Analysis of Vestibular Compensation Following Clinical Intervention for Vestibular Schwannoma

Temporal Synthesis of Vestibular and Extra-Vestibular Sensory Signals

Multiple sensory cues are typically generated by discrete events, and while they do not reach the cerebrum simultaneously, the brain can bind them temporally if they are interpreted as corresponding to a single event. The temporal binding of vestibular and non-vestibular sensory cues is poorly understood and has not been studied in detail, despite the fact that the vestibular system operates in an inherently multimodal environment. In this study, the researchers are investigating the physiology and pathophysiology of vestibular temporal binding by studying normal subjects, patients with peripheral and central vestibular dysfunction, and patients with vestibular and cochlear signals provided by prosthetic implants in the inner ear.

Multiple sensory cues are generated by discrete events (e.g., the vestibular-visual signals after hitting a pothole) and while they do not reach the cerebrum simultaneously, the brain can synthesize them if they are interpreted as corresponding to a single event. This is critical because the central representation of an event is improved if two or more relevant cues are integrated but conversely is degraded if unrelated inputs are synthesized. Little research has focused on temporal binding of vestibular signals with other sensory cues, even though the vestibular system operates in an inherently multimodal environment, and virtually nothing is known about temporal binding abnormalities in patients with peripheral or central vestibular disorders. The investigators will use psychophysical tests (quantifying the PSS [point of subjective simultaneity] and TBW [temporal binding window]) to study vestibular temporal binding in normal people, patients with combined vestibular and cochlear prostheses, and patients with peripheral or central vestibular dysfunction. The researchers will investigate two fundamental aspects of temporal binding: its dependence on signal precision and adaptation driven by habitual exposure to sensory patterns. Furthermore, the researchers will investigate how and why temporal binding differs from normal in patients with peripheral and central vestibular dysfunction.

Inclusion Criteria:

Normal subjects

• normal vestibular-oculomotor exams
• normal low-frequency standard rotational testing
• normal hearing

Migraine

• meets International Headache Society (IHS) criteria for migraine with or without aura
• tested more than 2 weeks after most recent migraine headache

Vestibular Migraine

• meets Barany Society criteria for vestibular migraine, which includes:
• episodic vestibular symptoms that occur with headaches that meet the IHS criteria for migraine
• tested more than 2 weeks after most recent migraine headache or vestibular episode

Vestibular Schwannoma

• existence of unilateral vestibular schwannoma (pre & post clinical intervention e.g. surgical resection)
• must plan to have clinical intervention such as sub-occipital surgical approach with complete sectioning of the vestibular nerve
• rotational testing to assess pre-surgical vestibular function
• audiogram
• brain MRI consistent with vestibular schwannoma
• audiography in each ear

Vestibular (VI) and Cochlear (CI) Implant subjects

• scheduled for CI surgery because of deafness
• minimum 5 year history of documented absence of auditory and vestibular function, based on review of their audiograms and vestibular tests
• specific vestibular criteria: peak ice water caloric response of less than 3deg/s for each ear; yaw VOR time constant <3s and gain <0.25; and reduced head impulse gain (<0.25) for all canal planes
• specific audiographic criteria: 80dB or greater sensorineural hearing loss in both ears

Exclusion Criteria:

Normal subjects

• history of otologic or neurologic disease
• on vestibular suppressant medication (benzodiazepine, antihistamine, anticholinergic)
• pregnant or recently (<6mos) pregnant

Migraine

• history of vestibular symptoms (other than motion sickness)
• evidence of other neurologic or otologic dysfunction
• on migraine prophylactic medications
• on vestibular suppressant medication (benzodiazepine, antihistamine, anticholinergic)

Vestibular Migraine (VM)

• other neurologic or otologic dysfunction as defined above except for central eye movement findings that are consistent with VM and therefore not exclusionary.
• on migraine prophylactic medication
• on vestibular suppressant medication (benzodiazepine, antihistamine, anticholinergic)

Vestibular Schwannoma

• other otologic disease (other than presbycusis) or any neurologic disease (other than migraine)
• on vestibular suppressant medication (benzodiazepine, antihistamine, anticholinergic)