Introduction to Electrodiagnosis

Study Notes

Electrodiagnosis (EDX) studies are crucial for evaluating neuromuscular disorders.
EDX studies involve nerve conduction studies (NCSs), repetitive nerve stimulation, late responses, blink reflexes, and needle electromyography (EMG).
NCSs and needle EMG are core EDX procedures.

Stimulating electrodes:
- Cathode
- Anode
Recording electrodes:
- Actively picks up signals (pickup/active electrode)
- Reference electrode
Ground electrode: Filters out background noise.
Specific NCV electrode types:
- Sensory ring electrodes
- Stimulation probes with anode and cathode electrode tips
- Bar electrodes
- Disc electrodes

Knowledge and Understanding:
- Discuss theories, principles, and updates in advanced electrodiagnosis.
- Explain electrophysiological concepts needed for electromyography and nerve conduction studies.
Intellectual Skills:
- Demonstrate basic anatomy and physiology of connective tissue, bone, joints, and muscles, along with clinical care of patients.
- Examine electrical activities of muscles and nerves.
- Fill in the diagnostic section of electrophysiologic testing on patient evaluation sheets.
Professional & Practical Skills:
- Demonstrate basic clinical reasoning and problem-solving abilities, and sound rationales underlying physical therapy role, client diagnosis/prognosis.
General and Transferable Skills:
- Utilize technology for up-to-date neurorehabilitation techniques.
- Express thoughts and ideas effectively in various languages, both verbally and in writing.

EDX studies provide critical information about the underlying neuromuscular disorder.
These studies allow clinicians to appropriately and efficiently use other laboratory tests.
Often, these studies lead to specific medical or surgical therapy decisions.

A directed neurologic examination should always precede EDX studies.
This ensures key clinical abnormalities can be identified and a differential diagnosis established.

NCSs and EMGs are primarily used to diagnose peripheral nervous system disorders.
These disorders include conditions affecting primary motor neurons (anterior horn cells), primary sensory neurons (dorsal root ganglia), nerve roots, brachial and lumbosacral plexuses, peripheral nerves, and neuromuscular junctions.
Disorders originating in the central nervous system, such as tremors or upper motor neuron weakness, are sometimes diagnosed.

NCSs and EMGs are extensions of the clinical examination, and a good clinical examination is essential for their proper interpretation.
When in doubt, review technical factors such as equipment integrity, electrode placement, stimulating electrode intensity, and the electromyographer's performance of the study.
Review possible technical errors, such as type I (false positive) and type II (false negative) errors.
When encountering unexpected abnormal findings that don't match the clinical presentation, investigate potential technical issues.
Consider factors like electrode placement, stimulus intensity.
Re-examine the patient in situations of doubt.
Report EDX findings in the context of the clinical presentation and referring diagnosis.
Exercise caution in over-diagnosing, given that electrophysiologic tests are sensitive to minor abnormalities that might not always have clinical significance.
Always consider the clinical-electrophysiologic correlation when interpreting EDX results, ensuring clinical findings match with respective NCSs and EMG results.