Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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August 5, 2021
Cochlear Incomplete Partition Type II and Large Vestibular Aqueduct
- Background:
- Incomplete cochlear partition type II (IP-II) was described in 2002 by Sennaroglu and Saatci. It is the most common dysplasia, representing 50% of all inner ear malformations, and the least severe radiologically detectable cochleovestibular malformation.
- It is thought to be a result of developmental arrest at the seventh week of gestation, explaining the normal size of the cochlea, normal to mildly enlarged vestibule, and more developed internal organization of these structures than in the incomplete partition type I anomaly, which occurs due to developmental arrest in the fifth week.
- Historically, the triad of a cystic cochlear apex, dilated vestibule, and large vestibular aqueduct was referred to as the Mondini deformity.
- Clinical Presentation:
- Clinically, IP-II malformation may be isolated or part of a syndrome, namely Pendred syndrome.
- It may present as progressive or fluctuating hearing loss in the child or as an acute posttraumatic hearing loss.
- In rare cases, the discovery is late in adults in the setting of hearing loss, dizziness, or worsening of childhood deafness.
- Key Diagnostic Features:
- Radiologically, IP-II is defined by a cystic apex of the cochlea secondary to a deficiency of the apical part of the modiolus and deficiency of the interscalar septa between the apical and middle turns, resulting in a smooth contour of the apical and middle turns.
- An enlarged vestibule and a dilated vestibular aqueduct may be associated.
- Differential Diagnoses:
- The principal differential diagnoses are incomplete partition type I (IP-I) and type III (IP-III). In contrast with IP-II, IP-I lacks the entire modiolus and interscalar septa, giving the appearance of an empty cystic structure. Vestibular aqueduct enlargement is more often associated with IP-II than IP-I. The cochlea in IP-III has interscalar septa but an absent modiolus.
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Cochlear hypoplasia type IV has a normal basal turn and severely hypoplastic middle and apical turns, which are located anterior and medially. The labyrinthine segment of the facial nerve is usually located anterior to the cochlea rather than in its normal location.
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Treatment:
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Treatment is based on cochlear implantation as well as surgical management of an oval window fistula if present.
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Patients are advised to wear helmets when playing sports, and total avoidance of contact sports is necessary.
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