Praxis is the ability to perform skilled or learned movements. Apraxia is a neurologic movement disorder characterized by the inability to carry out such learned, skilled motor acts, even though the command is understood, the patient is willing to perform the task, and the muscles and sensory systems needed to perform the action are intact.¹ Apraxia is further classified into subtypes such as ideomotor, ideational, and limb-kinetic apraxia and is seen in a variety of neurological disorders.²,³

Apraxia of eyelid opening (AEO) is a nonparalytic inability to initiate eyelid opening in the absence of clinically evident contraction of the orbicularis muscle, ocular motor nerve or sympathetic nerve dysfunction, or myopathy of the levator palpebral superior muscle.⁴ A variety of different names have been used for this condition, attributed to different proposed etiologies. Goldstein and Cogan⁵ first introduced the term apraxia of eyelid opening in 1965, based on four patients with basal ganglia disease who experienced difficulty in initiating the act of eyelid elevation. Nearly 40 years earlier, Schilder⁶ described two patients with difficulty of eyelid opening who also had difficulty closing their eyes, and 3 years later, Riese⁷ reported a similar condition in a patient with a frontotemporal injury. Subsequent reports have demonstrated AEO associated with extrapyramidal diseases such as multiple system atrophy, Parkinson disease, MPTP (1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine) intoxication, and progressive supranuclear palsy.⁸,⁹,¹⁰ Boghen¹¹ first drew attention to the association between AEO and blepharospasm, with which it is often confused. The occurrence of AEO in patients with blepharospasm was reported as 7% in one study⁹ and 10% in another.¹² Tolosa et al¹³ found AEO in 12 of 22 (55%) consecutive patients with blepharospasm. AEO can also occur in isolation, not associated with any other central nervous system abnormalities.⁹,¹⁴,¹⁵,¹⁶,¹⁷

AEO is a very rare condition. In a study of three neighboring towns in Italy with a combined population of 67,606, only four cases of AEO were identified, giving a crude prevalence rate of 59 per million population.¹⁸ In that study of 34 clinical cases of AEO, about 30% were isolated and 30% were associated with blepharospasm, 10% each with other dystonias, 10% with Parkinson disease and 18% with progressive supranuclear palsy.¹⁸

The diagnosis of AEO is usually made according to clinical criteria outlined in 1985 by Lepore and Duvoisin.⁸ These include no clinical signs of orbicularis oculi muscle contraction, no lowering of the brows beneath the superior orbital margins (Charcot sign) as seen with blepharospasm, marked frontalis muscle overaction and brow elevation during the period of eyelid elevation failure, and no dysfunction of the ocular motor or ocular sympathetic nerves. Some authors also include transient failure to sustain eyelid elevation, although this condition is not included among these criteria for the diagnosis of AEO.⁴,¹⁹

Several different terms, besides AEO, have been used for this condition, none of them adequate to represent the presumed pathophysiology of the condition. One term, “focal eyelid dystonia,”⁹ was based on the assumption that the syndrome is a dystonia and not an apraxia. The term “involuntary levator palpebrae inhibition”⁸ was based on the concept of a supranuclear inhibition of levator muscle function. “Blepharocolysis”²⁰ and “pretarsal blepharospasm”¹⁴ were based on the observation that the levator muscle is reciprocally inhibited by subclinical contractions of the pretarsal orbicularis muscle. Even though AEO does not adequately conform to the usual definitions of apraxia, where there is a dissociation between the praxis action plan and its execution, the term “apraxia of eyelid opening” remains widely embedded in the literature and is still the most commonly used term for this disorder.