Anterior striatum with dysmorphic neurons associated with the epileptogenesis of focal cortical dysplasia

Neuroimaging of the patient. Magnetic resonance imaging (MRI) (A–C) showed unclearness of corticomedullary border in the left frontal lobe. Magnetoencephalography (MEG) (D–F) revealed a cluster of spike dipoles at the deep white matter of the left frontal lobe and the anterior striatum. MEG was measured using a 204-channel MEG system (VcctorView; Neuromag Co., Helsinki, Finland). Dipole sources with a goodness of fit greater than 80% (circles) were accepted and overlaid on the MRI results. ^99mTc-ethyl cysteinate dimer single photon emission computed tomography (SPECT) with superimposition on the magnetic resonance imaging (MRI) (G–I) after the first operation demonstrated ictal hyperperfusion at the left deep frontal lobe and the nucleus accumbens in red with Z scores greater than 2. MRI after the second operation (J–L) illustrated that the left deep frontal lobe and a part of the nucleus accumbens and the head of the caudate nucleus had been removed. A, D, G, and J: axial view; B, E, H, and K: coronal view; C, F, I, and L: sagittal view.

Intraoperative electroencephalography from the depth electrode inserted stereotactically at the second operation revealed spike discharges from the left anterior striatum. Tentative target of the nucleus accumbens was between A1 and A2 of grids. The interval of each electrodes of the inserted part was 5mm.

Light micrographs of surgical specimen taken at the second operation. (A) Low-power magnification of the area close to the ventricle (ven) demonstrates orientation of the subventricular zone (SVZ) and the anterior caudate head (ch). The ependymal cell lining is indicated by arrowheads. (B and C) Dysmorphic neurons in the caudate head (B) and nucleus accumbens (C). They are scattered between the axon bundles (p: pencil fibers) in the striatum, or closely packed. (D) Dysmorphic neurons in the insular cortex. Klüver-Barrera stain. Bar=370μm for A, and 40μm for B–D.