1. Central Auditory Nervous System Disorders Lecture 16

2. Auditory Nerve Pathways Nerve fibers pass from cochlea through 4 relay stations before auditory cortex ---

4. VIIIth Nerve Tumors Acoustic Neuroma – slow growing, benign tumor Incidence: 1/100,000 Location: VIIIth nerve fibers pass through a bony canal, from the inner ear to BS called the internal auditory canal (IAC)

5. Acoustic Neuromas Small (less than 1.5 cm) Medium (1.5 cm to 2.5 cm) Large (more than 2.5 cm)

6. Patient Characteristics Onset from 30-50 years of age 55% female/ 45% male 95% unilateral These nerves lie adjacent to each other

7. Clinical Course Symptoms arise from compression, atrophy and invasion of auditory and vestibular nerve 1 st symptom: unilateral SNHL, becomes progressive Tinnitus Dizziness, unsteadiness Pressure in affected ear With increased size of tumor may present with headaches, dysphagia, dysarthria etc. Other cranial nerves may be involved

8. Differential Diagnosis MRI or C/T Scan Vestibular Tests Audiometric Battery:  PTA:  Sp.Recognition  Tympanogram:  OAE’s:  ABR:  I-V  Threshold where wave V observed

9. Treatment Observation Repeat audiological evaluations Amplification Surgical Removal: Partial Total Radiation

10. Multiple Sclerosis (MS) Degenerative autoimmune disease of CNS Plaques develop and result in demyelination Onset in early adulthood 20-40 Caucasians 2x more likely than other ethnic groups Genetic influence: 1/1000 If family hx, 3/100 Hearing problems HL uncommon @6 % 40%w audios WNL report difficulty hearing in BN

11. MS PTA: Sp Recognition: Tympanogram: OAE: ABR: I-V Lowest level wave V threshold

12. Neurofibromatosis Genetic disorder of the nervous system that affects development of neural cells Causes dozens of neuromas in internal auditory canal Causes skin changes and bone deformities New cases without a genetic cause can arise Present with bilateral SNHL Two types NF1 NF2

13. NF 1 NF1: Autosomal Dominant changes in skin appearance, Café au lait spots Non cancerous tumors develop under the skin, around eyes, spinal cord Symptoms evident at birth or during infancy and almost always by the time a child is about 10 years old Incidence 1/4000

14. NF 2 NF2 : AD Bilateral tumors on the VIII th cranial nerve Tumors cause pressure damage to other cranial nerves – more often affect hearing HL as early as the teen years Headache, tinnitus, often affects the eyes Incidence; 1/33,000

15. Treatment Control of symptoms Surgical removal Risk of regrowth Genetic testing NF2 – Auditory Brainstem Implant

16. Auditory Neuropathy/Auditory Dysynchrony (AN/AD) Describes a condition where client has normal hair cell function, but abnormal neural function “Synchrony” disorder within the spiral ganglion cells or the auditory nerve BEFORE it enters the brainstem Can co-exist with any degree of hearing impairment (mild – mod)

17. Estimates of Incidence No clear cause Jaundice, LBW, prematurity, inadequate supply or oxygen 10% of children who have been in the NICU 0% of children who have been in the well baby nursery Can co-occur with other disorders  Charcot-Marie Tooth – Motor & sensory nerves  Friedreich’s Ataxia - vision, HL, and slurred speech

18. Characteristics No single entity, patient variation Greatest effect is on neural processing of auditory stimuli No progress with auditory skill or inconsistent skills No benefit from HA’s Difficulty learning language by auditory means alone Expressive and receptive S/L problems Strong visual learners

19. Developmental Profile of AN/AD Changes in abilities over time Wide variation in audiogram responses over time Some infants with AN/AD have recovered Some children with ANAD have been successful CI users

20. Audiometric findings PTA SpRecognition Tympanogram OAEs ABR: Cochlear microphonic –

21. Interventions Alternatives to auditory only input Visual input, Sign Language, Speech Reading Ongoing ENT consult Cochlear Implant The VALUE of a REFERRAL

22. Useful websites on AN/AD www.kresgelab.org (see section on information on deafness) www.kresgelab.org Listserve for parents and patients: www.auditoryneuropathy.com www.auditoryneuropathy.com