Stereocilia are mechanoreceptors within the ear that sense head position, head movement, and when the body is in motion. Head position is sensed by the maculae of the utricle and saccule. Head movement is sensed via the semicircular canals. The movement of fluid within the semicircular canals generates nerve impulses that travel to cranial nerve VIII (vestibulocochlear nerve) and then to the brainstem and cerebellum.
Inner ear anatomy
Anatomy & Physiology by Lindsay M. Biga, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Matern, Katie Morrison-Graham, Devon Quick & Jon Runyeon
Vestibular dysfunction can develop at any age. Factors precipitating vestibular disorders can be external or internal. External factors could be whiplash, a fall, an airplane ride, or pollutants. Internal factors may be infections, use of medications, stroke, brain injury, or migraine. Vestibular dysfunctions can further be divided into central and peripheral disorders - management of symptoms will be based on the classification of the vestibular disorder.
Generalized symptoms of vestibular disorders
Dizziness
Balance deficits
Vertigo
Blurred vision
Recurrent falls
Nausea and vomiting
The examination for vestibular dysfunction is critical in determining the type of disorder and the appropriate treatment options.
Determining the type of disorder
Symptom history and duration
Vestibular ocular reflex testing - assessing nystagmus, clarity of vision with head movements, and body movements
Vertebral artery testing
Sensory testing
Clinical test of sensory interaction on balance (CTSIB)
Functional testing - transfers, gait, dynamic sitting, and dynamic balance
Vestibulospinal reflex testing - examining posture and balance in all positions
Positional changes and their impact on symptoms
Cervical range of motion
Outcome measures as appropriate, such as the dynamic gait index
The CTSIB is conducted with the patient standing with their hands at their sides and feet together, performing the following six sensory conditions:
Stand on a firm surface with eyes open - baseline condition, with vision, somatosensory, and vestibular input all available
Stand on a firm surface with eyes closed - removes visual input, so balance relies on the somatosensory and vestibular systems
Stand on a firm surface with a visual conflict dome - vision is inaccurate, challenging the patient to rely on somatosensory and vestibular input instead
Stand on a foam surface with a visual conflict dome - somatosensory input is degraded and vision is inaccurate, placing heavy demand on the vestibular system
Stand on a foam surface with eyes open - somatosensory input is degraded, so balance relies on vision and the vestibular system
Stand on a foam surface with eyes closed - both vision and reliable somatosensory input are removed, isolating and testing the vestibular system
Central vestibular disorders
Central vestibular dysfunction symptoms
Nystagmus in vertical, horizontal, or rotational planes
Non-fatigable nystagmus
No hearing loss or tinnitus
Vertigo is sometimes present
Disequilibrium is severe
Can be associated with other cranial nerve or cerebellar signs
Visual fixation and head position have no impact
Treatment for central vestibular dysfunction
Identify triggers, if any, that are noted to be external
Gaze stabilization exercises to assist with improving the vestibular ocular reflex
Coordination activities to address cerebellar symptoms
Adaptation exercises to decrease dizziness to allow for retraining of the brain
Substitution of visual and somatosensory systems in the presence of vestibular dysfunction
Peripheral vestibular dysfunction
Most peripheral vestibular dysfunction is unilateral. The following are common causes:
Symptoms of peripheral vestibular dysfunction
Nystagmus is horizontal and torsional
Nystagmus decreases with visual fixation
Nystagmus is fatiguable and lasts less than one minute
Vertigo is always present
Loss of hearing
Ringing in the ears
Disequilibrium
Feeling of fullness in the ear
Vestibular system overview
Inner ear + nerves orient head/eyes with position changes
Stereocilia sense head position (maculae of utricle/saccule) and movement (semicircular canals)
Signals travel via cranial nerve VIII (vestibulocochlear) to brainstem/cerebellum
Key inner ear structures
Macula: sensory epithelium detecting linear acceleration/gravity position
Utricle: detects horizontal movement; Saccule: detects vertical movement
Semicircular canals: fluid-filled channels for equilibrium
Large vestibular schwannoma can compress brainstem/cerebellum, adding central signs
Symptoms: nystagmus (vertical/horizontal/rotational), non-fatigable, no hearing loss/tinnitus, severe disequilibrium, possible other cranial nerve/cerebellar signs
Visual fixation and head position do NOT affect symptoms
Stereocilia are mechanoreceptors within the ear that sense head position, head movement, and when the body is in motion. Head position is sensed by the maculae of the utricle and saccule. Head movement is sensed via the semicircular canals. The movement of fluid within the semicircular canals generates nerve impulses that travel to cranial nerve VIII (vestibulocochlear nerve) and then to the brainstem and cerebellum.
Vestibular dysfunction can develop at any age. Factors precipitating vestibular disorders can be external or internal. External factors could be whiplash, a fall, an airplane ride, or pollutants. Internal factors may be infections, use of medications, stroke, brain injury, or migraine. Vestibular dysfunctions can further be divided into central and peripheral disorders - management of symptoms will be based on the classification of the vestibular disorder.
Generalized symptoms of vestibular disorders
Dizziness
Balance deficits
Vertigo
Blurred vision
Recurrent falls
Nausea and vomiting
The examination for vestibular dysfunction is critical in determining the type of disorder and the appropriate treatment options.
Determining the type of disorder
Symptom history and duration
Vestibular ocular reflex testing - assessing nystagmus, clarity of vision with head movements, and body movements
Vertebral artery testing
Sensory testing
Clinical test of sensory interaction on balance (CTSIB)
Functional testing - transfers, gait, dynamic sitting, and dynamic balance
Vestibulospinal reflex testing - examining posture and balance in all positions
Positional changes and their impact on symptoms
Cervical range of motion
Outcome measures as appropriate, such as the dynamic gait index
The CTSIB is conducted with the patient standing with their hands at their sides and feet together, performing the following six sensory conditions:
Stand on a firm surface with eyes open - baseline condition, with vision, somatosensory, and vestibular input all available
Stand on a firm surface with eyes closed - removes visual input, so balance relies on the somatosensory and vestibular systems
Stand on a firm surface with a visual conflict dome - vision is inaccurate, challenging the patient to rely on somatosensory and vestibular input instead
Stand on a foam surface with a visual conflict dome - somatosensory input is degraded and vision is inaccurate, placing heavy demand on the vestibular system
Stand on a foam surface with eyes open - somatosensory input is degraded, so balance relies on vision and the vestibular system
Stand on a foam surface with eyes closed - both vision and reliable somatosensory input are removed, isolating and testing the vestibular system
Central vestibular disorders
Central vestibular dysfunction symptoms
Nystagmus in vertical, horizontal, or rotational planes
Non-fatigable nystagmus
No hearing loss or tinnitus
Vertigo is sometimes present
Disequilibrium is severe
Can be associated with other cranial nerve or cerebellar signs
Visual fixation and head position have no impact
Treatment for central vestibular dysfunction
Identify triggers, if any, that are noted to be external
Gaze stabilization exercises to assist with improving the vestibular ocular reflex
Coordination activities to address cerebellar symptoms
Adaptation exercises to decrease dizziness to allow for retraining of the brain
Substitution of visual and somatosensory systems in the presence of vestibular dysfunction
Peripheral vestibular dysfunction
Most peripheral vestibular dysfunction is unilateral. The following are common causes:
Symptoms of peripheral vestibular dysfunction
Nystagmus is horizontal and torsional
Nystagmus decreases with visual fixation
Nystagmus is fatiguable and lasts less than one minute
