-------------------------------------------------------------------------------- TITLE: SENSORINEURAL HEARING LOSS IN CHILDREN SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: September 29, 1993 RESIDENT PHYSICIAN: Denise V. Guendert, M.D. FACULTY: Amy R. Coffey, M.D. DATABASE ADMINISTRATOR: Melinda McCracken, M.S. -------------------------------------------------------------------------------- "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." I. Classification A. Congenital Hearing Loss 1. Genetic a. hearing loss alone b. hearing loss associated with other anomalies 2. Acquired a. infection b. ototoxins c. other B. Postnatal Hearing Loss 1. Genetic a. hearing loss alone b. hearing loss associated with other anomalies 2. Acquired a. infection b. trauma c. ototoxins d. other II. General Information -50% of the sensorineural hearing loss presenting in childhood can be classified as genetic in nature. -20-25% of sensorineural hearing loss presenting in childhood can be attributed to environmental causes. -There are at least 100 different genetic syndromes that include hearing loss as one of the findings. -Most childhood SNHL not part of syndrome III. Congenital Hearing Loss A. Spectrum of Inner Ear Malformations -Most widely accepted classification by Ormerod and Schuknecht recognizes 5 degrees of deformity -Only 20% if neonates with congenital SNHL have morphogenetic defect that appears on radiographs. The other 80% have defects confined to membranous labyrinth. -SNHL determined not to be secondary to classic form of malformation can be classified as either neuroepithelial (primary pathologic changes of the organ of Corti with later degeneration of spiral ganglion and nerve fibers) or cochleosaccular (malformation or malfunction of stria vascularis) 1. Michel Aplasia -Most severe form of aplasia -Complete failure of bony and membranous labyrinth development -In some cases, petrous temporal bone not developed -No residual hearing -Neither conventional amplification nor cochlear implant helpful -Vibrotactile devices have been used with some success 2. Mondini Malformation -Incomplete formation of the bony and membranous labyrinth -Middle and apical turns of cochlea occupy common bony space -Auditory function varies from essentially normal to profound SNHL -Often asymmetrical -Should attempt amplification 3. Bing-Siebenmann Malformation -Well-formed bony labyrinth but malformed membranous labyrinth in its entirety -Radiographically normal 4. Scheibe Malformation -Most common form of aplasia -Membranous aplasia of pars inferior (cochlea and saccule). Utricle and semicircular canals are normal. -Radiographically normal since bony labyrinth well-formed -Audiogram will reveal profound SNHL with residual low frequency hearing -Amplification may be helpful -Present in Jervill and Lange, Refsum's, Usher's, and Waardenburg's syndromes 5. Alexander Malformation -Least severe form -Partial aplasia of cochlear duct (basal turn) -High frequency hearing loss -Amplification helpful B. Genetic Congenital SNHL 1. General information -Of the genetic congenital SNHL, 20-25% is inherited via an autosomal dominant pattern, 75-80% is recessive and 2% is sex-linked. -SNHL transmitted via autosomal dominant mode is often progressive whereas that transmitted recessively is often stable. 2. Genetic Congenital SNHL Without Other Organ Involvement -66% autosomal dominant. -25% of unilateral SNHL is genetic -Consider if strong family history, h/o consanguineous marriage, 2 or more affected siblings 3. Congenital Genetic SNHL with Other Organ Involvement a. Waardenburg Syndrome -Autosomal dominant with variable penetrance -Most frequently diagnosed hereditary deafness syndrome comprising 1-3% of all congenital deafness -Six predominant features: 1.SNHL, 2. widely spaced medial canthi with shortening of palpebral fissures, 3. broad nasal root, 4. hypertrichosis of eyebrows, 5. white forelock, 6. heterochromia of irides -Two types exist, type I includes widely spaced medial canthi type II does not. Type I is associated with 25% incidence of SNHL. Type II is associated with a 50% incidence of SNHL. -Other feature include cleft lip/cleft palate, hypopigmentation and absent vestibular responses -Histologically have atrophy of stria and organ of corti b. Usher's Syndrome -Autosomal recessive -Accounts for ~50% of the deaf/blind population in the U.S. -Heterogeneous syndrome - three