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|LETTER TO EDITOR
|Year : 2016 | Volume
| Issue : 6 | Page : 1309-1310
Hypertropic and exotropic strabismus fixus following neurotoxic snake bite
Kasturi Nirupama, Srinivasan Renuka
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
|Date of Web Publication||11-Nov-2016|
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nirupama K, Renuka S. Hypertropic and exotropic strabismus fixus following neurotoxic snake bite. Neurol India 2016;64:1309-10
A 36-year-old female patient presented with a history of cobra bite in 1994. Previous medical records showed that she had developed severe envenomation causing profound neurological abnormalities such as an altered sensorium, generalized muscle paralysis, and respiratory arrest. She had a protracted course requiring intensive care unit (ICU) treatment for 2 months. Following recovery, she continued to have drooping of both upper eyelids and inability to move the eyes predominantly in downgaze. Ophthalmic examination showed head nodding due to alternate chin elevation to overcome the ptosis, and chin depression for the hypertropia. Hirschberg test revealed bilateral large hypertropia with more than 45° left exotropia with marked limitation of adduction and depression [Figure 1]a. Forced duction test was positive and confirmed extremely tight superior and lateral rectus in both eyes. On manual retraction of her upper lids, her visual acuity was 6/18 in the right eye and 3/60 in the left eye. She had bilateral ptosis with a poor levator function and frontalis overaction [Figure 1]a. Anterior segment and fundus examination were normal in both eyes. She underwent squint and ptosis correction in both eyes. The ocular posture improved in the right eye, but the left eye continued to remain hypertropic and exotropic [Figure 1]b.
|Figure 1: (a) Clinical photograph showing bilateral ptosis with hypertropia and exotropia. (b) Postoperative photograph showing improvement in the ptosis, hypertropia, and exotropia|
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Strabismus fixus is a rare ocular motor abnormality, occurring in congenital and acquired forms, wherein the affected eye is more or less fixed in extreme adduction or abduction. The congenital form occurs as a part of the manifestation of congenital fibrosis of extraocular muscles; while, the acquired forms have been described in association with high myopia, lateral rectus palsy, orbital trauma, inflammation, and malignancy. External ophthalmoplegia following neurotoxic snake bite is temporary, which usually recovers spontaneously within 2 weeks with antivenom or following anticholinesterase therapy.,, The symptom evolution and recovery depend on the snake species, neurotoxicity, and geographical variations.
The polypeptide neurotoxins cause muscle paralysis by blocking the nicotinic acetylcholine receptors at the postsynaptic motor endplates, or they affect the mode of neurotransmitter release at the presynaptic motor nerve endings. Neurotoxic paralysis may begin within the first hour of snake bites and is seen first as ptosis and then as blurred vision and diplopia. This is followed by facial weakness, dysphagia, and dysarthria. The postsynaptic toxicity may be reversed by antivenom that may facilitate the dissociation of toxin from the receptor and accelerate recovery or facilitate a response to anticholinesterase therapy.
Our case is an atypical presentation of acquired strabismus fixus following a neurotoxic snake bite. This occurrence could be as a result of unresolved prolonged oculomotor paresis or due to a prolonged up rolling of eyes due to Bell's phenomenon in an unconscious state during the ICU stay.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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