Abducens nerve palsy in a young adult after COVID-19 infection

Mridula V Amarnath

Consultant Ophthalmologist – Dept. of Ophthalmology, Kauvery Hospital, Marathahalli, Bangalore

Introduction

The coronavirus pandemic – COVID-19 even today stands as a major global health and social burden. The clinical spectrum can vary from asymptomatic subjects to patients with severe fatal illness. The virus can cause a large spectrum of clinical manifestations including respiratory, heart, kidney, vascular damage and even neurological damage. The involvement of the nervous system is increasingly seen with symptoms varying from hyposmia to meningoencephalitis and cranial neuropathies.

Studies have shown that the neurotropic and neuro-invasive nature of the SARS-CoV-2 virus can damage the central and peripheral nervous system and even the muscles [1].

Case Presentation

A young 30-year-old male came to the OPD with complaints of headache and double vision for 2 days .

The patient was diagnosed with COVID-19 infection which was RT-PCR positive 2 week ago and was started on oral antibiotics and supplements.  There was no history of fever, diabetes, hypertension, skull injury or trauma or use of any substance abuse in the past. Other neurological symptoms like hyposmia, hypogeusia, weakness of the limbs, paresthesia, gait disturbances were not observed.

Systemic examinations showed no abnormality. Ocular examination was done. The best corrected visual acuity in both eyes were 6/6 with a near vision of N6 in both eyes. Colour vision was normal. Extra ocular movements showed mild restriction of abduction in the right eye – grade 2 due to palsy of the right lateral rectus muscle. The cover test showed 20 prism diopter esotropia for distance and 15-prism diopter esotropia for near.

On slit lamp examination the anterior segment was normal, the pupils were round and reactive to light . Fundus examination in both eyes showed no abnormality.

Further neurological examination revealed that the other cranial nerves were spared. Therefore, the patient was diagnosed with isolated sixth cranial nerve palsy.

Investigations

The patient underwent blood tests including a complete blood count, metabolic profiles which included blood sugar and hemoglobin A1c (HbA1c), D- dimer test, erythrocyte sedimentation rate (ESR) and C- reactive protein.

Blood investigations showed a low white blood cell count (2.6*10/L) along with random blood sugar was 90 mg/dl while the other parameters were found to be within normal limits. MRI of the brain and orbit with and without gadolinium showed no abnormal signs, enhancements or lesions.

Management

The patient was immediately started on oral steroids (Prednisolone 60 mg). The dose was tapered over 6 weeks. Vit B12 and folic acid supplements and oral Pantoprazole 40 mg were added on.

The patients was reviewed 4 weeks later. The cover test revealed a esotropia of 3 dioptres for distance and orthophoric for near . There was only grade 1 limitation of abduction in the right eye.

Discussion

Sixth cranial nerve palsy also known as Abducens nerve palsy is the most common isolated cranial nerve palsy. It refers to the dysfunction of the abducens nerve most commonly due to etiologies that include idiopathic, inflammation, ischemia, trauma, space-occupying lesions and infections – bacteria or viral [2]. They usually present with acute esotropia with limited abduction on the affected side.

Isolated sixth cranial nerve palsy has been reported in patients with Covid -19 infection along with other symptoms like fever, sore throat , anosmia and ageusia 3 but however in our case the associated symptoms did not occur throughout the course of treatment .

Various mechanisms have been proposed to study about the pathogenesis of the cranial nerve palsy. The most common factor being the break down of the blood barrier permeability due to infected leukocytes inciting pro inflammatory mediators and direct invasion of the endothelial cells [4]. It could also be due to the hematological spread by the breakdown of the blood brain barrier or via retrograde transmission to the neuronal tissues .Studies have shown that the hypercoagulable and proinflammatory condition due to covid 19 infection can also be a causative factor [5]. It has been seen that injury to the abducens nerve could be due to a neurotropic effect of the infectious agent, demyelination from an immune mediated reaction or a localised arteritis and microinfaction of the abducens nerve.[6]

Hypoxia, which is seen in patients with SARS-CoV-2 – 2 infection, causes neuronal and astrocytic injury leading to ischemic damage7.  Such patients will generally present with symptoms of encephalopathy. This is however not related to our case report as the patient was non hypoxemic.

