Nystagmus only with fixation in the light: a rare central sign due to cerebellar malfunction

Fixation nystagmus refers to the nystagmus that appears or markedly increases with fixation. While relatively common in infantile (congenital) nystagmus, acquired fixation nystagmus is unusual and has been ascribed to lesions involving the cerebellar nuclei or the fibers projecting from the cerebellum to the brainstem. We aimed to report the clinical features of patients with acquired fixation nystagmus and discuss possible mechanisms using a model simulation and diagnostic significance. We describe four patients with acquired fixation nystagmus that appears or markedly increases with visual fixation. All patients had lesions involving the cerebellum or dorsal medulla. All patients showed direction-changing gaze-evoked nystagmus, impaired smooth pursuit, and decreased vestibular responses on head-impulse tests. The clinical implication of fixation nystagmus is that it may occur in central lesions that impair both smooth pursuit and the vestibulo-ocular reflex (VOR) but without creating a spontaneous nystagmus in the dark. We develop a mathematical model that hypothesizes that fixation nystagmus reflects a central tone imbalance due to abnormal function in cerebellar circuits that normally optimize the interaction between visual following (pursuit) and VOR during attempted fixation. Patients with fixation nystagmus have central lesions involving the cerebellar circuits that are involved in visual-vestibular interactions and normally eliminate biases that cause a spontaneous nystagmus.

Vogt-Koyanagi-Harada disease – A diagnostic pitfall for neurologists

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VKH is an idiopathic autoimmune disease presenting with uveomeningeal syndrome.

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Granulomatous uveitis and serious retinal detachments are the most common findings of VKH.

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VKH can masquerade as IIH by presenting with severe headache and optic disc edema.

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The characteristic retinal finding of VKH can be easily missed by direct funduscopy.

Clinical Reasoning: A 48-Year-Old Woman Presenting With Vertigo, Ptosis and Red Eyes

We describe acute vestibular syndrome in a 48-year-old woman with breast cancer who was finally found to have anti-Ma2-associated encephalitis. Even though the initial diagnosis was vestibular neuritis elsewhere, progression of symptoms and additional findings of bilateral ptosis and circumlimbal injections, vertical saccadic slowing, and impaired convergence led to a suspicion of a rostral midbrain lesion and final diagnosis. The patient's symptoms and ocular motor signs improved markedly after administration of intravenous methylprednisolone and oral tacrolimus. Our patient again stresses the importance of scrutinized ocular motor evaluation for detection of central lesions even in patients with the clinical features of unilateral peripheral vestibulopathy.

Head-impulse tests aid in differentiation of multiple system atrophy from Parkinson's disease

The integrity of the vestibulo-ocular reflex (VOR) remains to be delineated in patients with parkinsonism. We aimed to define the findings of the VOR using head-impulse tests (HITs) and their differential diagnostic value in patients with Parkinson's disease (PD) and multiple system atrophy (MSA). From December 2019 to January 2021, 30 patients with PD and 23 patients with MSA (17 with cerebellar-type MSA and 6 with parkinsonian-type MSA) had a video-oculographic recording of HITs at two university hospitals in South Korea. Reversed (p = 0.034) and perverted (p = 0.015) catch-up saccades were more frequently observed in MSA than in PD during HITs. The gain difference between the ACs and the PCs were larger in MSA than in PD (p = 0.031), and positively correlated with the disease duration in patients with MSA (Spearman's coefficient = 0.512, p = 0.012). Multivariate logistic regression analysis showed that reversed (p = 0.044) and perverted (p = 0.039) catch-up saccades were more frequently associated with MSA than with PD during HITs. In conclusion, HITs aid in differentiation of MSA from PD, and may serve as a surrogate marker for the clinical decline.

Effects of smoking on delayed neuropsychiatric sequelae in acute carbon monoxide poisoning: A prospective observational study

Smoking is a well-known risk factor for cardio-cerebrovascular disease. However, several studies have reported the "smoker's paradox" whereby smokers have a better prognosis for cardio-cerebrovascular diseases. Similar to cardio-cerebrovascular diseases, hypoxia is one of the major mechanisms of injury in carbon monoxide (CO) poisoning. This study investigated the association between smoking and delayed neuropsychiatric sequelae (DNS) in acute CO poisoning.This study involved patients with CO poisoning treated at a university hospital in Bucheon, Korea between September 2017 and March 2020. The exclusion criteria were age <18 years, discharge against medical advice, loss to follow-up, persistent neurological symptoms at discharge, transfer from another hospital 24 hours after exposure, and transfer from another hospital after hyperbaric oxygen therapy. Logistic regression analysis was performed to find factors associated with DNS.Two hundred sixty three patients visited the hospital due to CO poisoning and of these, 54 were excluded. DNS was evaluated up to 3 months after discharge, and until this time, DNS occurred in 35 (16.8%) patients. And the incidence rate of DNS was lower in smokers than non-smokers (15, 12% vs 20, 23.8%, P = .040). Multivariable logistic regression analysis revealed that CO exposure time (odds ratio [OR] 1.003; confidence interval [CI] 1.001-1.005; P = .003), the Glasgow coma scale (GCS) (OR 0.862; CI 0.778-0.956; P = .005), and pack-years (OR 0.947; CI 0.903-0.993; P = .023) were statistically significant for DNS development.These results indicate that more pack-years smoked were associated with reduced risk of the development of DNS in acute CO poisoning, and that CO exposure time and GCS is a predictive factor for DNS occurrence.

