Basic Nerve Conduction Studies

When a nerve is electrically stimulated a reaction should occur. This response can be recorded and measured.

Grounding

• Ground leads must be applied first to patients
• Never use multiple grounds simultaneously, as this creates dangerous “ground loops”
• Positioning should be between stimulating and recording electrodes at equal distances when possible
• Grounds are typically large metal plates or uninsulated needles

Stimulation

• Electrodes are placed 1.5-3 cm apart
• The cathode should point toward conduction direction
• Current must be increased until maximal response is achieved, then increased 25-50% more
• Difficulties include improper placement, edema, obesity, and electrode cream bridging
• Stimulus duration can be increased to overcome tissue resistance
• Bare-tip insulated needles can be positioned near nerves as cathodes with surface electrodes as anodes

Recording

• Motor responses: Place active electrode over muscle belly at motor point
• Sensory nerves: Position active electrode over nerve itself for nerve action potential
• Reference electrodes placed distally
• Motor recording typically uses surface disc electrodes (0.5-1 cm diameter)
• Sensory recording uses various surface electrode styles or bare-tip insulated needles