Proximal nerve conduction studies in chronic inflammatory demyelinating polyneuropathy.

OBJECTIVE

The purpose of this study was to evaluate the sensitivity and specificity of proximal upper limb motor nerve conduction study abnormalities in chronic inflammatory demyelinating polyneuropathy (CIDP), using standard percutaneous stimulations up to Erb's point.

METHODS

Electrophysiologic data relating to proximal conductions of median and ulnar nerves of 22 patients with CIDP were retrospectively analyzed and compared to those of 22 controls with sensory neuropathy. Distal conduction results were also reviewed.

RESULTS

The findings demonstrate independent high sensitivity of abnormal upper limb proximal nerve conduction studies in CIDP. Demonstration of conduction block of >20% and temporal dispersion of >15% had low specificity. However, conduction block was highly specific with cut-off values of >30% at axilla and >50% at Erb's point. Specificity was considerably improved using a cut-off value of >30% at proximal levels for temporal dispersion. Diagnostic sensitivity improved significantly with proximal studies with the criteria used in this population. No adverse effects had occurred as result of proximal stimulations.

CONCLUSIONS

Proximal studies are safe, sensitive and reliable procedures in cases of suspected CIDP. Their use appears justified although adequate cut-off values are desirable to optimize their specificity.

SIGNIFICANCE

This study indicates that proximal upper limb nerve conductions are appropriate in investigating suspected CIDP, as detailed in recently established electrophysiologic criteria. However, specificity is largely dependent on cut-off values for conduction block and temporal dispersion.