This thesis describes several studies on migraine and cluster headache which associate these primary headache syndromes with macrostructural and microstructural changes. Some of these brain changes... Show moreThis thesis describes several studies on migraine and cluster headache which associate these primary headache syndromes with macrostructural and microstructural changes. Some of these brain changes may be congenital, some may represent reversible or irreversible neuroplastic changes as a response of the brain to adapt to external stimuli and others should be considered as brain damage associated with these primary headache syndromes. Cluster headache patients have larger anterior hypothalamic volumes and wider skulls, observations that oppose previous neuroimaging findings and pathophysiological theories. Migraine is associated with microstructural changes in particularly visual processing areas in both cortical and subcortical grey matter and in white matter tracts connecting these structures. These changes might in part be irreversible or mSome migraineurs are also at increased risk of visually detectable changes on MRI, such as infratentorial microbleeds, and in male migraineurs, infratentorial hypertensities. Some migraineurs are also at increased risk of visually detectable changes on MRI, such as infratentorial microbleeds and, in male migraineurs, infratentorial hyperintensities. The underlying etiology of these types of cerebrovascular damage remains elusive and is probably the consequence of a multifactorial process. Show less