Evaluating transient impairment of consciousness is critical to diagnose epileptic seizures, syncope, parasomnias, organic encephalopathies, and psychogenic nonepileptic seizures. Effective evaluation of episodic unconscious events demands interactive interviewing of the patient and witnesses of the events, with judgment as to historians' observational abilities. When generalized tonic-clonic seizures have been witnessed by medical staff or other reliable observers, a search for concomitant nonconvulsive events and for comorbid illnesses often elucidates diagnoses unsuspected by the referring physician. Consultation for stupor-coma should not miss a potentially reversible acute severe encephalopathy, particularly when reversibility requires timely therapy. Perspicacious analyses of complex cognitive-motor phenomena support judicious application of diagnostic procedures, including brief or prolonged EEG and video-EEG, EKG tilt-table testing, EKG loop monitoring, and brain imaging.
[Show abstract][Hide abstract] ABSTRACT: To identify patients most likely to have seizures documented on continuous EEG (cEEG) monitoring and patients who require more prolonged cEEG to record the first seizure.
Five hundred seventy consecutive patients who underwent cEEG monitoring over a 6.5-year period were reviewed for the detection of subclinical seizures or evaluation of unexplained decrease in level of consciousness. Baseline demographic, clinical, and EEG findings were recorded and a multivariate logistic regression analysis performed to identify factors associated with 1) any EEG seizure activity and 2) first seizure detected after >24 hours of monitoring.
Seizures were detected in 19% (n = 110) of patients who underwent cEEG monitoring; the seizures were exclusively nonconvulsive in 92% (n = 101) of these patients. Among patients with seizures, 89% (n = 98) were in intensive care units at the time of monitoring. Electrographic seizures were associated with coma (odds ratio [OR] 7.7, 95% CI 4.2 to 14.2), age <18 years (OR 6.7, 95% CI 2.8 to 16.2), a history of epilepsy (OR 2.7, 95% CI 1.3 to 5.5), and convulsive seizures during the current illness prior to monitoring (OR 2.4, 95% CI 1.4 to 4.3). Seizures were detected within the first 24 hours of cEEG monitoring in 88% of all patients who would eventually have seizures detected by cEEG. In another 5% (n = 6), the first seizure was recorded on monitoring day 2, and in 7% (n = 8), the first seizure was detected after 48 hours of monitoring. Comatose patients were more likely to have their first seizure recorded after >24 hours of monitoring (20% vs 5% of noncomatose patients; OR 4.5, p = 0.018).
CEEG monitoring detected seizure activity in 19% of patients, and the seizures were almost always nonconvulsive. Coma, age <18 years, a history of epilepsy, and convulsive seizures prior to monitoring were risk factors for electrographic seizures. Comatose patients frequently required >24 hours of monitoring to detect the first electrographic seizure.
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