Imaging description

Intracranial hypotension (IH) is characterized by cerebrospinal fluid (CSF) hypovolemia induced by lumbar puncture, surgical CSF leaks, or spontaneously developing CSF leak (spontaneous intracranial hypotension, SIH). Irrespective of the causation, the imaging findings tend to be similar and rather pathognomonic. These imaging features have been best described in the context of SIH.

Characteristic imaging features include presence of diffuse pachymeningeal enhancement, subdural fluid collections, engorgement of venous structures, pituitary hyperemia, and sagging of the brain (pseudo-Chiari malformation). The subdural collections are generally thin, bilateral hygromas and seen over the convexities (Fig. 48.1). However, subdural hematomas with variable mass effect on the brain parenchyma may also be noted. Pachymeningeal enhancement is the best-known manifestation; it is typically diffuse and non-nodular, and spares the basal meninges. Sagging of the brain is quite specific and can be accompanied with downward bowing of the optic chiasm, effacement of the prepontine cistern, and descent of cerebellar tonsils (Fig. 48.2). Numerous findings have also been described on spinal imaging (Fig. 48.3), including diffuse dural enhancement, subdural CSF collections, dilated epidural veins, and retrospinal C1–C2 fluid collections. The localization of CSF leak may require CT myelography or MRI with intrathecal gadolinium administration.