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Of 17 Keywords A-Waves Sometimes Called Axon Reflex. Seen Keywords A-waves Sometimes called Axon reflex. Seen when using sub- maximal stimulation during the F-wave recording. Consistent in latency and amplitude and usually occurring before the F-wave. Thought to be a result of reinnervation of the nerve. Abduct Move away from the median plane Abductor digiti minimi Sometimes called abductor digiti quinti. Ulnar innervated (ADM or ADQ) muscle on the medial side of the little finger along side the 5th metacarpal. The most superficial muscle in the hypothenar eminence. Commonly used when recording ulnar motor studies. Abductor digiti quinti Lateral plantar, thus tibial nerve, innervated muscle on the pedis (ADQp) lateral side of the foot along side the 5th metatarsal. Abductor hallucis (AH or Sometimes called abductor hallucis brevis. Medial plantar, AHB) thus tibial nerve, innervated muscle on the medial side of the foot below the navicular bone. Commonly used when recording tibial motor studies. Abductor pollicis brevis Median innervated muscle just medial to the 1st metacarpal (APB) bone. The most superficial muscle of the thenar eminence. Commonly used when recording median motor studies. Accessory peroneal nerve A branch of the superficial peroneal nerve that partly supplies the extensor digitorum brevis (EDB) in 18-22% of people. The EDB is normally innervated by the deep peroneal. The accessory peroneal nerve is seen when the peroneal amplitude, recording from the EDB, is larger when stimulating at the fibular head than when stimulating at the ankle. It can be confirmed by stimulating behind the lateral malleous, adding that amplitude to the ankle amplitude. The sum of which should closely equal the amplitude when stimulating at the fibular head. Acetylcholine The chemical transmitter in a neuromuscular junction Action potential Whenever a stimulus reached or exceeds threshold an action potential is generated propagating along a single axon. Active electrode Synonymous with recording electrode, G1 or E1. To complete the circuit a differential amplifier requires the Active electrode and a Reference electrode. Acute Inflammatory Guillain-Barré Syndrome. An acute areflexic ascending Demyelinating sensory-motor polyneuropathy where deficit is maximum in Polyneuropathy (AIDP) 4 weeks. Characterized by absent or prolonged F-waves, Page 1 of 17 slowed conduction velocities, prolonged latencies and conduction block (especially proximally) Sensory NCS may be normal in early cases, but as the disease advances low amplitudes and slowed conductions may be seen. Adduct Move toward the median plane Afferent Otherwise known as sensory neurons – carry nerve impulses from receptors or sense organs toward the central nervous system. Age Affects time and amplitude so normative values reflect different age groups. All or none response When depolarization occurs it either causes an all response it reaches threshold, or no response if the depolarization is insufficient to reach threshold. Alternating Current Current that is forced rapidly back and forth along a circuit, repeatedly reversing its direction. Ampere A measure of current, designated by the letter A. Amplifier The hardware component used to increase the size of the small physiological signal. Amplitude A measurement of the vertical size of the waveform. The representation of the total number of nerve fibers or sensory axons. Usually expressed as millivolts (mV) for MNC and microvolts (µV) for SNC Amyotrophic lateral Often referred to, as “Lou Gehrig's disease.” Motor neurons sclerosis (ALS) go from the brain to the spinal cord and from the spinal cord to the muscles throughout the body. The progressive degeneration of the motor neurons in ALS eventually leads to their death. See www.alsa.org Anodal block Hyperpolarization occurring under the anode prevents the depolarization, that occurs under the cathode, from passing thus, causing a reduction in the resulting potential. Anode The positive terminal of the stimulating electrode Anomalous Innervation Anomalous pathways that can cause erroneous results in some people. Common anomalies include Martin-Gruber anastomosis and Accessory peroneal nerve. Antecubital fossa The triangular area on the anterior view of the elbow joint of the arm. A common stimulation site for the median and radial nerves. Anterior In the front or in the forward part, ventral surface Anterior horn cells Motor unit cell bodies in the ventral gray matter of the Page 2 of 17 spinal cord. Eventually become the motor nerves. Anterior interosseous A branch the median nerve originating several centimeters nerve distal to the elbow. Innervates several muscles in the forearm including the flexor digitorum profundus and the flexor pollicis longus muscles. Antidromic conduction Nerve