Imaging Findings
The patient was admitted for epilepsy. Besides conventional MRI sequences, proton MR spectroscopy (TR=1500, TE=40 msec), echo-planar diffusion imaging (TR=5700, TE=139.03 msec), and gradient-echo anisotropic diffusion imaging called PSIF (reverse FISP, fast imaging in steady state precession) imaging (TR=21.6, TE=5 msec) were performed.
Discussion
Neurons are generated and proliferate at the 7th week of gestation in the subependymal layer of the ventricles, which is called the germinal matrix. At 8th week the neurons begin to migrate from the germinal matrix to the cerebral cortex, and to the deep nuclei of the brain along the radial glial fibers. This process continues predominantly through the third, fourth, and fifth months of gestation in the cerebrum. Neuronal migration can be inhibited by intrauterine destructive (i.e. ischemia, infections) or metabolic (i.e. inhibition of chemotaxis of neurons) events, resulting in a diverse group of migrational disorders of the brain. In polymicrogyria the neurons reach the cerebral cortex normally (normal migration), however, they distribute abnormally resulting in the formation of multiple small gyri (abnormal organization). Therefore this condition may be classified as a disorder of neuronal-cortical organization. It is generally believed that most of the so-called cortical dysplasias which manifest as focal or diffuse cortical thickenings and infoldings, consist of poymicrogyric cortices, while some may show pachygyria. Findings in the current patient is in conformity with focal cortical dysplasia of the right frontal lobe. Normal MR spectroscopy, and diffusion MRI findings are expected in focal cortical dysplasia, that would contribute to exclusion of a focal or an infiltrating cortical tumor in equivocal conditions.
Differential Diagnosis List
Focal cortical dysplasia of the right frontal lobe
Final Diagnosis
Focal cortical dysplasia of the right frontal lobe