different types -Characteristics include SNHL, progressive retinitis pigmentosa, cataracts, mental retardation, spinocerebellar ataxia, psychosis, vestibular dysfunction -Almost all have no vestibular response to caloric tests or ice-water calorics -Hearing loss usually precedes visual loss -Most common presentation is that of SNHL at birth with onset of night blindness by 10 and decreased visual acuity noted in light by second decade -Diagnosis: Electroretinography may identify changes in retina prior to detection by ophthalmoscope. On latter, see granular accumulation of pigment beginning at fundus and extending to periphery. -Important to do routine fundoscopic exams during first two decades in children born with SNHL of unclear etiology and/or if Usher's suspected -Must initiate special habilitative intervention early especially with deaf/blind -Important to assess family members to identify carriers c. LEOPARD Syndrome -Autosomal dominant -Findings include Lentigines, Electrocardiographic abnormalities, Ocular hypertelorism, Pulmonary stenosis, Abnormal Genitalia, Retardation of growth, bilateral sensorineural Deafness (25% affected). d. Jervell and Lange-Nielsen Syndrome -Autosomal recessive -Comprises 1% of all recessive hearing loss -Characteristic of syndrome include profound predominantly high frequency SNHL, recurrent syncope (Stokes-Adams attack), life usually terminates in sudden death before 15 years if not treated -See large T waves and prolonged QT interval on EKG. During syncopal episode, see asystole followed by V-tach -Syncopal episodes usually begin in second decade, may occur as often as once a day, and usually last 5-10 minutes. Severity of syncopal episodes decreases with age -Histology- atrophy of organ of corti and loss of spiral ganglion cells. Cardiac histo reveals hypertrophy of intima of artery to SA node, infarction of SA node, and abnormal purkinje fibers. -Treatment: Propranolol 5 mg. per day with or without phenobarbital. Those refractory to medications should undergo placement of cardioverter defibrillator. e. Pendred's Syndrome -Autosomal recessive -Severe to profound predominantly high frequency bilateral SNHL -Comprises 1-10% of congenitally hearing impaired children -Decreased vestibular responses in many -These children develop goiter that is clinically apparent between 3 and 8 years of age and are euthyroid though may have bouts of hypothyroidism early in life. Defect is abnormal organification of iodine resulting in large stores of inorganic iodine -Children may also have mental retardation -Diagnosis based on abnormal perclorate test -Many have Mondini-type morphogenetic defect -Treatment: thyroid hormone. Thyroidectomy is not indicated as goiter returns. B. Acquired Congenital SNHL 1. Teratogens and Ototoxins a. Thalidomide b. Quinine - cochlear hypoplasia c. Aminoglycosides 2. Intrauterine Infection a. Rubella -Previously the most common cause of acquired congenital SNHL. There has been a downward trend in the last decade -The earlier infection acquired during pregnancy, the more severe the effect on fetus -50% of infants infected first trimester have SNHL, 20- 30% of those infected in second and third trimester have SNHL -Hearing loss usually severe to profound and may be progressive and/or asymmetric. May also have conductive component due to fixed stapes. Speech discrimination poor. -Other findings include pigmentary retinitis (most common and consistent finding), cataracts, microcephaly, mental retardation, cardiovascular abnormalities, intrauterine growth retardation, hyperbilirubinemia -Histologically see collapse of Reissner's membrane, cochleosaccular degeneration -Diagnosis: Isolate virus from throat or urine culture during first week of life or assess for increased IgM titer in cord blood or infant serum in first 6 months of life. More difficulty to diagnose older children. -Prevention is the key. Vaccine-wild type virus. b. Cytomegalic Inclusion Disease -2000 infants born per year in the U.S. with SNHL due to CMV. -Children of immune mothers just as likely to develop congenital CMV as children of nonimmune mothers, suggesting that the virus is reactivated. -60-70% of pregnant women have positive CMV titers, but only 10% of infants born to these mothers will have CMV infection. -~90% of infected infants are asymptomatic at birth and only 10% of these will have hearing loss on later testing. -SNHL may range from