Presence of focal neurological deficits on examination.
Papilodema on fundus exam.
Very young child (<3yr old), VP shunt in situ.
New onset headache(less than 6 months onset) with relentless worsening quality or very severe headache.
Headaches associated with early morning worsening/worsening on awakening.
Headache for more than 6 months duration are unlikely to be associated with positive findings on neuro-imaging. When neuro-imaging is ordered MRI brain should always be preferred (over CT head) and if it does not reveal any definite cause of headache,an MRI-Venography should be done in the same sitting.