Electrical stimulation as a therapeutic option to restore eyelid movements in patients with seventh nerve damage

Damage to the seventh nerve is a relatively common clinical problem, the most important consequence of which can be the inability to close the eyelid. The purpose of this study was to investigate whether electrical stimulation could be used to restore eyelid function. Two electrical stimulation regimes were investigated. The first was based on a commercial electrical stimulator and used rectangular pulses (pulse width 200s, pulse repetition frequency 10 Hz, burst length 5s, applied for 1 hour daily for a period of 3 months) on ten patients. The second regime, (based on 15 ms rectangular pulses applied at a pulse repetition frequency of 10 Hz burst length 5s, applied for one hour daily for a period of three months), was implemented using a programmable stimulator designed specifically for this task and was used on seven patients. Treatment outcome was assessed in terms of maximum displacement and velocity of eyelid movement during blinks compared to normal values, and was measured with a purpose built imaging system.;Key results from this study were that both stimulation methods improved the amplitude of voluntary eyelid closure, but spontaneous eyelid movements were not affected. Eyelid velocities during closure remained below normal values for both stimulation regimes. The observed increases in voluntary closure were attributed to a reduction in stiffness of the eyelid mechanics rather than an improvement in muscle function. Some functional movement (<2 mm) was obtained with the regime based on long pulses in direct response to electrical stimulation, which was not observed with the shorter pulses. The observed function was attributed to stimulation of surviving motorneurons. The regime using shorter pulses was better tolerated by patients because long pulses induced a visual aura and were more uncomfortable.