Long-Term management of DBS in dystonia: response to stimulation, adverse events, battery changes, and special considerations.

Multiple independent case series have documented sustained benefit of bilateral pallidal deep brain stimulation (DBS) up to 3 years in patients with primary dystonia. Growing evidence exists for positive outcomes extending up to 10 years. The beneficial effects from DBS are usually reported to be stable, thus requiring little long-term modifications of the parameters of stimulation. Speech and swallowing abnormalities are less responsive than other dystonic symptoms. Symptom exacerbation after initial benefit has been reported in a few cases. It is not known whether this is related to potential tolerance or habituation to stimulation or to progression of the underlying disease. Failures of pallidal DBS, at least in primary dystonia patients, should not be accepted without further re-evaluation of each individual case, including possible revisions of the electrode location. Both hardware- and stimulation-related adverse effects, including insufficient relief of speech function, have been reported in the long-term. Despite early reports suggesting that hardware problems might be more frequent in dystonia, more recent studies did not confirm these observations. In patients with severe segmental (e.g., axial) or generalized dystonia, sudden cessation of stimulation may become a medical emergency and should be anticipated changing the neurostimulator before its natural end of life.