Headache attacks which are believed to be a type of 3. Trigeminal autonomic cephalalgia, but which are missing one of the features required to fulfil all criteria for any of the subtypes coded above, and do not fulfil all criteria for another headache disorder.
A. Headache attacks fulfilling all but one of criteria A-D for 3.1 Cluster headache, criteria A-E for 3.2 Paroxysmal hemicrania, criteria A-D for 3.3 Short-lasting unilateral neuralgiform headache attacks or criteria A-D for 3.4 Hemicrania continua
B. Not fulfilling ICHD-3 criteria for any other headache disorder
C. Not better accounted for by another ICHD-3 diagnosis.
Patients may be coded 3.5.1 Probable cluster headache, 3.5.2 Probable paroxysmal hemicrania, 3.5.3 Probable short-lasting unilateral neuralgiform headache attacks or 3.5.4 Probable hemicrania continua. Such patients either have not had a sufficient number of typical attacks (for example, a first bout of cluster headache), or have had, but fail to fulfil one of the other criteria.