SNAP: sensory nerve action potential. Electrical signal traveling along sensory nerve. Recorded on skin surface overlying nerve; measured in microvolts.

Sensory nerve conduction: stimulate nerve (usually a pure sensory branch) distally, record SNAP proximally.

CMAP: compound motor action potential. Electrical signal from contracting muscle. Recorded on skin surface overlying muscle; measured in millivolts.

Motor nerve conduction: stimulate nerve proximally, record CMAP from muscle distally.

Amplitude of waveform: indicates strength of electrical impulse. Reduced with axonal loss.

Latency: time between stimulation and action potential (SNAP or CMAP).

Nerve conduction velocity: latency of action potential/distance between stimulation and recording sites. Slowing usually reflects demyelinating injury.

Conduction block: severe, focal demyelinating lesion prevents action potentials from being transmitted downstream, causing loss of waveform amplitude on one segment of the nerve.

F response: stimulate motor nerve antidromically (toward nerve root) with supramaximal intensity. Action potential reaches anterior horn cells via ventral root, then travels back down motor nerve orthodromically (in direction of normal flow); time for round trip = F wave latency. Measures integrity of proximal motor pathways (root, anterior horn cell); no synapse involved.

H reflex: electrical equivalent of ankle jerk reflex; stimulate sensory afferents of tibial nerve at knee, activating
monosynaptic stretch reflex pathway to record soleus muscle contraction. Measures integrity of segmental reflex pathway, including sensory nerve and root, spinal segment (dorsal column, synapse, anterior horn), motor root and nerve. Mainly used to assess L5-S1 nerve root compression.