Headache as a manifestation of a delusion whose content involves a mechanism that the patient believes explains the headache (eg, headache is the result of a device implanted in the head by aliens).
A. Any headache fulfilling criterion C
B. Presence of a delusion whose content involves a mechanism that would explain the headache (eg, the patient believes that a device has been implanted into his or her head, which is causing a headache, or that he or she has a brain tumour causing headache despite irrefutable proof to the contrary)
C. Evidence of causation demonstrated by either or both of the following:
1. headache has developed with or after the onset of the delusion
2. headache has remitted after remission of the delusion
D. Not better accounted for by another ICHD-3 diagnosis.
Delusions are false fixed beliefs, based on incorrect inferences about reality, that are firmly held despite obvious proof to the contrary. They may involve a false belief that a serious medical condition (eg, brain tumour or aneurysm) is present and causes the headache, despite repeated proofs and appropriate authoritative reassurances that no such medical condition is present. The content of the delusion may be more bizarre, such as the idea of a transmitter being surgically implanted into one’s head and causing the headache.
When the patient first develops a headache (eg, one of the primary headache disorders classified in Part One of ICHD-3 [beta]) and then develops a delusional explanation for the headache, such as its being due to a brain tumour despite no medical evidence in support of that belief, the headache may not be attributed to the psychiatric disorder; instead, the headache should be coded as a primary headache disorder and the patient given the additional psychiatric diagnosis of delusional disorder, somatic type.