▁n erve ▁cells ▁of ▁the ▁my enter ic ▁p lex us ▁in ▁its ▁walls , ▁also ▁known ▁as ▁gang l ion ▁cells , ▁are ▁absent . ▁Hir sch spr ung ' s ▁disease ▁is ▁a ▁form ▁of ▁functional ▁low ▁bow el ▁obst ruction ▁due ▁to ▁failure ▁of ▁ca ud al ▁migration ▁of ▁ne uro bl asts ▁within ▁developing ▁bow el ▁– ▁this ▁results ▁in ▁an ▁absence ▁of ▁par as ym path etic ▁intr insic ▁gang l ion ▁cells ▁in ▁both ▁A uer bach ' s ▁and ▁Me iss ner ' s ▁p lex uses . ▁The ▁dist al ▁large ▁bow el ▁from ▁the ▁point ▁of ▁neur onal ▁arrest ▁to ▁the ▁an us ▁is ▁continu ously ▁ag ang l ionic . ▁It ▁is ▁a ▁rare ▁dis order ▁( 1 : 5 0 0 0 ), ▁with ▁pre val ence ▁among ▁males ▁being ▁four ▁times ▁that ▁of ▁females . ▁ ▁Ach al asia ▁is ▁a ▁motor ▁dis order ▁of ▁the ▁es oph ag us ▁character ized ▁by ▁decrease ▁in ▁gang l ion ▁cell ▁density ▁in ▁the ▁my enter ic ▁p lex us . ▁The ▁cause ▁of ▁the ▁les ion ▁is ▁unknown . ▁▁ ▁My enter ic ▁p lex i ▁destruction ▁has ▁been ▁found ▁to ▁be ▁secondary ▁to ▁Ch agas ▁disease ▁( T . ▁cru zi ▁in fection ▁sequ ela e ). ▁Dest ruction ▁occurs ▁in ▁the ▁es oph ag us , ▁int est ines , ▁and ▁u re ters . ▁This ▁d ener v ation ▁can ▁lead ▁to ▁secondary ▁ach al asia ▁( lower ▁es