Transmantle sign (brain)

The transmantle sign is an MRI feature of focal cortical dysplasia (FCD), almost exclusively seen in type II focal cortical dysplasia (Taylor dysplasia - also known as transmantle cortical dysplasia for this reason). However, it is not always present, seen in ~45% (range 21-72%) of patients with type II FCD.

In addition to being specific for type II FCD it is also associated with excellent post surgical seizure free outcomes .

Pathology

The transmantle sign is believed to be related to abnormal function of, or injury to radial glial fibers (which go on to transform into astrocytes) and form the scaffolding over which neurons migrate from the periventricular germinal matrix to the cortex .

Radiographic features

MRI

The key feature of the transmantle sign is high T2/FLAIR signal extending from the ventricle to the cortex . It is variably associated with other features of focal cortical dysplasia, such as cortical thickening, blurred grey/white junction and decreased T1 signal (see focal cortical dysplasia article).

Differential diagnosis

The main differential is that of radial band sign of tuberous sclerosis.