late response# edited. .pptx

Medical

1. LATE RESPONSE

2. L ATE RESPONSE F wave H reflex

3. F- WAVE F waves were named in reference to “foot” A supramaximal stimulus applied at any point along the course of a motor nerve elicits an F wave in a distal muscle that follows the CMAP (M response). The impulse travels antidromically to the spinal cord and the F wave is produced by backfiring of motor neurons. An average of 5–10% of the motor neurons available in the motor neuron pool backfire after each stimulus .

4. CHA R A C TER They are typically variable in latency, amplitude, and morphology..

5. L ATENCY ; MINIMAL F WAVE LATENCY IS THE MOST RELIABLE AND USEFUL . It represents conduction of the largest and fastest motor fibers. Depend on the length of motor axons which correlates with the height and limb length The most sensitive criterion of abnormality in a unilateral disorder is a latency difference between the two sides, or between two similar nerves in the same limb .

6. PARAMETERS AVERAGE LATENCY The average minimal F- wave latencies tend to be 25-32 msec. in the upper extremities and 45-56 msec in the lower extremities, height dependent Persistence >50% Configuration :Usually polyphasic& varies with each stimulation

7. Amplitude 1%-5% CMAP -the gain should be increased 200 µv cant be elicited in low amplitude of M response This varies between individuals and is inhibited by muscle activity while it is enhanced by relaxation or the use of Jendrassik maneuver.

8. F -wave chronodispersion is the degree of scatter among consecutive F waves and is determined by the difference between the minimal and maximal F wave latencies Chronodispersion <4 ms (median/ulnar) &<6 ms (peroneal/tibial)

9. SIGNIFICANT OF F WAVE 1 - - EA R L Y NE U RO P A T HY If the neuropathy is in its early stage, the delayed F wave may be the first indication for the diagnosis. Guillain-Barre Syndrome can affect any segment of the nerve, but it will commonly affect the most proximal segment first As the patient starts to recover the F waves that were absent will start to return, or the latencies that were prolongated will return to a more normal value. 2-Plexipathy

10. 3 - SPINAL SHO C K This is due to the altered state of excitability of the motor neurons. In acute paraparesis, the waves below the injury or lesion in the spinal cord will be absent or prolonged very soon after injury and may not return for days or weeks following

11. F WAVES . L IMITATIONS IN RADICULOPATHY Slowing at the root level can be obscured (“diluted”) by the normal conduction along the long axon. Most muscles are innervated by two or more roots. In U L commonly used are F median & ulnar ns which demonstrates C8& T1 roots ( uncommon sites of radiculopathy) If rediculopathy affects sensory nerve root F wave affected when most of nerve fibers involved

12. C ENTRAL LATENCY is the conduction time from the stimulus to the spinal cord and back down. There is a one msec delay turn around time at the anterior horn cell that is subtracted and then divided by two. Formula (F-M-1) / 2 ( Kimura, 2001).

13. F- WAVE VELOCITY The approximate nerve length divided by the conduction time from the spinal cord makes up the F- wave velocity Formula, FWCV= (2D) / (F-M-1)

14. A XILLARY F- LOOP LATENCY AFLL= F-wave wrist + distal motor latency - 2(axillary motor latency ). Normal values for median & ulnar nerves were reborted as 14:16 ms

15. H –REFLEX The name H-wave was derived from that of Johann Hoffmann, who found the response for the first Weak electrical stimulation can excite group Ia fibers from muscle spindle, and the antidromic impulse gets conducted to the spinal cord. Afferent fibers connect, via a synapse, with the alpha motor neuron in the spinal cord. Excitatory postsynaptic potential (EPSP) causes the excitement of the alpha motor neuron of the anterior horn cells in the spinal c ord.

16.  H )  Normal: 28 – 30 milliseconds Side to side difference: greater than 0.5 – 1.0 ms is significant Above 60 years: adds 1.8 milliseconds  Soleus muscle: tibial nerve: S1 pathway Flexor carpi radialis: median nerve: C7 pathway Vastus medialis : femoral n : L4 pathw