mild to profound, the latter being more common in symptomatic infants. HL may also be progressive. -Of the infants symptomatic at birth, 30-40% that survive will have SNHL, 61% will have mental retardation. -Other findings in symptomatic infants are microcephaly, hepatosplenomegaly, mental retardation, palatal abnormalities, intracerebral calcifications. -Diagnosis: Isolation of CMV from fresh urine during first 2 weeks of life. Can also see "owl eye" bodies in urine which represent infected renal tubular cells. Identification of antiCMV IgM in umbilical cord blood or infant's serum supports diagnosis. c. Toxoplasma gondii -Incidence of infection is 1 per 1000-3000 births. -90% have subclinical infection at birth. -Host is the cat. -Other findings include chorioretinitis, hydrocephalus, intracranial calcifications, lymphadenopathy, pulmonary lesions. -Can test inutero. Look for IgM specific toxo antibodies in fetal blood. -Treatment: If mother infected treat with spiramycin. If baby infected, treat with pyrimetamine and sulfadiazine. d. Congenital Syphilis i. Infantile form (early) -Usually fatal outcome -Multisystem involvement -Other signs include; bossing of skull, sabre shins, Hutchinson's teeth, interstitial keratitis, snuffles ii.Tardive form (late) -Usually presents with sudden SNHL in childhood that tends to be profound and symmetric and associated with vestibular symptoms -May have later onset (up to fifth decade), which is usually associated with more severe vertigo and less severe HL. -+Hennebert's (secondary to fibrous band formation between footplate and vestibular membranous labyrinth or excessively mobile footplate). +Tullio's phenomenon (vertigo and nystagmus with high intensity sound) -Rx: 2.4 mill U benzathine PCN IM for early stage, 1.8 mill U procaine PCN IM daily for 3 weeks with 500 mg. probenecid po Q6h then 2.4 mill U benzathine PCN G IM weekly for 3 mos. for late stage dz. Also give 80 mg steroids po Q day for 1 month then taper. -35-50% will improve with treatment especially in speech discrimination scores. 3. Other a. Placental or umbilical cord disruption -Interference with oxygenation. -Pathology probably lies within the cochlear nucleus and other portions of CNS. -Will usually have other CNS findings and handicaps -Usually bilateral and symmetric SNHL involving high frequencies the most b. Maternal alcoholism -Fetal alcohol syndrome i.e. microcephaly, mental retardation c. Maternal endocrine diseases -Including thyrotoxicosis, diabetes, pseudohypoparathyroidism IV. Postnatal Sensorineural Deafness A. Genetic 1. Hearing Loss Alone a. Familial Progressive Sensorineural Deafness -Autosomal dominant. -Occurs in approximately 1 in 40,000. -Usually presents at 7-13 years. -Usually bilateral, progressive, worse in high frequencies with good speech discrimination. -See degeneration of organ of corti, stria vascularis mostly in basal turn. -Presymptomatic gene carriers may demonstrate elevated thresholds for stapedial reflexes and positive recruitment 2. Hearing Loss With Other Abnormalities a. Associated With Renal Disease i. Alport's Disease -All three classic forms of inheritance are found, though the x-linked type involving a collagen gene mutation is most common. Mode of inheritance and sex are prognostic factors as the mean survival for x-linked form is 25 years and that for autosomal dominant is 51 years -See bilateral, progressive sensorineural hearing loss arising during adolescence greatest loss in high frequencies. Hearing usually helped significantly with hearing aids. -Other features include: recurrent macroscopic hematuria (often in infancy -red diaper syndrome), proteinuria, uremia, visual change due to anterior lenticonus and/or cataracts. May have vestibular hypofunction. -Anterior lenticonus quite specific for Alports. Can be diagnosed by slit lamp. See conical protrusion of lens substance anteriorly. -Consider diagnosis in child with SNHL and elevated serum Cr/BUN or abnormal UA (elevated WBCs, protein, RBCs) -Diagnosis confirmed by renal biopsy which shows thickening of glomerular basement membrane and lymphocytic infiltrate. -See atrophy or complete absence of organ of corti, degeneration of stria vascularis, spiral ligament, and cochlear neurons. and collapse of Reissner's membrane -Develop progressive renal insufficiency. -If untreated, men typically die by 30. -Have case reports of auditory recovery after renal