How often is a contrast-enhanced brain MRI truly normal in the setting of spontaneous intracranial hypotension?  

I am aware that the radiological signs can be subtle or overlooked, or confused with a Chiari malformation, hence, I will typically review images with a fellowship-trained neuroradiologist when the clinical suspicion is high. I have read that contrast brain MRI is ~80% sensitive, so I will sometimes order heavily T2-weighted spine imaging as well and/or refer to a subspecialist, but I am not sure if this is necessary.