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Inventis - June 2023

Downbeat Nystagmus: What You Need to Know – An Expert Perspective

V. Marcelli, MD

January 22, 2025
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Downbeat nystagmus (DBN) is a common form of acquired central nystagmus, often linked to central vestibular dysfunction. This condition significantly affects a patient's vision and balance, making its diagnosis and management crucial. In this interview, we explore the clinical characteristics, underlying causes, diagnostic approaches, and available treatment options for DBN. We also discuss the role of Inventis Nystalyze, a modular system designed for precise eye movement analysis, in supporting the evaluation and management of DBN.

 

AudiologyOnline: What is downbeat nystagmus (DBN) and how does it present clinically?

Dr. Vincenzo Marcelli: DBN is a form of vertical nystagmus where the eyes exhibit involuntary downward movements, particularly noticeable when the patient looks to the side. It is the most common type of acquired central nystagmus and is frequently associated with cerebellar or brainstem abnormalities. Clinical symptoms include oscillopsia (a sensation of moving surroundings), difficulty perceiving motion, and postural instability. These symptoms often result in chronic imbalance and a significant reduction in daily functioning.

AudiologyOnline: What is the pathophysiology behind DBN?

Dr. Vincenzo Marcelli: DBN results from a disruption in the vestibulo-ocular reflex (VOR), which is responsible for stabilizing vision during head movements. The VOR relies on the cerebellum, particularly the flocculus, paraflocculus, and nodulus, to regulate eye movements. Damage to these areas disrupts VOR function, leading to an imbalance in vertical eye control. This imbalance causes the eyes to drift upwards, triggering a compensatory downward correction, which characterizes DBN.

AudiologyOnline: What are the primary causes of DBN?

Several conditions affecting the cerebellum and brainstem can result in DBN, including:

  • Degenerative diseases (e.g., spinocerebellar ataxias, multiple system atrophy) leading to progressive cerebellar deterioration.
  • Vascular lesions, such as strokes or hemorrhages, impairing blood supply to the cerebellum.
  • Infections and inflammation, including multiple sclerosis and other central nervous system infections.
  • Structural anomalies, such as Arnold-Chiari malformation, causing compression of the cerebellum and brainstem.
  • Medication toxicity and metabolic factors, including chronic use of anticonvulsants or vitamin deficiencies.

Table 1 provides an overview of cerebellar and extracerebellar lesion sites contributing to DBN.

Cerebellar flocculus/paraflocculus

Cerebellar vermis

Nodulus/Uvula

Dorsal larger cell Y-group (Yd) of the Y-group nucleus

Otolith-ocular circuit

Vertical neural integrator

Floor of the fourth ventricle

Pons

Medulla oblongata

Table 1. Cerebellar and extracerebellar sites of lesion and the mechanisms underlying them [1]

AudiologyOnline: How is DBN diagnosed?

Dr. Vincenzo Marcelli: Patients with DBN often report visual disturbances such as oscillopsia and blurred vision, especially when they move their eyes laterally or tilt their head. This constant movement of the visual field can make it difficult for patients to perform tasks that require steady gaze, such as reading or walking. In addition to visual disturbances, many patients experience a sense of imbalance, which may worsen in environments with complex visual stimuli, such as crowded areas or busy streets.

To diagnose DBN, clinicians conduct a detailed eye movement examination, often using video-oculography to capture the nystagmus. The presence of downbeat nystagmus when looking to the side, combined with symptoms of oscillopsia and postural imbalance, typically suggests a central cause rather than a peripheral vestibular disorder. Neuroimaging, especially MRI, is essential in identifying the underlying structural abnormalities or lesions in the cerebellum and brainstem.

AudiologyOnline: What treatment options are available for DBN?

Dr. Vincenzo Marcelli: Managing DBN can be challenging, as treatment focuses primarily on symptom relief rather than a cure. Medications such as 4-aminopyridine have shown some effectiveness in reducing the intensity of DBN by enhancing the excitability of neurons in the cerebellum, which helps stabilize eye movement. In some cases, other drugs like baclofen or clonazepam may be considered, although their effects can vary widely among patients.

In addition to medication, vestibular rehabilitation therapy (VRT) can assist patients in adapting to their visual and balance disturbances. VRT includes exercises to improve gaze stability, balance, and proprioception, aiming to help patients cope with their symptoms. In cases where DBN is caused by structural issues, such as Arnold-Chiari malformation, surgical intervention might be an option to relieve compression on the brainstem and cerebellum.

AudiologyOnline: How does the Inventis Nystalyze system support the assessment and management of DBN?

Dr. Vincenzo Marcelli: Inventis Nystalyze is a modular vestibular diagnostic system designed to enhance eye movement analysis. It consists of two key components:

VideoScope Module: This module enables both diagnostic and rehabilitative applications, featuring a wireless camera option for flexible patient assessments. It allows video and audio recording, ensuring comprehensive documentation of eye movements.

SYNAPSYS VNG Module: This component provides a full suite of vestibular and oculomotor tests, making it an invaluable tool for evaluating DBN and other central vestibular disorders.

By integrating advanced visualization and recording capabilities, Nystalyze allows clinicians to capture and analyze DBN with high precision, improving diagnostic accuracy and treatment planning.

AudiologyOnline: What is the prognosis for patients with DBN?

Dr. Vincenzo Marcelli: The prognosis for DBN depends on its underlying cause. Some patients show gradual improvement with pharmacological and rehabilitative therapy, while others—especially those with progressive neurodegenerative conditions—experience symptom worsening over time. Given that chronic DBN impacts quality of life, regular follow-ups are crucial for monitoring symptom progression and adjusting treatment strategies.

AudiologyOnline: What are the key takeaways for clinicians managing DBN?

Dr. Vincenzo Marcelli: DBN is a complex disorder requiring a multidisciplinary approach to diagnosis and treatment. Advances in diagnostic technology, pharmacology, and vestibular rehabilitation have improved symptom management, but further research is needed to refine treatment protocols. Tools like Inventis Nystalyze provide critical diagnostic support, leading to improved patient care.

References

[1] Marcelli V, Giannoni B, Volpe G, Faralli M, Fetoni AR and Pettorossi VE (2024) Downbeat nystagmus: a clinical and pathophysiological review. Front. Neurol. 15:1394859. doi: 10.3389/fneur.2024.1394859

Resources for More Information 

For more information about Inventis, visit https://www.inventis.it/en-na



v marcelli

V. Marcelli, MD

Dr. Marcelli is the head of the Audiology and Vestibology clinic at the ENT Department of the Mare Hospital, ASL-NA 1, Naples. He holds the position of Professor at the Faculty of Medicine and Surgery, University of Naples "Federico II". For several years, he has been engaged in scientific activities as a speaker at conferences, courses, seminars, masterclasses, distance learning programs, lectures, and lessons. He is also an author of articles in scientific journals and serves as a reviewer for articles in the field of Audiology and Vestibular disorders at the local, national, and international levels.



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