Anatomy Abraham Jacob, MD Otolaryngology Head and Neck Surgery - PDF document

Sudden Sensorineural Hearing Loss (SSNHL) Anatomy Abraham Jacob, MD Otolaryngology – Head and Neck Surgery Otology, Neurotology, and Cranial Base Surgery The Ohio State University Images used in this lecture were obtained from the presenter’s collection, various textbooks and internet websites. Their use is for educational purposes only. Learning Objectives • Understand the basic anatomy and physiology of the peripheral auditory system • Define Sudden Sensorineural Hearing Loss (SSNHL) • Describe the epidemiology, diagnostic www.scienceline.org evaluation, and treatment options for patients with SSNHL • Distinguish between idiopathic SSNHL and autoimmune hearing loss www.sfu.ca • Understand the basics regarding aural rehabilitation 1

• The middle ear contains 3 ossicles: the malleus, incus, and stapes . http://biology.clc.uc.edu/fankhauser/Labs/Anatomy http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiol www.dcip.org/?q=img_assist/gen/11 ogy/A&P202/Special_Senses/Ear/cochlear_nerve_40x_P2182 170lbd.JPG • The cochlea has 2.5-2.75 turns around a bony core (modiolus). Auditory Science Laboratory • The inner ear consists of the cochlea , the utricle , the saccule , the endolymphatic duct/sac , and the semicircular canals . http://www.indiana.edu/~pietsch/innerear400Alabeled.jpg www.faculty.une.edu 2

Peripheral Auditory Physiology Sudden Sensorineural Hearing Loss Definition & Etiology www.hearingaidscentral.com Definition Peripheral Auditory Physiology • Hearing loss can be categorized as conductive (loss of vibratory energy) or sensorineural (related to the inner ear or auditory nerve) • The most common definition of SSNHL is sensorineural hearing loss > 30 dB in 3 contiguous pure tone frequencies occurring in < 3 days www.hearingaidscentral.com 3

Epidemiology Differential Diagnosis Neurologic Infectious : Viral/idiopathic Other causes - Meningococcal meningitis; Multiple sclerosis; Focal pontine Herpesvirus (simplex, zoster, varicella, ischemia; Migraine • SSNHL was first described in 1944 CMV); Mumps; Human immunodeficiency virus; Lassa fever; Mycoplasma; Cryptococcal meningitis; Toxoplasmosis; • Estimated incidence is 10-20/100,000 Syphilis; Rubeola; Rubella; Human spumaretrovirus Neoplastic : Acoustic Neuroma Vascular : Alteration of cochlear • Highest incidence in patients between (vestibular schwannoma) microcirculation Other causes – Leukemia; Myeloma; Vertebrobasilar insufficiency; Red blood 40 and 60 years of age Metastasis to the internal auditory cell deformability; Sickle cell disease canal; Meningeal carcinomatosis Cardiopulmonary bypass � Can affect patients of all ages Autoimmune : Autoimmune Inner Ear Traumatic : Intracochlear membrane Disease rupture and Perilymph fistula Other causes - Ulcerative colitis; • > 95% are unilateral Temporal bone fracture; Inner ear Relapsing polychondritis; Lupus concussion; Otologic surgery erythematosus; Polyarteritis nodosa; Surgical complication of non-otologic Cogan’s syndrome; Wegener’s surgery • No gender preference granulomatosis Viral Cochleitis For idiopathic SSNHL, treatments have focused on: • The dominant cause of idiopathic • Minimizing inflammation SSNHL • Improving inner ear blood flow/oxygenation • Re-establishing the endocochlear potential. � 17-33% of patients recall a viral illness within a month of SSNHL • Majority of cases are idiopathic � Compared with controls, the rates • No single cause accounts for all cases of herpes virus sero-conversion are • Treatments are directed towards the higher in patients with SSNHL cause if the cause is known 4

Intra-cochlear Viral Cochleitis Membrane Rupture • The most compelling evidence comes from temporal bone histopathology • Allows mixing of consistent with viral injury to the inner ear endolymph and perilymph • Loss of inner ear hair cells • Disrupts the • Atrophy of the stria vascularis endocochlear potential • Atrophy of the tectorial membrane � The stria vascularis www.faculty.une.edu generates an endocochlear potential of • Neuronal loss +80 mV within the scala media. • Diagnosis of exclusion � Ion pumps within hair cells create an intracellular potential of -70mV. Perilymph Fistula Vascular Compromise • Leakage of perilymph thru • The cochlea is an end the oval or round windows organ supplied by the • Inciting events: labyrinthine artery � Physical trauma to the head � vertebrobasilar system www.hearingaidscentral.com � Sneezing � no collateral circulation. � Bending/Lifting heavy objects • Thrombosis, embolic phenomena, vasospasm, � Sudden barometric and hyper-coagulable pressure changes (flying or diving) states can compromise inner ear oxygenation. � Acoustic trauma exposure to a loud noise. 5

