Introduction
A 40-year-old female patient, with a history of chronic allergic rhinosinusitis, presented to the emergency department with a 1-day history of a painless horizontal binocular diplopia on left-sided gaze. Neurological examination revealed an isolated limited abduction of the left eye, consistent with left abducens nerve paresis. No other cranial nerve involvement, sensorimotor deficits, ataxia, or hyporeflexia were present.
Two days before presentation, she developed mild upper respiratory symptoms with hyposmia and had a positive COVID-19 PCR test. General laboratory results including protein electrophoresis showed no abnormalities. Serological workup was negative for HIV, Borrelia, HSV, VZV, EBV, CMV, and Treponema pallidum, sACE was normal, and anti-GQ1b as well as anti-GM1 antibodies were negative.
MRI of the brain with IV gadolinium contrast, obtained 2 days after onset of the diplopia, showed multiple pathologically enhancing cranial nerves (III, IV, V, and VII nerves cisternal segment bilateral), including left abducens nerve (Figs. 1 and 2). Cerebral spinal fluid analysis showed a mildly elevated protein level (50 mg/dL) without signs of an active viral or bacterial infection on the CSF count, microscopy, culture, or PCR.
Fig. 1.
3D T1 DANTE-SPACE after intravenous gadolinium injection demonstrates bilateral enhancement of the cisternal oculomotor nerves
Fig. 2.
3D T1 vibe after intravenous gadolinium injection shows enhancement of left abducens nerve in the cisternal segment and in Dorello’s canal
The diagnosis of an acute mildly symptomatic COVID-19 infection with associated cranial neuropathy was deemed most likely. The patient’s neurological and respiratory symptoms improved gradually, without treatment, during hospital stay. Follow-up after 2 weeks showed a spontaneous complete recovery of eye movement abnormalities, although mild hyposmia persisted.
Discussion
Many neurological symptoms have been observed in association with COVID-19 infection, including cranial neuropathies. The most frequently affected cranial nerves are the olfactory nerve (27.2%), resulting in a loss of smell, while the facial nerve (30.8%) and glossopharyngeal nerve (25.2%) are associated with a loss of taste. However, the abducens nerve is a less commonly affected cranial nerve in COVID-19 infections (0.7%) [1]. The pathophysiology of cranial neuropathy associated with COVID-19 infection has not yet been established. Possible hypotheses include direct viral neurological injury or indirect neuroinflammatory and autoimmune mechanisms. The absence of the virus in the cerebrospinal fluid (CSF) pleads in favor of an indirect or parainfectious etiology of the cranial nerve palsy, and the actual pathophysiology of the cranial nerve involvement remains elusive.
Multiple cases of COVID-19-related cranial neuropathies were found to have cranial nerve abnormalities on MRI of the brain [2, 3]. These include increased T2 signal and increased gadolinium enhancement [3]. Abnormal cranial nerve enhancement on brain MRI has a broad differential diagnosis including neoplasm (peritumoral spread, leptomeningeal metastasis), infection (tuberculosis, Lyme disease, viral infections), para- or postinfectious and demyelination (Bell’s palsy, Guillain-Barré syndrome, Miller-Fisher syndrome, multiple sclerosis, recurrent painful ophthalmoplegic neuropathy), granulomatosis (sarcoidosis, vasculitis), trauma, and postradiation [4]. Clinical history, laboratory results, and cerebral spinal fluid analysis help narrowing the differential diagnosis.
Declarations
Ethical approval
Ethical approval was waived by the local Ethics Committee of University Antwerp in view of the retrospective nature of the study and all the procedures being performed were part of the routine care.
Conflict of interest
The authors declare no competing interests.
Informed consent
This article does not have information that could identify the subject. No informed consent was needed.
Human rights and animal participants
This article does not involve research with human/animal participants.
Footnotes
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References
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