pseudo-conductive hearing losses bastaninejad, shahin, md, assistant professor of orl, tums,...
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Pseudo-conductive Hearing Pseudo-conductive Hearing LossesLosses
Bastaninejad, ShahinBastaninejad, Shahin, , MD, Assistant MD, Assistant Professor of ORL, TUMS, Amir’Alam Professor of ORL, TUMS, Amir’Alam
HospitalHospital
Definition
Apparent conductive hearing loss on
audiometric testing, that is notnot due to
pathology in the external or middle ear
of Pseudo-conductive Hearing Lossof Pseudo-conductive Hearing Loss
Case Presentation
• 10yr old boy
• CHL in Left ear, found during a routine school-hearing test
• Left side Rinne’s test was negative
• AR in Left ear: Ipsi.neg., Contra.Pos.
• CTnl.
• No history of trauma and…
Hamad Al Muhaimeed, et al. Conductive hearing loss: investigation of possible inner ear origin in three cases studies. The Journal of Laryngology & Otology November 2002, Vol. 116, pp. 942–945
Case Cont.
• The provisional diagnosis was ossicular
disruption medial to the neck of the stapes (to
explain the presence of the contralateral stapedial
reflex)�
• Exploration performed all ossiceles were
mobile, FP was mobile, but Round window
reflex was negative
Importance
Some causes of these pseudo-conductive
hearing losses can be diagnosed without
resorting to surgery
Bibliography
• The concept of inner ear conductive
hearing loss was proposed as early as the
1960s1960s by Gloris and Davis and by Nixon
and Glorig. They proposed stiffness of the
cochlear partition as a possible cause
Proposed Mechanisms for a True Pseudo-CHL
• Third window effect
• lesions in the:– Scala vestibuli– Helicotrema – Scala tympani– Basilar membrane
• Obliterated round window membrane
Transmission ProblemTransmission Problem
Inner ear conductive hearing lossInner ear conductive hearing loss
Normal Cochlear TransmissionsNormal Cochlear Transmissions
key discriminating features
• Presence of AR in the ear with CHL
– Exception: crossedcrossed or may be a normal
stapedial reflexes can be present if there is
fracture in the stapes crura or footplate medial medial
toto the insertion of the stapedius tendon
key discriminating features
• Round window reflex findings:
– Presence When Otosclerosis is suspected
– Absence In the presence of an obviously
mobile footplate
Other differentiating features
Sup.SCC Dehiscence - AudiogramSup.SCC Dehiscence - Audiogram
Differential Diagnosis
• Poor Masking Poor Masking and Poor AudiometryPoor Audiometry:
– Perhaps the most common cause of
pseudoconductive hearing loss is the presence of
a unilateral or asymmetric sensorineural hearing
loss in which the better hearing inner ear is poorly
masked perform tuning fork test in all subjects
– Collapsing ear canals
DDx Cont.
• Functional Hearing Loss:Functional Hearing Loss:
– Must be considered in any patient with an unusual
conductive hearing loss pattern:
• Some subjects who are exaggerating their hearing loss
have difficulty estimating the loudness level of the two
different stimuli different CHL in two consecutive
assessments…
• Also they may have an inverse air–bone gap!
DDx Cont.
• Third Window Third Window can arise from a fistula into the cochlea or the labyrinthine portion of the inner ear– Semicircular Canal Dehiscencies (Superior, Inferior
and Lateral)– LVA– X-Linked Deafness With Stapes Gusher– Dehiscence Between the Cochlea and Carotid Canal– Paget Disease of the Temporal Bone– Some inner Ear Malformations
Saumil N. Merchant and John J. Rosowski. Conductive Hearing Loss Caused by Third-Window Lesions of the Inner Ear. Otol Neurotol. 2008 April ; 29(3): 282–289
DDx Cont.
• Round Window Obliteration
• Inner Ear Mechanical Conductive Loss– One of the types of presbycusis (CHL with
Mixed loss at 4k and 8k)– Changes in BM pliability– Lesions in the scala vestibuli, helicotrema and
scala tympani– Co-existed with some forms of the congenital
hearing losses
DDx Cont.• Missed Middle Ear PathologyMissed Middle Ear Pathology
– Otosclerosis with a flexible suprastructure– Malleus or incus fixation or stiffness– Pathology at the lenticular process of the
incus– Floppy tympanic membrane– Adhesions lysed during the approach for
exploration– Transient pathology at the time of audiogram
Conclusion
Think about plausibility of Pseudo-
conductive hearing loss and include it’s
possibility in your pre-operative evaluation pre-operative evaluation
and patient consentpatient consent before proceeding to
the middle ear exploration