Observations on the misdiagnosis of generalized epilepsy as partial epilepsy: causes and consequences

More therapeutic options (surgical and pharmacologic) are available for partial than for generalized epilepsies. This report describes and analyzes a possible bias to diagnose focal epilepsies. Data were prospectively collected on patients who underwent noninvasive prolonged EEG-video monitoring over a 2-year period at an epilepsy program. Cases where the diagnosis of 'partial seizures' (after monitoring) was questionable were identified and the data reviewed. Sixteen cases were identified. (a) Six had an idiopathic generalized epilepsy. All had generalized tonic-clonic (GTC) seizures, two had myoclonic seizures, and three had typical absences. All patients had generalized spikes and spike-wave complexes. All had normal IQs and normal brain imaging. One patient underwent invasive EEG. (b) Ten patients had a symptomatic or cryptogenic generalized epilepsy. IQs ranged from 49 to 74 (mean: 63). All patients had diffuse EEG slowing, and generalized ictal EEG patterns. Interictal EEG showed generalized spike-wave complexes in nine, and multifocal spikes in five. Seizures included GTC in all, generalized tonic in four, and atypical absences in two. Two of the 10 patients underwent invasive EEG. The misdiagnosis of generalized epilepsy as partial epilepsy occurs for both idiopathic and cryptogenic or symptomatic generalized epilepsies, more often in the latter case. Risk factors may include: asymmetry in EEG or seizure semeiology, the eagerness to enroll in drug studies or surgical programs, and the lack of team thinking involving several epileptologists. This problem is almost certainly under-reported and may occasionally result in unwarranted invasive procedures.