DBS can help generalised (whole body) or focal (e.g. torticollis) dystonia. Abnormal movement and also pain may improve. DBS can thereby improve function such as eating and driving and improve quality of life. DBS can reduce the need to take dystonia medication and botulinum toxin injections. The effect on dystonia is not immediate, but accrues over months and years.
The degree of benefit from DBS on dystonia is variable and hard to predict, ranging from no effect to almost total relief, but averages around 40%. Dystonia of the limbs (arms and legs) usually improves more than dystonia of the midline (e.g. speech and neck/back). DBS is not a cure for dystonia – and dystonia recurs if stimulation is switched off. However, the benefit of DBS usually remains, as long as stimulation continues (it does not usually wear off).
For dystonia, we almost always implant the Globus Pallidus interna (GPi). Unlike other conditions – we usually perform DBS for dystonia under a general anaesthetic.
Side effects from this type of stimulation are relatively uncommon and typically mild but can include slower movement (and rarely ‘freezing of gait’), tingling, slurred speech and visual ‘flashes’. These effects are usually temporary. If persistent, such side effects can usually be reversed upon turning down or switching off stimulation.
The greatest issue with DBS for dystonia is not usually side effects – but incomplete response of the dystonia. This is a limitation we are addressing through research (link).