Kerala Journal of Ophthalmology

CASE REPORT
Year
: 2022  |  Volume : 34  |  Issue : 2  |  Page : 164--166

Off-center presentation of ocular myasthenia


Mary A Stephen, P Jayasri, PJ Harigaravelu 
 Deparatment of Ophthalmology, IGMC&RI, Puducherry, India

Correspondence Address:
Dr. Mary A Stephen
No 6, Vallalar Street, Kadhirkamam - 605 009, Puducherry
India

Abstract

Myasthenia gravis is an autoimmune condition with varied presentations. In this, we report a 70 years old diabetic male who came complaining of diplopia. On examination, he had ptosis and restriction of extraocular movements on the right side with bilateral normal pupillary reflexes. We diagnosed him to have diabetic neuropathy initially, however his ptosis worsened, leading us to revise the diagnosis. Ice pack test was positive, repetitive nerve stimulation showed a decremental response, and serum acetylcholine receptor antibodies were positive, confirming the diagnosis of ocular myasthenia. We started the patient on oral pyridostigmine and steroids and his symptoms improved. This report emphasizes the need for a high degree of suspicion for the timely diagnosis of ocular myasthenia gravis.



How to cite this article:
Stephen MA, Jayasri P, Harigaravelu P J. Off-center presentation of ocular myasthenia.Kerala J Ophthalmol 2022;34:164-166


How to cite this URL:
Stephen MA, Jayasri P, Harigaravelu P J. Off-center presentation of ocular myasthenia. Kerala J Ophthalmol [serial online] 2022 [cited 2023 Feb 2 ];34:164-166
Available from: http://www.kjophthal.com/text.asp?2022/34/2/164/355049


Full Text



 Introduction



Myasthenia gravis is an autoimmune disease where autoantibodies directed against the acetylcholine receptors will lead to abnormal functioning of the neuromuscular junction resulting in weakness of the skeletal muscles, which in turn results in varied clinical features. Ocular muscles are often involved at the earliest and can be the only affected group in certain situations as isolated ocular myasthenia.[1],[2] The typical features of ocular myasthenia gravis include drooping of eyelids, ophthalmoplegia, and features of orbicularis muscle weakness. Medical professionals related to ophthalmology should have extensive knowledge about the nature of the disease and its prompt diagnosis with existing treatment options as in some circumstances it can be life-threatening as in myasthenic crisis. Many cases often require neurologist consultation and electrophysiological testing for the confirmation and initiation of treatment. This case report emphasizes clinical awareness about atypical presentation and prompt treatment about myasthenia.

 Case Report



A 70 years old male patient presented with complaints of drooping of the right eyelid for the past 4 days, which was preceded by a history of trivial trauma. The patient also had complaints of double vision for both distance and near objects, which disappeared on closing either eye. No history of any other neurological complaints, no headache and scalp pain, jaw claudication, and dysphagia. He is a known case of non-insulin-dependent diabetes mellitus for the past 15 years and is on regular oral medications.

Detailed ocular examination was carried out for the patient and Snellen's visual acuity of the patient was 6/6 in both eyes, both eyes' pupils were round and reacting briskly to light. Right eye 15° exotropia noted with ptosis [Figure 1] and [Figure 2]. Levator palpebrae superioris function of the right eye is 5 mm and left eye examination was normal. Dilated fundus examination of both eyes was normal. Relevant investigations have been carried out and found to have glycated hemoglobin of 8.2. A provisional diagnosis of right eye pupil sparing third nerve palsy secondary to microvascular abnormality (diabetes mellitus) has been made and diabetic medications have been revised with close follow-up. Three weeks after the initial presentation, the patient came with complaints of worsening of drooping of right eyelids and minimal drooping in the left eyelid. Ice pack test carried out was found to have an improvement in levator palpebrae superioris function of both eyes and fatigability noted in both eyes. We shifted our diagnosis from diabetic mononeuropathy to ocular myasthenia. To confirm the diagnosis, we performed myasthenia gravis including acetylcholine receptor antibodies (turned positive), and a repetitive nerve stimulation test showed a decremental response. We started the patient on oral pyridostigmine and minimal improvement was noted on a subsequent visit. Oral Prednisolone was started with Pyridostigmine. Patient was switched to mycophenolate mofetil under tapering steroid cover after 1 month. Ptosis and extraocular movements improved without any residual defects over a period of 2 months.{Figure 1}{Figure 2}