The presence of headache along with diplopia can be due to  micro-vascular damage  as seen in ischemic cranial nerve palsies.  This can be attributed the the fact that the viral spike proteins bind to the endothelial cell receptor angiotensin – converting enzyme 2(ACE-2), that converts angiotensin 11 to angiotensin (1-7). The angiotensin has vasodilator, antiprolifertaive, antifibrotic and antithrombotic properties.[8]

In our study, it was considered a case of an immune-meditated nerve injury and hence the patient was started on corticosteroids in a tapering dose. A lot of studies have shown that the condition is self-resolving but a study conducted by John et al [9] showed that a group of 5 pediatric patients with abducens nerve palsy showed better and quicker results when treated with immunomodulators. There was an improvement in the symptoms in 5- 6 weeks and a complete recovery within 12–14 weeks.

In our case study the patient showed improvement of symptoms in four weeks .

Conclusion

Severe acute respiratory syndrome corona virus (SARS- CoV-19) is primarily a respiratory virus. Various ophthalmological manifestations have been seen which includes optic neuritis, papilledema, ocular myasthenia gravis and even  cranial neuropathies like the third and sixth nerve palsies[10].

Sixth nerve palsy in adults is mainly due to microvascular ischemia and trauma. Abducens nerve palsy can sometimes be the only presenting symptom in a patient with Covid 19-.A lot of  studies have been still going on to understand the full spectrum of neurological complication and its pathophysiological mechanisms.

Treatment of the neurological manifestations due to Covid is done after ruling out other infectious causes.  Symptomatic treatment is recommended along with steroids with constant monitoring for opportunistic infections and altered blood sugar levels.

Since Covid -19 is a novel disease , literature regarding the ophthalmic manifestations  are still evolving , hence evaluating every patient  with subtle clinical presentations followed by a diagnostic assessment with appropriate laboratory tests and imaging modalities is essential.

Declaration of the Patient Consent

The authors certify that they have obtained all appropriate patient consent forms. The patient has given his/ her consent for  the clinical information to be reported in the journal . The patient has been informed that their names and initials will not be published  and due effort will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial Support and Sponsorship

Nil

Conflicts of Interest

There are no conflicts of interest

Bibliography

  • Romero – Sanchez CM,Fernandez-Diaz E. Neurological manifestations in hospitalised patients with covid -19. The ALBACOVID registry. Neurology . 2020: 95:e1066-e1075.
  • Rong AJ, Salazar H. Acute abducens nerve palsy in a patient with novel corona virus disease. J AAPOS. 2020;24:222-223
  • Bhatt JM, Oliveria CA . Isolated cranial sixth nerva palsy with COVID-19 infection. J Neuroophthalmol. 2021;40: 444-456
  • Erickson MA, Banks WA. Neuroimmune axes of the blood -brain barriers and blood barrier- interfaces. Pharmacol Rev.2020:70:278-334
  • Connors JM, Levy JH. Thromboinflammation and the hypercoagulabiliy of COVID-19. J Thromb Haemost. 2021;12:1559-1662
  • Kanberg N,Ashton NJ. Neurochemical evidence of astrocytic and neuronal injury commonly found in COVID-19. Neurology . 2022:95:e1777-e1882
  • .Engin AB, Engin ED. Current opinion in neurological manifestations of SARS-CoV-2 infection. Curr Opin Toxicol. 2021:12:55-63
  • Strawn WB, Ferrario CM. Angiotensin -(1-7) reduces smooth muscle growth after vascular injury .Hypertension. 1999: 33: 222-342
  • Johnet al. Use of immunomodulators in pediatric patients with abducens nerve palsy. N Engl.J.Med. 2021; 12: 134-230
  • Dinkin M, Gao V et al. Covid -19 presenting with ophthalmoparesis from cranial nerve palsy. Neurology. 202:95: 221-322

Kauverian Bookshelf

Applied Medical Statistics

Journals

Kauvery Hospital
Find Doctor
Book Appointment