Malformations of cortical development of the human brain: a pictorial essay.

During development in utero of the human brain, an error in one or more of the orderly processes of neuroblast proliferation and differentiation, neuroblast migration and cortical organization may result in disordered neocortical development. Nowadays, the consequent malformations of the cerebral cortex and associated structures are detectable on pre- and postnatal examination with growing frequency, thanks to the evolution of modern imaging modalities. In particular, magnetic resonance imaging (MRI), due to its excellent contrast differentiation and multiplanar capabilities as well as the development of even newer techniques, such as diffusion tensor imaging and spectroscopy, has surpassed all other forms of imaging for the thorough exploration and analysis of congenital anomalies of the central nervous system. These malformations comprise a heterogeneous group of conditions in terms of both the timing and etiology of the developmental aberration as well as the resulting morphological phenotype, including epilepsy, developmental delay/intellectual disability and focal neurological deficits. This study briefly presents some typical examples of congenital malformations of cortical development of the human brain that are encountered in practice. It is our belief that familiarity with the MRI presentations of these conditions can be of considerable value for adequate disease management and genetic counseling.

Reversible acquired epileptic frontal syndrome and CSWS suppression in a child with congenital hemiparesis treated by hemispherotomy.

A boy with a right congenital hemiparesis due to a left pre-natal middle cerebral artery infarct developed focal epilepsy at 33 months and then an insidious and subsequently more rapid, massive cognitive and behavioural regression with a frontal syndrome between the ages of 4 and 5 years with continuous spike-waves during sleep (CSWS) on the EEG. Both the epilepsy and the CSWS were immediately suppressed by hemispherotomy at the age of 5 years and 4 months. A behavioural-cognitive follow-up prior to hemispherotomy, an per-operative EEG and corticography and serial post-operative neuropsychological assessments were performed until the age of 11 years. The spread of the epileptic activity to the "healthy" frontal region was the cause of the reversible frontal syndrome. A later gradual long-term but incomplete cognitive recovery, with moderate mental disability was documented. This outcome is probably explained by another facet of the epilepsy, namely the structural effects of prolonged epileptic discharges in rapidly developing cerebral networks which are, at the same time undergoing the reorganization imposed by a unilateral early hemispheric lesion. Group studies on the outcome of children before and after hemispherectomy using only single IQ measures, pre- and post-operatively, may miss particular epileptic cognitive dysfunctions as they are likely to be different from case to case. Such detailed and rarely available complementary clinical and EEG data obtained in a single case at different time periods in relation to the epilepsy, including per-operative electrophysiological findings, may help to understand the different cognitive deficits and recovery profiles and the limits of full cognitive recovery.