Nerve Conduction Velocity Lecture Notes PDF

Physiology Nerve Conduction Velocity LECTURE (7) Nerve conduction velocity DR. El-Sawy 0  Physiology...

Physiology Nerve Conduction Velocity LECTURE (7) Nerve conduction velocity DR. El-Sawy 0  Physiology Nerve Conduction Velocity Type A fibers Type B fibers Type C fibers Type  Thick myelinated  Thin myelinated  Thin unmyelinated  Somatic sensory  Autonomic  Somatic motor & carrying slow pain Site preganglionic sensory nerves  Autonomic nerves postganglionic Diameters  2-20 μm  1-3 μm  0.5-1 μm Speed  10-120 m/sec  3-15 m/sec  0.5-2 m/sec  Prolonged deep Sensitive  O2 lack (Hypoxia)  Local anesthetics to pressure  Alpha, beta, delta Subtypes ----------------- ------------------ and gamma. DR. El-Sawy 1  Physiology Nerve Conduction Velocity Physiological factors affecting conduction velocity:  Conduction velocities in newborns are about half adult values  Normal adult values: typically reached by age 4. Age  Conduction velocities in upper extremities decrease by about 1m/s for every 10 years of age  Conduction velocity in female is less than male especially in Sex lower limb Sural nerve  The conduction velocities of most motor and sensory nerves are positively and linearly associated with body temperature Temperature a. Low temperatures → slow nerve conduction velocity b. Higher temperatures → increase conduction velocity  Conduction velocities are negatively related to individual's height. Height  Conduction velocities between wrist and digits of individual's hand decrease by 0.5 m/s for each inch increase in height  Conduction velocity is directly proportional to degree of nerve myelination Degree of a. Higher in thick myelinated nerve fibers myelination b. Less in thin myelinated nerve fibers c. Least in unmyelinated nerve fibers DR. El-Sawy 2  Physiology Nerve Conduction Velocity Def :  Electro-physiology test used to evaluate function of peripheral nerves. Types : 1) Motor NCV 2) Sensory NCV 3) Mixed NCV. Medical Uses :  Nerve conduction studies (NCV) with ElectroMyography (EMG) measure nerve and muscle function  Indicated in : 1) Pain in limbs 2) Weakness from spinal nerve compression 3) Neurologic injury as Carpal tunnel syndrome : Median nerve is compressed by flexor retinaculum DR. El-Sawy 3  Physiology Nerve Conduction Velocity How To Test :  Start button in PRO (h03) software window.  The nerve is ulnar nerve and motor response is measured over abductor digiti minimi.  Realize that time from stimulation of nerve to EMG response includes not only nerve conduction , but also all the events that occur at the neuron-muscular junction : a. Release of neuron-transmitter b. Binding to receptors c. End-plate potentials  However , if you subtract the Delta T for S1 from the delta T for S2 , it reflects only the time required for conduction of action potentials DR. El-Sawy 4  Physiology Nerve Conduction Velocity POSITION Of ELECTRODS SITE OF STIMULATION ANALYSIS :  Measure ( Delta T ) in seconds from the start of stimulus to the start of the response wave form for each segment and note the value. a. S1 =.. sec from Stimulus to Response b. S2 =.. sec from Stimulus to Response.  Measure the Distance between S2 and S1 in cm  Calculate conduction velocity = (Distance between S2 and S1) / (Delta T for S2 - Delta T for S1 ) = …. IN (M / SEC) DR. El-Sawy 5  Physiology Nerve Conduction Velocity  This distance between S 2 and S1 divided by this time equals conduction velocity: NCV = Distance between S 2 and S 1/ (Delta T for S2 - Delta T for S1 in M/Sec). DR. El-Sawy 6  Physiology Nerve Conduction Velocity DR. El-Sawy 7  Physiology Nerve Conduction Velocity Normal values of CV in nerves of UL & LL: ① The following NF is thick myelinated a. Type c b. Type b c. Type a d. Type d ② Post ganglionic NF is a. Type A b. Type b c. Type c d. Type A delta ③ About salutatory conduction a. Occurs in unmylinated NF b. Slow conduction c. Consume more energy d. Rapid and consume less energy DR. El-Sawy 8