3-Motor nerve conduction study PDF

❑ Electrodiagnostic (EDX) studies play a key role in the evaluation of patients with neuromuscular disorders. Among these studies are included nerve conduction studies (NCSs), repetitive nerve stimulation, late responses, blink reflexes, and needle electromyography (EMG). ❑ NCSs and needle E...

❑ Electrodiagnostic (EDX) studies play a key role in the evaluation of patients with neuromuscular disorders. Among these studies are included nerve conduction studies (NCSs), repetitive nerve stimulation, late responses, blink reflexes, and needle electromyography (EMG). ❑ NCSs and needle EMG form the core of the EDX study. They are complementary, and therefore are always performed together and during the same setting. ❑ In practice, EDX studies serve as an extension of the clinical examination. directed neurologic examination should always be performed before EDX studies in order to identify key clinical abnormalities and establish a differential diagnosis. ❑ The principal goal of every EDX study is to localize the disorder. EMG Machine  Surface Electrode Ground strap electrode Plate Grounding Electrode Ring electrodes stimulating electrodes In addition to the EMG needle, there is: ▪ Needle cable ▪ Gloves  Nerve conduction studies Motor Sensory Mixed Every study begins with nerve conductions. Peripheral nerves can be easily stimulated and potentials elicited with a brief electrical pulse applied to the overlying skin.  Nerve conduction studies 1- Motor Nerve conduction studies Preparation: Wash electrodes after each use All electrodes are electrically tested A thin film of electrode gel Clean and abrade patient’s skin All electrodes fastened securely Mark recording and stimulating points Measure with a metal tape Stimulus grades  Median Motor conduction studies MEDIAN MOTOR STUDY Recording Site: Abductor pollicis brevis (APB) muscle (lateral thenar eminence): G1 placed over the muscle belly G2 placed over the first metacarpal-phalangeal joint Stimulation Sites: Wrist: Middle of the wrist between the tendons to the flexor carpi radialis and palmaris longus Antecubital fossa: Over the brachial artery pulse Distal Distance: 7 cm Nerve conduction studies Distal stim. Proximal stim. --- CV Distal stim. --- CV If an initial positive deflection exists, it may be due to: Inappropriate placement of the active electrode from the motor point Volume conduction from other muscles or nerves Anomalous innervations  Measurements Latency in milliseconds (msec) Amplitude in millivolts (mV) or microvolt Duration in milliseconds (msec) Conduction velocity (m/s) of a nerve is calculated by measuring the distance (mm) between two stimulation sites and divided by difference in latency (msec) from proximal to distal stimulus Area: The area above the baseline to the negative peak Put a manual at your fingertips Motor conduction studies N.B: both latency and conduction velocity reflect only the fastest conducting fibers in the nerve being studied. By definition, conduction along these fibers arrives first and thus it is these fibers that are the ones measured. The many other slower conducting fibers participate in the CMAP area and amplitude but are not reflected in either the latency or conduction velocity measurements.