Electrodes placed on the skin and brief electrical stimuli are used to measure how quickly and strongly a nerve conducts. It is used in the diagnosis of nerve entrapments, polyneuropathy, and nerve injury.
Indication
- Numbness, tingling, or weakness in the hands, arms, or legs
- Suspected nerve entrapment such as carpal tunnel syndrome or cubital tunnel syndrome
- Evaluation of polyneuropathy related to diabetes, vitamin deficiencies, or chemotherapy
- Monitoring of nerve injury and recovery after trauma or surgery
- Differential diagnosis of Guillain-Barré syndrome and chronic inflammatory polyneuropathy
- Evaluation of nerve root involvement due to lumbar or cervical disc herniation, together with EMG
- Investigation of unexplained muscle weakness
Preparation
- Do not apply cream, lotion, or oil to the skin before the procedure
- Inform the physician about your medications, blood-thinning therapy, and implanted devices (pacemaker, deep brain stimulator)
- Keeping the area to be tested clean and dry improves measurement quality
- You do not need to fast; in cold weather, you may wait for the area to warm up before testing, as cold extremities can affect measurements
- Wear loose, easy-to-remove clothing
How it's performed
- Adhesive recording electrodes are placed on the skin surface over the nerve and muscle to be tested
- Brief, low-intensity electrical stimuli are delivered to specific points along the nerve path
- The device records the time for the stimulus to traverse the nerve (conduction velocity) and the signal amplitude
- Both motor (muscle-activating) and sensory (sensation-conducting) nerves can be examined separately
- Depending on the number of nerves tested, the procedure takes 15-45 minutes; it is often performed together with EMG
- At the end of the procedure, the electrodes are removed; the skin is wiped, and you can return to daily activities immediately
Post-procedure
- Results are usually ready the same day and interpreted together with clinical findings and EMG if needed
- Based on the results, physiotherapy, medication, splint use, or surgical evaluation is planned
- Repeat testing at intervals may be needed for monitoring recovery after nerve injury and surgery
- A follow-up nerve conduction study may be requested to assess treatment response
- You are advised to return for new or worsening complaints
Risks
- The electrical stimulus delivered is very brief and of low intensity; most patients describe it as a mild shock or pinprick
- Transient mild redness or skin irritation may occur on the skin surface
- No permanent harm or nerve damage is expected after the procedure
- In patients with a pacemaker, implanted defibrillator, or other medical device, the application area and technique must be selected carefully
- Results may be misinterpreted in very cold extremities; the area is warmed before measurement
FAQ
Is the electrical stimulus dangerous? Can it harm the heart?
The stimulus is very brief and quite low intensity; it does not cause permanent harm in healthy individuals. Even in patients with devices like pacemakers, it can be applied safely with proper technique; if you have a device, be sure to inform the staff.
Is it the same as EMG?
Not exactly. The nerve conduction study is performed on the skin surface and measures nerves. EMG, on the other hand, evaluates the electrical activity of muscles using a needle electrode. The two are often performed in the same session.
Do I need to stop my medications before the procedure?
Generally not. Still, inform your physician about blood thinners, muscle relaxants, and neurological medications; dose adjustment may be recommended if needed.
If the result is normal, what is causing my symptoms?
The nerve conduction study only evaluates peripheral nerves and usually large-fiber nerves. Small fiber neuropathy, muscle diseases, or central nervous system problems can present with normal results. Your physician will decide whether further testing is needed.
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