Neuroepidemiology Department
Examinations Performed
Nerve conduction studies
Nerve conduction studies (NCS) evaluate the function of individual nerves. During NCS, a nerve is stimulated (electrical pulse) at one location while electrodes (wires taped to the skin) record from a different place along the same nerve. The NCS is performed to measure the timing (latency, conduction velocity), size (amplitude), and shape (morphology) of the nerve’s response to the stimulus across any given segment of its pathway. NCS can be performed on motor, sensory, or mixed (both motor and sensory fiber) nerves.
Late Responses
Late responses are performed to evaluate nerve conduction in more proximal portions of the nerve (near the spine). The EMG lab performs H-reflexes and F-waves of various nerves.
Repetitive nerve stimulation
This is the procedure of evaluating the neuromuscular junction by recording muscle responses to a series of electrical stimuli both before and after exercise, or following a train of high-frequency stimuli.
Electromyography
Electromyography (EMG) utilizes a disposable needle to view the spontaneous and volitional electrical activity of muscle, or motor unit potentials (MUPs). Specialized EMG techniques include Quantitative EMG (QEMG) and Single Fiber EMG (SFEMG). QEMG techniques record and analyze a representative sample of MUPs from a given muscle, whereas SFEMG assesses the neuromuscular junction by activating a motor nerve and recording its individually generated muscle fiber action potentials.
Brainstem reflex studies
These studies assess different brainstem pathways by recording muscle responses to a series of electrical or mechanical stimuli. The EMG Lab performs three types of reflex studies: Blink Reflex, Jaw Jerk Reflex and Masseter Inhibitory Reflex.
Autonomic testing
The sympathetic, or galvanic, skin response (SSR) detects changes in skin resistance (i.e., sweat gland activation) in response to a sudden stimulus (e.g., cough, gasp, acoustic, electrical). As the SSR provides a measure of sympathetic cholinergic sudomotor fiber activity, abnormal SSR results may help to confirm a diagnosis of autonomic dysfunction.