Objective Vestibular Assessment
Top Contributors - Jess Bell, Kim Jackson, Rucha Gadgil and Robin Tacchetti
Objective Evaluation[edit | edit source]
Vision Screening[edit | edit source]
Oculomotor screen[edit | edit source]
When conducting any vision screening or testing, it is important to watch and ask the patient how must effort a task requires and the degree of symptoms provoked. The basic oculomotor screen during a vestibular assessment should include:[1]
- Fixation in primary and eccentric gaze
- Smooth pursuit or tracking
- VOR cancellation
- Saccades
Oculomotor Testing[edit | edit source]
Spontaneous Nystagmus[edit | edit source]
- Tested in primary and eccentric gaze
- It occurs due to the unopposed tonic neural activity of the intact side when there are lesions in the peripheral vestibular systems (acute) or central vestibular pathways[1]
Primary gaze is tested as follows: [1]
- The patient looks forward and visually fixates on a target
- This position is held for 10 seconds and the therapist looks for any nystagmus
Eccentric gaze:
The most common pathological type of nystagmus driven by the CNS is gaze evoked nystagmus (GEN). It is tested as follows:[1]
- The patient to fixate on a position 30 degrees to each side, up and down (i.e. an eccentric position)
- Each position is held for 10 seconds and the therapist looks for nystagmus
- GEN is only present with eccentric gaze, not in primary gaze
It is important to differentiate between GEN and end point nystagmus. End point nystagmus occurs when gaze is held at the end of range. End point nystagmus is considered normal, so in order to test for GEN it is essential that the patient only holds his / her gaze 30 degrees off-centre.[1][2]
For a summary of the difference between peripheral and central nystagmus, please see Table 2.
| Findings | Peripheral | Central |
|---|---|---|
| Effect of fixation (room light) | Nystagmus is typically absent within 2-3 days in room light | Nystagmus either does not change or it increases |
| Direction of nystagmus | Usually mixed plane (horizontal and torsional) | Usually single plane (sustained down beating) |
| Effect of gaze | Nystagmus increases with gaze toward direction of quick phase | Nystagmus either does not change or it reverses direction |
Smooth Pursuit and VOR Cancellation[edit | edit source]
- Slow, tracking eye movements that maintain images of smaller moving targets (20 to 30 degrees per second) on the fovea.[1][3]
- Centrally mediated reflex[1]
Smooth Pursuit Eye Movements[edit | edit source]
- Refixation saccades occur during target motion toward the side of the lesion
- There may be unilateral or bilateral refixation saccades[1]
VOR Cancellation[edit | edit source]
- Head and eyes move with a target - suppressing the VOR
- Refixation saccades will occur during head movement toward the side of the lesion[1]
Smooth Pursuit Torsion Test[edit | edit source]
- The smooth pursuit neck torsion test measures smooth pursuit eye movement with the head / trunk in neutral and when the trunk and neck are rotated relative to a stationary head[4]
- Smooth pursuit neck torsion test is considered to be specific for detecting eye movement disturbances due to altered cervical sensory input[5][6]
- A decrease in velocity gain of smooth pursuit eye movements during the test is only seen in patients with neck pain[1]
Saccadic Eye Movements[edit | edit source]
Saccades are defined as: “fast conjugate eye movements that shift the eyes from one target to another, bringing an object of interest into focus on the fovea where visual acuity is highest”.[7]
Saccades are centrally mediated – there are volitional saccades and reflexive saccades[8][9]
In order to test saccadic eye movements:[1]
- Instruct the patient to look between two targets as quickly as possible – vertical and horizontal
- During these fast changes in eye position, the therapist looks at the amplitude, velocity and accuracy of targeting
- Hypometric saccade = when the patient ‘undershoots’ the target
- Hypermetric saccade = when the patient ‘overshoots’ the target[10]
One hypometric saccade is typically considered normal. Two or more hypometric or one or more hypermetric saccades is considered abnormal.[1]
Vestibulo-Ocular Reflex (VOR) Testing
- The VOR is the primary mechanism for gaze stability during head movement
- There are two tests of VOR function that can be done effectively in the clinic without an infrared camera system
- The Head Thrust Test
- The Dynamic Visual Acuity (DVA) Test
The Head Shaking Test can also be conducted, but it works better with an infrared camera system. WEB
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Cite error: Invalid
<ref>tag; no text was provided for refs named:0 - ↑ Serra A, Leigh RJ. Diagnostic value of nystagmus: spontaneous and induced ocular oscillations. J Neurol Neurosurg Psychiatry. 2002;73(6):615-8.
- ↑ Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. Types of Eye Movements and Their Functions. Available from: https://www.ncbi.nlm.nih.gov/books/NBK10991/
- ↑ Tjell C, Rosenhall U. Smooth pursuit neck torsion test: a specific test for cervical dizziness. Am J Otol. 1998;19(1):76-81.
- ↑ Daly L, Giffard P, Thomas L, Treleaven J. Validity of clinical measures of smooth pursuit eye movement control in patients with idiopathic neck pain. Musculoskelet Sci Pract. 2018;33:18-23.
- ↑ Majcen Rosker Z, Vodicar M, Kristjansson E. Inter-visit reliability of smooth pursuit neck torsion test in patients with chronic neck pain and healthy individuals. Diagnostics (Basel). 2021;11(5):752.
- ↑ Termsarasab P, Thammongkolchai T, Rucker JC, Frucht SJ. The diagnostic value of saccades in movement disorder patients: a practical guide and review. J Clin Mov Disord. 2015;2:14.
- ↑ Patel SS, Jankovic J, Hood AJ, Jeter CB, Sereno AB. Reflexive and volitional saccades: biomarkers of Huntington disease severity and progression. J Neurol Sci. 2012;313(1-2):35-41.
- ↑ McDowell JE, Dyckman KA, Austin BP, Clementz BA. Neurophysiology and neuroanatomy of reflexive and volitional saccades: evidence from studies of humans. Brain Cogn. 2008;68(3):255-270.
- ↑ Bourrelly C, Quinet J, Goffart L. Pursuit disorder and saccade dysmetria after caudal fastigial inactivation in the monkey. J Neurophysiol. 2018;120(4):1640-54.
