Cryptogenic late-onset epileptic spasms is a rare epilepsy syndrome characterized by late-onset (after 1 year old) epileptic spasms that occur in clusters, associated with tonic seizures, atypical absences and cognitive deterioration. Language difficulties and behavior problems are frequently present. EEG is characterized by a temporal, or temporofrontal, slow wave or spike focus combined with synchronous spike-waves and no hypsarrhythmia or background activity. The disease is Monarch Disease Ontology entry MONDO_0015585 (cryptogenic late-onset epileptic spasms). Also known as: late-onset infantile spasms.