Vertical nystagmus in Wernicke’s encephalopathy: pathogenesis and role of central processing of information from the otoliths

Downbeat nystagmus: a clinical and pathophysiological review

Downbeat nystagmus (DBN) is a neuro-otological finding frequently encountered by clinicians dealing with patients with vertigo. Since DBN is a finding that should be understood because of central vestibular dysfunction, it is necessary to know how to frame it promptly to suggest the correct diagnostic-therapeutic pathway to the patient. As knowledge of its pathophysiology has progressed, the importance of this clinical sign has been increasingly understood. At the same time, clinical diagnostic knowledge has increased, and it has been recognized that this sign may occur sporadically or in association with others within defined clinical syndromes. Thus, in many cases, different therapeutic solutions have become possible. In our work, we have attempted to systematize current knowledge about the origin of this finding, the clinical presentation and current treatment options, to provide an overview that can be used at different levels, from the general practitioner to the specialist neurologist or neurotologist.

Generalized vestibular hyporeflexia and chronic upbeat nystagmus due to thiamine deficiency

BACKGROUND

Ocular motor and vestibular manifestations of Wernicke's thiamine deficiency (WTD) are frequent and heterogeneous. Previous neuropathological and neuroimaging findings identified brainstem and cerebellar lesions responsible for these findings, however, peripheral vestibular lesions are probably uncommon in human WTD, though noted on an avian thiamine deficient study.

MATERIAL

Single case study of a WTD patient post-gastric bypass who developed ataxia, oscillopsia and nystagmus, with low serum thiamine, and increased MRI T2 signal in the thalami, but normal brainstem and cerebellum. Vestibular evaluation showed significant vestibular hyporreflexia affecting all six canals, and a chronic upbeat nystagmus, now for 14 months after WTD onset.

METHODS

Serial clinical, video head impulse, nystagmus analysis, cervical and ocular vestibular evoked responses. She is undergoing treatment with Memantine, Clonazepam and vestibular rehabilitation, and feels improvement.

CONCLUSION

This report shows a novel combination of central and peripheral vestibular findings, of relevance for diagnosis and treatment, in addition to the development of a coherent hypothesis on the ocular motor and vestibular findings in WTD.

Spontaneous nystagmus with an upbeat component: Central or peripheral vestibular disorders?

Objective

To determine the topical diagnosis and etiologies of spontaneous nystagmus (SN) with an upbeat component.

Methods

We retrospectively recruited 43 patients with SN with an upbeat component at a university hospital in China from 2020 to 2022. SN with an upbeat component was divided into pure upbeat nystagmus (UBN), SN with a predominant upbeat component, and SN with a non-predominant upbeat component. We analyzed their clinical and neurotologic findings and the final diagnosis.

Results

Fourteen (32.6%) of them showed pure UBN, while 29 (67.4%) exhibited SN mixed with an upbeat component, mixed upbeat-horizontal in 15, mixed upbeat-horizontal-torsional in 13, and upbeat-torsional in the remaining one. Pure UBN and SN with a predominant upbeat component were more common in central than in peripheral vestibular disorders [16 (80.0%) vs. 0 (0%), Chi-Square test, p < 0.001]. Central vestibular disorders were diagnosed in 20 (46.5%) patients, peripheral in 14 (32.6%), and undetermined in nine (20.9%) patients. The underlying causes mainly included acute unilateral peripheral vestibulopathy (n = 11), posterior circulation infarction (n = 9), benign recurrent vertigo (n = 4), vestibular migraine (VM, n = 3), and VM of childhood (n = 2).

Conclusion

SN with an upbeat component can be seen in both central and peripheral vestibular disorders. Pure UBN was a characteristic sign of central vestibular dysfunction. Central vestibular disorders should be highly suspected when patients show pure UBN or SN with a predominant upbeat component.

