The effects of add-on lamotrigine (LTG) therapy on EEG paroxysmal abnormalities and background activity are evaluated retrospectively in 53 children and adolescents (mean age 12.5 years) with refractory epilepsy followed at Children’s Hospital, Boston, MA. Multiple seizure types occurred in 25, generalized seizures in 15, and complex partial seizures in 13 patients. After adding LTG, seizures were controlled in 22%, a greater than 50% reduction in seizure frequency occurred in 26%, and less than 50% reduction in 13% of patients. Improvement in the EEG correlated with reduction in seizure frequency, and 12 of 82 EEGs were reported as normal for age after LTG therapy. Compared to baseline records, background activity was improved in 22% and was unchanged in 73%. Interictal abnormalities improved in 38% and were unchanged in 51%. Ictal EEG activity improved in 7 (41%) of 17 patients tested. EEGs of patients with complex partial seizures showed improvement more frequently than those with generalized seizures, 61% cf 41%, respectively. EEG improvement with LTG occurred in patients with childhood absence seizures and Landau-Kleffner syndrome but not with other epilepsy syndromes. EEGs were improved in 28% of patients with idiopathic epilepsy compared to 18% with symptomatic epilepsy. 
COMMENT. LTG add-on therapy improves EEG background activity in addition to decreasing the frequency of interictal and ictal epileptiform discharges. Interictal EEG abnormalities are reduced especially in patients with complex partial seizures, absence, and idiopathic epilepsies. Improvements in the EEG may be expected even in children with severe intractable epilepsy.
Adjunctive LTG therapy in 54 patients, 12 years of age or older, with refractory epilepsy and mental retardation showed decreased seizure frequency and improved behavior in an open-label multicenter study, while the dosage of concomitant antiepileptic drugs was reduced. 
Reversible neurotoxicity (confusion and disorientation) occurred in 3 adult patients with absence status epilepticus following administration of an IV bolus and oral doses of valproic acid. LTG levels were elevated (18-22 mcg/mL) compared to baseline (2.9-7.7 mcg/mL), whereas serum VPA and ammonia levels were in the normal range. Improvement correlated with discontinuing or reducing the dosage of LTG.