Endogenous benzodiazepine somnolence is very rare and is characterized by recurrent drowsiness with fast EEG waves (beta waves), and the GABAA antagonist flumazenil is effective. Sleeping episodes are triggered by endozepines, a class of non-benzodiazepine, non-protein molecules that act as constitutional modulators of GABAA receptors and exert the same biological effects as exogenous benzodiazepines in the central nervous system. Epidemiology: more males than females, age of onset 18-67 years. No obvious risk factors, but respiratory disorders (obstructive sleep apnea, COPD, etc.) are present in 30% of cases. Clinical features: lethargy or coma, dysarthria, ataxia, and reduced deep reflexes. The patient cannot remember the course of the attack and the events of the hours or even days before the attack. The seizures last from 2 to 120 hours and their frequency is variable. They can occur at any time of the day. There may be fatigue, mental retardation, tiredness, and behavioral changes such as aggressiveness or excessive compliance in the hours to days before the attack. Other causes of impaired consciousness such as intoxication, metabolic encephalopathy, and exogenous benzodiazepine use need to be excluded. In published cases, there are no sequelae in the interictal period. EEG manifestations: EEG was normal during the interictal period. During seizures, the EEG showed diffuse, low-amplitude, unresponsive beta rhythm (13-16 Hz). Intravenous administration of flumazenil, 0.5-2 mg, resulted in the conversion of abnormal EEG waves to a normal reactive alpha rhythm, accompanied by improvement of clinical symptoms. Pathophysiology: endogenous diazepam is the biochemical substance responsible for the pathogenesis. It is currently believed that neurons regulate the release of endogenous benzodiazepines, which in turn regulate GABA-mediated neurotransmission processes. A subtype of endogenous benzodiazepines, endozepine4, was significantly elevated in blood during the onset of the disease, as confirmed by high-pressure liquid chromatography. The cause of its elevation is not known.