Diagnosing and localizing the acute vestibular syndrome - Beyond the HINTS exam

When assessing the acutely dizzy patient, the HINTS 'Plus' (Head Impulse, Nystagmus, Test of Skew, 'Plus' a bedside assessment of auditory function) exam is a crucial component of the bedside exam. However, there are additional ocular motor findings that can help the clinician distinguish peripheral from central etiologies and enable accurate localization, especially when the patient has acute dizziness, vertigo and/or imbalance but without spontaneous nystagmus. We will review the literature on these findings which are 'beyond HINTS' and include saccades/ocular lateropulsion, smooth pursuit, and provocative maneuvers including head-shaking and positional testing (not part of the HINTS exam). Additionally, we will expound on the localizing value of nystagmus, ocular alignment and the ocular tilt reaction (parts of the HINTS exam). The paper has been organized neuroanatomically, based on brainstem and cerebellar structures that have been reported to cause the acute vestibular syndrome.

The pharmacological treatment of acute vestibular syndrome

Acute vestibular syndrome (AVS) represents a clinical picture that involves urgent management due to the important procession of symptoms accompanying the event, which can be positively or negatively influenced by therapeutic choices and intervention timing. This forces a differential diagnosis and therapeutic choices to be made in conditions that are not always favorable and often not in the specialist field. In this work, we will examine in detail the pharmacological therapeutic possibilities, correlating them to the differential and, as far as possible, to the etiological diagnosis. In particular, the pharmacological possibilities for the two main conditions we can face will be investigated, namely, vestibular neuritis and posterior circulation stroke.

Downbeat nystagmus: a clinical review of diagnosis and management

PURPOSE OF REVIEW

This review will extensively cover the clinical manifestations, causes, diagnostic evaluation, and management strategies of downbeat nystagmus (DBN).

RECENT FINDINGS

Historically, MRI to assess for structural lesions at the cervicomedullary junction has been the primary diagnostic test in the evaluation of DBN since the 1980s. In recent years, there is increasing awareness of nonstructural causes of DBN including gluten ataxia, nutritional deficiencies, and paraneoplastic syndromes, among others. Medical management with aminopyridines has become first-line therapy in addition to disease-specific therapies.

SUMMARY

DBN is a common form of acquired nystagmus and the differential diagnosis remains broad, including both benign and potentially fatal causes. For practical purposes, the causes can be categorized as structural vs. nonstructural with MRI as the ideal, initial diagnostic study to differentiate the two. General therapeutic options include pharmacotherapy to enhance Purkinje cell function, strabismus surgery or prisms to shift null points, and behavioural changes. Disease-specific treatment is necessarily broad, though a significant proportion of patients will be idiopathic.

[Vertical nystagmus]

The review article provides a definition and classification of different nystagmus types, a comparative description of the central and peripheral vestibular nystagmus. The pathogenetic patterns of up-beating and down-beating nystagmus are accurately described. The features of nystagmus formation in various diseases are discussed, such as Wernicke encephalopathy, Arnold-Chiari anomaly, spinocerebellar ataxia and vestibular migraine. The authors provide their own data on oculomotor disorders in 100 patients with vestibular migraine and migraine with a brain stem aura. This article considers approaches to treatment: surgical and conservative. In conclusion, was noted the possibility of differentiating the central and peripheral vestibular nystagmus by means of clinical study. As well, the differences between vertical nystagmus associated with organic lesions of the brain stem or cerebellum and transient nystagmus with vestibular migraine are highlighted. The authors note the need for in-depth studies of nystagmus in vestibular migraine patients and methods of dealing with it.

[Clinical diagnosis and treatment of chronic dizziness]

Chronic dizziness is defined as a complex of symptoms lasting months or years, including oscillopsia, nystagmus, and postural instability. Diagnostic search includes peripheral vestibulopathy - chronic unilateral vestibulopathy resulting from vestibular neuronitis, schwannoma of the 8th pair of cranial nerves, medical or surgical ablation of the labyrinth, and bilateral vestibulopathy; central vestibulopathy - syndromes accompanied by central vertical nystagmus, small vessel disease in patients with chronic cerebral ischemia; general somatic diseases, peripheral polyneuropathy, side-effects of medications as well as persistent postural-perceptual dizziness. Often, when collecting an anamnesis, it is not possible to identify specific features of dizziness and instability, therefore, clinical and instrumental examination of the patient is of particular importance. In the otoneurological examination, the greatest attention is paid to static/coordination tests, oculomotor tests aimed at identifying signs of damage to the vestibulo-ocular reflex. The principles of treatment depend on the diagnosed cause of dizziness and instability and can, to varying degrees, combine pharmacotherapy, vestibular rehabilitation and psychotherapy, as well as correction of therapy for the underlying disease that caused vestibulopathy.

