Quantitative Ocular Motor / Vestibular Assessment in Patients with Spinocerebellar Ataxia Type 3 (SCA3, Machado Joseph Disease) - Systematic Review of the Literature

Clinical Snapshot

Key Findings

• P Value: Not reported

• Effect Size: VOR gain reduction in 117/133 patients (88%), gaze-evoked nystagmus in 65/82 patients (79%)

• Primary Outcome: Frequency of ocular motor and vestibular abnormalities in SCA3 patients

• Nnt Or Sensitivity: High sensitivity for VOR gain reduction (88%) and gaze-evoked nystagmus (79%) as disease markers

• Confidence Interval: Not reported

Clinical Application

Requires specialised vestibular testing equipment and trained personnel, available in tertiary neurology centres Relevant for Australian neurology and balance disorder services; testing available through major hospitals with vestibular laboratories; may inform genetic counselling and early intervention strategies Patients with confirmed or suspected SCA3, including at-risk family members

Abstract

Spinocerebellar ataxia type 3 (SCA3 or Machado-Joseph disease) is the second most common autosomal-dominant hereditary ataxia and often presents with ocular motor and vestibular impairment. The value of ocular motor testing for early disease detection, monitoring disease progression and as a potential treatment biomarker has been acknowledged in several studies. This systematic review aims to summarise the current evidence supporting quantitative eye movement testing in SCA3. Studies reporting on quantitative ocular motor and/or vestibular measurements in SCA3 were searched for in MEDLINE and Embase. Thirty studies reporting on 432 SCA3 patients (including 64 pre-symptomatic carriers) were included. Information on various ocular motor parameters were extracted and correlations with other parameters (including clinical scales, imaging, and genetic testing) were assessed. Ocular motor abnormalities observed comprised (horizontal) pursuit eye-movement (PEM) gain reduction (14/19 patients), saccadic intrusions (principally square-wave jerks (SWJ, 29/45)), gaze-evoked nystagmus (GEN, 65/82), and rebound nystagmus (8/10). Additionally, saccades to target displayed increased latency (13/29), reduced peak velocity (16/49) and dysmetria (33/49). Vestibular deficits measured included vestibulo-ocular reflex (VOR) gain-reductions during quantitative head-impulse testing (qHIT, 117/133) and abnormal responses during caloric irrigation (7/9), impaired visually-enhanced VOR-responses (5/6), and impaired cervical (19/66) and ocular (10/14) vestibular-evoked myogenic-potential testing. In summary, impaired VOR-gains (qHIT), GEN, horizontal PEM-gain decreases, dysmetric saccades, and SWJ were most frequently reported and therefore seem most suitable as potential disease markers. The quantitative ocular motor/vestibular assessment may facilitate early diagnosis, distinction of disease stages and also potentially allow monitoring of disease progression and treatment response.

References

1. 1.Melzer, I., Szmulewicz, D. J., & Tarnutzer, A. A. (2026). Quantitative ocular motor / vestibular assessment in patients with spinocerebellar ataxia type 3 (SCA3, Machado Joseph disease) - systematic review of the literature. Cerebellum, advance online publication. https://doi.org/10.1001/archneur.55.7.949