Electromyography Nerve conduction study (NCS) Electromyography (EMG) Evoked potential study (EP)

Abnormal Wave Latency (msec) Amplitud e (uV) - + Decreased amplitude: axonal/neuronal damage ;axono- /neuronopathy Prolonged latency, decreased velocity: myeline damage ;demyelination A B C

Nerve Conduction Study Motor NCS Sensory NCS Reflex study –F-wave –H-reflex –Blink reflex Repetitive nerve stimulation study

Electromyography Needle EMG –Conventional needle EMG –Quantitative EMG –Single Fiber EMG Surface EMG

Mortor NCS

Axonal degeneration vs Demyelination CharaterAxonalDemyelinating NCVN  Amplitude  N or CB DurationNDispersion(  ) F-latency 

F-wave, H-reflex

Blink reflex

RNS

Electromyography Insertional activity Spontaneous activity –Positive sharp wave –Fibrillation potential –Fasciculation Motor unit potential Recruitment

Amplitude Duration Phase

Neuropathy vs Myopathy CharacterNeuropathyMyopathy IA   SPA(+)(+)(-) MUP amp  duration  phase  Recruitment 

- Peripheral neuropathy: DM, Entrapment neuropathy, Radiculopathy, Guillain-Barre syndrome (AIDP), CIDP - Motor neuron disease: ALS, PLS - Myopathy: inflammaotory polymyositis, dermatomyositis - Neuromuscular junction disoder (Myasthenia gravis, Lambert-Eaton syndromes): Repetitive nerve stimulation test (Jolly test) - Autonomic function test and sphincter EMG: MSA vs. IPD - Blink reflex and facial NCS: Bell’s palsy, Trigeminal neuralgia, Blephalospasm Clinical utility of EMG and NCS