Eye movements in demyelinating, autoimmune and metabolic disorders

PURPOSE OF REVIEW

In the last three decades, the use of eye movements and vestibular testing in many neurological disorders has accelerated, primarily because of practical technologic developments. Although the acute vestibular syndrome is a prime example of this progress, more chronic neurologic and systemic disorders have received less attention. We focus here on recent contributions relating vestibular and ocular motor abnormalities in inflammatory, demyelinating, metabolic, and peripheral nervous system disorders RECENT FINDINGS: Vestibular abnormalities have been identified in acute demyelinating neuropathies (AIDP), in novel genetic mutations responsible for CANVAS (cerebellar ataxia, neuropathy vestibular areflexia syndrome), and in other inherited neuropathies (variants of Charcot-Marie-Tooth disease). In addition, there are differentiating characteristics between the most common CNS demyelinating disorders: multiple sclerosis and neuromyelitis optica (NMO). We summarize new information on Vitamin D metabolism in benign paroxysmal positional vertigo (BPPV), followed by a brief review of the vestibular and ocular motor findings in Wernicke's encephalopathy. We conclude with findings in several paraneoplastic/autoimmune disorders.

SUMMARY

This literature review highlights the impact of a careful vestibular and ocular motor evaluation in common neurologic disorder, not only for the initial diagnosis but also for monitoring disease and rehabilitation. A careful examination of eye movements and vestibular function, supplemented with new video techniques to quantify the findings, should be part of the standard neurologic examination.

Update on Nystagmus and Other Ocular Oscillations

This review reports on recent advances in understanding nystagmus and other involuntary eye movements. Advances in quantitative evaluations of eye movements using oculography, computational model simulations, genetics, and imaging technologies have markedly improved our understanding of the pathophysiology of involuntary eye movements, as well as their diagnosis and management. Patient-initiated capture of eye movements, especially when paroxysmal, and the online transfer of these data to clinicians would further enhance the ability to diagnose involuntary eye movements.

The Use of Video-Head Impulse Test in Different Head Positions in Vertical Nystagmus and Ataxia Associated with Probable Thiamine Deficiency

Upward and downward bias of eye movement signals in the semicircular canals (SCC)- and/or otolith-related central pathways have been proposed to explain the occurrence of vertical nystagmus (downbeat nystagmus [DBN] and upbeat nystagmus [UBN]) and its frequent modulation with head position. Video-head impulse test (VHIT), usually performed in upright position, is a recent development for measuring SCC function. We performed longitudinal nystagmus and VHIT assessments in different head positions in a patient with probable thiamine deficiency, in order to explore a possible relationship between the positional behavior of vertical nystagmus and SCC function. Initially, UBN in upright position changed to DBN in prone position and remained relatively unchanged in supine position. This was associated with both anterior and posterior SCC hyperactive responses in upright position, and a relative enhancement of the anterior SCC responses in prone position and the posterior SCC responses in supine position. Over 1 year, in prone position, change from UBN to DBN and the enhancement of anterior SCC responses remained, while in supine position, UBN either decreased or changed to DBN, when compared to upright position. This was associated with a relative enhancement of the anterior SCC responses in supine position, albeit inconsistently, and the presence of posterior SCC hypoactive responses in all positions, including prone. While not contradicting a primary otolithic dysfunction in the genesis of UBN change to DBN with head position, we provide evidence for positional modulation of SCC function in thiamine deficiency and a possible relationship with nystagmus positional behavior.