EMG

Electromyography (EMG)fact file

An electrical activity recorded from the muscles is known as an Electromyogram (EMG), EMG activity is generated by temporal and spatial summation of the postsynaptic MAPs.

What is an EMG

• EEG recordings are used to display the bioelectric potentials in muscle fibres, whole muscles and motor units.
• The focus is on the muscle but the purpose is to asses the nerve or nerve root activity
• When monitoring in IONM, there is a rough positive correlation between the EMG activity observed and the amount of irritation on the nerve root

Purpose

Provides instantaneous feedback of motor nerves and nerveroots Detects mechanical irritation ◦ Corrective actions ◦ Severity and duration of irritation Documentation of nerve root irritation Triggered EMG is used to identify nerves and test pedicle screws

aDvantages vs disadvantages

• EMGs are real time recordings and therefore clincians can have direct impact on outcomes if there is a perceived issue
• Along with this, they can give constant updates to the surgeons, so they are informed about the patients state throughout the duration of the surgery

• EMGs can be distrupted by various artifacts, caused by necessary equipment such as ECGs
• Though IONM utlised the use of EMG to assess nerves and nerve roots, the muscle is the main component, therefore any kind of muscle relaxant interferes with the recordings