The<unk>  is characterized by the sudden or gradual development of aphasia (the inability to understand or express language) and an abnormal electroencephalogram (EEG). LKS affects the parts of the brain that control comprehension and speech (Broca's area and Wernicke's area). The disorder usually occurs in children between the ages of 3 and 7 years. There appears to be a male dominance in the diagnosis of the<unk>  (ratio of 1.7:1, men to women). Typically, children with LKS develop normally, but then lose their language skills. While many affected individuals have clinical seizures, some only have electrographic seizures, including electrographic status epilepticus of sleep (ESES). The first indication of the language problem is usually auditory verbal agnosia. This is demonstrated in patients in multiple ways including the inability to recognize familiar noises and the impairment of the ability to lateralize or localize sound. In addition, receptive language is often critically impaired, however in some patients, impairment in expressive language is the most profound. In a study of 77 cases of<unk> , 6 were found to have this type of aphasia. Because this<unk>  appears during such a critical period of language acquisition in a child's life, speech production may be affected just as severely as language comprehension. The onset of LKS is typically between 18 months and 13 years, the most predominant time of emergence being between 3 and 7 years. Generally, earlier manifestation of the disease correlates with poorer language recovery, and with the appearance of night seizures that last for longer than 36 months. LKS has a wide range of symptom differences and lacks a uniformity in diagnostic criteria between cases, and many studies don't include follow-ups on the patients, so no other relationships between symptoms and recovery have been made known. Language deterioration in patients typically occurs over a period of weeks or months. However, acute onset of the condition has also been reported as well as episodic aphasia. Seizures, especially during the night, are a heavily weighted indicator of LKS. The prevalence of clinical seizures in acquired epileptic aphasia (LKS) is 70-85%. In one third of patients, only a single episode of a seizure was recorded. The seizures typically appear between the ages of 4 and 10 and disappear before adulthood (around the age of 15). Often, behavioral and neuropsychologic disturbances accompany the progression of LKS. Behavioral issues are seen in as many as 78% of all cases. Hyperactivity and a decreased attention span are observed in as many as 80% of patients as well as rage, aggression, and anxiety. These behavior patterns are considered secondary to the language impairment in LKS. Impaired short-term memory is a feature recorded in long-standing cases of acquired epileptic aphasia.
Landau–Kleffner syndrome
Smith–Lemli–Opitz syndrome
Letterer–Siwe disease
Kapur–Toriello syndrome
Klüver–Bucy syndrome
Smith–Magenis syndrome
Pelger–Huët anomaly
Schinzel–Giedion syndrome