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We aimed to investigate the incidence, prevalence, and etiology of sixth cranial nerve (CN6) palsy in the general Korean population. The nationally representative dataset of the Korea National Health Insurance Service–National Sample Cohort from 2006 through 2015 was analyzed. The incidence and prevalence of CN6 palsy were estimated in the cohort population, confirming that incident cases of CN6 palsy involved a preceding disease-free period of ≥4 years. The etiologies of CN6 palsy were presumed using comorbidity conditions. Among the 1,108,256 cohort subjects, CN6 palsy developed in 486 patients during the 10-year follow-up. The overall incidence of CN6 palsy was estimated to be 4.66 per 100,000 person-years (95% confidence interval [CI], 4.26–5.08) in the general population. This incidence increased with age, accelerating after 60 years of age and peaking at 70–74 years of age. The mean male-to-female incidence ratio was estimated as 1.41 in the whole population, and the incidence and prevalence of CN6 palsy showed an increasing trend over time in the study period. Surgical incidence for CN6 palsy was only 0.19 per 100,000 person-years (95% CI, 0.12–0.29). The etiologies were presumed to be vascular (56.6%), idiopathic (27.2%), neoplastic (5.6%), and traumatic (4.9%). In conclusion, the incidence of CN6 palsy increases with age, peaking at around 70 years, and shows a mild male predominance in Koreans.

Background: Isolated abducens nerve palsies from COVID-19 infections are rarely described in literature. Their clinical features are poorly understood, and guidance on their treatment is lacking. Objective: To describe the clinical features of isolated abducens nerve palsies from COVID-19 infection, and provide guidance on their management. Methods: We performed a literature review and analyzed the clinical features of patients with isolated abducens nerve palsy from COVID-19 infections reported in literature. Results: In total, 16 cases from 15 studies published between January 2020 and December 2023 were identified. Their median age was 44 years (range 3-71, including two children). Nearly two-thirds (10/16, 63%) were without medical history. Abducens nerve palsies mostly occurred early with COVID-19 symptoms (median of 5.5 days, range 0-21 days). They were all unilateral, and displayed neither clear gender nor left-right predilections. Brain magnetic resonance imaging scans were often unremarkable (9/13, 69%). More than half (9/16, 56%) received no treatment or symptomatic treatment only, while only two received steroids. Regardless, nearly all experienced clinical of diplopia (14/16, 88%), of which most recovery were either complete or near-complete (at least 10/14, 71%) within a median period of 26 days (range 5-240 days). Conclusion: Isolated abducens nerve palsies are early but uncommon complications of COVID-19, mainly affecting patients with mild infections. Prognosis appears fair even when without corticosteroid treatment, and recovery is significant and early in most. Observation and early outpatient clinical review within a month are reasonable measures. Patients without significant improvement within a month should be re-assessed for other aetiologies.

We present the case of a 23-year-old young man with left-eye abducens nerve palsy following the COVID-19 vaccination. Given the temporal relationship between vaccination and the onset of symptoms, the lack of systemic history, and unremarkable magnetic resonance imaging, the patient's abducens nerve palsy was related to his vaccination. The ophthalmologist should be aware of this neurotropic sequela of COVID-19 vaccination in young adults.

The complete features of the neurological complications of coronavirus disease 2019 (COVID-19) still need to be elucidated, including associated cranial nerve involvement. In the present study we describe cranial nerve lesions seen in magnetic resonance imaging (MRI) of six cases of confirmed COVID-19, involving the olfactory bulb, optic nerve, abducens nerve, and facial nerve. Cranial nerve involvement was associated with COVID-19, but whether by direct viral invasion or autoimmunity needs to be clarified. The development of neurological symptoms after initial respiratory symptoms and the absence of the virus in the cerebrospinal fluid (CSF) suggest the possibility of autoimmunity.

Purpose The purpose of this study is to describe a case series of infants with isolated congenital sixth nerve palsy (ICSNP) and suggest a management algorithm based on our experience and a review of the literature. Methods A retrospective cohort design was used. The clinical database of a single tertiary medical center was reviewed to identify all patients diagnosed with ICSNP from January 2020 to November 2022. Data were collected as follows: demographic parameters, age at initial presentation, presenting symptoms and signs, findings on ophthalmic and neurologic examinations, findings on follow-up, and outcome. Results Six patients were included. All were born at term. The average gestational weight was 3675.7 ± 262.7 g. Three mothers had gestational diabetes. Five deliveries necessitated labor induction either by oxytocin ( n  = 4) or by membrane stripping followed by oxytocin ( n  = 1). One had also gone a forceps assisted delivery. Symptoms were noticed in all newborns by their parents within the first week of life. Ophthalmological and neurological examinations were otherwise unremarkable apart of one patient with a head turn to the side of the involved eye. Four patients underwent brain imaging that were unremarkable. All abduction deficits resolved by 1 to 3 months of age. Follow up examinations were unremarkable (mean follow up 14.3 ± 5.0 months, range 4–23). Conclusions This case series, together with previous reports, support ICSNP’s benign nature. We suggest an initial basic work-up that solely includes ophthalmological and neurological examinations which will be elaborated in case of any additional pathologic findings or if ICSNP does not fully resolve by 3 months.

