Migraine-like headache attributed to a causative disorder: primary migraine or secondary headache with a migraine-like phenotype?

BACKGROUND: Migraine-like headaches can accompany or be the initial manifestation of many neurological disorders. When a migraine-like headache develops or worsens in the presence of another neurological disorder, there is often uncertainty about whether the headache is true migraine (i.e., the primary headache) or is a secondary headache with migraine-like symptoms. To answer this question, we analyzed headache characteristics and the effect of treatment in several neurological disorders.

MATERIALS AND METHODS: The study was a retrospective analysis of five existing datasets collected by the authors: 1) 670 patients with acute ischemic cerebrovascular disease (550 patients with first-ever ischemic stroke, mean age 63.1 years, 46% females and 120 patients with transient ischemic attacks-TIA, mean age 56.1 years, 54.2% females); 2) 199 patients with intracranial saccular aneurysms (mean age 43.2 years, 52% females); 3) 77 patients with newly diagnosed definite idiopathic intracranial hypertension (IIH) (mean age 28.8 years, 96% females); 4) 169 patients with post-traumatic headache (PTH) attributed to mild traumatic brain injury (mTBI) (mean age 41.5 years, 52.1% females); 5) 59 patients with PTH followed prospectively with a focus on treatment response to prophylactic migraine medication (mean age 37.1 years, 78% females). Detailed information about headache characteristics and outcomes were collected.

RESULTS: Our results demonstrate that a headache phenotypically fulfilling the diagnostic criteria for 1.1 Migraine without aura and/or 1.2 Migraine with aura can be due to a causative disorder with the following incidence: 13.3% in TIA, 6.9% in ischemic stroke, 44.2% in saccular intracranial aneurysm, 51.9% in IIH, 70.8% in acute PTH, and 90% in persistent PTH. Among individuals who had acute headache following stroke, 45.4% developed persistent headache. These headaches attributed to a secondary cause often responded poorly to migraine treatment, at least suggesting that they differ from primary migraine. The migraine-like headaches disappeared after treatment or remission of the causative disorder in 38.5% of cases with IIH, and 47.7% after clipping of intracranial aneurysms, an outcome that would not be expected if the headaches were primary migraine.

CONCLUSION: Our study supports the ICHD-3 statement that migraine-like headache attributed to a secondary cause should be coded as a secondary headache of the migraine type and that it is a migraine mimic attributed to a causative disorder.