Studies also show that stage one and three non-rapid eye movement sleep become more efficient when the episodes end. The Multiple Sleep Latency Test has yielded inconsistent results when given to KLS patients. In many cases, hours are spent in a withdrawn sleep-like state while awake during episodes. Most sleep studies have been performed while subject is near the end of their episodes. Some patients experience brief insomnia and become very happy and talkative after the episode ends.The first time a patient experiences KLS, it usually occurs along with symptoms that are similar to those of the flu or encephalitis. In at least 75 percent of cases, symptoms occur after an airway infection or a fever. Viruses observed before the development of the condition include Epstein–Barr virus, varicella zoster virus, herpes zoster virus, influenza A virus subtypes, and adenovirus. Several days after symptoms first occur, patients become very tired. In cases that occur after an infection, KLS usually starts within three to five days for teenagers and fewer for children. In other cases, alcohol consumption, head injury, or international travel precede symptoms. Lifestyle habits, such as stress, alcohol abuse and lack of sleep and stress, have also been proposed as possible triggers. First episodes of KLS are preceded by a clear event in about 90 percent of cases. Recurrences generally do not have clear triggers; only about 15 percent have a precipitating event.The condition generally disrupts the social lives and academic or professional obligations of those with KLS. Some patients also gain weight during episodes.
It has been reported to be effective in about 25 to 60 percent of cases. Its use carries the risk of side effects in the thyroid or kidneys. Antipsychotics and benzodiazepines can help alleviate psychotic and anxiety related symptoms, respectively. Carbamazepine has been reported to be less effective than lithium but more effective than some drugs in its class. Electroconvulsive therapy is not effective and worsens symptoms.KLS patients generally do not need to be admitted to hospitals. It is recommended that caregivers reassure them and encourage them to maintain sleep hygiene. It may also be necessary for patients to be prevented from putting themselves in dangerous situations, such as driving. Prognosis
The frequency of KLS episodes can vary from attacks one week in length occurring twice a year to dozens of episodes that follow each other in close succession. The median duration of KLS episodes is about ten days, but some last several weeks or months. A study of 108 patients found an average of 19 episodes over the duration of the disease. Another study found a median of 3.5 months between episodes. Outside of episodes, there is no disturbance in patients sleep patterns and they are generally asymptomatic. Patients do not experience the same symptoms in each episode.About 80 percent of patients are adolescents when they first experience KLS. On some occasions though, its first occurrence comes in childhood or adulthood. In most adolescent-onset patients, symptoms cease by the time they are 30 years old.