Transependymal edema

Last revised by Frank Gaillard on 13 Jan 2024

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.

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 acute obstructive hydrocephalus.

In more chronic forms of hydrocephalus, including normal pressure hydrocephalus, an increase in periventricular interstitial fluid is also encountered but this can be challenging to distinguish from chronic small vessel periventricular ischemic disease 6.

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

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 3.

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