Executive functions in patients with bilateral and unilateral peripheral vestibular dysfunction

Abstract

Previous research suggests that patients with peripheral vestibular dysfunction (PVD) suffer from nonspatial cognitive problems, including executive impairments. However, previous studies that assessed executive functions are conflicting, limited to single executive components, and assessments are confounded by other cognitive functions. We compared performance in a comprehensive executive test battery in a large sample of 83 patients with several conditions of PVD (34 bilateral, 29 chronic unilateral, 20 acute unilateral) to healthy controls who were pairwise matched to patients regarding age, sex, and education. We assessed basic and complex executive functions with validated neuropsychological tests. Patients with bilateral PVD performed worse than controls in verbal initiation and working memory span, while other executive functions were preserved. Patients with chronic unilateral PVD had equal executive performance as controls. Patients with acute unilateral PVD performed worse than controls in the exact same tests as patients with bilateral PVD (verbal initiation, working memory span); however, this effect in patients with acute PVD diminished after correcting for multiple comparisons. Hearing loss and affective disorders did not influence our results. Vestibular related variables (disease duration, symptoms, dizziness handicap, deafferentation degree, and compensation) did not predict verbal initiation or working memory span in patients with bilateral PVD. The results suggest that bilateral PVD not only manifests in difficulties when solving spatial tasks but leads to more general neurocognitive deficits. This understanding is important for multidisciplinary workgroups (e.g., neurotologists, neurologists, audiologists) that are involved in diagnosing and treating patients with PVD. We recommend screening patients with PVD for executive impairments and if indicated providing them with cognitive training or psychoeducational support.

Keywords: Executive function; Peripheral vestibular dysfunction; Verbal initiation; Working memory.

Fig. 1

Neuropsychological tests to assess basic and complex executive functions. Basic and complex executive functions were measured with validated neuropsychological tests. Basic executive functions (on the left) were measured with the following tests: a initiation: a1 general initiation with the Alertness test, a2 nonverbal initiation with the Design Fluency test, a3 verbal initiation with the Word Fluency test; b inhibition with the Inhibition condition of the Color–Word Interference test; c cognitive flexibility with the Switching condition of the Color–Word Interference test, d working memory: d1 performance with the 2-back task, d2 maximal span with the digit span backwards test. Complex executive functions (on the right) were measured with the following tests: e problem solving with the two groups test; f planning with the Tower of London; g monitoring by computing a mean score of errors, rule violations, and perseverations of the other neuropsychological tests. See appendix for detailed task descriptions and references

Fig. 2

Verbal initiation performance of patients with bilateral, chronic unilateral, and acute unilateral peripheral vestibular dysfunction and their respective pairwise matched healthy controls. Verbal initiation was assessed with a word fluency task. Results are presented as means. Error bars show standard errors. Significant differences between patients and controls are indicated with asterisks (*p < 0.001)

Fig. 3

Working memory span of patients with bilateral, chronic unilateral, and acute unilateral peripheral vestibular dysfunction and their respective pairwise matched healthy controls. Working memory span was assessed with a digit span backwards task. Results are presented as means. Error bars show standard errors. Significant differences between patients and controls are indicated with asterisks (*p < 0.001)