ABSTRACT
Case Presentation ................................................................................................... 191 Differential Diagnosis ............................................................................................ 192 Diagnostic Approach ............................................................................................. 193 Treatment Strategy ................................................................................................. 194 Long-Term Outcome .............................................................................................. 194 Pathophysiology/Neurobiology of Disease ............................................................ 195 Clinical Pearls ........................................................................................................ 195 Suggested Reading ................................................................................................. 195
This is a nearly 3-year-old boy who was completely well until 6 months ago when he experienced two brief (<2 minute) generalized convulsions 1 month apart, both associated with fever. Although these were diagnosed as simple febrile seizures, he was referred to a pediatric neurologist who ordered a routine 1.5T brain magnetic resonance imaging (MRI) scan. This study was interpreted as normal. However, the outpatient electroencephalogram (EEG) study revealed generalized background slowing and generalized atypical spike-wave discharges occurring at a frequency of 2.0-2.5Hz (See Figure 25.1). A follow-up 24-hour video-EEG study captured multiple generalized myoclonic and tonic seizures, both associated with generalized spike-wave discharges, followed by voltage suppression. No focal or lateralizing features were noted. This patient was placed on valproic acid monotherapy. Despite serum levels (in the 100-120 range), he continued to have frequent seizures and then developed “drop” seizures that became progressively more frequent. Further medication trials with topiramate, zonisamide, levetiracetam, and clonazepam were unsuccessful, and he was ultimately placed on the ketogenic diet. His generalized myoclonic seizures improved substantially, but he was still experiencing several drop seizures per day. Notably, his speech and attention became slowly impaired, and he developed difculty walking, with mild ataxia. A high-resolution (3T) brain MRI was interpreted as normal, and a comprehensive metabolic/genetic workup
Lennox-Gastaut syndrome (LGS) rst appeared in the medical literature in 1969, even though important clinical and EEG features in this subgroup of epileptic patients had been noted as early as 1939. This syndrome comprises a clinical triad consisting of (1) diffusely slow spike-wave discharges (occurring at a frequency of 1.5-2.5 Hz), (2) psychomotor retardation, and (3) multiple electroclinical seizure types refractory to medical therapy (including generalized tonic, atonic, atypical absence, myoclonic, and tonic-clonic seizures). The hallmark seizure type is the generalized tonic seizure that most often occurs while falling asleep. In most cases, LGS manifests between 2-8 years of age, represents 3-10% of all pediatric epilepsies and, in this condition, affects males more frequently than females. There are two general subtypes: (1) cryptogenic (i.e., there is no identiable cause) in approximately
(including genetic testing for severe myoclonic epilepsy of infancy) failed to reveal an etiology. As his neurological condition steadily worsened, he underwent an anterior two-thirds corpus callosotomy as a palliative procedure, to which he responded favorably. Although he experienced a transient left foot drop after surgery, his speech returned slowly (but not fully), and within a month he was able to put three words together again. He was weaned off the ketogenic diet, and remained on a regimen of zonisamide and levetiracetam. His gait and ataxia improved, and he was having only 1-2 “drop” seizures per day, but none of the myoclonic or tonic seizures.
