decreased hindbrain size hindbrain hypoplasia 2013-11-14T09:53:41Z MP:0012264 MPheno.ontology csmith hypoplastic hindbrain hypoplastic rhombencephalon rhombencephalon hypoplasia underdevelopment or reduced size, usually due to a reduced number of cells, of the part of the brain developed from the posterior of the three primary brain vesicles of the embryonic neural tube from which the metencephalon and myelencephalon are derived