Pseudo-conductive Hearing
Losses
Bastaninejad, Shahin, MD, Assistant
Professor of ORL, TUMS, Amir’Alam
Hospital
Definition
of Pseudo-conductive Hearing Loss
Apparent
conductive
hearing
loss
on
audiometric testing, that is not due to
pathology in the external or middle ear
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.
• CTnl.
• 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 refl•
ex)
• 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
1960s 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
Transmission Problem
Inner ear conductive hearing loss
• Obliterated round window membrane
Normal Cochlear Transmissions
key discriminating features
• Presence of AR in the ear with CHL
– Exception: crossed or may be a normal
stapedial reflexes can be present if there is
fracture in the stapes crura or footplate medial
to 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 - Audiogram
Differential Diagnosis
• Poor Masking and Poor 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:
– 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  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 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
and patient consent before proceeding to
the middle ear exploration