Specific Imaging Findings

Spontaneous Intracranial Hypotension (SIH) typically presents with a “sagging brain” imaging appearance with downward displacement of the brain stem and cerebellar tonsils, loss of the basal cisterns, flattened brainstem, bowing of the optic chiasm over the sella, pituitary hyperemia, and effacement of the ventricles and sulci. Diffuse pachymeningeal thickening is bright on FLAIR images with characteristic contrast enhancement, although absent in some cases. Subdural hygromas or less commonly hematomas can also be found. Clinical improvement is not always accompanied by prompt resolution of the MRI findings. Spinal MRI and CT myelography can demonstrate extra-dural fluid collections indicating the location of the CSF leak. MRI may also show meningeal enhancement and dilation of the internal vertebral venous plexi, especially at C1–C2 level. High T2 signal intensity between the spinous processes of C1 and C2 is highly characteristic for SIH.

Pertinent Clinical Information

SIH is a clinical syndrome in which low CSF volume results in orthostatic headache, occurring within 15 min after a change from supine to standing position, and improvement or resolution after lying down. The headache may be diffuse or localized, most commonly to the occipital and suboccipital regions. Associated symptoms in severe cases include nausea, vomiting, photophobia, vertigo, tinnitus, visual loss, diplopia, and even coma. It can occur following a minor trauma, strenuous exercise, sexual activity, or a bout of sneezing or coughing.