Great video, I'm getting an EMG tomorrow due to sciatica at the least that has lasted 5-6 months and tingling,right foot also turns outward about 45 degrees. Long time runner. Does the waveform show less activity and slower velocity?
How did your EMG go for your sciatica? I have piriformis syndrome which affects my sciatic nerve but never thought to get an EMG done on it (it's been hurting for a year, even with physical therapy and consistent yoga) Hope you're feeling better!
Hi Karan, if you stimulate distal to the conduction block (CB), the CMAP is normal. If you stimulate proximal to the CB, however, the action potential can't travel normally through the CB and there is a sudden drop in CMAP. Hope that helps.
@@bacolive Hi Brad. So basically the conduction block is a focal area of myelin damage right? If it's just damaging the myelin, only the velocity of conduction should be affected right? Why the amplitude (CMAP)?
Action potentials travel in trains. If you stimulate proximal to the CB, you will affect the rate at which APs in a train reach the muscle fibre (reduced rate, fewer APs/second). Some of these APs might not even make it through the CB. This causes fewer concurrent depolarizations of the muscle fibres. CMAP is reduced because it is dependent on how many times fibres depolarize simultaneously.
