Abstracts

Rationale: Acute mental status changes (AMS) are commonly seen in elderly patients due to multiple factors, including infections, toxic and/or metabolic disorders, hypoxic or anoxic insults, neurodegenerative diseases, or other structural brain lesions. Older patients may take longer time than younger patients to return to their baseline mental status following an acute encephalopathy, which raises the concerns for possible subclinical seizures or nonconvulsive status epilepticus. Although routine EEGs are frequently used to look for subclinical seizures contributing to the prolonged mental status changes in the elderly, their value as screening tool to detect seizures or to provide guidance for requests of prolonged EEG (cEEG) monitoring is unclear.  Methods: We reviewed retrospectively EEGs performed during the period of one year (from May 1st, 2015 to April 30th, 2016) in patients aged 60 years or older who were admitted at JFK Neuroscience Institute in Edison (NJ) due to AMS. The EEG results were described as normal or abnormal. The EEG abnormalities were then subdivided in nonspecific abnormalities (focal and generalized slowing), interictal epileptiform discharges (IEDs), clinical or electrographic (subclinical) seizures, or periodic patterns (PP).  PP included lateralized periodic discharges (LPDs), generalized periodic discharges (GPDs), triphasic pattern (TP), and burst suppression pattern (BS). All patients had neuroimaging studies, including head CT and/or brain MRI. Results: There were 160 patients with AMS, their ages ranged from 60 to 93 year-old (mean = 73), and 79 (49.4%) patients were female. Fifteen (9.4%) EEGs were normal and 145 (90.6%) EEGs showed abnormalities. Nonspecific abnormalities were seen in 100 (62.5%) EEGs, whereas electrographic seizures were seen in eight  (5%) EEGs. Three of these EEGs had both LPDs and seizures. Seizure etiology was variable and included ischemic stroke, gliomatosis cerebri, viral encephalitis, intracerebral hemorrhage (ICH), diabetic ketoacidosis, and sepsis. Focal IEDs were seen in 16 (10%) EEGs, most (n= 15) of these patients had structural brain lesions.  PP were seen in 21 (13.1%) EEGs. Among these, TP was seen in patients with acute or chronic kidney disease, anoxic encephalopathy or sepsis; LPDs were present in patients with neoplastic lesions, strokes, chronic alcohol intake, ICH, and viral encephalitis; and GPDs or BS were found in patients with severe anoxic encephalopathy. Conclusions: The majority (62.5%) of elderly patients with AMS had nonspecific EEG abnormalities or normal (9.4%) EEGs. Seizures were seen in 5%, IEDs in 10% and PP, including TP, LPDs, GPDs and BS, in13.1% of these EEGs. Although routine EEG could detect seizures in very few patients, it could identify epileptogenic patterns or severe encephalopathy in 20% or more of these patients, potentially leading to changes in management and/or to the request of cEEG monitoring. Funding: None.