Lithium carbonate in chronic cluster headache assessment of therapeutic efficacy and possible mechanisms of action.

6 patients with chronic cluster headache were treated with lithium carbonate in order to establish the individual lowest effective dose and to assess the possibility of suspending treatment after prolonged administration. Lithium was give at rising doses until more than 90\% improvement was obtained. This was achieved in 1 case with only 300 mg daily, in 3 cases with 600 mg and in 2 with 900 mg daily. Of the 5 patients in whom drug administration was suspended 3 had an immediate return of daily attacks of headache, 1 after a 4-month free interval and 1 has maintained the improvement after 6 months without the drug. The sharp decline of the effectiveness of lithium on administration of an antimitotic (Melphalan) provides the starting-point for a discussion on the possible mechanisms of action of lithium in cluster headache.