Blink reflex abnormalities in Tourette syndrome

Tourette syndrome (TS) is a not uncommon disorder which represents the most complex manifestation of the spectrum of tic disorders, with onset during childhood or early adolescence. There are no definitive tests for diagnosis of TS. The objective of this study has been to demonstrate whether neurophysiological abnormalities of the blink reflex can be observed in patients affected with TS and correlate with the severity of TS.

We enrolled 17 patients with Tourette syndrome, diagnosed according to DSM IV Diagnostic Criteria, and 10 healthy volunteers. Tic severity was assessed using a self rating scale (Tourette Syndrome Symptom List, TSSL) and examiner ratings (Yale Global Tic Severity Scale (YGTSS), and Tourette-Syndrome Global Scale (TSGS)). The blink reflex was elicited by stimulating the supraorbital nerve in order to measure the early response (R1), homolateral and contralateral R2 (late) responses, amplitude of R1 and duration of R2.

We observed a mean duration of R2 significantly longer in the patient group than in the control group (P<0.01, Student t test), without any statistically significant differences of R1 and R2 latencies and of R1 amplitude between the patient group and the control group. Correlations between changes in clinical rating scores and R2 duration were tested by simple linear regression analysis, which has not demonstrated a significant correlation between TSSL scores, clinical rating scores (measured by TSGS and YGTSS) and duration of R2.

A pattern as to excitability of the blink reflex can be a frequent abnormality in TS patients, not correlated with its severity.