A Few Imp Points:
Is it Intra Cranial Cause ?
Most important aspect is to exclude any intracranial pathology of headache. If associated with any signs of raised ICP , signs of meningeal irritation or neurological signs/symptoms, it is alarming and needs neuroimaging like CT brain/ MRI. And may also need CSF pressure measurement & CSF analysis.
SAH usually cause sudden onset headache which may be very severe ( severity doesn’t exclude SAH) may be associated with signs of meningeal irritation without signs of infection. Meningitis will usually has inflammatory clues with signs of meningeal irritation.Space occupying lesions (SOL)like Tumour, abscess, aneurysm, hydrocephalus etc usually cause headache with papilledema, headache worse during sleep and patients wakes up with headache.
SOL headache usually wakes the patient from sleep, whereas depression related headache starts after waking up.
Is it a complex migraine ?
Migraine can also be associated with focal neurological s/s due to vasospastic element, but these deficits are reversible. Migraine can present just with neurological deficit without headache. Commonly confused with TIA/ Stroke. Patient may have first episode of complex migraine presenting with neurological deficit. So absent past history of migraine doesn’t exclude migraine as a possibility but of course this situation will be diagnosis of exclusion.
Typical migraine may have aura ( warning symptoms due to vascular/chemical brain dysfunction). Usually unilateral, throbbing, associated with nausea/vomiting, worse with activity and lasting for 2-48 hours. But chronic migraine is a well known entity which may last for week(s). It can be occipital or retro-orbital as well.
Is it GCA ?
Any one above 50-60 with headache it’s important to exclude Giant Cell arteritis ( Temporal artery tenderness/ hardness etc, high ESR, inflammatory s/s, poly myalgia rheumatica etc).
Is it Trigeminal Neuralgia?
Trigeminal Neuralgia is an important cause with hyper aesthesia. Pain get worse by touching the skin, air blowing the cheeks, brushing the teeth , chewing etc but HYPER AESTHESIA is important feature which differentiate it from other local cause. Aneurysm irritating trigeminal nerve is imp cause to exclude.
Is it Extra Cranial Cause ?
Headache can be due to any structure in head & neck. So thorough assessment of head and neck anatomical structures like ENT, visual assessment, tooth, cervical muscles, cervical spine etc is essential.
Is it Psych related Headache ?
Psychiatric/Psychogenjc cause like Tension headache, depression etc are important and very common especially in long standing headache which is more like constant pressure like headache more common in females.
Is it a systemic Cause?
Systemic causes of headache like Constipation, Cough, OSA, sleep deprivation, hunger, hypoglycemia,Fever etc are important.