron 91, no. 3 (2016): 529- 539.