In intracranial hypertension, how will they measure pressure ?

It depends on your signs and symptoms. Testing involves brain scans (CT/MRI) to rule out certain known causes like an SOL (Space Occupying Lesion) though in many patients, these scans may be normal. Venography / Cisternography with or without contrast agents may also be done to rule out thrombosis/ blocked flow. A Guarded Lumbar Puncture with all aseptic precautions may be done to measure / relieve CSF pressure and to test the CSF for known causes. Continuous monitoring is possible, if required,  If your intra-cranial hypertension has existed for more than four to six weeks, an eye examination may show papilledema (swelling of the optic disc). A detailed history may also help solve the issue.