The diagnosis of LGS requires the combination of the EEG criteria and clinical seizure types previously noted. The frequent tonic and atypical absence seizures, with an EEG that has slow spike-and-wave complexes and fast rhythms (polyspikes in sleep) on a diffusely slow background are the most indicative features of this syndrome. The onset is typically in a pre-school age child. However, not all of the features may be present at onset, and tonic seizures in sleep are not always easy to detect. An EEG during sleep may be necessary to detect the tonic seizures or generalized polyspike bursts. In children without a cause, diagnosis at onset can be difficult, as there is no biologic marker for LGS. Close follow-up, with repeat EEG may be necessary to establish the diagnosis.

The initial evaluation consists of detailed birth history, history of the seizures over time, history of any associated medical problems and a complete physical and neurological examination. A minimum initial work-up consists of a high quality MRI of the brain using an epilepsy protocol, and EEG with wake and sleep recorded (with photic stimulation and hyperventilation, if the patient can cooperate for the latter), and baseline hematology, serum chemistries and liver function tests.

Other testing may not be needed if a cause is determined from the initial history or examination. Children with no apparent cause may require further testing to define an underlying metabolic or genetic cause. This typically includes assays of blood or urine specimens, but may also include assay of cerebrospinal fluid by lumbar puncture.

Author: James Wheless, M.D.
Topic Editor: Robert Fisher, M.D., Ph.D.
Last Reviewed: 8/7/09