Visual influences on vestibular compensation and postural control
Author
Summary, in English
This thesis aimed to investigate visual-vestibular interactions in healthy subjects and in patients with a well defined unilateral vestibular lesion (vestibular schwannoma before and six months after translabyrinthine surgery).
Visual information is particularly important for balance control during perturbed stance. The physical act of having the eyes open or closed affects motion strategy in postural control. Standing with eyes open in darkness during balance perturbations is initially of disadvantage compared to standing with eyes closed. The postural control system appears to expect visual feedback information when eyes are open, which delays a re-weighting to vestibular and proprioceptive information.
A pathologic deviation of the subjective visual horizontal (SVH) and vertical (SVV) toward the lesioned side is still present six months after unilateral vestibular deafferentation. There is great SVH and SVV variability between patients which proposes an idiosyncrasy in the compensation of graviceptive vestibular tone imbalance.
Postural sway is not related to the deviation of the SVH and SVV which indicates that utriculo-ocular compensation is not related to postural compensation.
Patients with a unilateral vestibular schwannoma are not more visually field dependent than healthy subjects are, but have an increased ipsilesional deviation in the rod and frame test. This suggests asymmetric visual field dependence, and that the rod and frame test can reveal a hidden vestibular imbalance.
Older patients with a vestibular schwannoma have increased visual dependency and decreased compensation of the SVH and SVV compared to younger patients.
Alcohol intoxication impairs the ability to use gravitational vestibular cues in SVH and SVV tests, and increases visual field dependence.
Visual dependence and visual-vestibular interactions are important factors to consider when investigating and rehabilitating patients with balance disorders. With conflicting gravitational and visual information a re-weighting from a vestibular to a more visual dependency in balance control might increase the risk of misinterpreting the visual information and thus increase the risk of accidents. It is important with good lighting conditions to provide patients with adequate sway referencing visual information.
Visual information is particularly important for balance control during perturbed stance. The physical act of having the eyes open or closed affects motion strategy in postural control. Standing with eyes open in darkness during balance perturbations is initially of disadvantage compared to standing with eyes closed. The postural control system appears to expect visual feedback information when eyes are open, which delays a re-weighting to vestibular and proprioceptive information.
A pathologic deviation of the subjective visual horizontal (SVH) and vertical (SVV) toward the lesioned side is still present six months after unilateral vestibular deafferentation. There is great SVH and SVV variability between patients which proposes an idiosyncrasy in the compensation of graviceptive vestibular tone imbalance.
Postural sway is not related to the deviation of the SVH and SVV which indicates that utriculo-ocular compensation is not related to postural compensation.
Patients with a unilateral vestibular schwannoma are not more visually field dependent than healthy subjects are, but have an increased ipsilesional deviation in the rod and frame test. This suggests asymmetric visual field dependence, and that the rod and frame test can reveal a hidden vestibular imbalance.
Older patients with a vestibular schwannoma have increased visual dependency and decreased compensation of the SVH and SVV compared to younger patients.
Alcohol intoxication impairs the ability to use gravitational vestibular cues in SVH and SVV tests, and increases visual field dependence.
Visual dependence and visual-vestibular interactions are important factors to consider when investigating and rehabilitating patients with balance disorders. With conflicting gravitational and visual information a re-weighting from a vestibular to a more visual dependency in balance control might increase the risk of misinterpreting the visual information and thus increase the risk of accidents. It is important with good lighting conditions to provide patients with adequate sway referencing visual information.
Department/s
Publishing year
2007
Language
English
Document type
Dissertation
Publisher
Department of Otorhinolaryngology, Lund University
Topic
- Otorhinolaryngology
Keywords
- Otorhinolaryngology
- audiology
- auditive system and speech
- Otorinolaryngologi
- Medicin (människa och djur)
- Vestibular schwannoma
- Alcohol intoxication.
- Medicine (human and vertebrates)
- Vestibular deafferentation
- Visual-vestibular interactions
- Subjective visual horizontal and vertical
- Visual dependence
- Utriculus
- Balance
- Vision
- audiologi
- hörsel- och talorganen
Status
Published
Supervisor
- Måns Magnusson
- Mikael Karlberg
- Rolf Johansson
ISBN/ISSN/Other
- ISBN: 978-91-85559-48-0
Defence date
12 May 2007
Defence time
11:45
Defence place
"Kulturanatomen", Inst. för Kulturvetenskaper, Biskopsgatan 7, Lunds Universitet
Opponent
- Jan Ygge (Professor)