AANEM Connect

Good evening,

I recently encountered an unusual case of carpal tunnel syndrome (CTS) that I found quite challenging, and I am seeking some insights from this esteemed group.

A 77-year-old right-handed woman presented with various right hand symptoms, including paresthesias, stiffness, and coldness, which were sometimes worse at night. A cursory examination was normal, except for mild APB atrophy.

Her nerve conduction studies (NCS) showed the following:

• Median motor potential: Normal latency (3.8 ms), low amplitude (3.0 mV), and normal velocity (53 m/s)
• Right median SNAP: Borderline increased peak latency (3.60 ms), borderline low amplitude (19.5 μV), and normal velocity (53 m/s)
• Radial SNAPs were normal
• Palmar studies and studies to the fourth digits were entirely normal

I did not perform the ulnar motor potential or a needle EMG due to time constraints and the assumption that the low median motor potential was artefactual. I concluded with an essentially normal report, attributing her symptoms to musculoskeletal issues.

She was later evaluated at another institution, where her history was described as more typical of CTS. Their NCS results were also normal, but a restricted EMG examination revealed severe chronic neurogenic changes in the APB and a normal FDI. They diagnosed severe CTS and referred her for surgery.

I was surprised by this conclusion and would have considered a radicular or myeloradicular origin, likely imaging the cervical spine.

My questions are:

• Can CTS present solely with axonal motor findings, even with sensory symptoms?
• Is this potentially a case of isolated thenar motor branch involvement?
• How would you have proceeded with a case like this?

Thank you for your guidance.

Sincerely,
Repentant EMGer