Abstracts

Rationale: Lennox–Gastaut Syndrome (LGS) is characterized by intractable seizures, cognitive impairment, and abnormal electroencephalogram (EEG) with generalized 1.5–2.5 Hz slow spike-wave (SSW) discharges. However, an accurate diagnosis of LGS is more complex than simply identifying this triad of characteristics, as its etiologies and features are not pathognomonic. Further, LGS symptoms are not static but tend to change over time, thus its features at onset may not be consistent with those present later in life. To improve LGS diagnosis, we describe the progression of several LGS cases to illustrate changes over time of its symptoms, particularly in EEG features.Methods: A retrospective chart review was conducted for several LGS patients, focusing on symptom changes over time. Two cases are presented below:Results: Case 1: An 8-year-old patient with a history of atonic and tonic seizures and developmental regression was diagnosed with LGS following an EEG showing the characteristic SSW discharges (Figure 1). Despite a normal birth and no history of brain injury/infection, the patient showed signs of developmental delay by early infancy and had partial seizures by 18 months. Fourteen years later (age 22), the patient’s EEG no longer showed SSW discharges, but instead showed low-amplitude background activity with infrequent, low-amplitude generalized discharges and isolated multifocal sharp waves (Figure 2). Case 2: A male patient with multiple intractable seizure types and EEG showing near continuous SSW discharges with frontal predominance, and intermittent spike-waves predominating in the left occipital region, was diagnosed with LGS at age 8. He had a history of severe encephalomalacia with partial seizures and global delay caused by meningoencephalitis in infancy. By age 4, patient had generalized atonic, tonic, and atypical absence seizures. Prior to his sudden unexplained death at age 12, the patient had good, but incomplete, control of partial and generalized tonic seizures, and his EEG showed low amplitude background with infrequent isolated low amplitude generalized discharges and infrequent multifocal sharp waves. We will also describe cases of adult patients that show similar changes over time in LGS features. SSW discharges observed at onset appear to decrease in incidence and be replaced by EEG abnormalities that may be indicative of later (adolescent or adult) stages of LGS. Additionally, seizure types evolve over time, and those observed in adult patients may vary from the seizure types that are more characteristic of early LGS.Conclusions: These cases illustrate the progressive evolution of LGS features and demonstrate the importance of continually evaluating all aspects of a patient’s encephalopathy, while also considering the dynamic nature of LGS. Given the potential for decreased incidence over time of SSW complexes, an LGS diagnosis should not be ruled out when the characteristic encephalopathies are present in the absence of SSW discharges, particularly in adult patients with intractable seizures. Funded by Lundbeck, LLC