An episode of migraine triggered by fasting is coded as 1. Migraine or one of its subtypes.
Diffuse non-pulsating headache, usually mild to moderate, occurring during and caused by fasting for at least eight hours. It is relieved after eating.
A. Diffuse headache not fulfilling the criteria for 1. Migraine or any of its subtypes but fulfilling criterion C below
B. The patient has fasted for ≥8 hr
C. Evidence of causation demonstrated by both of the following:
1. headache has developed during fasting
2. headache has significantly improved after eating
D. Not better accounted for by another ICHD-3 diagnosis.
10.5 Headache attributed to fasting is significantly more common in people who have a prior history of headache. Even though the typical headache attributed to fasting is diffuse, non-pulsating and mild to moderate in intensity, in those with a prior history of migraine the headache may resemble 1.1 Migraine without aura. If the criteria for this disorder are met, the headache should be coded accordingly (fasting being a precipitating factor).
The likelihood of headache developing as a result of a fast increases with the duration of the fast. Nevertheless, 10.5 Headache attributed to fasting does not appear to be related to duration of sleep, to caffeine withdrawal or to hypoglycaemia. Although headache may occur under conditions of hypoglycaemia-induced brain dysfunction, there is no conclusive evidence to support a causal association. 10.5 Headache attributed to fasting can occur in the absence of hypoglycaemia, insulin-induced hypoglycaemia does not precipitate headache in migraine sufferers, and headache is not a complaint of patients presenting to the emergency department with symptomatic hypoglycaemia.