Lissencephaly (agyria-pachygyria) is an abnormality of neural migration characterized by absent or reduced cerebral convolutions, affecting the entire brain or distinct cortical districts. Clinical manifestations include mental retardation, hypotonia, intractable epilepsy, microcephaly, dysmorfisms' EEG abnormalities. Exitus, usually, occurs within the first two years of life. Prior to availability of CT and MRI techniques, diagnosis was possible only post-mortem. We present 3 cases with pachygyria confirmed by MRI studies. MRI revealed in all the patients anomalies of neuronal migration (pachygyria, thickened cortex and thinned subcortical white matter). All patients (22, 16, 15 years old) presented severe mental retardation and medically intractable epilepsy. In 2 of them was also evident spastic paraplegia. Different forms of epileptic manifestations were reported with a high frequency of seizure: generalized convulsive, absences and infantile spasms. One patient presented also extremely frequent atonic seizures. EEG findings included high voltage slow waves, spikes and atypical spike-and-wave complexes. The cases are discussed with reference to the late age of observation, the presence of atonic seizures, and of spastic paraplegia. Possible ethiopathogenetic factors are also discussed.
