Chronic steady pattern comprising 1 to 2-hour daily delays in sleep onset and wake times in an individual living in society.
Usual circadian rhythm is 24.2 to 24.5 hours.
Patients sleep “around the clock”. The sleep phases travel in and out of phase. When “in phase”, patients are asymptomatic, but when they advance and become out of phase, symptoms develop because they are awake at night and sleepy during the day. At times, patients may be awake for 40 hours and other times they may sleep for 24 hours.
Pattern is similar to “free-running” pattern of time-isolated people.
Normal sleep periods are never achieved, even when on vacation.
Most commonly seen in blind patients (without optic tract connections to the suprachiasmatic nucleus), or those with involvement of the optic chiasm by tumor. This disorder may also been seen in schizoid personalities.
Patient may complain about oscillations in effectiveness of drugs which wake them or put them to sleep (despite no change in dose).
Treatment: May respond to strict 24-hour scheduling.
PSG: No studies available
Suspect the diagnosis in blind individuals with sleep complaints.