iMAX: un nouvel outil pour évaluer l'excitabilité des axones moteurs périphériques (une étude prospective multicentrique)

iMAX: un nouvel outil pour évaluer l'excitabilité des axones moteurs périphériques (une étude prospective multicentrique)

iMAX: a new tool for the assessment of motor axon excitability (a multicenter prospective study)

Objectifs
The aim of this study was to validate by a multicentric approach a new electrodiagnostic technique called iMAX to evaluate the peripheral motor axons excitability.

Matériel / Patients et méthodes
iMAX (the lowest intensity allowing a maximal response) and two other excitability parameters, iUP and threshold were prospectively derived from three nerves (median, ulnar and fibular) in four university centers (Liège, Marseille, Fraiture and Nice). iMAX procedure was applied in 28 healthy volunteers and 32 patients with a demyelinating (CIDP, GBS, CMT1a) or axonal peripheral neuropathy.

Résultats
The iMAX parameters of healthy volunteers were not significantly different in the four centers. The test-retest reproducibility was good (Spearman's correlation coefficient > 0.5). Upper limits of normal were established using the 95th percentile. Comparison of the results between volunteers and patient groups indicated significant increases in iMAX parameters especially with the CMT1a and CIDP groups. In CMT1a, iMAX abnormalities were homogeneous at the three stimulation sites, which was not the case for CIDP.

Discussion - Conclusion
The iMAX procedure is reliable and allows to demonstrate disorders of motor axons excitability. The iMAX technique should prove useful in routine clinical practice as it is a fast (5'), non-invasive procedure, easily applicable without dedicated software or devices.