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Vestibular Function and Anatomy Prof. Hamad Al-Muhaimeed Professor/Consultant Department of Otorhinolaryngology King Abdulaziz University Hospital System of balance Membranous and bony labyrinth embedded in petrous bone 5 distinct end organs – 3 semicircular canals: superior, lateral, posterior – 2 otolith organs: utricle and saccule Semicircular canals sense angular acceleration Otolithic organs (utricle and saccule) sense linear acceleration Embryology 3rd week of embryonic development Otic placode formed from neuroectoderm and ectoderm Otocyst or otic vesicle 4th week Semicircular canals are orthogonal to each other Lateral canal inclined to 30 degrees Superior/postereor canals 45 degrees off of sagittal plane Utricle is in horizontal plane Saccule is in vertical plane Anatomy There are five openings into area of utricle Saccule in spherical recess Utricle in elliptical recess 45% from AICA 24% superior cerebellar artery 16% basilar Two divisions: anterior vestibular and common cochlear artery Superior vestibular nerve: superior canal, lateral canal, utricle Inferior vestibular nerve: posterior canal and saccule Membranous labyrinth is surrounded by perilymph Endolymph fills the vestibular end organs along with the cochlea Perilymph – Similar to extracellular fluid – K+=10mEQ, Na+=140mEq/L – Unclear whether this is ultrafiltrate of CSF or blood – Drains via venules and middle ear mucosa Endolymph – Similar to intracellular fluid – K+=144mEq/L, Na+=5mEq/L – Produced by marginal cells in stria vascularis from perilymph at the cochlea and from dark cells in the cristae and maculae – Absorbed in endolymphatic sac which connected by endolymphatic, utricular and saccular ducts Sensory structures Ampulla of the semicircular canals Dilated end of canal Contains sensory neuroepithelium, cupula, supporting cells Cupula is gelatinous mass extending across at right angle Extends completely across, not responsive to gravity Crista ampullaris is made up of sensory hair cells and supporting cells Sensory cells are either Type I or Type II Type I cells are flask shaped and have chalice shaped calyx ending One chalice may synapse with 2-4 Type I cells Type II cells – cylinder shaped, multiple efferent and afferent boutons Hair cells have 50-100 stereocilia and a single kinocilium. stereocilia are not true cilia, they are graded in height with tallest nearest the kinocilium. Otolithic organs Utricle and saccule sense linear acceleration Cilia from hair cells are embedded in gelatinous layer Otoliths or otoconia are on upper surface Calcium carbonate or calcite 0.5-30um Specific gravity of otolithic membrane is 2.71-2.94 Central region of otolithic membrane is called the striola Saccule has hair cells oriented away from the striola Utricle has hair cells oriented towards the striola Striola is curved so otolithic organs are sensitive to linear motion in multiple trajectories Senses and controls motion Information is combined with that from visual system and proprioceptive system Maintains balance and compensates for effects of head motion DEFINITION & TERMINOLOGIES DEFINITION & TERMINOLOGIES VERTIGO (illusion of rotational, linear or tilting movement such as “spinning”, “whirling” or “turning” of the patient or the surrounding . DISEQUILBRIUM sensation of instability of the body positions, walking or standing described as “off balanced” or “imbalanced”. DEFINITION & TERMINOLOGIES OSCILLOPSIA (inability to focus on objects with motion, such as reading a sign while walking , seen with bilateral or central vestibular loss). DEFINITION & TERMINOLOGIES LIGHTHEADEDNESS (sense of impending faint, presyncope). PHYSIOLOGIC DIZZINESS (motion sickness, height vertigo), EVALUATION OF THE DIZZY PATIENT History Dizziness is a term used to describe any of a variety of sensation that produce spatial disorientation. Onset and Duration of Symptoms: EVALUATION OF THE DIZZY PATIENT History Character of Dizziness: Contributing Factors: Associated Symptoms: PHYSICAL EXAMINATION H & N and General Physical Exam: Otoscopy: Vestibular Testing: Neurological Exam: General Characteristics of Peripheral and Central Causes of Vertigo Characteristic Intensity Fatigability Associated Peripheral Central severe fatigues, adaptation fatigue mild does not General Characteristics of Peripheral and Central Causes of Vertigo Characteristic Peripheral Symptoms nausea, hearing loss, sweating Eye closed symptom, worse with eyes closed Central weakness, numbness falls more likely symptoms better with eyes closed General Characteristics of Peripheral and Central Causes of Vertigo Characteristic Peripheral Nystagmus horizontal, may be unilateral rotary suppresses nystagmus (may not suppress during acute phase ) Ocular Fixation Central vertical bilateral no effect or enhances nystagmus CAUSES OF VERTIGO PERIPHERAL VERTIGO: Benign Paroxysmal Positional