Acoustic Neuroma Autoimmune Disease (Vestibular Schwannoma) • May be part of systemic autoimmune diseases • Nerve sheath tumors originating from Schwann � Cogan's syndrome cells (8th cranial nerve). � Wegener’s granulomatosis � Polyarteritis nodosa • Significant patient morbidity due to their critical location � Temporal arteritis � Buerger’s disease (thromboangitis • 1% of patients with SSNHL obliterans) have a vestibular schwannoma � Systemic lupus erythomatosis • 3-12% of patients with VS • May be isolated to the inner ear without presented with SSNHL systemic involvement. Autoimmune Disease Autoimmune Disease • Introduced in 1979 by McCabe and • Diagnosis: Response to steroids colleagues as rapidly progressive bilateral SNHL that responds to � CBC with diff immunosuppressive medications. � Bilateral but onset and progression may � ESR be asymmetric � Timeline is weeks to months � RF � 50% have vestibular (balance) � ANA symptoms � Unknown epidemiology but much rarer � Anti-double stranded DNA than SSNHL antibodies 6

Autoimmune Disease Autoimmune Disease � Anti SSA/B antibodies � Continue steroids until monthly � Anti-phospholipid antibodies audiograms demonstrate that hearing has stabilized � C3 and C4 complement levels � Slowly taper steroids over 8 weeks to a � Western blot for 68 kD protein maintenance dose of 10-20 mg every other day � Raji cell assay for circulating � Most patients require > 6 months of immune complexes steroid therapy • Rule out syphilis and central • Rheumatology consult! pathologies Autoimmune Disease • Treatment with immunosuppressive medications Evaluation and � Prolonged course of high dose oral Management steroids • 60 mg oral prednisone per day for 4 weeks for adults • 1mg/kg oral prednisone per day for pediatric patients � Many do not improve until week 4 7

History Physical Examination • The immediate goal is discovering a • Otoscopy treatable or defined cause of the sudden � Believe your physical exam! hearing loss. � If there is no ear canal obstruction, ear • Ask about the onset, time course, and drum pathology, or fluid in the middle characteristics of the hearing loss ear… be worried � Is it constant or intermittent? • Cranial nerve examination Associated with position changes? � Especially cranial nerves 5,7,10,11,12 � Is it mild, moderate, severe, or • Balance Examination profound? � Gait testing, Romberg, cerebellar tests, � Can the patient use a telephone? look for nystagmus History Tuning Fork Tests • Weber: Lateralizes to the • Always ask about balance function, tinnitus , ear with a conductive HL prior ear surgery , a history of noise exposure , recent sick contacts , travel history, and inquire about facial nerve dysfunction • Rinne: A positive Rinne indicates that • Past medical history may reveal risk air conduction is greater factors for hearing loss. than bone conduction. A negative Rinne indicates • All medications, including over-the-counter that bone conduction is products, must be described. greater than air conduction 8

Audiograms Lab Tests • Audiograms are graphic representations of auditory sensitivity and are used clinically to test hearing. � International normalized radio • Most audiologists test the 250 Hz – 8000 Hz range (x- (INR),activated partial thromboplastin axis) time (aPTT), and clotting time for • The y-axis of an audiogram is plotted in decibels coagulopathy (dB), a logarithmic scale. � CBC and differential for infection � Thyroid-stimulating hormone (TSH) for thyroid disease � Fasting blood glucose for diabetes mellitus � Cholesterol and triglycerides for hyperlipidemia www.ilh.org www.dizziness-and-balance.com Lab Tests Imaging • A shot-gun approach to laboratory • MRI of the head with and without contrast examinations is not cost-effective for is the imaging modality of choice SSNHL • Laboratory studies should be directed by the history and physical examination � Fluorescent treponemal antibody- absorption (FTA-Abs) for syphilis � Antinuclear antibodies (ANA), rheumatoid factor, erythrocyte sedimentation rate (ESR), and 68kD protein Western blot for autoimmune diseases www.ent.uci.edu 9