ABSTRACT
The peroneal nerve anatomy of the rabbit distal hindlimb is similar to humans, but reports of distal peroneal nerve conduction studies were not identified with a literature search. Distal sensorimotor recordings may be useful for studying rabbit models of length-dependent peripheral neuropathy. Surface electrodes were adhered to the dorsal rabbit foot overlying the extensor digitorum brevis muscle and the superficial peroneal nerve. The deep and superficial peroneal nerves were stimulated above the ankle and the common peroneal nerve was stimulated at the knee. The nerve conduction studies were repeated twice with a one-week intertest interval to determine measurement variability. Intravenous vincristine was used to produce a peripheral neuropathy. Repeat recordings measured the response to vincristine. A compound muscle action potential and a sensory nerve action potential were evoked in all rabbits. The compound muscle action potential mean amplitude was 0.29 mV (SD ± 0.12) and the fibula head to ankle mean motor conduction velocity was 46.5 m/s (SD ± 2.9). The sensory nerve action potential mean amplitude was 22.8 µV (SD ± 2.8) and the distal sensory conduction velocity was 38.8 m/s (SD ± 2.2). Sensorimotor latencies and velocities were least variable between two test sessions (coefficient of variation â=â 2.6-5.9%), sensory potential amplitudes were intermediate (coefficient of variation â=â 11.1%) and compound potential amplitudes were the most variable (coefficient of variation â=â19.3%). Vincristine abolished compound muscle action potentials and reduced sensory nerve action potential amplitudes by 42-57% while having little effect on velocity. Rabbit distal hindlimb nerve conduction studies are feasible with surface recordings and stimulation. The evoked distal sensory potentials have amplitudes, configurations and recording techniques that are similar to humans and may be valuable for measuring large sensory fiber function in chronic models of peripheral neuropathies.
Subject(s)
Hindlimb/innervation , Neural Conduction , Peripheral Nervous System Diseases/physiopathology , Peroneal Nerve/physiopathology , Action Potentials , Animals , Disease Models, Animal , Evoked Potentials , Female , RabbitsABSTRACT
OBJECTIVE: Median nerve entrapment neuropathy at the wrist can be accompanied by slowed motor conduction within the forearm. Existing studies conflict regarding a correlation between the severity of the entrapment neuropathy in carpal tunnel syndrome (CTS) and slowing of median motor nerve conduction velocity (MNCV) in the forearm. Here, it was asked if there is a correlation between markers of CTS severity and median forearm MNCV, and if there is an explanation for the preceding conflicting results. METHODS: Median MNCV in the forearm was correlated with neurophysiologic markers of severity of a median neuropathy at the wrist in 91 hands from 64 patients with clinical and electrodiagnostic evidence of CTS. RESULTS: Median MNCV within the forearm segment was negatively correlated with the median nerve distal motor latency (r=-0.64, P<0.001, n=91) and positively correlated with the CMAP amplitude of the abductor pollicis brevis muscle (r=0.45, P<0.001, n=91). These correlations only occurred in patients with a prolonged median distal motor latency. Previous investigations that failed to find such correlations used variable or non-standardized methods or analyzed smaller numbers of patients. CONCLUSIONS: Slowing of median MNCV in the forearm is related to the severity of the entrapment of median motor fibers at the wrist. SIGNIFICANCE: Slowed forearm median MNCV can be a marker of motor nerve injury at the wrist.
Subject(s)
Carpal Tunnel Syndrome/physiopathology , Forearm/innervation , Median Nerve/physiopathology , Neural Conduction/physiology , Reaction Time/physiology , Action Potentials/physiology , Action Potentials/radiation effects , Adult , Aged , Aged, 80 and over , Carpal Tunnel Syndrome/pathology , Electric Stimulation/methods , Electromyography/methods , Female , Humans , Male , Middle Aged , Reaction Time/radiation effects , Statistics as TopicABSTRACT
TMS is a non-invasive tool for measuring neural conduction and processing time, activation thresholds, facilitation and inhibition in brain cortex, and neural connections in humans. It is used to study motor, visual, somatosensory, and cognitive functions. TMS does not appear to cause long-term adverse neurological, cardiovascular, hormonal, motor, sensory, or cognitive effects in healthy subjects. Single-pulse (<1Hz) TMS is safe in normal subjects. High frequency, high-intensity repetitive TMS (rTMS) can elicit seizures even in normal subjects. Safety guidelines for using rTMS have been published.
