Cochlea Project

Question 1

Main points:

Answer 1

• Cochlear hyperintensity on T1 is more common in preterm than term patients
• This hyperintensity is potentially associated with hearing loss
• Cochlea should be scrutinized in premature infants
• Signal alterations should prompt early ENT referral for potential treatment

Question 2

Weissman, Jane, Hugh, Curtin: High Signal from the Otic Labyrinth on Unenhanced MRI

Answer 2

• 2 Case reports showing increased precontrast T1 signal in labyrinth (associated with hearing loss) - in adults
• Presumed hemorrhage (although no histologic proof)
• Discusses other potential causes of high signal: elevated protein content, fat, slow flow.
• Things that this article does that you should too:
  
  • Defines what T1 bright means (normally the labyrinth is low on T1 - intermetdiate b/w CSF and brain - high signal is hyperintense to contralateral labyrinth and iso to adjacent cerebellum) (this doesn’t make sense?) but they do use ROI signal intensity measurements (should we do that?) - seems more quantitative?
  • Reference: experimental venous occlusion in animals has been shown to cause hemorrhage into perilymphatic/endolymphatic spaces (Perlman, Kimura - Experimental Obstruction of venous drainage and arterial supply…)

Question 3

Casselman: Pathology of the Membranous Labyrinth

Answer 3

Value of Non-Con T1 in differntiating labyrinthitis from proteinaceous fluid/subacute hemorrhage

Question 4

Tan: Deafness due to hemorrhageic labyrinthitis…

Answer 4

Shows that bright signal can be related to suppurative labyrinthitis .

• References: Animal studies/electrophysiological studies demonstrating cochlea as site of lesion - S.Suis entering the perilymph via the cochlear aqueduct through lytic actions of exotoxins
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Question 5

Tarlow: Endotoxin induced damage to the cochlea in guinea pigs

Answer 5

Showed that bacterial endotoxin can damage cochlea in guinea pigs

Question 6

Bachor: The cochlear aqueduct in pediatric temporal bones

Answer 6

1. Cochlear aqueduct connects perilymphatic space of basal turn of cochlea with subarachnoid space of the posterior cranial cavity.
2. The cochlear aqueduct has been shown to be patent in newborns.

Question 7

Shogo Shinohara: Clinical features of sudden hearing loss…

Answer 7

• 5 case reports of sudden hearing loss with increased signal unenhanced T1
• Good info: reference #3 (Pathology of the ear by Schuknecht) - can’t find - basically two things:
  
  • Spontaneous hemorrhage into the inner ear occurs as a complication of bleeding disorders (bleeding diathesis) most commonly leukemia - confirmed on histological studies.
  • Red blood corpuscles typically have a life span of 120 days in the vascular system, but in 2 cases, increased signal lasted for 6 months. This same reference showed that in experimental animals, red blood corpuscles were shown to have an extended lifespan of more than 5 months in perilymphatic fluid. (may be why signal was longer than expected)