electrodiagnosis

Electrodiagnosis refers to a collection of diagnostic techniques that assess the electrical properties of the nervous system to help identify and characterize disorders of the peripheral nervous system, neuromuscular junction, and muscles. It is typically used in conjunction with history, physical examination, and other tests to determine the location and nature of a problem, guide management, and monitor disease progression or response to treatment.

The core tools are nerve conduction studies (NCS) and electromyography (EMG). NCS measure the speed and size of electrical impulses as they travel along peripheral nerves, helping distinguish demyelinating from axonal neuropathies and identifying focal conduction blocks or radiculopathy. EMG involves recording electrical activity from muscles, often with a needle electrode, to assess motor unit potentials, insertional activity, and spontaneous activity at rest. Together, NCS and EMG can localize disease to nerves, nerve roots, plexuses, or muscles and provide information about chronicity and severity.

Additional techniques include evoked potentials, such as somatosensory and visual evoked potentials, which evaluate central sensory pathways and are used in diseases like multiple sclerosis or to assess spinal cord integrity. Repetitive nerve stimulation and single-fiber EMG are used to diagnose disorders of the neuromuscular junction, such as myasthenia gravis. Autonomic testing, including quantitative sudomotor testing and other autonomic reflex assessments, can evaluate autonomic involvement in systemic or neurologic diseases.

Limitations include dependence on patient cooperation and technique, contraindications for invasive procedures, and the fact that electrodiagnosis complements but does not replace imaging or clinical assessment. Results must be interpreted within the broader clinical context to arrive at a diagnosis.