Evolution of caloric responses during and between the attacks of Meniere's disease

Caloric tests are useful for disease surveillance of Meniere's disease (MD), although the interpretation of caloric tests remains controversial during the attacks of MD. Therefore, we aimed to characterize the findings of caloric tests during the attacks of MD. We analyzed the results of bithermal caloric tests during and between the attacks in 43 patients with unilateral definite MD. Evaluation was performed during the irritative/recovery phase in 22 and during the paretic phase in 26 patients. During the irritative/recovery phase, less than half of patients (10/22, 45%) showed a caloric asymmetry of more than 25%, lesser responses in the affected ear in six and in the healthy ear in the other four. In contrast, patients usually showed a caloric asymmetry of more than 25% during the paretic phase (19/26, 73%) with a decreased response almost always in the affected ear (18/19, 95%). Between the attacks, caloric asymmetry was found in less than half of the patients (20/43, 47%) with a decreased response almost always in the affected ear (19/20, 95%) when observed. The caloric asymmetry was less during the irritative/recovery phases than between the attacks (p = 0.007). In contrast, the caloric asymmetry was larger during the paretic phase than between the attacks (p = 0.041). The caloric asymmetry decreased during the irritative/recovery phases with an estimated mean difference of 34% (adjusted 95% CI 16-53%, p < 0.001) and 23% (adjusted 95% CI 8-38%, p = 0.002) compared to the paretic and interictal phases. Caloric responses fluctuate during and between the attacks of MD depending on the electrophysiologic status of the vestibular afferents. The results of caloric tests in MD, thus should be interpreted with consideration of each phase when the evaluation was done.

Cox regression model of prognostic factors for delayed neuropsychiatric sequelae in patients with acute carbon monoxide poisoning: A prospective observational study

OBJECTIVE

A major challenge for physicians is to identify patients with acute carbon monoxide (CO) poisoning who are likely to develop delayed neuropsychiatric sequelae (DNS). DNS is defined as neuropsychological sequelae that develops after 2-40 days of lucid interval after CO intoxication. Currently, there is no consensus on factors that predict the prognosis of CO poisoning. Thus, the purpose of this study was to identify factors predicting the development of DNS using a Cox regression model.

METHODS

This prospective observational study included 310 CO-poisoned patients admitted to an emergency department in South Korea from July 2017 to February 2020. Demographic, clinical, and laboratory data were analyzed. Kaplan-Meier curves were constructed to estimate the cumulative incidence of DNS. A multivariate Cox regression model was used to identify the main predictors of the development of DNS.

RESULTS

The incidence of DNS was 18.8 %, and the median onset time was 23.7 days (interquartile range, 14-30 days). The Kaplan-Meier survival curve showed that a serum creatine kinase (CK) level > 175.5 U/L and initial Glasgow Coma Scale (GCS) score ≤ 9 were associated with a higher cumulative incidence of DNS (log-rank test; p < 0.01 and p = 0.02, respectively). Cox regression analysis showed that a serum CK level > 175.5 U/L (hazard ratio [HR]: 2.862, 95 % confidence interval [CI]: 1.491-5.496; p < 0.01) and an initial GCS ≤ 9 (HR: 2.081, 95 % CI: 1.048-4.131; p = 0.04) were significant prognostic factors.

CONCLUSION

In acute CO poisoning, an initial GCS score ≤ 9 and serum CK level > 175.5 U/L are significant predictors of DNS development.

Ictal downbeat nystagmus in Ménière disease: A cross-sectional study

OBJECTIVE

To determine the mechanism of ictal downbeat nystagmus in Ménière disease (MD), we compared the head impulse gain of the vestibulo-ocular reflex (VOR) for each semicircular canal between patients with (n = 7) and without (n = 70) downbeat nystagmus during attacks of MD.

METHODS

We retrospectively analyzed the results of video-oculography, video head-impulse tests, and cervical vestibular-evoked myogenic potentials (VEMPs) in 77 patients with definite MD who were evaluated during an attack.

RESULTS

Pure or predominant downbeat nystagmus was observed in 7 patients (9%) with unilateral MD during the attacks. All 7 patients showed spontaneous downbeat nystagmus without visual fixation with a slow phase velocity ranging from 1.5 to 11.2°/s (median 5.4, interquartile range 3.7-8.5). All showed a transient decrease of the head impulse VOR gains for the posterior canals (PCs) in both ears (n = 4) or in the affected ear (n = 3). Cervical VEMPs were decreased in the affected (n = 2) or both ears (n = 2) when evaluated during the attacks. Downbeat nystagmus disappeared along with normalization of the VOR gains for PCs after the attacks in all patients. During the attacks, the head impulse VOR gains for the PC on the affected side were lower in the patients with ictal downbeat nystagmus than in those without (Mann-Whitney U test, p < 0.001), while the gains for other semicircular canals did not differ between the groups.

