Patient Education and Consent

Patient instructions

No patient preparation is necessary, but patients should remove their jewelry and avoid using any skin lotions on the day of testing.

Consent

Verbal or written consent must be obtained from patient or caretaker if the patient lacks decision-making capacity. Diagnostic purpose and benefits should be explained. The patient should also be informed about what to expect from different components of the exam to help reduce anxiety that may occur. With EMG, there is a risk of minimal bleeding and hematoma and the patient should disclose any bleeding disorders or use of anticoagulants. The patient should also disclose whether they have implanted electrical devices such as pacemakers, defibrillators, AICDs, spinal cord stimulators, and so on. There is minimal risk of infection from needle insertion and any recent infections or use of antibiotics should be disclosed.^[13]

Equipment

Many commercial EMG and nerve conduction study units are available.

Several manufacturers produce computer-based EMG equipment. This generally includes a stimulator, amplifier, preamplifier, speaker, computer, printer, and many different electrodes.

Patient Preparation

EMG and nerve conduction studies are routine studies done in a physician’s office or ambulatory clinic. No special preparation is necessary except that patients should refrain from using any skin lotions prior to the test.

Patients should be thoroughly evaluated to plan the study. The procedure should be explained to the patient prior to commencing the study.

Anesthesia

No anesthesia is generally used for this procedure.

Positioning

The patient will have to move in different positions depending on what areas of the body are examined.

Monitoring & Follow-up

There is no recovery period as anesthesiology is generally not used.

Technique

Media Gallery

Median sensory nerve conduction set up
Median sensory nerve response
Distal median motor nerve conduction set up
Proximal median motor nerve conduction set up
Median motor nerve responses.

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Table 1. Findings of Nerve Conduction Studies and EMG in Carpal Tunnel Syndrome ^[1]

Severity of Carpal Tunnel	Sensory Nerve Action Potential	Compound Motor Action Potential	Needle EMG Activity
Mild	Prolonged latency	Normal	Normal
Moderate	Prolonged latency and decreased amplitude	Prolonged latency	Normal
Severe	Absent	Prolonged latency and decreased amplitude	Abnormal activity

Table 2. Common Disorders ^[2]

Disorder	Distal Motor Latency	Distal Sensory Latency	Conduction Velocity	Amplitude of the Evoked Response
Motor neuron disease	Normal	Normal	Normal	Reduced
Axonal polyneuropathy	Normal	Normal	Slight decrease	Reduced
Demyelinating polyneuropathy	Prolonged	Prolonged	Decreased	Normal
Entrapment neuropathy	Normal (may be prolonged if this is a distal entrapment such as carpal tunnel syndrome)	Normal (May be prolonged if this is a distal entrapment such as carpal tunnel syndrome)	Decreased at the entrapment region	May be decreased when stimulating proximal to the site of entrapment
Radiculopathy	Normal	Normal	Normal	Motor response may be decreased
Myopathies	Normal	Normal	Normal	Decreased motor amplitudes