Morphological investigation of tractus spiralis foraminosus and macula cribrosa

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  • Matsuda Shinsaku
    National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center Department of Otolaryngology, Nerima Hikarigaoka Hospital
  • Kaga Kimitaka
    National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center Auditory Clinic attached to Kamio Memorial Hospital

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Other Title
  • ラセン孔列と上，中篩状斑の形態学的検討
  • ラセンコウレツ ト ウエ,チュウフルイジョウ ハン ノ ケイタイガクテキ ケントウ

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Abstract

<p>There are four foraminal structures at the bottom of the internal auditory canal, namely, the tractus spiralis foraminosus (TSF), macula cribrosa superior (MCS)/media (MCM), and facial canal. The cochlear, superior vestibular, inferior vestibular, and facial nerves pass through TSF, MCS, MCM, and facial canal, respectively. TSF, MCS, and MCM show bony cribriform structures. The role and developmental process of these bony cribriform structures has remained unclear, so far.</p><p>The present study aimed to assess 1) the sizes of small holes composing these bony cribriform structures (TSF, MCS, and MCM), 2) the developmental process of ossification of bony cribriform structures during the fetal period and the number of weeks for its completion, and 3) the morphological features and role of bony cribriform structures based on the observation of a case of cerebellar hemorrhage.</p><p>1) The size of small holes of TSF, MCS, and MCM was measured from the continuous pathological specimen sections of the human temporal bone. The results show that the size of small holes of MCS located above the transverse crest is significantly larger than that of TSF and MCM located below the transverse crest. 2) The observations of human fetal specimens showed that the cochlear nerve formation and its distribution into the cochlea precedes the formation of the bony cribriform structure, and the formation of the bony cribriform structure begins around week 17 and is considered to be complete by 21 weeks. 3) In a case of cerebellar hemorrhage, blood had flown into the cochlea at the side of the inner auditory canal of the Scala tympani, but was localized. The bony cribriform structure was composed of the small holes densely packed with the periosteum and the nerves and perineurium that pass through the cribriform structure. The results suggest that one of the roles of the cribriform structure might be to act as a size barrier to protect the inner ear.</p>

Journal

  • Otology Japan

    Otology Japan 32 (1), 47-51, 2022

    Japan Otological Society

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