Deep brain stimulation effect on freezing of gait

The majority of patients with Parkinson's disease suffer from freezing of gait (FOG), which responds more or less to levodopa. Thalamic stimulation, mainly used in the treatment of tremor dominant Parkinson's disease is ineffective in FOG. GPi stimulation moderately improves FOG, but this effect may abate in the long term. STN stimulation was reported to improve levodopa-responsive FOG. In some patients, the benefit from levodopa is greater than that from STN stimulation, and levodopa and STN stimulation can have additive effects. On the contrary, STN stimulation is ineffective on levodopa-resistant FOG. In the few cases of levodopa-induced FOG, STN stimulation can indirectly be effective, thanks to a great decrease or arrest of levodopa. Stimulation of the pedunculopontine nucleus has recently been performed in small groups of patients suffering from both off- and on-levodopa gait impairments. The first results appear encouraging, but they need to be confirmed by controlled studies in larger series of patients.