increased hindbrain size hindbrain hyperplasia 2013-11-14T09:53:41Z MP:0012266 MPheno.ontology csmith hyperplastic hindbrain hyperplastic rhombencephalon overdevelopment or increased size, usually due to a increased 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 rhombencephalon hyperplasia