transplant. ii.Hermann's Syndrome -Autosomal dominant -Onset of progressive bilateral sensorineural loss during late childhood or adolescence. -Other features include pyelo or glomerulonephritis, diabetes mellitus, and progressive dementia. b. Hearing Loss Associated With Ocular Abnormalities i. Refsum's Disease -Autosomal recessive absence of enzyme for metabolism of phytanic acid (from chlorophyll). -50% have progressive sensorineural loss. Usually begins in second decade with the visual impairment -Other features include retinitis pigmentosa, ichthyosis (alligator skin), polyneuropathy and ataxia, cataracts, absent reflexes. -Rx.: eliminate items with phytanic acid, phytol, and phytic acid from diet (chlorophyll and butterfat). c. Hearing Loss Associated With Skeletal Abnormalities i. Klippel-Feil Syndrome -Autosomal recessive or dominant. Females>males. -Severe progressive sensorineural loss. May have conductive component due to ossicular chain abnormalities or canal atresia. -May have Mondini-type malformation -Associated findings include: fusion of cervical vertebrae, spina bifida, scoliosis. ii. Friedreich's Ataxia -Autosomal recessive -Onset of bilateral sensorineural hearing loss with ataxia, nystagmus, diminished deep tendon reflexes, muscle wasting, optic nerve atrophy during early childhood. Vestibular function may be impaired -Patients have degeneration of the spinocerebellar tracts, pyramidal tracts, and dorsal columns iii.Van Buchem's Syndrome -Autosomal recessive. -Progressive unilateral or bilateral sensorineural hearing loss. -Also see generalized osteosclerotic overgrowth of skull, mandible, ribs, and long bones with obstruction of foramina and cranial nerve palsies -Have increased alkaline phosphatase. iv. Paget's Disease -Autosomal dominant with variable penetrance. -Increased resorption and disorderly bone formation resulting in poorly mineralized, vascular bone. -Progressive sensorineural loss beginning in middle age. May be related to AV shunting in new bone. -Associated with bony pain, pathologic fractures cranial nerve palsies, enlargement of skull. -X-rays show radiolucency initially then increased density. Also have increased alkaline phosphatase. -Rx: Reduce osteoclastic activity with calcitonin or etidronate. d. Hearing Loss With Endocrine Abnormalities i. Alstrom's Disease -Autosomal recessive. -Progressive sensorineural loss beginning at ~10. -Associated features include: Diabetes mellitus, obesity, retinitis pigmentosa with visual loss starting at one year and nearly total visual loss by 20 years. ii.Richards-Rundel Syndrome -Autosomal recessive. -Progressive sensorineural loss, severe by 5-6 yrs. -Patients have hypogonadism with decreased urinary estrogen, pregnanediol, and total 17-ketosteroids. Also see mental retardation, ataxia and muscle wasting. e. Hearing Loss With Integumentary Abnormalities i. Neurofibromatosis 1.Type I or Von Recklinghausen's Disease -Occurs in 1 in 3000. Onset in first decade. -Autosomal dominant, single gene defect, thought ~50% are spontaneous mutations. -Defect on chromosome # 17. -Have unilateral sensorineural loss, poor speech discrimination, stapedial reflex elevation or absence secondary to eighth nerve schwannoma. Average age of onset of symptoms is 21 years -Also see Cafe au lait spots >6 in number, lisch nodules (hamartomas of the iris), and cutaneous neurofibromas. -Up to 96% will have abnormal ABR. 60-80% have abnormal caloric testing. -Gadolinium-enhanced MRI has highest diagnostic sensitivity for schwannoma. -Rx.: Surgical excision. Approach depends on size of tumor and degree of residual hearing 2.Type II or central neurofibromatosis -Occurs in 1 in 100,000. Onset in 2nd or 3rd decade. -Autosomal dominant with gene defect on chromosome # 22. -50% present with bilateral sensorineural loss. -Bilateral eighth nerve schwannomas common. There are larger than in NF1 and multicentric. -Also see meningiomas and gliomas. -Rarely have lisch nodules and have fewer cafe au lait spots. 