Cannabinoid agonists in the treatment of blepharospasm--a case report study.

The benign essential blepharospasm is a subliminal form of primary torsion dystonia with still uncertain aetiology. It is characterized by involuntary convulsive muscle contractions of the M. orbicularis occuli, accompanied by unbearable pain of the cornea, eye bulb and the muscle itself. It has been suggested that blepharospasm is neurobiologically based on a dysfunction of the basal ganglia and an impairment of the dopamine neurotransmitter system. Therefore, therapy of blepharospasm contains administration of anticholinergic- and tranquillizing drugs as well as botulinum toxin as neuromuscular blocking agent. However serious side effects can be observed as well as failure of therapy. In the brain a dense co-localisation of cannabinoid (CB1) and dopamine (D2)-receptor was identified which had been associated with the influence of cannabinoids on the dopaminergic reward system. Additionally, it has been demonstrated that cannabinoids may have an impact on the central GABAergic and glutaminergic transmitter system and thus might be involved in the influence of movement control. In the present case we administered the cannabinoid receptor agonist Dronabinol (Delta-9-Tetrahydrocannabinol) to a woman suffering from severe blepharospasm. Multiple treatments with botulinum toxin did not reveal a long-lasting beneficial effect. By contrast, treatment with 25 mg Dronabinol for several weeks improved the patients' social life and attenuated pain perception remarkably. This case study demonstrates that the therapy with a cannabinoid agonist may provide a novel tool in the treatment of blepharospasm and maybe of other multifactorial related movement disorders.