Clinical ResearchAccelerated Long Term Forgetting in patients with focal seizures: Incidence rate and contributing factors

- ALF is an important memory disorder that can be identified by adding a long term recall to standard memory measures.
- ALF for the RAVLT word list was seen in 18% of patients with focal epilepsy.
- ALF is more prevalent in patients with a hippocampal lesion.
- Incidence of ALF is influenced by the number and type of memory tasks considered.
- Incidence of ALF is affected by the definition of an "impaired" score" and characteristics of the epilepsy patient sample.

BackgroundAccelerated Long Term Forgetting (ALF) is usually defined as a memory impairment that is seen only at long delays (e.g., after days or weeks) and not at shorter delays (e.g., 30 min) typically used in clinical settings. Research indicates that ALF occurs in some patients with epilepsy, but the incidence rates and underlying causes have not been established. In this study, we considered these issues.MethodsForty-four patients with a history of focal seizures were tested at 30 min and 7 day delays for material from the Rey Auditory Verbal Learning Test (RAVLT) and Aggie Figures Test. Recently published norms from a matched group of 60 control subjects (Miller et al., 2015 ) were used to determine whether patients demonstrated ALF, impairment at 30 min or intact memory performance.ResultsThe incidence of ALF in the epilepsy patients (18%) was > 3 times higher than normal on the RAVLT, but no different (7%) from the incidence in normal subjects on the Aggie Figures. A different, but again significantly high, proportion of patients (36%) showed shorter-term memory deficits on at least one task. ALF was found mainly in patients with temporal-lobe epilepsy, but also occurred in one patient with an extratemporal seizure focus. Presence of a hippocampal lesion was the main predicting factor of ALF.ConclusionsMany patients with a focal seizure disorder show memory deficits after longer delays that are not evident on standard assessment. The present study explored the factors associated with this ALF memory profile. These new findings will enhance clinical practice, particularly the management of patients with memory complaints.