Final answer:
Classic or Type 1 lissencephaly is characterized by a 'smooth brain' due to inadequate brain folds and grooves along with neurological symptoms like muscle stiffness, seizures, and developmental delay.
Step-by-step explanation:
Classic or Type 1 lissencephaly is characterized by a smooth cerebral cortex with inadequate or absent brain folds (gyri) and grooves (sulci), resulting in a simplified or 'smooth brain' appearance. This malformation is indicative of a neurological disorder in which the normal process of creating these folds is disrupted early in the embryonic development of the nervous system. Common symptoms of lissencephaly include muscle stiffness or hypotonia, seizures, difficulty swallowing, developmental delay, and other neurological deficits. The condition is often caused by gene mutations affecting neural migration. It is crucial to differentiate between lissencephaly and other disorders such as craniosynostosis, spina bifida, or neural tube defects, all of which involve distinct developmental issues within the nervous system.