Pontine tegmental cap dysplasia: the neurotologic perspective

Otolaryngol Head Neck Surg. 2011 Dec;145(6):992-8. doi: 10.1177/0194599811412729. Epub 2011 Jun 25.

Abstract

Objectives: Pontine tegmental cap dysplasia (PTCD) is a rare congenital malformation. Clinical and imaging findings in 3 patients and the authors' experience with bilateral cochlear implantation in 1 patient are described.

Study design: Retrospective review.

Setting: Two tertiary medical centers.

Subjects and methods: Three patients were evaluated by an otolaryngologist and underwent magnetic resonance imaging (MRI) of the temporal bones and brain. High-resolution computed tomography (CT) scanning of the temporal bones was performed in 2 patients. Imaging findings of the brain, the presence and course of resolvable cranial nerves, the membranous labyrinth, and internal auditory canals were reviewed. Clinical data were reviewed.

Results: All patients demonstrated typical brain characteristics of PTCD. Mild, bilateral cochlear dysplasia was noted in 2, and all had a normal vestibular labyrinth. The cochleovestibular nerves were universally absent bilaterally. The facial nerves were subjectively deficient bilaterally in 1 patient, unilaterally in the second patient, and normal in the third. An accessory canal for the seventh cranial nerve, referred to as a duplicated internal auditory canal, was present in all patients. Auditory brainstem response testing revealed profound bilateral sensorineural hearing loss in all of the patients; none suffered facial weakness. A single patient underwent bilateral cochlear implantation with only minimal response.

Conclusion: The authors report 3 cases of PTCD with emphasis on imaging of the seventh and eighth cranial nerves and clinical neurotologic findings. All patients manifested duplicated internal auditory canals, a previously unreported finding in PTCD. Bilateral profound sensorineural hearing loss is due to absence of the cochleovestibular nerve. Prognosis for cochlear implantation is poor.

MeSH terms

  • Audiometry
  • Brain Stem / abnormalities*
  • Child
  • Cochlear Implantation / methods
  • Electroencephalography / methods
  • Female
  • Hearing Loss, Sensorineural / congenital
  • Hearing Loss, Sensorineural / diagnosis*
  • Hearing Loss, Sensorineural / surgery
  • Humans
  • Infant
  • Magnetic Resonance Imaging / methods
  • Male
  • Nervous System Malformations / diagnosis*
  • Nervous System Malformations / surgery
  • Pons / abnormalities*
  • Prognosis
  • Rare Diseases
  • Retrospective Studies
  • Sampling Studies
  • Syndrome
  • Tomography, X-Ray Computed
  • Vestibular Nerve / abnormalities*