increased hindbrain size hindbrain hyperplasia MPheno.ontology hyperplastic rhombencephalon 2013-11-14T09:53:41Z 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 hyperplastic hindbrain rhombencephalon hyperplasia csmith MP:0012266