Cubital Tunnel Syndrome

[PMR 4 MSK]

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Do you consider the ulnar antidromic sensory response across the elbow to be neccesary to diagnose cubital tunnel syndrome (CuTS), after the motor response shows an abnormal response - i.e. does it have to be done, and does it have to be abnormal?

The reason I ask is that I periodically see signficiantly abnormal motor responses but normal sensory responses across the elbow, and I also see other docs' reports showing a Dx of CuTS without a proximal segment sensory being done - it seems many electromyographers only know how to do a distal stim for sensories.

I also periodically see EMG'ers who do a motor stim at the wrist, another above the elbow and diagnose CuTS without an across the elbow segment - no below elbow stim.

 

[Ludicolo]

Not necessary. It is hard, if not impossible, to diagnose sensory conduction block or focal slowing. I have also seen motor slowing/dispersion/conduction block across the elbow, with normal sensory responses.

If you motor stim at the wrist, then above elbow, and demonstrate a block/slowing; then you should stim below the elbow to confirm that the lesion is across the elbow, and not somewhere in the forearm. All of the criteria for significant slowing or amplitude drop involves the AE-BE segment.

 

[topwise]

I'm just a lowly resident, but none of the attendings I've worked with have asked me to do sensory responses across the elbow to confirm cubital tunnel. In fact, I've only done sensory across the elbow once when the motor was normal but the symptoms were very convincing.

Aren't sensory responses fairly hard to obtain when stimulating proximally (when recording distally) due to temporal dispersion and phase cancellation?

 

[CubitalThinker]

I am not a doctor nor a medical student. Rather, I am a cubital tunnel patient, and the administrator of a cubital tunnel website and forums, and I have studied cubital tunnel syndrome extensively.

Based on the medical studies I've read and anecdotal evidence on the Web, here are my layman's conclusions about EMG/NCV tests for CuTS:

• NCV (nerve conduction velocity, also known as MCV) tests are more reliable indicators of CuTS than EMG.
• For some reason, many doctors give EMG but not NCV tests to patients they suspect have CuTS.
• Many people with CuTS symptoms of pain and muscle weakness have negative results with EMG and NCV tests. (Personally, I had two years of moderate CuTS symptoms and negative EMG/NCV tests, before my NCV tests results were ultimately positive for nerve problems.)

I would love to hear the perspective of the experts in this forum as to whether my conclusions are valid and why or why not. Thank you for your insight.

 

[axm397]

just a reminder to sdn posters that advertising and promoting (websites, products, etc.) is against sdn rules. if anyone is interested in entering into a sponsorship agreement with sdn, you can contact one of the administrators. sdn is also NOT a site for getting medical advice. the above post not specifically asking for medical advice but rather asking in general about sensitivity/specificity of ulnar NCS and EMGs so we will let this stand. just wanted to remind everyone. thanks!