central nervous system malformation cystic malformation of the posterior fossa https://github.com/monarch-initiative/mondo/issues/6752 https://github.com/monarch-initiative/mondo/issues/6876 MONDO:0020134 ICD9:742.4 Orphanet:98520 SCTID:35111000119109 MEDGEN:783289 GARD:0025153 UMLS:C3662134