Nerve Conduction studies

Nerve Conduction studies NCS - ANS used to evaluate function of motor & sensory nerves of body NCV - ANS study mainly for evaluation of parethesis &/or weakness of arms & legs disorders commonly diagnosed - ANS peripheal neuropathy, myopathy, diseases of neuromuscular junction Current-NCS - ANS electrodes measure current that travels down nerve pathway EMG - ANS sometimes combined w/ NCS NCS components - ANS Compound Motor Action Potential (CMAP) Sensory Nerve Action Potential (SNAP) Latency - ANS time it takes for electrical impulse to travel from stimulation to recording site. measured in millisec (ms) Amplitude - ANS size of response. measured in millivolts (mv) Motor Nerve Conduction Study - ANS can be abnormal w/ normal SNAPS Motor Nerve Sites - ANS median nerves (R/L), ulnar nerves (R/L), peroneal nerves (R/L), tibial (R/L) Sensory Nerve - ANS represents conduction of impulse along sensory nerve fibers Sesnory Amps - ANS much smaller that motor, usually in mv microvolt range Sensory NCV latency - ANS useful in localizing lesion in dorsal root ganglion (DRG) DRG - ANS located in neural foramen & contains sensory cell body Sensory Nerve Sites - ANS median nerve (R/L), ulnar (R/L), sural nerves (R/L), saphenous nerves (R/L) antidromic motor - ANS conduction opposite of normal direction response to spinal cord orthodromic motor - ANS conduction in correct normal direction response to recording electrode Conduction velocity - ANS derived by measuring limb length in millimeters from stimulation site to corresponding spinal segment H-Reflex - ANS NCS creates late repsonse that is electrically evoked analogue to monosynaptic reflex Interpretation of nerve conduction - ANS speed related to diameter of nerve & degree of myelination 50-60 meters per/sec - ANS approx normal conduction velocity different pathological processes - ANS result in changes in latencym changes in amp, slowing of conduction velocity slowing - ANS damage to myelin slowing across wrist - ANS carpal tunnel slowing of all nerve conductions - ANS generalized peripheral neuropathy (DM)