EMG question

[Phantom Spike]

---

Members don't see this ad.

How would you interpret nerve conduction/EMG studies in a patient with diabetes and suspected peripheral neuropathy (tingling, numbness, burning, balance issues), that showed normal amplitudes in the motor and sensory nerves and conduction velocities slightly slowed (high 30s) in the legs, normal nerve conduction studies in the arms, and EMG in the legs showing slightly reduced recruitment in all the muscles of the legs, with only slightly increased MUAP amplitudes and durations, and no polyphasia except in the most distal muscles? Technically, this would be a demyelinating neuropathy if we were to go by the numbers, but the lack of conduction blocks, the sparing of the arms, as well as the mildness of slowing (and frankly, the clinical picture) argue against AIDP/CIDP; and the conduction velocities are too fast to be thinking of CMT (which again is not a clinical suspicion). I've seen this pattern quite a few times and wonder how others would read the study.

 

[neurologist]

Were those legs warmed up before doing the nerve conductions?
Cold feet = slow velocities!!!!!

 

[neurodoc]

Were those legs warmed up before doing the nerve conductions?
Cold feet = slow velocities!!!!!

Good point. You should measure the skin temp when you do NCS, as NCV drops in a predictable way with lower temperature. Not everyone checks the skin temperature when they perform NCS.

That being said, diabetics tend to have what's called "small fiber" neuropathy, which can produce neuropathic symptoms but which may not show significant changes in the SNAP or CMAP responses on routine NCS.

Checking for the galvanic skin response sometimes shows abnormalitites in these cases. I also like to check the H-reflex responses (this is the electrophysiologic equivalent of the ankle jerk reflexes). These are sometimes prolonged or low-amplitude due to diabetic polyneuropathy (rather than S1 radiculopathy). You could also try checking SNAPs from the great toe (gives a more distal view of sensory conduction than the sural SNAP checked antidromivally at the ankles).

 

[NancyNancy]

Age and height are the other variables with an inverse relation to conduction velocities 🙂