History: 15-month-old girl with seizures
Findings: Axial T1- and T2-weighted MR images show diffuse subependymal nodules lining both lateral ventricles. The nodules maintain isointensity with
cortical gray matter on both pulse sequences.
Subependymal grey matter heterotopia
Gray matter heterotopia is a relatively common congenital abnormality that results from an in utero arrest of neuronal migration. The abnormally located gray matter is usually found in the subependymal region of the lateral ventricles, especially around the trigones. Occasionally, the heterotopias will be more peripherally located near the cerebral cortex. Patients come to clinical attention becuase of seizures and developmental retardation.
The grey matter heterotopias are a relatively common group of conditions characterized by interruption of normal neuronal migration from near the ventricle to the cortex, thus resulting in “normal neurons in abnormal locations” .
Heterotopias may be classified into three groups: subependymal heterotopia, focal subcortical heterotopia, and diffuse (band) heterotopia. The imaging hallmark is the isointensity with cortical gray matter on all imaging sequences and the lack of contrast enhancement. These characteristsis allow the radiologist to distinguish the abnormality from the subependymal nodules that occur in tuberous sclerosis.
Tuberous sclerosis (also known as tuberous sclerosis complex [TSC]) is a rare multisystem genetic disease that causes benign tumors to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, intellectual disability, developmental delay, behavioral problems, skin abnormalities, and lung and kidney disease. TSC is caused by a mutation of either of two genes, TSC1 and TSC2, which code for the proteins hamartin and tuberin, respectively. These proteins act as tumor growth suppressors, agents that regulate cell proliferation and differentiation.
Aunt Minnie’s Pearls:
To diagnose gray matter heterotopia, the nodules mist follow the intensity of gray matter on all pulse sequenxes and show no enhancement after contrast administration.