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Neurology (Expert Forum)
Poorly Functioning Tibial Nerve
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Poorly Functioning Tibial Nerve
by Leghurts, Oct 08, 2005 12:00AM
I have been diagnosed with sensori-motor, axonal, distal pheripheral neuropathy. I have had two EMG/NCS done.
First EMG after five weeks of onset: The left gastrocnemius showed increased insertion activity and 2+ psw. There was normal motor unit morphology and normal interference pattern. The left tibial nerve showed somewhat slowed latency, normal conduction velocity, and severely reduced amplitude (1.04 uv/mv with normal value set >2).
Second EMG after 8 1/2 months of onset: The left gastrocnemius showed no spontaneous activity (normal IA, no Fib, no PSW, no Fasc, no H.F.). The MUAP showed normal amplitude, normal duration, and 1+ PPP. The recruitment pattern was normal. The left tibial nerve showed normal latency and normal conduction velocity, but severely reduced CMAP amplitude (0.7 mV). Minimal F wave latency of the left tibial nerve was prolonged and repeater units were noted (M Lat 5.25; F Min 55.85).
My interpretation of the above is pretty grim. The second EMG shows normal recruitment and NOT reduced recruitment. This means, I think, that there has been no nerve sprouting in the grastrocnemius since onset. I am uncertain how to intrepret the "normal" MUAP amplitude and duration. I do believe that "normal" is not good in the second EMG. I do not know what the tibial nerve F wave readings mean.
Could someone please give me an opinion of the above? It does seems that after 8 1/2 months nothing has changed, which is not good. How long do I have before atrophy sets in? And if my calf muscles atrophy, how will that affect walking?
First EMG after five weeks of onset: The left gastrocnemius showed increased insertion activity and 2+ psw. There was normal motor unit morphology and normal interference pattern. The left tibial nerve showed somewhat slowed latency, normal conduction velocity, and severely reduced amplitude (1.04 uv/mv with normal value set >2).
Second EMG after 8 1/2 months of onset: The left gastrocnemius showed no spontaneous activity (normal IA, no Fib, no PSW, no Fasc, no H.F.). The MUAP showed normal amplitude, normal duration, and 1+ PPP. The recruitment pattern was normal. The left tibial nerve showed normal latency and normal conduction velocity, but severely reduced CMAP amplitude (0.7 mV). Minimal F wave latency of the left tibial nerve was prolonged and repeater units were noted (M Lat 5.25; F Min 55.85).
My interpretation of the above is pretty grim. The second EMG shows normal recruitment and NOT reduced recruitment. This means, I think, that there has been no nerve sprouting in the grastrocnemius since onset. I am uncertain how to intrepret the "normal" MUAP amplitude and duration. I do believe that "normal" is not good in the second EMG. I do not know what the tibial nerve F wave readings mean.
Could someone please give me an opinion of the above? It does seems that after 8 1/2 months nothing has changed, which is not good. How long do I have before atrophy sets in? And if my calf muscles atrophy, how will that affect walking?
Doctor's Answer
by CCF-Neuro-M.D.-PW, Oct 13, 2005 12:00AM
Your prognosis depends on the underlying cause, which I assume has been worked up. Unfortunately about 30% of peripheral neuropathies remain undiagnosed, although this number is dwindling due to advances in testing. Make sure that you have hada full workup for the neuropathy by an experienced neurologist.
The first EMG by the report seems to show evidence of 'active' denervation - reduced MUAPs with positive waves - although as the above report one muscle and one nerve I cannot comment on whether it is a symmetric peripheral neuropathy or a S1 radiculopathy or sciatic nerve lesion. Also, you do not report the senory nerve action potentials which are critical to make the diagnosis - they would be expected to be abnormal in an axon loss PN). The natural history is for the positive waves and insertional activity to disappear within a few weeks (if there is no ongoing active denervation), and the MUAPs become larger with reduced recruitment if a SEVERE injury to NORMAL if there is enough recovery. 'Normal' is usually always a good thing! So it looks like your gastroc did recover significantly. The tibial nerve by conduction studies (CMAP) is low signifiying prior damage which may not be improved on at this point. Again I cannot commment on what the actual diagnosis or pattern of involvement is based on so few muscles/ nerves
The F wave latency is prolonged and just reflects the problem with the motor tibial nerve as you already know.
Orthotics and walking assist devices are readily available from your physical therapist if leg wasting or weakness develops
Good luck
The first EMG by the report seems to show evidence of 'active' denervation - reduced MUAPs with positive waves - although as the above report one muscle and one nerve I cannot comment on whether it is a symmetric peripheral neuropathy or a S1 radiculopathy or sciatic nerve lesion. Also, you do not report the senory nerve action potentials which are critical to make the diagnosis - they would be expected to be abnormal in an axon loss PN). The natural history is for the positive waves and insertional activity to disappear within a few weeks (if there is no ongoing active denervation), and the MUAPs become larger with reduced recruitment if a SEVERE injury to NORMAL if there is enough recovery. 'Normal' is usually always a good thing! So it looks like your gastroc did recover significantly. The tibial nerve by conduction studies (CMAP) is low signifiying prior damage which may not be improved on at this point. Again I cannot commment on what the actual diagnosis or pattern of involvement is based on so few muscles/ nerves
The F wave latency is prolonged and just reflects the problem with the motor tibial nerve as you already know.
Orthotics and walking assist devices are readily available from your physical therapist if leg wasting or weakness develops
Good luck