Sensorineural Hearing loss

SENSORINEURAL HEARING LOSS
  • Lesions of cochlea – sensory type
  • Lesions of VIII nerve and its connections – neural type
  • Lesions of VIII nerve – retro-cochlear lesions
  • Lesions of central auditory connections – central deafness.
  • Tuning Fork Tests:
  1. Positive Rinne test (AC > BC)
  2. Weber lateralized to better ear
  3. Bone conduction reduced on ABC and
  4. Schwabach test
  • Audiometry tests
  1. More often involving high frequencies
  2. Audiometry: No air-bone gap
  3. Difficulty in hearing in the presence of noise
  4. Loss may exceed 60 dB
  5. Speech discrimination poor
CAUSES OF SENSORINEURAL HEARING LOSS
  • Genetic:Nail-patella syndrome,Pendred's syndrome,Treacher-Collins syndrome,Noonan Syndrome,Alport Syndrome,Bartter syndrome and distal renal tubular acidosis
  • The diagnosis of classic alport syndrome is based on X-linked inheritance of hematuria, sensorineural hearing loss, and lenticonus
  • Congenital:Infection by Rubella,Cytomegalovirus,Toxoplasmosis,Hypoplastic Auditory Nerves or Abnormalities of the Cochlea.Presbyacusis; Hearing loss due to aging.
  • Congenital malformations of the cochlea are not contraindications to cochlear implantation
  • Noise induced Hearing loss
  • Malformation of the inner ear
  • Head trauma
  • Disease or Disorder
  1. Inflammatory-Suppurative Labyrinthitis
  2. Kernicterus
  • Late features of kernicterus include upward gaze palsy,sensorineural deafness,choreoathetosis.
  1. Menier's Disease- Episodic vertigo, fluctuating hearing loss, tinnitus and sense of fullness or pressure in the involved ear
  2. Perilabyrinthine Fistula-Fluctuating recurring variable sensorineural deafness is seen .
  3. Cochlear Otosclerosis.
  4. Meningitis
  • In chidren suffering from meningitis,sensorineural hearing loss may occur despite prompt initiation of appropriate antimicrobial therapy.
  1. Diabetes
  2. Viral infections like Measles,Mumps,HIV,Ramsay Hunt Syndrome(Herpes Zoster)
  • Ramsay Hunt Syndrome may present with facial palsy ,facial pain ,vesicles on the canal and pinna,vertigo and sensor neural hearing loss .
  1. Bacterial infection-Syphilis
  2. Paget's DiseaseBasilar Migraine:Headache which is intermittent in episode in associated with tinnitus, vertigo and hearing los
  • Paget's Disease may present with abnormality at upper tibia,Hip and back pain,Sensorineural Hearing loss,Elevated Alkaline Phosphatase,Ivory Vertebra and Cotton Wool Spots in Skull X Ray
  • Tumor:Cerebellopontine angle tumour,Acoustic Neuroma(vestibular schwannoma),MeningiomaHead Trauma
  • The earliest symptom of Acoustic Nerve Tumor is Sensorineural hearing loss.
Ototoxic drugs
  1. AminoglycosidesAntimalarials:Quinine,Chloroquine.
  2. Aminoglycoside class of drugs causes hearing loss by damaging Outer hair cells of basal turn.
  • Irreversible hearing loss is caused by Gentamycin.
  • Analgesic-Salicylates,Indomethacin,Ibuprofen
  • Diuretics:Furosemide,Ethcrynic Acid
  • Cytotoxic drugs:Nitrogen mustard,Cisplatin ,Carboplatin
  1. Miscellaneous:
  2. Alcohol, tobacco, marijuana
  3. Carbon monoxide poisoning
  4. Erythromycin, Ampicillin
  5. Propranolol
  6. Propylthiouracil
  7. Desferrioxamine
  8. Tetanus antitoxin
NOISE TRAUMA
  • Acoustic trauma (single brief exposure)
  • Exposure to noise above 160dB can cause permanent loss of hearing.
  1. Noise induced hearing loss (chronic exposure)A noise of 90 dB SPL, 8 hours a day for 5 days per week is the maximum safe limit as recommended by ministry of labour, govt of India-rules under factories act
  2. Prolonged exposure to noise levels greater 100 dB can impair hearing permanently.
  3. The acceptable noise level that can be tolerated without any damage to hearing is 85 dB.
  • Noise may be expressed in psycho-acoustic index of loudness - the phon
  • Frequency of 2000 to 3000 Hz causes more damage than lower or higher frequencies
  • In Pure Tone Audiogram,Maximum Hearing loss at 4000 hz is seen.
PRESBYACUSIS
  • Sensory neural hearing loss associated with physiological aging in ear
  • Hear well in quiet surroundings but have difficulty in hearing in the presence of background noise
  • Speech heard but not understood
  • Test – Recruitment positive
WHO CLASSIFICATION OF DEGREE OF HEARING LOSS
  • Mild : 26 – 40 dB
  • Moderate : 41 – 55 dB
  • Moderately severe : 56 – 70 dB
  • Severe : 71– 90 dB
  • In Severe hearing loss, the patient fails to understand normal speech, but can understand shouted or amplified speech.
  • Profoud :>90 dB
Exam Question
  • v Paget's Disease may present with abnormality at upper tibia,Hip and Back pain,Sensorineural Hearing loss,Elevated Alkaline Phosphatase,Ivory Vertebra and Cotton Wool Spots in Skull X Ray.
  • Basilar Migraine presents with intermittent headache in association with tinnitus,vertigo and hearing loss.
  • Ramsay Hunt Syndrome may present with facial palsy ,facial pain ,vesicles on the canal and pinna,vertigo and sensor neural hearing loss .
  • Exposure to noise above 160dB can cause permanent loss of hearing.
  • The diagnosis of classic alport syndrome is based on X-linked inheritance of hematuria, sensorineural hearing loss, and lenticonus
  • Psycho-acoustic index of loudness is indicated by the term 'Phon'.
  • In chidren suffering from meningitis,sensorineural hearing loss may occur despite prompt initiation of appropriate antimicrobial therapy.
  • Alport Syndrome,Nail-patella syndrome,Pendred's syndrome,Treacher-Collins syndrome,Noonan Syndrome,Bartter syndrome and distal renal tubular acidosis may be associated with Sensorineural Deafness.
  • Air Conduction is more than Bone Conduction in case of Sensorineural Deafness.
  • Late features of kernicterus include upward gaze palsy,sensorineural deafness,choreoathetosis.
  • Prolonged exposure to noise levels greater 100 dB can impair hearing permanently.
  • Measles,Mumps and Rubella can cause Sensorineural Hearing loss.
  • Fluctuating recurring variable sensorineural deafness is seen in PeriLabyrinthine Fistula.
  • Congenital malformations of the cochlea are not contraindications to cochlear implantation.
  • Aminoglycoside class of drugs causes hearing loss by damaging Outer hair cells of basal turn.
  • Threshhold for moderate hearing loss is 41-55dB.
  • The earliest symptom of acoustic nerve tumor is Sensorineural hearing loss.
  • Presbycusis is Hearing loss due to aging.
  • The acceptable noise level that can be tolerated without any damage to hearing is 85 dB.
  • Menier's Disease is characterised by Episodic vertigo, fluctuating hearing loss, tinnitus and sense of fullness or pressure in the involved ear.
  • Irreversible hearing loss is caused by Gentamycin.
  • In Severe hearing loss, the patient fails to understand normal speech, but can understand shouted or amplified speech.
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