3. Syndromes That Tend to Have Mixed Hearing Loss a. Hurler's Syndrome -Autosomal recessive mucopolysaccharide storage disease. -Deficiency of alpha-L-Iduronidase. -Usually mixed loss with AB gap in high frequencies. -Also see mental retardation, hepatosplenomegaly, dwarfism, coarsening of facial features, low set ears, corneal opacities. -Death in early adolescence. b. Hunter's Syndrome -X-linked recessive mucopolysaccharide storage disease -Deficiency of iduronate sulfate sulfatase. -May have sensorineural loss but usually mixed. -Longer lifespan than Hurler's and not as severely retarded. c. Crouzon's Disease (Craniofacial Dysostosis) -Autosomal dominant. -Hearing loss, which is usually mixed, seen in 33%. -Other features include: premature closure of cranial suture lines, hypertelorism, mandibular prognathism, exophthalmos, canal atresia, parrot-beaked nose, and wide forehead. IV. Postnatal Acquired Sensorineural Deafness A. Infectious 1. Meningitis -Causes approximately 7% of postnatal hearing loss. -Incidence S/P meningitis is 20%. -Often develops despite adequate treatment and can progress for several years after treatment. ~3% show worsening or fluctuation of hearing over time -Hearing loss may be unilateral or bilateral and can be associated with vestibular symptoms. -Greater incidence of hearing loss with delay of treatment and/or if other neurologic sequela occur -Bacteriology: a) Neonates: group B streptococci and E.coli b) Children 6-9 months: Hemophilus influenza, Neisseria meningitides, and Streptococcus pneumonia (latter causes highest incidence of hearing loss) -Histologically see labyrinthitis with destruction of organ of corti. During adolescence see ossification which causes the significant deterioration often seen at this age. -~40% of these children may also have other complications such as mental retardation, hemiparesis, seizure disorder, and visual impairment leading to the need for intense special education. -Studies inconsistently show increased occurrence of profound SNHL without steroids 2. Labyrinthitis a. Suppurative -Results from infiltration of bacteria and inflammatory cells into labyrinth from CSF via IAC or cochlear aquaduct, from middle ear during suppurative OM, or via hematogenous spread. -Symptoms: sudden, usually unilateral sensorineural loss (mixed when OM present), nausea, vomiting, intense vertigo, tinnitus, and nystagmus. Fever especially if meningitis present. -Organisms: Streptococci pneumonia, N. meningitides, H. influenza. -Basilar membrane more vulnerable to passage of leukocytes than Reissner's membrane. Develop differential osmotic pressure leading to hydrops and destruction of neuroepithelium. -Results in permanent profound sensorineural loss. -Rx.: Admission, IV antibiotics, myringotomy if OM present, lumbar puncture for meningeal signs, mastoidectomy indicated if evidence of coalescent mastoiditis, CT scan to R/O intracranial abscess. b. Serous Labyrinthitis -Due to passage of toxins into labyrinth via round window. -One of most common complications of suppurative OM. -Toxins penetrate basilar membrane, invade labyrinth initially at basal turn then progress towards apex. Results in degeneration of neuroepithelium. OHCs more vulnerable. -See slowly progressive sensorineural loss in high frequencies first with vestibular symptoms less severe than suppurative labyrinthitis. -Usually does not result in permanent loss. -May develop into suppurative if inadequate Rx. c. Viral Labyrinthitis i. Mumps -Sensorineural loss occurs in 1 in 2000 cases. -Abrupt onset of unilateral (80%), high frequency sensorineural loss associated with nausea, vomiting and vertigo following parotitis. -Most common cause of unilateral sensorineural hearing loss in young. Loss usually permanent. -Dx.: 4-fold or greater rise in antibody titer. ii. Measles -Hearing loss in 1 in 1000 cases. -Before immunization caused 10% of deafness in children. -See abrupt onset of moderate to severe bilateral permanent sensorineural loss, greater in high frequencies and often associated with vertigo (70%). -Hearing loss occurs at time of maculopapular rash. Will also see Koplik spots,conjunctivitis -Dx.: 4-fold rise in antibody titer or positive throat culture. -No clear documentation that steroids or antivirals effective. B. Non-infectious Causes of Postnatal Sensorineural Deafness 1. Ototoxins a. Aminoglycosides -Neomycin, kanamycin, amikacin, gentamycin, tobramycin, and streptomycin. -Streptomycin mainly vestibulotoxic. Neomycin, tobramycin, and kanamycin strongly ototoxic. Gentamycin ototoxic and vestibulotoxic. -See bilateral, progressive, initially high frequency sensorineural loss with tinnitus and vertigo (Gentamycin). -Delayed ototoxicity has been seen with gentamycin and tobramycin (S/P termination of drug). -Cause destruction of hair cells. OHCs in basal turn first