hypnic headache https://github.com/monarch-initiative/mondo/issues/9097 https://www.malacards.org/card/hypnic_headache GARD:0010796 ICD9:339.81 Conditions in which the primary symptom is headache and the headache cannot be attributed to any known causes. MONDO:0017181 Orphanet:276429 MEDGEN:156012 HP:0012459 ICD10CM:G44.81 hypnic headache (disease) hypnic headache MESH:D051270 icd11.foundation:468065426 SCTID:122711000119109 hypnic headache (disease) UMLS:C0752150 headache disorder