DBS can directly improve movement including slowness, stiffness, tremor, walking difficulties and involuntary movement (dyskinesias). This can reduce the need to take Parkinson’s medication.
DBS does not directly improve non-movement issues such as intellect, sleep disturbance or bladder function. DBS does not cure Parkinson’s disease or slow progression of the disease. The aim of DBS is to improve quality of life – and can remain beneficial over the long term (e.g. over 10 years).
This is where the benefit of medication varies over the course of a day. Patients can experience ‘off’ periods (slowness and stiffness) and/or dyskinesias (involuntary movement). DBS can smooth the peaks and troughs – aiming to achieve the best ‘on’ state continuously, day and night. Typically, movement problems that respond to medication (even if briefly), respond to DBS. Movement issues that do not respond to medication do not usually respond to DBS (with the exception of tremor).
A rule of thumb is to consider DBS once motor fluctuations affect quality of life.
We target the subthalamic nucleus (STN) or globus pallidus interna (GPi).
Side effects can affect almost any aspect of brain function including speech, mood, intellect and movement. A mild and permanent word finding difficulty is common (although usually not noticed). Many side effects (if they occur) can be reversed by adjusting stimulation. A compromise may be necessary between the level of stimulation and any side effect.
Overall, taking the benefits and side effects into account, studies show that DBS for motor fluctuations can substantially improve quality of life.
When tremor is the major issue, we offer thalamic/posterior subthalamic area (PSA) stimulation (see below for essential tremor). However, when tremor co-exists with significant slowness and stiffness (or patients are young enough that those issues are likely to emerge), we may offer subthalamic nucleus (STN) stimulation (see above).