CONCLUSION

Downbeat nystagmus may be observed during attacks of MD due to an asymmetry in the vertical VOR or saccular dysfunction. MD should be considered in recurrent audiovestibulopathy and ictal downbeat nystagmus.

Bilateral Vestibular Dysfunction

Bilateral vestibular dysfunction (BVD) refers to hypofunction of the vestibular nerves or labyrinths on both sides. Patients with BVD present with dizziness, oscillopsia, and unsteadiness, mostly during locomotion, which worsen in darkness or on uneven ground. Although aminoglycoside ototoxicity, Meniere's disease, infection, and genetic disorders frequently cause BVD, the etiology remains undetermined in up to 50% of the patients. The diagnosis of BVD requires both symptoms and documentation of deficient vestibulo-ocular reflex function using head-impulse, bithermal caloric, and rotatory chair tests. Since various neurologic and systemic disorders may present with BVD, clinicians should be cautious not to overlook the symptoms and signs of central nervous system and systemic involvements. Vestibular rehabilitation, application of vibrotactile and auditory feedbacks, and vestibular prosthesis can aid the patients with BVD along with the correction of the underlying causes.

Acute vestibular syndrome associated with anti-GQ1b antibody

OBJECTIVES

To delineate the clinical features and ocular motor findings in acute vestibular syndrome (AVS) associated with anti-GQ1b antibodies.

METHODS

We reviewed 90 patients with positive serum anti-GQ1b antibody in association with various neurological syndromes at Seoul National University Bundang Hospital from 2004 to 2018. The diagnoses included typical Miller Fisher syndrome (n = 31), acute ophthalmoplegia without ataxia (n = 27), Guillain-Barre syndrome with ophthalmoplegia (n = 18), AVS (n = 11), and Bickerstaff brainstem encephalitis (n = 3). Of them, the 11 patients with AVS formed the basis of this study. We also conducted a systematic review on AVS reported in association with anti-GQ1b antibody.

RESULTS

Patients with AVS showed various ocular motor findings that included head-shaking nystagmus (n = 6), spontaneous nystagmus (n = 5), gaze-evoked nystagmus (n = 5), central positional nystagmus (n = 3), canal paresis (n = 2), and abnormal head-impulse tests (n = 1) without any internal or external ophthalmoplegia. Compared to those with other subtypes, patients with AVS mostly showed normal deep tendon reflexes (8 of 11 [73%], p = 0.002) and normal results on nerve conduction studies (4 of 4 [100%], p = 0.010). The clinical and laboratory findings resolved or improved markedly in all patients within 6 months of symptom onset. Systematic review further identified 7 patients with AVS and positive serum anti-GQ1b antibody who showed various ocular motor findings, including gaze-evoked nystagmus, saccadic dysmetria, central positional nystagmus, and ocular flutter or opsoclonus.

CONCLUSION

Anti-GQ1b antibody may cause acute vestibulopathy by involving either the central or peripheral vestibular structures. AVS may constitute a subtype of anti-GQ1b antibody syndrome.

Intralabyrinthine Schwannoma: Distinct Features for Differential Diagnosis

Objectives: The aim of this study was to delineate the clinical and laboratory features suggestive of intralabyrinthine schwannoma (ILS). Methods: We compared the clinical features of 16 patients with ILS, who had been diagnosed at the Seoul National University Bundang Hospital from 2003 to 2018, with those of 18 patients with symptomatic unilateral intracanalicular schwannoma and randomly selected 20 patients with definite or probable unilateral Meniere's disease (MD). Results: Patients with ILS presented with either recurrent spontaneous dizziness/vertigo combined with auditory symptoms (n = 8), isolated auditory symptoms without dizziness/vertigo (n = 7), or recurrent spontaneous dizziness/vertigo without auditory symptoms (n = 1). Most patients reported no improvement (n = 11) or worsening (n = 1) of the symptoms despite medical treatments including intratympanic (n = 5) or intravenous steroids (n = 2). Conventional brain MRIs failed to detect ILS in about a half of the patients (7/16, 44%). However, ILS showed a filling defect on 3-dimensional (3D) heavily T2-weighted MRIs (n = 12), and nodular enhancement on 3D contrast-enhanced T1 (n = 15) or FLAIR MRIs (n = 13) targeted for the inner ear. Compared to MD or intracanalicular schwannoma, ILS showed mostly abnormal head-impulse tests (HITs, p = 0.001). In contrast, the incidence of canal paresis did not differ among the groups (p = 0.513). Conclusion: ILS may mimic MD by presenting recurrent dizziness/vertigo and auditory symptoms. ILS should be suspected in patients with recurrent audiovestibulopathy especially when (1) the duration of the dizziness is not typical for MD, (2) the patients do not respond to medical treatments, or (3) HITs are abnormal.