Intermuscular coherence as a candidate biomarker for primary lateral sclerosis.

Objective

Reliable and widely accessible neurophysiological biomarkers are needed to assess upper motor neuron (UMN) dysfunction. We investigated whether intermuscular coherence in the beta-gamma frequency range (IMCβγ) and its imaginary component (ICOHβγ) can serve as a biomarker for PLS.

Methods

IMCβγ and ICOHβγ were evaluated in upper and lower limb muscle pairs in 21 individuals with PLS along with 42 age- and sex-matched neurotypical control participants. PLS participants underwent clinical evaluations including deep tendon reflex assessment and manual muscle strength testing.

Results

IMCβγ and ICOHβγ were significantly lower in PLS patients in both the arms and legs. Area under the receiver-operating characteristic curve ranged between 0.71 and 0.77 for differentiating PLS from neurotypical control participants based on measurements in a single limb. Using an abnormal coherence measurement in any two limbs as a diagnostic test for PLS, test sensitivity was 0.76, specificity was 0.86, and accuracy was 0.83.

Conclusions

Both IMCβγ in the arms and ICOHβγ in the legs distinguish PLS patients from neurotypical control participants, supporting their potential as accessible biomarkers of UMN dysfunction.