An episode of migraine triggered by trochleitis is coded as 1. Migraine or one of its subtypes.
Headache, usually frontal and/or periorbital in location, with or without eye pain, caused by peritrochlear inflammation. It is often exacerbated by downward movements of the eye.
A. Periorbital and/or frontal headache fulfilling criterion C
B. Clinical and/or imaging evidence of trochlear inflammation
C. Evidence of causation demonstrated by at least two of the following:
1. unilateral ocular pain
2. headache is exacerbated by movement of the eye, particularly downward in adduction
3. headache is significantly improved by injection of local anaesthetic or steroid agent into the peritrochlear region
4. in the case of a unilateral trochleitis, headache is localized ipsilateral to it
D. Not better accounted for by another ICHD-3 diagnosis.
Trochleitis, defined as inflammation of the trochlea and/or sheath of the superior oblique muscle, can lead to eye pain and frontal headache that are aggravated by movements of the eye involving the superior oblique muscle. While not common, it is not rare, and must be considered when evaluating unilateral periorbital head pain.
Trochleitis can also trigger an episode of 1. Migraine, which is coded accordingly.