Karsten Witt has been Professor of Neurology at the University's School of Medicine since 2017. In this interview, Witt talks about his specialism - deep brain stimulation in Parkinson's disease - and the challenges for clinics and research.
QUESTION: Professor Witt, around 12,500 people are diagnosed with Parkinson's disease in Germany every year. For a good 30 years, neurologists have been using deep brain stimulation as one of the treatment methods. As Director of the University Clinic for Neurology at the Evangelical Hospital in Oldenburg, you have established this method. What does this treatment look like?
ANSWER: Put simply, a weak current is administered to those affected via two electrodes, which they do not feel - for example in the subthalamic nucleus. This nucleus is located in the depths of the brain and is the size of a newborn baby's fingernail. Stimulation at this point noticeably alleviates Parkinson's symptoms.
QUESTION: How does this work in practice?
ANSWER: Movement is an interplay of signals from nerve cells that favour movement and inhibit movement. The perfect balance between these is what makes movement healthy. In Parkinson's disease, the neurotransmitter dopamine, which stimulates movement, is depleted. As a result, the impulse that prevents movement predominates. If we use an electrode to inhibit this overactive pathway, we can restore balance. Deep brain stimulation utilises this principle: it inhibits the subthalamic nucleus, which is pathologically overexcited in Parkinson's disease, and thus sustainably improves balance in the area of movement.
QUESTION: Which patients particularly benefit from deep brain stimulation?
ANSWER: In the early phase of Parkinson's disease - the first five to seven years - we can treat Parkinson's symptoms well with medication. After that, there is often a phase in which poor and good mobility alternate. The disease then takes control of those affected, as they have to expect unexpected stiffness of movement at any time. This means, for example, that sufferers do not know: "Can I get out of the car in the car park, or do I have to wait for medication to take effect?" If these fluctuations in motor function occur, deep brain stimulation could help.
QUESTION: What challenges do you face in everyday clinical practice?
ANSWER: Deep brain stimulation surgery requires smooth teamwork between neurosurgeons, anaesthetists, neurologists and staff from other disciplines. The technical challenge here is to place the electrodes precisely. After the operation, the attending physicians have to establish a new balance between the medication and the stimulation. The dose of medication can often be reduced by half or more. In many cases, this improves mobility so significantly that those affected have to readjust their social behaviour: A restrictive chronic illness determines interpersonal relationships and social rules for many years. The operation breaks these habits. Doctors and their staff should therefore select patients very carefully and provide them and their relatives with detailed counselling before the operation. Those affected also need advice afterwards on how they can adapt their everyday life to the new situation.
QUESTION: What role does the accompanying scientific research play?
ANSWER: There are many new aspects here: We are learning more and more about which patients are most likely to benefit from stimulation. We can also see that patients are still more mobile over eight to ten years with stimulation than before the operation without medication. Many research initiatives are also investigating the best way to achieve the goal. For example, whether so-called directional stimulation has advantages. This stimulation directs the current precisely in the direction that suppresses the symptoms of the disease.
QUESTION: Which research questions are you focussing on?
ANSWER: For example, we want to gain a better understanding of how visual and auditory impressions are processed and how movements arise from them. This does not put any further strain on those affected, as we receive the information via the already implanted electrode. We also want to investigate which circumstances stimulate movements and whether it makes a difference whether an acoustic or visual stimulus is the trigger. Thanks to the Oldenburg focus on hearing research, we have the expertise to further track acoustic signals in the brain. We know from animal experiments that these acoustic signals occur in the region that we stimulate in our patients. However, we have not yet deciphered exactly how hearing and movement are connected. There is a great need for research in this area.
Interview: Constanze Böttcher