Isolated Sleep Paralysis: A Web Survey
Giorgio Buzzi and Fabio Cirignotta2.
Sleep Medicine Unit, Department of Neurology, S.
Orsola-Malpighi Hospital, University of Bologna, Italy
Isolated Sleep Paralysis (SP) occurs at least once
in a lifetime in 40-50% of normal subjects, while
as a chronic complaint it is an uncommon and
scarcely known disorder. A series of messages
written by subjects who experienced at least one
episode of SP, containing more or less detailed
descriptions of this disorder, were collected from
the Sleep Web site of the University of California
in Los Angeles between January 1996 and July
1998. Two hundred and sixty-four messages
fulfilling the International Classification of Sleep
Disorders (ICSD) (Thorpy, 1990) minimal criteria
for SP were analyzed. A wide spectrum of
severity was evident, with a frequency of
episodes ranging from one in a lifetime to almost
every night, and a variety of emotional and
hallucinatory experiences associated with SP
episodes were reported. Clinical similarities
between the recurrent form of isolated SP and
channelopathies (in particular, periodic paralyses)
are discussed. An activation of limbic system
structures is suggested in order to explain some
of the most common subjective experiences
associated with SP.