Abstract 2- 1025-1040
Category: Clinical

At the end of the session, participants will be able to:

  1. Describe the spectrum of aqueductal stenosis in distinct brain anomalies.
  2. Review the presence of the median dorsal glial septum in primary and secondary brain anomalies.

COI Disclosure:

None to disclose.


Yael Fisher, M.D., is a pathologist, trained in Rambam Medical Center in Haifa, Israel. She completed her residency in
anatomical pathology in 2019. Currently Yael is on a clinical fellowship in molecular pathology at the Pathology and Laboratory
Medicine department in Mount Sinai Hospital.


Yael Fisher1, Orli Greenberg1, Patrick Shannon1

1Pathology and Laboratory Medicine, Mount Sinai, Toronto, ON, Canada

    Target Audience:

    Pathologists, Residents, Medical Students

    Medical Expert (the integrating role), Scholar

    Aqueductal Stenosis And Mesencephalosynapsis In Fetal Brains, Part 2: Associations.

    As part of our review of fetal aqueductal histopathology, we reviewed the brain and autopsy findings accompanying the morphologies of aqueductal stenosis (AS) and mesencephalosynapsis (MeS), the absence of the median dorsal glial septum, in 118 cases of fetal hydrocephalus.  We encountered some novel associations. 1. Rhombencephalosynapsis: 21 of 24 (87.5%) cases of rhombencephalosynapsis demonstrated AS with MeS and 6 cases (25%) demonstrated a mass of neurons resembling heterotopic Purkinje cells obstructing the rostral 4th ventricle/caudal aqueduct. 2. Hemifacial Hypoplasia: we encountered 7 cases of hemifacial hypoplasia (HH) with AS and MeS. On review of central nervous system pathology in HH, of the 21 cases of HH in our archives 7 had hydrocephalus, and all 7 had AS and MeS, including two rhombencephalosynapses. AS with MeS seems to be a principal pathology causing hydrocephalus in HH. 3. Tegmental Injury: we identified 3 cases of symmetrical tegmental injury with calcifications and microglial aggregates, in a pattern suggestive of fetal hypoxic ischemic injury. Two cases had AS with atresia, and one a slit like aqueduct, none had MeS. Tegmental injury in an hypoxic ischemic pattern is an infrequent but distinct pattern producing AS and hydrocephalus. Other distinctive pathologies associated with AS are the VACTERL association (2 with MeS, 5 without), holoprosencephaly (n=8) and ammonic rupture sequence (n=3, all with MeS).