Question: Encounter notes indicate that a patient suffered from “arnold chiari type 3.” How should I choose an ICD-10 code for this condition? Missouri Subscriber Answer: Your provider is referencing Arnold-Chiari syndrome, type III, which has a few diagnosis code options under the Q01.- (Encephalocele) heading in the ICD-10 manual. There is an answer to this question, but you need one more piece of information to choose the most accurate code: location of the encephalocele. Do this: Go back and check the notes; then, choose from one of the following ICD-10 codes: Other synonyms: According to ICD-10, you’ll choose from the Q01.- code set when a patient suffers from: