 Voluntary eyelid opening involves the simultaneous activation of the levator palpebrae superioris muscle and the inhibition of the orbicularis oculi muscle.Electromyographic studies have shown that ALO may involve either involuntary levator palpebrae superioris muscle inhibition, persistent pretarsal orbicularis oculi muscle contraction, or both.Hypometabolism of glucose may play a part, and has been documented in the basal ganglia, frontal lobe, and the primary visual cortex in some cases of ALO.