Normative data and long-term test-retest reliability of the triple stimulation technique (TST) in multiple sclerosis

Transcranial magnetic stimulation is useful for the assessment of cortico-spinal tract integrity in multiple sclerosis (MS). An advanced approach is the triple stimulation technique (TST), utilizing a combination of central and peripheral stimuli, reducing individual response variability. Although TST measures have been implemented in longitudinal studies, basic methodological data on temporal properties of abnormal TST values in MS are sparse.

Normative TST data were obtained from 48 healthy participants. Longitudinal measures were derived from 17 MS-patients (relapsing-remitting: N=10; clinically isolated syndrome: N=7) prior to, three and twelve months following therapy initiation. Intraclass correlations were used to examine test-retest reliability. Complementary, patient ambulation and cognition were assessed.

Patient TST parameters were abnormal, involving excellent test-retest reliability and stable mean values. Cognitive and motor performance improved.

Results are the first to show that abnormal TST values in MS, reflecting diagnostic utility, are highly reliable in a long-term follow-up. Methodological properties are adequate for a longitudinal implementation of TST. Parameters were insensitive to alterations in cognitive/motor functioning. Sensitivity may be verified in subgroups with different treatment regimes.

Results provide new normative data, support diagnostic utility of TST measures in MS, and confirm their long-term robustness.