Videonystagmography as a tool to assess blepharospasm before and after botulinum toxin injection.

Background: The aim of this paper was to study blinking parameters using a videonystagmography device, in order to objectively determine disability, and to assess the efficiency of botulinum toxin injection in patients with essential blepharospasm.
Methods: Blinking was studied using the features of pupillary occlusion (PO) as recorded on a videonystagmography device. In 23 patients presenting with essential blepharospasm, we studied the frequency, the percentage, the mean duration of PO, and the longest PO in a 5-minute test period. Patients were tested prior to botulinum toxin injection, and 1 month and 3 months after injection, respectively. PO levels lower than 0.3 s and higher than 0.3 s were studied separately.
Results: At 1 month after injection, botulinum toxin significantly influenced PO higher than 0.3 s, both in frequency (9.6/min +/- 8.2 on Day 0 and 4.7/min +/- 7.2 at Month 1; p = 0.004), and in mean duration (0.95 s +/- 0.84 on Day 0 and 0.58 s +/- 0.34 at Month 1; p = 0.03). On the other hand, we found no significant effect on PO lower than 0.3 s, both in frequency (32.4/min +/- 28.4 on Day 0 and 31.3/min +/- 29.0 at Month 1; p = 0.7) and in mean duration (0.16 s +/- 0.04 on Day 0 and 0.15 s +/- 0.03 at Month 1; p = 0.04). Botulinum toxin also significantly influenced the mean duration of the longest PO (6.44 s +/- 9.4 on Day 0 and 1.55 s +/- 1.9 at Month 1; p = 0.004) as well as the percentage of PO (29.95% +/- 24.6 on Day 0 and 13.44% +/- 11.1 at Month 1; p = 0.003).
Conclusions: PO can be used as the indirect sign of blinking. Videonystagmography provides a real-time result, and could be used to objectively evaluate the effect of botulinum toxin treatment in essential blepharospasm patients.