Low Cerebrospinal Fluid Pressure Headache.

Alterations in cerebrospinal fluid (CSF) pressure lead to neurologic symptoms, the most common clinical manifestation of which is headache. Typically, the headache is orthostatic and related to traction on pain-sensitive intracranial and meningeal structures, distention on periventricular pain-sensitive areas, and direct pressure on pain conveying cranial nerves. Low CSF headache is a distinct and familiar syndrome that is seen most frequently following lumbar puncture. In this clinical scenario, the diagnosis and proposed plan of treatment are obvious. Over the past decade, however, an emerging syndrome of spontaneous intracranial hypotension (SIH) is being recognized with increasing frequency. Most of these patients are found to have spontaneous CSF leaks and have unique, clinically distinct imaging findings, which confirm the diagnosis leading to appropriate treatment. Spontaneous intracranial hypotension is a relatively benign and usually self-limiting syndrome of orthostatic headache in association with one or more of numerous symptoms including nausea, vomiting, horizontal diplopia, unsteadiness or vertigo, altered hearing, neck pain/stiffness, interscapular pain, and occasionally visual field cuts. The headache itself, while often orthostatic, may initially be non-positional, may lose its orthostatic features, or rarely or never be orthostatic. It may be gradual, subacute, or thunderclap in onset. There may be a history of minor, antecedent trauma. By very definition, the opening CSF pressure is low, below 60 mm H(2)O, and often a "dry" tap is encountered. However, the pressure may be normal, especially with intermittent leaks and may vary tap to tap. Fluid analysis is normal. Brain (and occasionally spinal) MRI studies, with gadolinium enhancement should be undertaken. In patients with SIH, studies typically reveal diffuse pachymeningeal enhancement, frequently in association with "sagging"of the brain, tonsilar descent, and posterior fossa crowding. Spinal MRI is an up and coming investigational technique, which may be helpful even in the case of a normal brain MRI. Computed tomography myelography is the diagnostic study of choice and may follow radiocisternography, which often shows absence of activity over the convexities and early appearance of activity in the renal/urinary tract. Although conservative measures are often undertaken first, epidural blood patch (EBP) is the treatment of choice. For those who fail EBP, surgery may need to be undertaken in those cases with clearly identified leaks.