According to a 2015 KLS review by Arnulf (presenting evidence published by Laval, Ann Neurology, 2015):
• Complete responders: 36.6% • Partial responders: 51% • Non responders: 12.4% • 9.8% had « mini-episodes » (1 day) on lithium • 13 patients had an episode after stopping lithium 2 consecutive nights • Level IV evidence of benefit in KLS • Lithium : 1 month less in episode per year • The level should be high and monitored”
According to a 2014 KLS review by Miglis and Guilleminault:
“… Although an autoimmune mechanism has been suggested, there are likely heterogeneous factors at play in certain susceptible individuals. When combined with a precipitating event such as a minor infection, a transient multifocal encephalopathy ensues. It has been proposed that such a precipitating event may lead to transient permeability of the blood–brain barrier, thus predisposing these individuals to recurrent events. An animal model would add much to the understanding of the underlying pathophysiology. This is yet to be developed and should be considered in future research. …”
In Table 4 on page 2771 there is a list of attempted treatments for KLS:
http://brain.oxfordjournals.org/content/128/12/2763.full I. Arnulf, J. M. Zeitzer, et al. “Kleine–Levin syndrome: a systematic review of 186 cases in the literature.” Brain 128, no. 12 (2005): 2763-2776.
According to Tondo, et al. (2001) in a review of lithium carbonate therapy:
“… The majority of patients showed substantial reductions in episode frequency and the proportion of time ill; 28.9% had no new episodes of mania or depression during lithium maintenance treatment, and about a quarter of patients showed no improvement (Table 3).
… It is important to emphasise that only about a quarter of the patients in this study (29%) experienced complete remission from all recurrences of affective illness during maintenance treatment (see Table 3). This level of protection is in keeping with past reports suggesting that full protection is not commonly achieved with lithium or with alternative treatments (Rybakowsky et al, 1980; Prien et al, 1988; Gelenberg et al, 1989; Goodwin & Jamison, 1990; Tohen et al, 1990; Keller et al, 1993; Koukopoulos et al, 1995a; Baldessarini et al, 1996; Greil et al, 1997; Maj et al, 1998; Baldessarini & Tondo, 2000). Although perfect prophylaxis was uncommon, at least 60% of patients experienced reductions in episode frequency and in the proportion of time ill by at least one-half (see Table 3). These considerations strongly suggest that requiring complete protection against all recurrences of mania or bipolar depression as a test of effectiveness of a mood-stabilising agent is unrealistic and, specifically, would tend to lead to underestimates of the substantial, long-term, overall beneficial effects of lithium. …”
http://bjp.rcpsych.org/content/178/41/s184.full TONDO, L., BALDESSARINI, R. J., & FLORIS, G. (2001). Long-term clinical effectiveness of lithium maintenance treatment in types I and II bipolar disorders. The British Journal of Psychiatry, 178(41), s184-s190.
According to the empirical evidence cited in this posting, lithium carbonate has roughly the same efficacy for Kleine-Levin syndrome as for bipolar disorder.