then apex with even later effect on IHCs. Also see damage to stria vascularis and spiral ganglion. -Impaired renal function leads to accumulation of toxic levels. -Dosage in infants and young children should be based on body surface area and not weight -Fee has reported 55% recovery rate. -Avian studies have shown functional regeneration of hair cells lagging weeks behind anatomical regeneration. -Rx.: Aimed at prevention with monitoring of renal function, high frequency audiograms, and bi-weekly drug levels. b. Loop Diuretics -Furosemide and ethacrynic acid. -Bilateral sensorineural hearing loss usually transient. -Potential for hearing loss greater with rapid IV Lasix. -Interfere with ion transport from stria vascularis. See edema of stria and OHC loss. c. Cis platinum -Bilateral, not completely symmetric sensorineural loss at 3000-8000Hz with progression to lower frequencies with increased dosing. d. Salicylates -Hearing loss reversible -May be due to effect on cochlear blood flow. No cell damage on histopathologic studies. 2. Hypoxia -History of apgars of 0 to 3, failure to institute respirations within 10 minutes, persistent hypotonia are indications that hypoxia severe enough to cause CNS damage and result in SNHL, MR, neuromuscular disorders etc... 3. Kernicterus -Hyperbilirubinemia causes damage to ventrocochlear nucleus -Associated with choreoathetosis, eye movement disturbances, spasticity, and SNHL -Many of these children are also of low birth weight and/or premature 4. Sound Exposure a. Acoustic Trauma -Single short exposure to intense sound resulting in painful sudden sensorineural hearing loss and tinnitus. May have mixed loss due to ossicular discontinuity or TM perforation. -On audiogram have notch at 4000 Hz (noise notch) -Caused by mechanical disruption of organ of corti, mixture of endolymph and perilymph. b. Noise Induced Hearing Loss (NIHL) -Caused by a more chronic exposure to more moderate sound levels. -Factors influencing degree of damage include intensity and duration of exposure -Sound pressure levels in incubators range from 57-82 dB. -Potentiating effect with ototoxins -Two stages exist. First see temporary threshold shift. Continued exposure leads to permanent threshold shift secondary to damage to hair cells. -Initial loss at 3000-6000 Hz followed by progression to lower frequencies. -Now mandatory that workers exposed to noise > 85dB have hearing conservation program with annual hearing screen, instruction on use of ear protection, and referral if hearing loss occurs. -Ear plugs reduce noise by 15-30dB, earmuffs 20-45dB 5. Trauma a. Transverse Temporal Bone Fracture -Comprise 10-20% of temporal bone fractures. -Usually secondary to blow to occipital or frontal regions. -Fracture through bony labyrinth leads to profound sensorineural loss and vestibular symptoms. 40-50% have VII nerve paralysis (geniculate ganglion). -Study in 1971 by Tos revealed that 26 out of 26 patients with transverse fracture had complete and permanent anacusis. -Longitudinal fractures typically result in damage to EAC, TM, ossicles and cause CHL b. Labyrinthine Concussion -Microfractures of bony labyrinth and bleeding into perilymph/endolymph cause degeneration of neuroepithelium. c. Caisson's Disease -Rapid decompression leads to gas emboli in cerebral end arteries. -Sensorineural hearing loss often with vertigo and clouding of consciousness. -Rx.: Hyperbaric oxygen. 6. Perilymph Fistula -Audiometric variance common in children with PLFs. May present with sudden sensorineural hearing loss with or without vertigo or with fluctuating hearing loss. May have middle ear effusion on exam. -Recent animal studies have shown cochlear action potentials are not altered with round window breaks alone and propose that these must be combined with other defects such as Reissner's membrane tears to allow admixture of perilymph and endolymph through- out cochlea. -Predisposing factors include: previous stapes surgery, history of trauma or exertion, cholesteatoma, and developmental abnormalities (Mondini's, Scheib's etc.) -In children get CT to assess for inner ear malformations. -Rapid protein test by Silverstein developed to help in diagnosis. Sample fluid in micropipet from oval or round window, place on protein indicator paper to analyze protein concentration (normal perilymph is 200mg%) -Rx.: Rest, head elevation for 5 days (40% close spontaneously). If no improvement or hearing worsens, explore round window, oval window, fissula ante fenestrum. -Recent House review showed only 14% objective hearing improvement with surgical exploration and repair. 