Progressive Myoclonus Epilepsy (PME) with onset between late childhood and late adolescence includes several conditions:
Neuronal ceroid lipofuscinosis
Type I sialidosis
Myoclonic epilepsy with ragged red fibers
Unverricht–Lundborg Disease
Clinical Characteristics and Neurophysiology
Lafora disease
Unverricht–Lundborg disease (ULD)
EPM1, the ULD Gene
ULD is an autosomal recessive PME.
Onset: Between ages 6 and 15 years, following a period of normal development.
Principal characteristics:
Stimulus-sensitive myoclonus: Sudden, brief, shocklike muscle contractions interfering with activities like writing, swallowing, speaking, and walking. Can be precipitated by simple intention to move (Harenko 1961, Koskiniemi 1974a, Koskiniemi 1974b, Koskiniemi 1974c).
Tonic-clonic and myoclonic seizures: Appear early, with other types of seizures potentially presenting later.
