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June 01, 2022
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Case report: Acute recurrent abducens nerve paresis after COVID-19 vaccination

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COVID-19 vaccines not only protect the body from serious effects of the disease but also reduce the rate of hospitalization and improve herd immunity.

Dhivya Ashok Kumar, MD, FRCS, FICO, FAICO
Dhivya Ashok Kumar
Amar Agarwal
Amar Agarwal

Like any other vaccine, the COVID-19 vaccination can also have immune responses at various levels. In this column, we highlight a rare event of acute recurrent diplopia following a unilateral abducens nerve palsy in a recipient of the COVID vaccination.

Case report

A 70-year-old female patient who is a dentist by occupation presented to the ophthalmology clinic with acute onset of double vision for a period of 2 days. She had associated itching, nausea and frontal headache. She gave a history of receiving the Covishield vaccine (AstraZeneca/Serum Institute of India) against SARS-CoV-2 3 weeks prior. She has been on treatment for hypothyroidism with thyroxine 50 µg daily. No other systemic illness was noted.

On clinical examination, the patient was stable with orientation to time, person and place. On ocular examination, she had left eye mild proptosis with mild esotropia (Figure 1). On extraocular movement examination, mild limitation of abduction in the left eye was observed. There was limitation of extraocular movements on levoversion with minimal pain. There was horizontal uncrossed diplopia increasing in left gaze. Best corrected distance visual acuity was 20/20 in the right eye and 20/30 in the left eye. Pupil reaction was normal in both eyes. Slit lamp examination of the anterior segment was normal in both eyes.

Clinical picture of the patient at presentation showing left esotropia
1. Clinical picture of the patient at presentation showing left esotropia.

Source: Dhivya Ashok Kumar, MD, FRCS, FICO, FAICO, and Amar Agarwal, MS, FRCS, FRCOphth

On dilated fundus examination, the right eye was normal. In the left eye, there were few hard exudates in the macula (Figure 2). The optic disc was defined and healthy in both eyes. IOP was 15 mm Hg and 17 mm Hg in the right eye and left eye, respectively. Color vision and contrast sensitivity examination were within normal limits. Hertel exophthalmometry was 19 mm and 21 mm in the right eye and left eye, respectively, with a base distance of 99 mm. Automated perimetry of the visual field showed few defects near fixation in the left eye (Figure 3). Examination of other cranial nerves was normal.

Fundus photograph of both eyes showing defined optic nerve head
2. Fundus photograph of both eyes showing defined optic nerve head. Left eye (b) shows few hard exudates in macula.
Visual field analysis of both eyes
3. Visual field analysis of both eyes. Left eye (b) shows few depressed points near fixation.

Laboratory tests showed HbA1c of 5.7%, free T3 of 2.2 pg/mL, TSH of 4.9 µIU/mL, serum cholesterol of 242 mg/dL, triglycerides of 152 mg/dL, HDL of 62 mg/dL, LDL of 152 mg/dL, erythrocyte sedimentation rate of 21 mm, C-reactive protein of less than 3.12 mg/L, hemoglobin of 13.9 gm/dL, TC of 10.98 103/mm3, platelet of 327 103/mm3, packed cell volume of 42%, neutrophil of 81%, lymphocytes of 15% and monocytes of 4%. Liver enzymes, serum bilirubin and renal function tests including electrolytes were within normal limits. Anti-acetylcholine receptor antibody was negative. Radiological evaluation of the orbit and brain was performed. Magnetic resonance (MR) tomography of the brain showed chronic small vessel ischemic changes. MR venogram showed moderate to severe short segment narrowing of the right petrous segment internal carotid artery and mild narrowing of the left petrous segment internal carotid artery due to atherosclerosis. Hypoplastic right transverse sinus and sigmoid sinus were also observed. No thyroid orbitopathy or orbital mass lesion was noted.

Endocrinologist and neurologist consultations were obtained. However, no other neurological deficit was elicited by the neurologist except for left eye acute abducens nerve paresis. Endocrinological evaluation showed no change in the existing oral thyroxine prescription. Diabetes was ruled out after evaluation. The patient was started on prednisolone 1 mg/Kg body weight in the right eye daily for 2 weeks along with antacid. Multivitamin tablet supplementation was given. She was also provided with fogged glass to overcome diplopia during daily activities. On follow-up at 2 weeks, there was significant clinical recovery noted. The patient reported recurrence of double vision after the second dose of the vaccine after 2 weeks, and similar conservative management was followed.

COVID-19 vaccination and immune response

Vaccines for viral infections work by training and preparing the body’s immune system by recognizing and functioning against the specific target virus. As we know, the objective of vaccination is to prepare the immune cells or memory cells beforehand so they can self-trigger the immune response on subsequent exposure to the virus. In the COVID-19 pandemic, there have been various vaccines in different parts of world. In India, Covishield has been used in the initial vaccination drive (in two doses separated by a 4-week interval) since January 2021. Although there have been reports of mild allergic reactions, fever and myalgia, there have been no reports of acute neurological events in India after Covishield vaccination.

Vaccine-induced immune reactions

Abducens nerve, also known as the sixth cranial nerve, which emerges in the pontomedullary junction, has the longest subarachnoid course. This is also the common cranial nerve palsy in the adult population. Acquired benign post-inflammatory nerve palsy after immunization is not a rare entity. Recipients of the pentavalent vaccine and the hepatitis B vaccine also have shown transient abducens nerve palsy. Previously, acute abducens nerve palsy has also been reported with vaccines against the influenza virus. The known adverse events following viral vaccines, namely the H1N1 vaccine, are Guillain-Barre syndrome, motor nerve palsies, seizures and encephalomyelitis. In addition to the list of vaccines, recently we noted one of our patients who had taken immunization for SARS-CoV-2 complained of diplopia and was diagnosed with acute abducens nerve paresis.

According to WHO causality assessment criteria and Clinical Immunization Safety Assessment, the vaccine was given before the onset of symptoms, and the temporal relationship had been consistent with the biologic mechanism published already in previous literature on vaccine adverse events. There have been few or no reports on the causal relationship between the vaccine and adverse events until now. However, after the exclusion of other etiological causes (diabetes, hypertension, tumor, orbitopathy, myasthenia, giant cell arteritis) for the acute abducens nerve paresis, the concomitant nausea, itching and headache, and the recurrence after second dose, the adverse event of diplopia can be considered as a “probable” immune response after vaccination. The current vaccines are based on various principles such as live inactivated, recombinant, mRNA and vector based. The Covishield uses ChAdOx1 nCoV-19 recombinant replication-deficient chimpanzee adenovirus vector. Although rare neurological and neuromuscular manifestations after COVID infection have been reported, there have been no reports on adverse effects due to Covishield vaccine yet. The Australian Vaccine Safety Investigation Group reported the rare complication of thromboembolism with thrombocytopenia syndrome following Covishield immunization.

Conclusion

This initial case shows the probable rare event of acute transient diplopia due to abducens nerve paresis following vaccination. However, long-term effects and further follow-up will shed light on the cause-and-effect relationship in such cases. As the number of vaccine recipients and the number of different vaccines increase, vigilance is warranted.