Long latency trigemino-cervical reflex in patients with cervical dystonia.

Trigemino-cervical reflex (TCR) is elicited by stimulation of face using various modalities. TCR reflects the interaction between trigeminal system and cervical motoneurons. Such a specific interaction is assumed to play role in development of cervical dystonia (CD) through superior colliculus. In this study, we aimed to investigate alterations of the functional relationship between those structures in CD and in a subgroup with dystonic tremor. A total of consecutive 23 patients with primary CD (7 men, 16 women) and 16 age and sex matched control subjects (7 men, 9 women) were included in this study. TCR was obtained after percutaneous electrical stimulation (with duration of 0.5 ms) of infraorbital branch of trigeminal nerve while recording over splenius capitis and sternocleidomastoid muscles. Presence and onset latencies of TCR did not differ significantly between patients with CD and controls, and same pattern of muscle activation occurred in both groups. Responses of patient group seemed to have higher amplitudes and to be more persistent. There were no significant side-to-side differences of TCR probability, latency, amplitude or duration with respect to the side of head deviation in CD. Increased amplitudes and durations of responses probably reflect increased excitability of the reflex circuit. We suggest that similar latencies and response pattern in comparison to healthy individuals decrease the possibility of structural disturbance. TCR is probably under bilateral basal ganglia and dopaminergic control. Alterations of trigemino-cervical pathway are more extensive and are not solely due to local changes of brainstem interneurons.

Understanding the features of posterior auricular muscle response in a facial nerve disease prototype.

OBJECTIVES: This study aims to compare and investigate the changes of posterior auricular muscle response (PAMR) following peripheral facial nerve palsy (PFP) with blink reflex (BR). PATIENTS AND METHODS: A total of 75 idiopathic PFP patients and age and sex-matched 38 healthy volunteers were included. Patients with PFP were classified into two groups including early (≤6 months) and late (>6 months) based on the duration of symptoms. Following clinical evaluation, PAMR and BR were recorded. A comparison was performed among the early PFP group (n=52), late PFP group (n=23) and healthy volunteers (n=38). RESULTS: We obtained PAMR in 78.9% (n=30) of healthy volunteers, in 60.9% (n=14) of late and in only 38.5% (n=20) of early PFP patients (p=0.001). No habituation was observed following repeated stimuli. The mean latencies were 9.1±1.6, 10.9±1.9 and 12.3±2.0 msec., respectively (p=0.000). R1 and R2 latencies were longer in the early PFP group, compared to other groups (p=0.000). CONCLUSION: Posterior auricular muscle response exhibits changes in a manner similar to R1 and R2 of BR in early and late PFP. The occurrence rate of PAMR seems to be lowest or its latency is prolonged in the early PFP.