Abstracts

Rationale: Childhood absence epilepsy (CAE) and benign rolandic epilepsy (BRE) are distinct age-dependent epileptic syndromes, and are not considered entities within an electroclinical continuum (PMID: 10487473). However, generalized slow spike-wave (S-W) discharges are not uncommonly seen in patients with BRE. When present, these are thought to be due to secondary bilateral synchrony. In contrast, generalized 3Hz S-W discharges are only rarely seen in BRE. Here, we describe three patients who were diagnosed with both CAE and BRE at different time-points. Two of these patients first presented with CAE and subsequently developed BRE. Methods: We conducted a retrospective review of clinical and EEG records of patients diagnosed with either CAE or BRE at the Alberta Children's hospital from 2007 to 2012. Three patients at our institution were identified as having both CAE and BRE. All were female and age at initial presentation ranged from 6 to 9 years. Results: The first patient had a history of absence epilepsy successfully treated with valproic acid (VPA). She developed staring spells associated with generalized 3 Hz S-W discharges. After two years of seizure freedom, a follow-up EEG was obtained which showed independent left and right central temporal spikes with a tangential dipole consistent with BRE. The patient was not experiencing any clinical seizure activity and it was recommended that she be weaned off VPA. A second patient was diagnosed with CAE at 7 years of age. Her EEG showed generalized 3 Hz S-W discharges. Seizures were well-controlled on VPA. A follow-up EEG one year later showed electrographic features that were consistent with both BRE and CAE. A third patient was diagnosed at age 9 with BRE confirmed with a characteristic EEG pattern on initial EEGs. Clinical seizures were also consistent with BRE (nocturnal with sensory changes involving the face and mouth followed by secondary generalization). The patient was treated successfully with oxcarbazepine. On a follow-up EEG 2 years later, there was evidence of generalized 3 Hz S-W discharges. Conclusions: Our cases suggest that in some patients with idiopathic epilepsies, there may be an atypical course or perhaps a continuum between CAE and BRE. Another possibility is that electroclinical conversion from one phenotype to another may be induced by antiepileptic drugs such as ethosuximide and phenobarbital (PMID: 22467741 and 12018965). It is possible that oxcarbazepine may have induced 3 Hz S-W discharges in our third patient. Based on published reports, CAE is thought to develop rarely in patients who were initially diagnosed with BRE; however, two of our patients had a reverse presentation. It is important for clinicians recognize that patients may evolve from BRE to CAE and vice-versa. The mechanisms underlying this unusual ontogeny remain unclear and require further study.