 Discussion



Myasthenia gravis is a disease of neuromuscular junction affecting skeletal muscles. This autoimmune disease is due to antibodies attaching to acetylcholine receptors and in severe disease causes destruction of receptors leading to a reduction in the number of acetylcholine receptors, which impairs the function of muscle action resulting in varying manifestations like ptosis, orbicularis muscle weakness, and restriction of extraocular movements. Myasthenia is characterized by bimodal age distribution and congenital myasthenia can also occur.[3],[4] Thymus gland imaging is often required as the risk of thymoma is higher and thymectomy may be even beneficial.

About half of myasthenia gravis patients present with isolated ocular involvement. Most of them progress to have systemic involvement over a period.[5] The exact etiology for early involvement of extraocular muscles has not been defined and is probably due to increased response to minor changes in acetylcholine receptor activity. Most cases of ocular myasthenia will present with typical signs of drooping of eyelids which worsens as the day advances, and positive ice pack test, restriction of extraocular movements, presence of specific signs like Cogan's lid twitch, fatigability, see-saw sign, and pupil involvement usually is not seen.[6] In our report, an elderly patient had an atypical presentation in the form of sudden onset ptosis preceded by trivial trauma and diplopia with no history of any diurnal changes pointed towards ischemic third nerve palsy. Diagnosis of myasthenia was made with the help of investigation including antibody testing and repetitive nerve stimulation test. The patient was treated with oral pyridostigmine who eventually required oral steroids followed by mycophenolate mofetil.

Confirmation of myasthenia requires various investigations but most cases have a common presentation, and cases mimicking like ischemic third nerve palsy are rare, and prompt diagnosis is needed as management of the later is observation and undiagnosed myasthenia patient can have varied complications including respiratory failure in advanced cases and myasthenic crisis. The atypical presentation also requires specific enquiry about drugs that can precipitate myasthenia like fluoroquinolones.

 Conclusion



Myasthenia should be suspected in any patient with ptosis and diplopia despite the absence of specific clinical findings. Prompt diagnosis often requires a high index of suspicion so complications can be avoided. The diagnosis requires clinical knowledge and investigations are often required to conclude.

Acknowledgements

Sincere thanks to the colleagues who encouraged in writing this case report and to the patient for providing this valuable report.

Consent

Written informed consent has been obtained from patient father for publication of the case details including the photographs taken.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Smith SV, Lee AG. Update on ocular myasthenia gravis. Neurol Clin 2017;35:115-23.
2Fortin E, Cestari DM, Weinberg DH. Ocular myasthenia gravis: An update on diagnosis and treatment. Curr Opin Ophthalmol 2018;29:477-84.
3Gilhus NE. Myasthenia gravis. N Engl J Med 2016;375:2570-81.
4Peragallo JH, Bitrian E, Kupersmith MJ, Zimprich F, Whittaker TJ, Lee MS, et al. Relationship between age, gender, and race in patients presenting with myasthenia gravis with only ocular manifestations. J Neuroophthalmol 2016;36:29-32.
5Mee J, Paine M, Byrne E, King J, Reardon K, O'Day J. Immunotherapy of ocular myasthenia gravis reduces conversion to generalized myasthenia gravis. J Neuroophthalmol 2003;23:251-5.
6Sommer N, Melms A, Weller M, Dichgans J. Ocular myasthenia gravis. A critical review of clinical and pathophysiological aspects. Doc Ophthalmol 1993;84:309-33.