Temperature correction factors derived from normal subjects may be invalid in demyelinating neuropathies

Area of Science:

• Neurology
• Neurophysiology
• Clinical Electrophysiology

Background:

• Motor nerve conduction velocity (MNCV) is temperature-dependent.
• Neuropathic conditions like uremic polyneuropathies (UPN), diabetic polyneuropathies (DPN), and carpal tunnel syndrome (CTS) can affect nerve function.
• Standard electrodiagnostic studies often use temperature correction factors.

Purpose of the Study:

• To investigate the effect of temperature on MNCV in patients with UPN, DPN, and CTS.
• To determine if temperature correction factors differ across these neuropathic conditions and healthy controls.
• To explore the relationship between baseline nerve conduction and temperature sensitivity.

Main Methods:

• Studied 14 patients (UPN, DPN, CTS) and 10 controls.
• Cooled limbs for 30 minutes in a cold water bath.
• Measured skin temperature and MNCV at 2-3°C increments between 22°C and 33°C.

Main Results:

• Observed significant individual variability in temperature correction factors (0.1-2.0 m/s/°C).
• Found significant differences in correction factors between control and neuropathic groups (DPN, CTS, UPN).
• Demonstrated a positive correlation between baseline MNCV and correction factor size (r=0.746, p=0.0001).

Conclusions:

• The effect of temperature on MNCV is inversely related to the degree of demyelination or conduction slowing.
• Temperature correction factors may be unreliable for demyelinated nerves.
• Warming extremities to a standardized temperature before electrodiagnostic testing is recommended.