Clinical History: 29 year old with possible atypical absence seizures.
Diagnosis: Gray Matter Heterotopia
Discussion: Gray matter heterotopia is defined as abnormally positioned but otherwise normal neurons. These cells are found anywhere along their normal migration path along radial glial fibers from ependyma to cortex. Multiple variations are described including focal or diffuse, and nodular or band. The lesions always appear isodense and isointense to normal gray matter. No enhancement is demonstrable. Clinically patients present with seizures, in some cases these are intractable. Isolated familial occurrences are reported though the majority are sporadic. Nuclear studies have shown glucose metabolism equal to that of normally positioned gray matter.
In the case presented focal nodular gray matter heterotopia is shown on proton, T2, T! and T1 contrasted images. The abnormal neuronal collection is seen in a subependymal position along the superolateral border of the mid left lateral ventricle. Differential consideration might include a subependymal nodule of tuberous sclerosis. However no other associated abnormalities and no abnormal calcifications are present. Subependymal nodules in Tuberous Sclerosis do not follow gray matter signal.
References: Osborne,AG, Diagnostic Neuroradiology, Mosby, pp.44-52,1994.
Kamurok,K & Tenokuchi,Y, Familial and PeriventricularNodular Heterotopia, Brain & Development 15:237-41, 1993.
Huttenlocher,PR, Taravath,S & Mojtahedi,S,Periventricular Heterotopia and Epilepsy, Neurology 44:51-55,1994.
Miura, K, et al., Magnetic Resonance Imaging and PositronEmission Tomography of Band Heterotopia, Brain & Development15:288-90, 1993.
Submitted by:Jeffrey L. Sunshine, M.D.Jonathan S. Lewin, M.D.Neuroradiology