inner ear conductive hearing loss prof. hamad al muhaimeed prof. yousry el sayed dr. abdulrahman...
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INNER EAR CONDUCTIVE
HEARING LOSS
Prof. Hamad Al MuhaimeedProf. Yousry El Sayed
Dr. Abdulrahman RabahDr. Abdulrahman Essa
Department of ORLKing Abdul Aziz University
Riyadh, Saudi Arabia
Inner Ear Conductive HL
Cochlea prefers 2 functions:
1 )Transmission of sound energy = oval window to basilar membrane
2 )Transduction of the mechanical )acoustic) energy) --> electrical )neural energy) = organ of corti
Inner Ear Conductive HL
• Lesion of hair cells --> SNHL
• Lesions in scala vestibuli, helicotrema, scala tympani, or basilar membrane --> CHL
– Inner ear CHL will be characterized by absent RWR + normal contra- lateral stapedial reflex
Inner Ear Conductive HL
Case 1:
–10 year old boy – Lt. hearing loss – No history of trauma, infections, -ve family history of HL – Otoscopy: NAD – Tuning fork test: +ve Rt.; -ve Lt. = Weber --> Lt.
Inner Ear Conductive HL
Case 1: (cont.)
–PTA – Tympanometry: Ipsilateral stapedial reflex absence Lt., present Rt. > Contralateral - St. reflex was elicited in Lt. – C.T. scan Temporal bone: Normal cochlea, cochlear aqueduct, no signs of cholesteatoma
Inner Ear Conductive HL
Case 1: (cont.)
– Provisional diagnosis: Ossicular disruption medial to neck of the stapedius – Lt. tympanotomy: • intact & mobile ossicles • normal footplate movement • RW reflex -ve
– ABR: conductive nature of HL
Inner Ear Conductive HL
Case 2:
–20 year old girl – Progressive Lt. HL for 5 years – No hx of ear discharge, tinnitus, vertigo or trauma – Otoscopy: NAD – Tuning fork test: Consistent with Lt. CHL – PTA – Tympanometry: Contralateral St. reflex was elicited in Lt.
Inner Ear Conductive HL
Case 2: (cont.)
– C.T. scan : NAD– Lt. tympanotomy: NAD + -ve RWR– ABR: Hearing threshold is 80 dBHL with shifting of wave latency
Inner Ear Conductive HL
Case 3:
– 38 year old man– Bil. HL with tinnitus for 2 years– No hx of ear discharge, vertigo or trauma– Otoscopy: NAD– Rinne: -ve bilaterally Weber test is central– PTA– Tympanometry– Rt. Tympanotomy: NAD + -ve RWR– CT scan: NAD
Inner Ear Conductive HL
History
The concept of inner ear CHL has beenproposed as early as 1960s by Gloris &Davis, Nixon & Glorig )stiffness of thecochlear partition.
Shea: Inner ear CHL occurs in 1:700pts. with otosclerosis.
Inner Ear Conductive HL
Discussion
– Lesion of the external & middle ear affecting the sound conduction or/and the transformer functions --> CHL
– Lesions affecting hair cells [transduction] --> SNHL
– Lesions affecting scala vestibuli, helicotrema, scala tympani, or basillar membrane )sound conduction)--> CHL
Inner Ear Conductive HL
Discussion )cont.)
You should exclude: – Inorganic deafness – SNHL with shadow bone conduction
Diagnosis of CHL in the 3 cases hasbeen confirmed by: 1) Repeated tuning fork test 2) PTA with masking 3) ABR 4) Stapedial reflex
Inner Ear Conductive HL
Discussion: )cont.)
Surgical exploration had excluded anymiddle ear abnormalities includingcongenital cholesteatoma.
Consequently, CHL is most likely dueto an anatomic or functional lesion inthe cochlea proximal to the sensorypart )hair cells).
Inner Ear Conductive HL
Discussion )cont.)
Possible causes of inner ear CHL:
1) Abnormal perilymp pressure - Cremers et al, 1983
2) Stiffness of the basilar membrane - Nodal, 1979
This is more reasonable to cause HL in 3 cases.
Inner Ear Conductive HL
Causes:
– The 1st case is probably due to congenital cause since birth while the others may be acquired.
– The elevated bone conduction threshold seen in some frequencies may be inter- preted as mixed HL secondary to affection of the hair cells by the same aetiological agent.
Inner Ear Conductive HL
Discussion )cont.)
Bone conduction threshold is NOTjust a measure of hair cell function.
Some disorders may falsely enhancethe bone conduction while others mayfalsely decrease it e.g. Carhart effect.
- Dirks, 1985
Inner Ear Conductive HL
Discussion: )cont.)
– Diagnosis & treatment of CHL due to external or middle ear abnormalities are well documented. It includes clinical, audiological, radiological examinations.
– Diagnosis of inner ear CHL is a difficult task.
Inner Ear Conductive HL
Causes:
The 1st two young pts. showed unilateral HLwhile the 3rd case )38 yr) showed bil. HL
– Is the main lying pathology in all cases the same?
– Is this pathology progressive that involved the other side as the age advances?
Inner Ear Conductive HL
Discussion: )cont.)
The anatomic correlate to inner earCHL is not completely understood.
Probably the functional loss is due toimpairment of the vibration of thebasillar membrane as a result ofabnormality in the scala vestibuli,helicotrema, & scala tympani orbasillar membrane.
Inner Ear Conductive HL
Discussion )cont.)
Positive contralateral stapedial reflex:
1) Fractured crurae of the stapedes
2) Ossicular disruption with presence of soft tissue connection between stapes and incus.
Inner Ear Conductive HL
Conclusion:
Three cases of mainly CHL thought to be dueto derangements of the sound conductionfunction of the inner ear.
The pathophysiology is not clear due toinaccessibility of the cochlea for clinicalexamination and lack of histopathologicalstudies. More studies are needed to clarifythis matter.
These pts. need to be followed to see theprogress of inner ear pathologies.