Vertigo Meniere Disease Vestibular Neuronitis Perilymphatic Fistulas CAUSES OF VERTIGO CENTRL CAUSES Cerebellospontine Angle Tumuors Traumatic Vestibular Dysfunction CENTRAL AND SYSTEMIC CAUSES OF VERTIGO Multiple Sclerosis Other Neurological Disorder (stroke, seizures, middle cerebellar lesions, parkinsonism, psudobulbar palsy) Metabolic Disorders (hypo/hyperthyroidism, diabetes) CENTRAL AND SYSTEMIC CAUSES OF VERTIGO Medications and Intoxicants (psychotropic drugs, alcohol, analgesics, anesthetics, antihypertensives, anti-arrhythmics, chemotherapeutics) Vascular Causes (vertebrobasilar insufficiency, basilar migraine syndrome, vascular loop compression syndrome) VESTIBULAR TESTING HALLPIKE TEST ELECTRONYSTAGMOGRAPHY ROTATION TEST OCULOMOTOR TESTING POSTUGRAPHY CALORIC TESTING Only test that evaluates vestibular function in each ear independently, determines unilateral versus bilateral weakness Technique: Theoretical Normal Response: CALORIC TESTING Directional Preponderance: Unilateral Caloric Weakness: Bilateral Weakness: DIAGNOSIS Based on clinical history, physical examination and audiological findings (initial low-frequency SNHL) with exclusion of other causes of hearing loss and vertigo is adequate for diagnosis and initiating empirical therapy. Meniere’s Disease (Endolymphatic Hydrops) Signs and Symptoms Episodic Vertigo lasting minutes to hours Episodic fluctuating SNHL (usually unilateral), recovery between episodes may be incomplete resulting in a progressive SNHL (initially at lower frequencies) Tinnitus and episodic fullness associated with or without the hearing loss Meniere’s Disease (Endolymphatic Hydrops) Signs and Symptoms Classic Menieres Disease presents with all of the above symptoms (vertigo, hearing loss, tinnitus, and aural fullness), however Meniere Disease may also present as any combination of the above symptoms Meniere’s Disease (Endolymphatic Hydrops) DIAGNOSIS Vestibular testing may reveal unilateral weakness on affected side. Electrocochleography: MEDICAL MANAGEMENT OF MENIERE DISEASE Dietary Restrictions: Diuretics: Vestibular Suppressants: Corticosteroids: Allergy Management: Stress Reduction BENIGN PAROXYSMAL POSITIONAL VERTIGO (BPPV, Cupulolithiasis) BPPV Frequency- 50% of peripheral vertigo, 20% of pts over 80 have BPPV Clinical history: sudden onset, brief vertigo, brought on by changes in head position, particularly turning in bed, or tilting head back, may have prior history of vestibular neuritis or head trauma Exam: + Dix-Hallpike (don’t forget 5-10% have horizontal variant) Pathophysiology: loose calcium crystals in posterior semicircular canal Treatment: Epley manuever MANAGEMENT Education, reassurance and observation Particle Repositioning Maneuver (Epley’s Maneuver): Home vestibular positional exercises Antivertiginous medications Singular Neurectomy: Vestibular Neuritis Frequency: 15% of peripheral vertigo Clinical history: sudden onset severe vertigo c N/V, sx’s improve in days to weeks secondary to central compensation, can have chronic effects for months to years. Exam: unilateral nystagmus c fast phase away from affected ear, amplitude of nystagmus decreases when looking towards affected ear, +/- hearing loss or tinnitus Pathophysiology: probably secondary to viral infection & inflammation of vestibular nerve or labyrinth Treatment: steroids- 3 week tapering course, starting at 100 mg. – Strupp et al. (2004). Methylprednisolone, Valacyclovir, or the Combination for Vestibular Neuritis. NEJM 351, pp. 354-361. PERILYMPH FISTULA Pathophysiology: Causes: SSx: Diagnosis: Treatment: VERTEBRONBASILAR INSUFFICIENCY (VBI) Pathophysiology: SSx: Diagnosis: Treatment OTHER VESTIBULAR DISORDERS Basilar Migraine Syndrome: Vestibular Epilepsy: Multiple Sclerosis (MS): Labyrinthine Apoplexy: Subclavian Steal Syndrome: Hyperrinsulinemia/Diabetes: Etiology Recur Onset BPPV + Duration Associated features sudden <1 min elderly, induced by position change hours ear fullness, tinnitus, low freq hearing loss days-weeks 50% c preceding viral illness, +/- hearing loss sec-days young F, HA, positive visual phenomenon mins CN, long-tract sx’s/ signs days-months hearing loss +/- tinnitus Meniere’s + gradual Vestibular neuritis Migraine + gradual or sudden gradual VB TIA + sudden Labryinth stroke - sudden Brainstem stroke - sudden days-months CN, long-tract sx’s/ signs Cerebellar stroke - sudden days-months unil dysmetria, “central” nystagmus MANAGEMENT CONCEPT Safety: Acute Vestibular Suppression: Vestibular Rehabilitation: Surgical Management: SURGICAL MANAGEMENT OF VERTIGO SURGICAL MANAGEMENT OF VERTIGO Endolymphatic Sac Surgery: Vestibular Nerve Section: Transtympanic Or Intratympanic Aminoglycoside Injections: Labyrinthectomy Conclusion 1. Is this vertigo? 2. Is this central or peripheral? 3. History- focus on age, PMH, duration 4. Exam- focus on CN and coordination, focal neurological findings, Dix-Hallpike