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The Epidemiology and Clinical Presentation of the Acute Imbalance Syndrome (AIS)-A Systematic Review and Meta-Analysis

Schmidt K, Zwergal A, Kaski D, Tarnutzer AA

European journal of neurology, 2026

11,731 participants

Abstract

Objectives: The acute imbalance syndrome (AIS) refers to acute-onset and persistent vertigo, dizziness and/or imbalance without nystagmus, reflecting a subset of the acute vestibular syndrome (AVS) with or without nystagmus. While AVS with nystagmus is well characterized and the approach to these patients is validated, much less is known about patients presenting with AIS. This systematic review synthesizes current epidemiologic and clinical evidence on AIS.

Methods: MEDLINE and Embase (2000-2024) were searched for English-language original articles addressing acute imbalance, vertigo/dizziness and reporting on nystagmus and/or AVS/AIS. Two reviewers independently screened articles and extracted predefined parameters. The review was registered with PROSPERO (CRD42024623068).

Results: Forty studies (n = 11,731 patients) were included, with 2730 patients being classified as AVS. Prevalence of AVS (with/without nystagmus) amongst all acutely dizzy patients was 16.4% and 50.5%, respectively, in two studies. 49.4% of central AVS cases were classified as AIS. Whereas AIS presentation was rare in AICA strokes (9%), fractions reached 40% (PICA), 57% (SCA), and 62% (PCA) for other vascular territories. Data on underlying causes in noncentral AIS was limited, with dysautonomia, drug intoxication, and heart disease being most frequently identified.

Conclusions: With almost 50% of central AVS cases presenting as AIS, this emphasizes the importance of selecting bedside testing…

How strong is the evidence?

Evidence Hub reads this as a meta-analysis, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 11,731 participants or records.

How the five levels of evidence work. The level is assigned automatically from the abstract and can be wrong, so check the paper.

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