68% had subjective improvement (May not be of great benefit if explored for HL alone) -Recurrence not uncommon. Reported at up to 30%. 7. Neoplastic Disease ( Also see III.B.5) a. Meningiomas -3% of all cerebellopontine tumors. -Arise from posterior surface of petrous bone. -Form obtuse angle with cerebellum whereas acoustic neuromas form acute angle. -Usually have better pure tone hearing than VIII nerve schwannomas. -Are more vascular and image is less bright on MRI with gadolinium. b. Arachnoid Cysts -Duplication of arachnoid near IAC. -Smooth appearance on scans. Do not enhance. -Treat with surgical decompression via shunting or excision of cyst wall. -Very high recurrence rate. c. Medulloblastoma -Tumor extends from cerebellum to cerebellopontine angle on scan. 8. Sudden Sensorineural Hearing Loss -Definition: loss of at least 30 dB in three contiguous frequencies in not more than three day period. -Must rule out causes such as neoplasms, syphilis, autoimmune disorders, trauma, ototoxins. -Three hypothesis for SSNHL of unknown etiology a. Vascular compromise (less likely in young) b. Viral infection c. Labyrinthine membrane break -Histological and serological studies as well as a clinical response to steroids point to a viral etiology in up to 80% of cases. -Treatment should be directed at most likely cause. Young people with SSNHL and negative work-up should be started on steroids. If history suspicious for membrane break, rapid protein test and exploration for positive test may be beneficial. -Argument against PLFs as cause is finding of patencies of capsule without sudden SNHL. -Fisch showed oxygen tension in patients with SSNHL to be 33% of that in patients with otosclerosis. Carbogen has been shown to result in better one year hearing thresholds when compared to no treatment or treatment with vasodilators and may therefore be indicated in patients suspected of having vascular compromise. -Mattox has reported a 65% spontaneous recovery rate, with recovery less likely in patients over 40. -Recovery usually occurs in 2-4 weeks. After this time recovery unlikely. -Prognosis poor in patients with vestibular symptoms or evidence of embolic phenomenon. V. Diagnosis A. Key Points -Early diagnosis of hearing loss crucial as delay of intervention will result in delay of speech acquisition, cognitive abilities, social interaction etc.. -To facilitate optimum language development, acquisition of receptive language must be initiated preferably by 4 mos and no later than 8 mos. -No child is too young for audiologic testing B. History -Complete history essential -Inquire about noise exposure, ototoxin exposure, family history, vestibular symptoms, other cranial nerve deficits, history of meningitis, syphilis or otitis, pre and perinatal infections, perinatal trauma etc... -High risk registry screening questionnaire important. 1. blood relative with childhood hearing loss 2. non-bacterial fetal infection (TORCH) 3. anatomic malformations of head and neck 4. birth weight less than 1500 gms 5. unconjugated bili >25mg/dl 6. bacterial meningitis 7. severe asphyxia C. Physical -Complete physical, including exam for skin lesions or rashes, ophthalmic exam, neurological testing looking for nystagmus, cranial nerve and cerebellar dysfunction, and complete otoscopic exam including fork testing. D. Ancillary Studies -TORCH labs, ie urine for CMV, elevated IgM, FTA-Abs -UA for protein, RBCs -TFTs, perchlorate test (Pendred's) -EKG (Jervell and Lange-Nielsen) -CT looking for congenital malformations -MRI with gad. for acoustic neuroma E. Audiologic Exam 1. ABR -For screening of infants identified as "at risk" by High Risk Registry. -Sensitivity of ABR in determining presence of retrocochlear lesion is ~84%. Specificity is reported at up to 99% -Cornerstone of objective audiometry in neonate -Absolute latencies of waves I and V prolonged but normal interpeak latency associated with CHL -Normal absolute and interpeak latencies with increased thresholds associated with cochlear loss -Abnormal interpeak latencies associated with retrocochlear or CNS abnormality 2. Behavioral audiometry -See responses at ~ 2 mos . Useful up to ~ 12 mos -Calibrated pure tone stimulation, noise, and speech signals are used