Abstracts

Rationale: The diagnosis of paroxysmal events in the elderly presents particular difficulties because of co-morbid diseases complicating the analysis. In addition, common diagnostic modalities used routinely may be non-specific and confusing. We sought to assess the utility of outpatient EEGs in diagnosing paroxysmal events in the elderly.Methods: A retrospective analysis of consecutive patients above the age 60 admitted for Long Term Monitoring (LTM) between January 2005 and May 2007 was performed. Pre-surgical evaluations and patients with status epilepticus were excluded. LTM data was compared to outpatient EEG records obtained prior to LTM admission.Results: Adequate information, including prior outpatient EEG report, was available on 25 elderly patients. Based on the LTM data, epilepsy was diagnosed in 7 (28%), psychogenic non-epileptic attacks (PNEA) in 4 (16%), and in 14 (56%) there was no evidence for active epilepsy to explain the current spells. Of the 7 patients with epilepsy, 4 (57%) had prior abnormal outpatient EEGs: 3 with unequivocal interictal epileptiform discharges (IED) and 1 with sharply contoured waves (SCW). Of the 4 patients with PNEA, 1 had SCW on outpatient EEG. In the last group, three had unequivocal epileptiform discharges. All 3 patients had preexisting epilepsy, but the current paroxysmal events were not seizures. Two of the remaining 11 had SCW on the outpatient report. Overall, 40% of patients had either IED or SCW on the prior outpatient EEGs, including patients with preexisting epilepsy, PNEA, and other non-epileptic events. The positive predictive value (PPV) of IED for the diagnosis of epilepsy was 100% with a sensitivity of 60%. However, the PPV of IED for the diagnosis of seizures as etiology of current paroxysmal events was only 50% with a sensitivity of 43%. SCW had no predictive value in diagnosing paroxysmal events in the elderly. Conclusions: Although the presence of IEDs on outpatient EEGs has a high PPV and sensitivity in diagnosing epilepsy, these IEDs have a limited role in diagnosing paroxysmal events in the elderly. Outpatient EEGs without unequivocal IEDs, including those with SCW, have no predictive value in diagnosing paroxysmal events in the elderly. IED and sharply contoured activity are relatively frequent in elderly with and without diagnosis of epilepsy, including PNEA, and should be interpreted with caution. When equivocal, LTM should be considered to make a definitive diagnosis.