Strabismus surgery is required for some cases with abducens nerve palsy (ANP) without spontaneous resolution; however, whether the surgical corrective effect for ANP is similar to that of concomitant esotropia (ET) remains unclear. This study compared the 1-year surgical outcomes of recession and resection (RR) between patients with ANP (ANP group, 11 patients) and those with concomitant ET (ET group, 33 patients). The target angle of RR for ANP was added by 5 prism diopters (Δ) compared to concomitant ET. The 1-year corrective effect was relatively lower in the ANP group than in the ET group (2.1 ± 0.7 Δ/mm vs. 2.6 ± 0.6 Δ/mm, P  = 0.07), but the 3-month effect was similar (2.3 ± 0.6 Δ/mm vs. 2.6 ± 0.6 Δ/mm, P  = 0.31) because significantly larger drift occurred in the ANP group than in the ET group (2.3 ± 2.2 Δ vs. 0.2 ± 2.7 Δ, P  = 0.03). Motor success at 1 year was achieved in 90.9% of patients in both groups. Our findings suggested that the target angle of RR was suitable to add by 5 Δ in patients with ANP compared to concomitant ET in order to maintain a long-term favorable ocular position.

Purpose To present cases with idiopathic third and sixth cranial nerve neuritis. Study design Retrospective observational study Methods The results of high resolution pre- and post- cranial nerve magnetic resonance images (MRI) with three-dimensional sequences for visualizing cranial nerves in patients with third, fourth, and sixth cranial nerve palsies who were treated at the Neuro-ophthalmology Department of Samsung Medical Center were reviewed. Patients with cranial nerve enhancement confirmed by experienced radiologists were identified. The medical records of these patients were reviewed, and their demographics, clinical presentations, laboratory results, and clinical outcomes were analyzed. Results Of 265 patients with third, fourth, and sixth cranial nerve palsy, 60 were identified by high resolution MRI as having enhancement of the corresponding cranial nerve. Among these, 17 patients with infiltrative, granulomatous, or tumorous lesions were excluded. In addition, 28 patients with identifiable causes of cranial nerve palsy, such as Miller-fisher syndrome, virus infection, or radiation-induced neuropathy, as well as patients with vasculopathic risk factors, were also excluded. Ultimately, a total of 15 patients with idiopathic third and sixth cranial nerve neuritis were included in this study. The mean age of these patients was 43 ± 15 years. Eight patients had sixth cranial nerve palsy, six third cranial nerve palsy (two partial and four complete), and one patient with complete third and sixth cranial nerve palsy. Nine patients received steroid treatment. Eleven patients recovered fully within a period ranging from a few days to one year. Two patients were much improved up to 1 month after initial presentation, but were then ultimately lost to follow-up. Another patient was lost to follow-up after the initial work-up. The other patient lost to follow-up had partially recovered during the first 6 months. Conclusions We present patients with idiopathic third and sixth cranial nerve neuritis. They tended to respond well to steroid treatment and to have good prognoses. In order to better understand the long-term prognosis of cranial nerve neuritis and possible association with other neurologic disorders, a larger scale and longer-term study is needed.

Herpes zoster Ophthalmicus (HZO) affecting the ophthalmic division (V1) of the trigeminal nerve. HZO may cause extraocular muscle palsies, with the third nerve being the most commonly affected and the fourth nerve the least. The combined involvement of the optic nerve and isolated paralysis of the eye muscle is very rare, with only limited case reports documenting this complication of ocular herpes zoster. This case report also describes a case of optic nerve involvement with 6th nerve palsy, which was treated with corticosteroid and valacyclovir.

Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach. We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury. Ten anatomic specimens were dissected using endoscopes attached to an high-definition camera. A series of anatomic measurements and relationships of the abducens nerve were noted. Illustrative clinical cases are described to translate those findings into practice. Cisternal, interdural, gulfar, and cavernous segments of the abducens were identified intracranially. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; horizontal distance between both abducens nerves at the PMS was 10 mm, and between both abducens at the interdural segment was 18.5 mm. The upper limit of the lacerum segment of the internal carotid artery was at the same level of the dural entry point of the sixth cranial nerve posteriorly. The sellar floor at the sphenoid sinus marks the level of the gulfar segment in the craniocaudal axis. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm. Anatomic landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid, and the sellar floor for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

We report two adult cases of abducens nerve palsy presenting immediately (within weeks) after they received the first dose of Covishield vaccination. Magnetic resonance imaging (MRI) of the brain obtained after the onset of diplopia demonstrated demyelinating changes. The patients had associated systemic symptoms. Post-vaccination demyelination typically known as acute disseminated encephalomyelitis (ADEM) associated with several vaccines is more common in children. Although the mechanism of the nerve palsy remains unclear, it is suspected to be related to the post-vaccine neuroinflammatory syndrome. Cranial nerve palsies and ADEM-like presentations may represent part of the neurologic spectrum following COVID-vaccination in adults, and ophthalmologists should be aware of these sequelae. Although cases of sixth nerve palsy following COVID vaccination are already reported, associated MRI changes have not been reported from India.