Diagnostic testing
EMG and nerve conduction study
Electrodiagnostic testing measures how nerves and muscles are actually functioning, rather than how they appear on an image. A nerve conduction study measures the speed and strength of signals travelling along a nerve; electromyography records the electrical activity of muscle. The two are performed together because each answers a different part of the same question, and together they can establish whether a nerve is affected, where along its course, how severely, and roughly how long it has been so.
What the test can establish
It answers questions that imaging cannot, which is why the two are often used together rather than as alternatives.
-
Whether a structural finding is causing symptoms
A disc herniation on MRI may or may not be affecting the nerve root. Electrodiagnostic testing measures the nerve itself.
-
Where a nerve is affected
It distinguishes compression at the wrist from a nerve root problem in the neck, which can produce overlapping hand symptoms and are treated entirely differently.
-
How severe it is
Grading severity informs whether to continue conservative treatment or to consider surgery, particularly in carpal tunnel syndrome.
-
Whether the problem is widespread
A generalised peripheral neuropathy can present as a local problem. Testing several nerves identifies the pattern.
What the test involves
It is performed in an outpatient visit, usually taking between thirty and sixty minutes.
-
Nerve conduction study
Small surface electrodes are taped to the skin and brief electrical pulses are applied over the nerve. Most people describe it as a sharp tapping sensation rather than pain.
-
Electromyography
A fine needle electrode is placed into selected muscles to record activity at rest and during gentle contraction. There is brief discomfort as it is inserted; no electrical current is delivered.
-
Preparation
Avoid lotions and creams on the skin that day. Blood thinners, pacemakers and implanted stimulators should be mentioned in advance, as they affect how the test is performed.
Limitations
Like any test it has boundaries, and knowing them prevents a normal result being over-interpreted.
-
Timing matters
Changes in muscle take time to appear after a nerve injury. Testing very early can be falsely reassuring, and repeat testing is sometimes needed.
-
A normal study does not exclude pain
The tests measure large nerve fibres. Pain carried by small fibres, and many musculoskeletal causes of pain, produce normal results.
-
It is operator-dependent
Results depend on which nerves and muscles are studied and how findings are interpreted, which is why the study is planned around the clinical question.
Common questions
Is it painful?
Most people find it tolerable. The nerve conduction portion feels like brief electrical taps; the needle portion involves short-lived discomfort in each muscle tested. It is over within the appointment.
Why do I need it if I have already had an MRI?
They measure different things. MRI shows structure; electrodiagnostic testing shows function. A structural finding that is not affecting nerve function calls for different treatment from one that is.
Are there side effects?
Minor bruising or soreness at needle sites is possible and settles within a day or two. Serious complications are rare.
Can I take my usual medication?
Generally yes. Blood thinners should be declared in advance, as should a pacemaker or implanted stimulator, so the study can be adapted.
General reference information, and not advice about your own case. It may not reflect the most recent guidance or what is offered on a given day — call (201) 408-5151 to check.
Schedule an appointment
Dr. Yoo Rehab Clinic welcomes new patients from across Northern New Jersey and New York City, including Englewood, Teaneck, Fort Lee, Palisades Park and Ridgefield. Call today to learn more about insurance, scheduling, and how we can help.
