Transependymal edema

Transependymal edema, also known as interstitial cerebral edema or periventricular lucency (PVL), is a type of cerebral edema that occurs with increased pressure within the cerebral ventricles. FLAIR is the most sensitive MRI sequence for detection.

Pathology

The ventricular ependymal lining is eventually disrupted, allowing for the transependymal migration of cerebrospinal fluid into the brain parenchyma around the cerebral ventricles. This is usually seen surrounding the lateral ventricles in the setting of an acute obstructive hydrocephalus.

Radiographic features

CT
MRI 
  • halo of high T2 or FLAIR signal around the lateral ventricles

Practical points

It is important to distinguish interstitial edema from a commonly seen variant of a slight increase in signal anterior to the frontal horns, and posterior to the occipital horns, which is known as ependymitis granularis .

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