to elicit a response -Observe for arousal from sleep, eye-blinking, changes in respiratory rate in younger infants and head-turn in older infants 3. Visual reinforcement audiometry -~9-24 months of age -Calibrated sound stimulus reinforced with either a blinking light or an animated toy located above the speaker through which the sound presented -Decreases response habituation and increases examiner's control of child's response 4. Play audiometry -2-4 years -Child is told to listen and identify the picture that is named through the speaker or perform a task at the sound of a tone -Both air and bone conduction thresholds can be tested 5. Standard audiologic battery -Useful ~3 years of age -Air and bone conduction pure tones speech reception thresholds with tympanograms etc... -Stapedial reflex and reflex decay (decay to less than 50% original amplitude in 10 seconds is abnormal and sign of retrocochlear lesion. Reported to be 92% specific). -Recruitment (evidence of cochlear lesion) -Tone decay (change in threshold with continuous acoustic stimulation. Evidence of retrocochlear lesion) -Rollover (decreased speech discrimination of more than 20% at high intensities. 88% specific for retrocochlear lesion). 6. Otoacoustic emissions -Product of outer hair cells -Detected best at 1-2kHZ as transmission through middle ear most efficient -Less time-consuming than ABR, can potentially be tested by trained nursing staff in nursery and therefore be less expensive. -Allows more widespread screening -More false positives -Need to have essentially normal middle ear -Recent study of screening in infants revealed infants with ABR wave V thresholds less than or equal to 30 dBHL always had OAE those with thresholds >40 had no clicked evoked OAEs -4 classes of OAEs exist a. Spontaneous OAEs -occur despite absence of acoustic stimulus -detected in ~50% of people with normal hearing -occur in twice as many women as men b. Evoked OAEs -found in essentially all normal ears i. transiently evoked OAEs -evoked by short duration or transient signals (click or tone-burst ii. stimulus frequency OAE -evoked by low level continuous pure tones -most of the energy of emission at stimulus frequency iii.distortion product OAE -2 continuous pure tones separated in frequency by prescribed distance as stimulus -provides frequency specific information VI. Treatment A. Medical and surgical treatment as indicated by etiology of hearing loss and Rx of factors contributing to underlying HL, ie OM B. Counseling and Education 1. Oral training -recommended for child without developmental delay who has mod-severe HL or who is postlingually deaf. -emphasizes use of residual hearing -best channel for acquisition of speech and better voice quality 2. Total communication -sign language and lip reading in addition to above. -good for patient with developmental delay or late diagnosis of HL 3. Support group referrals. 4. Education on available resources for hearing impaired. 5. Education on prevention of further loss. C. Amplification Options 1. Assistive Learning Devices -Good for classroom, lecture setting -Amplification systems that improve signal to noise ratio by 15-20 dB in moderate noise. 2. Personal Hearing Aids 3. Cochlear Implants -Consists of microphone which sends acoustic information to processor which is worn externally. The latter serves as a transducer to convert mechanical information into electrical signals. The final component is the implanted electrode -Electrodes differ by number of channels, electrical configuration (mono verses bipolar), and site of placement (extra or intracochlear) -Multichannel implants attempt to produce tonal perception by stimulating different locations in cochlea. -Currently accepted minimum age for implantation is 2 years as mastoid and facial recess adequately developed -If patient can't attain an aided speech detection threshold of 70dB SPL and performs poorly on discrimination tests with HA, cochlear implant indicated -Patients should have no medical contraindications to surgery -Successful use in children requires participation in rehabilitation program not only to learn how to use the device but also for communication therapy. -------------------------------------------------------------------------------- Bibliography 1. Bluestone, C.D., and Stool, S.E.; Pediatric Otolaryngology, W.B. Saunders Co., 1990 2. 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