conduction propagation in a direction other that the normal physiological direction. Area The area under a curve; represents duration and amplitude. Measured in mVms (for MNC, its most useful place) and helps differentiate between a conduction block and simple dispersion. Artifact Unwanted electrical or physiological signals that obscure the desired response. Atoms Make up the elements found in all matter Axillary nerve Originates from the posterior cord of the brachial plexus via the upper trunk and the C5/6 nerve roots. Innervates the deltoid and teres minor muscles. Axolemma A semipermeable membrane that covers the axoplasm Axon Nerve fibers that transmit impulses to and from the periphery. Axons are in effect the primary transmission lines of the nervous system, and as bundles they help make up nerves. Axon wave or axon reflex See A-wave Axonotmesis Nerve conduction slowing without complete block (axons and myelin disrupted, but supporting connective tissue is intact, allowing reinnervation of the axons) Axoplasm Jelly-like substance contained in nerve cells Baseline The horizontal line representing the pre and post response. Baseline-to-peak Amplitude measurement from the baseline (takeoff point) to the highest negative peak. Sometimes simply referred to as the “Peak” amplitude. Bell’s Palsy A lesion of the facial nerve causing weakness in the muscles of the face. Usually idiopathic and most often unilateral. Common tests include facial nerve motor recordings and Blink reflex studies. Biceps brachii Muscle innervated by, and commonly used when performing musculocutaneous motor studies. Blink Reflex Essentially the same as the corneal reflex this electrical test evaluates the cranial nerves V and VII (trigeminal and facial Page 3 of 17 respectively) as well as central pathways in the brainstem. Brachial plexus Anatomical structure formed by spinal roots C5-T1 and terminating in the nerves of the arm. Composed of Roots, Trunks, Divisions, Cords and Branches (or nerves). Bulbar Signs and symptoms (or muscles) arising from the brainstem (medulla) Carpal Tunnel Syndrome A condition where the median nerve is compressed at the wrist as it travels under the transverse carpal ligament. Cathode The negative terminal (i.e. active terminal) of the stimulating electrode. Central motor conduction Conduction time from the motor cortex in the brain to the motor neurons in the spinal cord. Usually calculated using transcranial magnetic or transcranial electrical stimulation and subtracting the peripheral conduction time. Charcot-Marie-Tooth Hereditary sensorimotor neuropathy (HMSN) is an inherited (CMT) disorder that affects all nerves, both motor and sensory. Chronic Inflammatory Acquired motor and sensory demyelinating neuropathy that Demyelinating often has axonal features. Characterized by prolonged Polyneuropathy (CIDP) latencies, slowed conduction velocities, absent or prolonged F-waves. The findings can be asymmetric and the presence of conduction block help make the diagnosis of acquired possible. Sensory NCS have low amplitudes especially in the lower extremities. CMAP Compound Muscle Action Potential. The summation of muscle fibers contracting after stimulation of a nerve (or the muscle directly). Common Mode Rejection In an amplifier, large signals common to both points (active and reference) are rejected. Since noise is much larger than physiological signals, good Common Mode Rejection allows more cancellation of unwanted signals and better resolution of physiological signals. Common peroneal nerve The smaller branch of the sciatic nerve which later becomes the deep and superficial peroneal nerves. Complex Repetitive Seen in Needle EMG. Action potentials of a group of Discharges muscle fibers firing in near synchrony. CRD’s usually have abrupt onset and abrupt end while their amplitude, frequency and waveform remain constant during the train. Concentric needle An inner wire, serving as the recording electrode runs electrode through an outer cannula that serves as the reference electrode. Page 4 of 17 Conduction block Seen when a reduction in amplitude and area of a response is seen between the distal and proximal stimulation sites of a nerve. It is a failure of the action potential to propagate past a point, but conduction is possible beyond the same point. Seen most often in demyelinating disorders. Technical factors must be eliminated to confirm a true conduction block. Conduction Velocity A measurement of time between two points. Used as we move up the arm or leg to normalize for the height of the patient. Calculated from the ∆ dist (mm or cm x 10) fastest fibers as difference in ∆ time (ms) distance divided by difference in time. Measured in meters per second. Conductors Elements that readily pass electrons from one atom to the next atom.
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