Epidemiologic studies reveal a marked correlation between CH and prior head trauma (5,6). Narrow nasal passages, such as a deviated nasal septum, are often found on the painful side in CH sufferers (7,8). Surgical resections in this area, to eliminate narrow conditions, are sometimes beneficial (7). Craniometric measures in CH suggest narrowness of the cavernous sinus/hypophyseal fossa region (8). These findings may represent constitutional predisposing factors for CH. Investigations with magnetic resonance imaging (MRI) of the cavernous sinus region outside of CH attacks has not revealed any pathologic changes (9).

By the aid of voxel-based morphometric analysis of MRI scans, an increase in tissue volume within the posterior hypothalamic area has been found in CH sufferers (10). This finding was bilateral, remained outside periods of attacks, and was interpreted as an increase in neuronal density. The area is similar or identical to local findings during attacks of an ipsilateral increase in blood flow (see neuroimaging of cluster headache), as a cause or a consequence of pain.

Several symptomatic cases have been described in which CH-like attacks have evolved secondary to the growth of an intracranial expansive process, ipsilaterally, or in the midline: orbitosphenoidal aspergillus infection (11), parasellar meningioma (12), adenoma of the pituitary gland (12,13), calcified lesion in the region of the third ventricle (14), aneurysm of the anterior or posterior communicating artery (15,16), dilated ipsilateral and aneurysmatic contralateral internal carotid artery (ICA) intracranially (15), granulomatous tissue in the cavernous sinus (17) epidermoid tumor in the clivus expanding rostrally to the suprasellar cistern (18), large arteriovenous malformations in the ipsilateral frontal, temporal, parietotemporal, or occipital lobes (19, 20, 21, 22), meningioma or inflammatory myofibroblastic tumor on the undersurface of the tentorium cerebelli (23,24), and upper cervical meningioma (2).