Apraxia of eyelid opening (AEO) conventionally refers to the “nonparalytic abnormality characterized by difficulty in initiating the act of lid elevation”. 1 Two major pathophysiological mechanisms postulated for AEO include, involuntary levator palpebral inhibition (ILPI) and the overactivity of the pretarsal orbicularis oculi (OOc). 2 , 3 , 4
In AEO due to ILPI, eyebrows get elevated by forceful contraction of the frontalis in an attempt to overcome the levator palpebrae (LP) inhibition, while in blepharospasm, a related condition causing failure to open the eyes due to spasm of the entire OOc, eyebrows come down due to the contraction of the orbital part of OOc. 4 However, in pretarsal blepharospasm that is confined to the pretarsal OOc, there is no spasm of the orbital part of the OOc and the eye brows go up by frontalis contraction in an attempt to open the eyes, mimicking ILPI. 5
We put forth a simple clinical sign of elevation of the lower eyelid, that reveals the presence of pretarsal blepharospasm and distinguish it from AEO resulting from ILPI without the need for EMG.
Case Report
A 48‐year‐old gentleman presented with episodic inability to open the eyelids for the past 3 months. During these episodes, he could not open the eyes voluntarily, but occasionally could do it at random or after attempting to blink. He reported no spasm of the muscles around the eyes or other relevant symptoms. On examination, he had severe difficulty in opening the eyelids after spontaneous or forceful eye closure, but not during spontaneous or reflexive blinking. There was no difficulty in keeping the eyelids open. Neurological examination was otherwise normal. While attempting to open the eyes, lower eyelids were observed to go up due to spasm of the pretarsal OOc (Video 1). MRI brain and relevant biochemical tests were normal. EMG from the pretarsal OOc of both the upper and lower eyelids showed motor unit discharges on trying to open the eyes, indicating pretarsal OOc contraction. For comparison, we have also added the video of a patient with AEO showing absence of this sign of visible spasm of the lower eyelids on attempted eye opening, indicating the underlying mechanism to be ILPI as opposed to pretarsal blepharospasm (Video 2).
Video 1.
Patient with Pretarsal blepharospasm: Patient is asked to shut the eyes tightly that leads to inability to open the eyes thereafter. On attempt to open the eyes, spasm of the eyelids with elevation of the lower eyelids is observed.
Video 2.
Patient with “true” AEO without lower eyelid elevation: Inability to open the eyes voluntarily is observed without lower eyelid spasm indicating ILPI alone, without associated pretarsal blepharospasm as the possible mechanism.
Discussion
Under physiological conditions, there is reciprocal inhibition with simultaneous complete inhibition of the OOc and activation of the LP occurring during voluntary eye opening and the reverse during eye closure. However, in patients with AEO, EMG studies have shown that during attempted eye opening, there may be continuation of OOc activity limited to the pretarsal OOc, referred to as the Pretarsal Motor Persistence(PMP). 4 This is thought to be the initial event that leads to a “normal” reciprocal inhibition of the LP, leading to inability to open the eyelids. 5 , 6 There is also a smaller subset of patients with AEO, who have isolated ILPI without PMP. 2 , 4
Boghen has categorized isolated LP inhibition and pretarsal blepharospasm as pathophysiological mechanisms of AEO and suggested that these may be differentiated by EMG studies showing PMP in the latter. 7 However, many authors opine that those in whom there is pretarsal blepharospasm should be considered as a separate entity of focal dystonia as these patients share many characteristics of dystonia and since the term apraxia generally do not characterize such overactivity. 3 , 8 , 9 In this regard, AEO may be better defined as “the nonparalytic abnormality characterized by difficulty in initiating the act of lid elevation without evidence of any involuntary orbicularis activity''. 10 This is especially so since blepharospasm would also otherwise qualify for AEO as per the traditional definition.
The co‐occurrence of blepharospasm and AEO is common and is estimated to occur in 5%–30% of patients with blepharospasm. 10 However, in these patients, blepharospasm involves the entire OOc and is often noted independently of the AEO. The eyelid spasm also does not occur exclusively during the act of eye opening as in our case. Rarely, patients may manifest with only blepharospasm and AEO is unmasked by botulinum toxin therapy. 10 These features make the coexistence of both AEO and blepharospasm in our case unlikely.
In pretarsal blepharospasm, just as there is spasm in the upper eyelids, there also occurs simultaneous spasm of the pretarsal OOc of the lower eyelids during attempted eye opening. We believe that this spasm manifested as elevation of the lower eyelids is a reliable sign to differentiate the so‐called AEO due to pretarsal blepharospasm from a “true” AEO due to ILPI without the need for EMG, as illustrated in the videos.
It has also been noted that Botulinum toxin given for AEO is likely to be helpful in those with PMP and not in isolated ILPI. 4 , 9 Therefore, this clinical sign may also help in patient selection for botulinum toxin injection in AEO. However, we acknowledge that our report has the limitations of a single case report and that larger studies are warranted for its validation.
Author Roles
(1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript: A. Writing of the first draft, B. Review and Critique.
M.M.: 1A, 1B, 1C, 3A, 3B
R.T.: 1A, 1B, 1C, 3B
S.S.: 1A, 1B, 1C, 3B
Disclosures
Ethical Compliance Statement
We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. The authors also confirm that informed consent was obtained from the patient for the research work and the approval of an institutional review board was not required for this work.
Funding Sources and Conflict of Interest
No specific funding was received for this work. The authors declare that there are no conflicts of interest relevant to this work.
Financial Disclosures for the Previous 12 Months
The authors declare that there are no additional disclosures to report.
Contributor Information
Madhusudanan Mohan, Email: mohan.madhusudanan@gmail.com.
Sheetal Sasikumar, Email: sheetalrehaan@gmail.com.
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