The challenges of diagnosing non-convulsive status epilepticus

   Nonconvulsive status epilepticus (NCSE) is a clinically difficult-to-diagnose form of status epilepticus, often presenting as acute or subacute impairment of consciousness without marked motor symptoms. The limited clinical symptoms and variability of electroencephalographic (EEG) patterns result in a high risk of delayed diagnosis and poor outcomes. There is little data on the frequency of NCSE in patients with impaired consciousness of unclear etiology, its clinical features, etiological structure, and the results of long-term video-EEG monitoring.

   Objective: to investigate the prevalence of NCSE in patients with altered consciousness of unknown etiology, to describe the characteristics of NCSE from the perspectives of etiology and semiology, and to analyze the results of long-term video-EEG monitoring in this condition.

   Material and methods. Data from 73 adult patients with suspected NCSE who underwent continuous video-EEG monitoring were analyzed. Diagnosis was made using the Salzburg criteria (2015) in conjunction with the standardised terminology of the American Clinical Neurophysiology Society (ACNS, 2021). The study group included 32 patients with a confirmed diagnosis of NCSE.

   Results. NCSE was confirmed in 32 (43.8 %) patients. In the vast majority of these (84.4 %), the condition occurred against a background of coma; in 15.6 %, a reduced level of consciousness was observed, mimicking aphasic and cognitive disorders. In 53.1 % of cases, NCSE developed as a transformation from convulsive status epilepticus, whilst in 46.9 % it occurred as a primary event. Only 37.5 % of patients had previously been diagnosed with epilepsy (idiopathic generalized epilepsy – n = 7; focal structural epilepsy – n = 5); in the remaining cases, NCSE was acute and symptomatic in nature, with the most common causes being New-Onset Refractory Status Epilepticus (NORSE), acute cerebrovascular accident, traumatic brain injury, hypoxic and metabolic encephalopathy. Based on EEG analysis, definite NCSE was confirmed in 81.2 % of patients, and probable NCSE in 18.8 %. During treatment, NCSE was controlled with first- and second-line drugs in only 8 (25 %) patients. In the remaining cases (n = 24; 75 %), pharmacological sedation was required. Thus, refractory and super-refractory forms of the condition pre-dominated, with a mortality rate of 21.9 %.

   Conclusion. NCSE is a common yet under-recognised cause of altered consciousness, particularly in critically ill patients. The timely use of long-term video-EEG monitoring and a active diagnostic approach are crucial for the early detection of NCSE and the optimisation of treatment.

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