"may suggest cerebral venous sinus thrombosis, preeclampsia, post-dural puncture headache from a spinal anaesthetic, etc."
"cluster headache is a rare primary headache disorder, affecting ~0.1% of the population 5"
"part III: neuropathies & facial pains and other headaches"
"Headache, also known as cephalgia (cephalalgia), is defined as pain or discomfort originating from pain-sensitive structures within the head or face. They may affect extracranial (skin, muscles, and blood vessels of the head and neck, mucosa of the sinuses, and dental structures) or intracranial structures (regions of large arteries near the circle of Willis, the great intracranial venous sinuses, parts of the dura mater and dural arteries, and cranial nerves). Although most causes of headache are benign, sometimes headache can herald serious underlying medical conditions."
"Generally, headache pain originates from the stimulation of surrounding pain-sensitive structures, which include blood vessels, meninges (the protective membranes surrounding the brain and spinal cord), muscle fibres, facial structures, and cranial or spinal nerves 7. The perception of headache results from the stretching, dilatation, constriction, or any other nociceptor stimulation within these structures 7. While the general mechanisms of pain perception are understood, the precise pathophysiology of primary headaches remains complex and is not yet fully elucidated, with multiple interacting mechanisms likely contributing to their manifestation 7."
"this section is reserved for research purposes, containing diagnoses or alternative criteria for which there is currently insufficient evidence for inclusion in the main body of the classification 2"
"systemic symptoms (e.g. fever)"
"neurological deficit or dysfunction (e.g. weakness, diplopia, visual field loss, seizure, altered conscious state)"
"may suggest any intracranial pathology or a systemic process (e.g. giant cell arteritis)"
"pathology of the immune system (e.g. HIV, immunosuppression)"