Somatosensory evoked blink response in hemifacial spasm and peripheral facial palsy.

Somatosensory blink response (SBR) is produced by electrical stimulation of peripheral nerves or skin areas remote from the face. We investigated the presence of SBR in cases with hemifacial spasm (HFS) and peripheral facial palsy (PFP). Fifty-seven cases of HFS, 54 cases of PFP and 39 normal subjects were included in the study. A routine blink reflex study was performed in all subjects. Supramaximal stimulation of the median nerve was given ipsilateral to the either spasm or paralytic side for SBR. Recordings were made at the orbicularis oculi (o.oc) bilaterally and ipsilaterally at the orbicularis oris (o.or) muscles. SBR was elicited in 12 of 39 control subject. Twenty four of 48 HFS cases were SBR positive. Twelve of them had o.or response. An SBR was elicited at the ipsilateral o.oc in 35 of 46 patients with PFP with synkinesia. Twenty-six patients had an SBR at the ipsilateral o.or. In the 13 patients with PFP without synkinesia only 3 people had an SBR. SBR positivity was seen more often in PFP with synkinesia than in cases with HFS. SBR if positive spreads to the lower part of the face in most of cases with HFS and PFP with synkinesia.

Relationship between reflex excitability and symptom duration in hemifacial spasm.

Changes in excitability and symmetry characteristics have been analyzed with blink reflex recovery curve method applied with dual stimuli at 200, 600 and 1000 ms in patients with hemifacial spasm (HFS), spasm duration shorter than 1 year (HFS 1), spasm duration longer than 8 years (HFS 2), and control group. When compared with controls, while HFS cases with short symptom duration had significant decreases in inhibition at 200 ms in the spasm and healthy sides, those with long symptom duration had this finding only in the spasm side at the 200 ms interval. When HFS groups were compared with each other, in cases with HFS 1, decreased inhibition in the spasm side was significant at 200 and 600 ms, while this was significant only at 200 ms in HFS 2 cases. HFS groups were not found to be different in terms of R2 recovery grade. In conclusion, in cases with HFS, decreased inhibition attributed to facial motor neuron and brain stem interneurons is more predominant on the side of the spasm and this was shown to be present also, to some extent, in the contralateral side. It can be said from our findings that the abnormalities of the blink reflex recovery do not progress in cases with HFS when the symptom duration becomes longer.