ABSTRACT
The differential diagnosis in a child/teenager who develops progressive neurological regression, ataxia, and myoclonic epilepsy includes the progressive myoclonic epilepsies. Early on in the evaluation process, the hereditary ataxia syndromes would be a consideration if the ataxia component was predominant. However, the presence of myoclonia and myoclonic seizures would be more consistent with the progressive myoclonic epilepsies. There are four main elements of the progressive myoclonic epilepsies: (1) myoclonic jerks that are segmental, fragmentary, and erratic in region; (2) epileptic seizures-mainly generalized tonic-clonic and massive myoclonic seizures; (3) progressive mental deterioration; and (4) variable neurological signs and symptoms-mainly cerebellar, extrapyramidal, and action myoclonus. Most are genetically determined, and all have a neurologically degenerative course. The signs and symptoms are usually specic or highly suggestive of a particular type of epilepsy. The typical progressive myoclonic epilepsies include: Unverricht-Lundborg disease, myoclonus epilepsy with ragged red bers (MERRF), Lafora body disease, Sialidosis type 1, neuronal ceroid lipofuscinoses, juvenile neuronopathic Gaucher disease, dentatorubral-pallidoluysian atrophy, and juvenile neuroaxonal dystrophy. Most feel that the concept of a denite syndrome of progressive myoclonic epilepsy is archaic, as many epileptic syndromes may have transient episodes of ataxia and/or mental regression and are not genetic. However, the term progressive myoclonic epilepsy has been maintained in the new guidelines for classication of seizures and syndromes.
