Chiari malformation Chiari malformation type I https://www.malacards.org/card/chiari_malformation_type_i MONDO:0007316 MEDGEN:196689 Arnold-Chiari malformation type 1 OMIM:118420 icd11.foundation:1383121646 GARD:0009233 SCTID:253185002 UMLS:C0750929 Chiari malformation type I Arnold-Chiari malformation type I is a central nervous system malformation characterized by caudal displacement of the cerebellar tonsils exceeding 5mm below the foramen magnum with or without syringomyelia. Symptoms vary in onset and severity and include suboccipital headache, neck pain, vertigo, tinnitus, ocular symptoms (diplopia, blurred vision, photofobia, nystagmus), lower cranial nerve signs, cerebellar ataxia, and spasticity. Some affected individuals can be asymptomatic. MedDRA:10056944 Arnold-Chiari malformation type I Chiari malformation type 1 Orphanet:268882 neural tube defect hereditary neurological disease