Neurological disorders can have a devastating impact on the lives of sufferers and their families.
Drug treatments are often ineffective in these disorders. But what if there was a way to simply switch off a devastating tremor, or boost a fading memory?
Recent advances using Deep Brain Stimulation (DBS) in selective brain regions have provided therapeutic benefits and have allowed those affected by these neurological disorders freedom from their symptoms, in absence of an existing cure.
A pacemaker for the brainArtificial cardiac pacemakers are typically associated with controlling and resynchronising heartbeats by electrical stimulation of the heart muscle.
In a similar manner, DBS sends electrical impulses to specific parts of the brain that control discrete functions. This stimulation evokes control over the neural activity within these regions.
Prior to switching on the electrical stimulation, electrodes are surgically implanted within precise brain regions to control a specific function.
The neurosurgery is conducted under local anaesthetic to maintain consciousness in the patient. This ensures that the electrode does not damage critical brain regions.
Following recovery from surgery the electrodes are activated and the current calibrated by a neurologist to determine the optimal stimulation parameters.
The patient can then control whether the electrodes are on or off by a remote battery-powered device.
- Deep Brain Stimulation surgery.
Turning off tremorsPerhaps the most documented success of DBS is in the control of tremors and motor coordination in Parkinson’s disease.
The administration of L-DOPA temporarily reduces the motor symptoms by increasing dopamine concentrations in the brain. However, side effects of this treatment include nausea and disordered movement.
DBS has been shown to provide relief from the motoric symptoms of Parkinson’s disease and essential tremors.
These are regions innervated by the deteriorating substantia nigra, therefore the DBS boosts stimulation to these areas.
Patients can then switch on the electrodes, stimulating these brain regions to enhance control of movement and diminish tremors.
Restoring fading memoriesRecently, DBS has been used to diminish memory deficits associated with Alzheimer’s disease, a progressive and terminal form of dementia.
The pathologies associated with Alzheimer’s disease involve the formation of amyloid plaques and neurofibrillary tangles within the brain leading to dysfunction and death of neurons.
By stimulating neural activity within the hippocampi via the fornix, memory deficits associated with Alzheimer’s disease can be improved, enhancing the daily functioning of patients and slowing the progression of cognitive decline.
Deactivating addictionAnother use of DBS is in the treatment of substance abuse and drug addiction. Substance-related addictions constitute the most frequently occurring psychiatric disease category and patients are prone to relapse following rehabilitative treatment.
Understanding of the reward systems affected in addiction has created a range of treatment options that directly target dysregulated brain circuits in order to normalise functionality.
Translational animal research has indicated that stimulation of the nucleus accumbens decreases drug seeking in models of addiction. Clinical studies have shown improved abstinence in both heroin addicts and alcoholics.
Studies have extended the use of DBS to potentially restore control of maladaptive eating behaviours such as compulsive binge eating.
In a recent study, binge eating of a high fat food in mice was decreased by DBS of the nucleus accumbens. This is the first study demonstrating that DBS can control maladaptive eating behaviours and may be a potential therapeutic tool in obesity.
Despite its therapeutic use for more than a decade, the neural mechanism of DBS is still not yet fully understood.
The remedial effect is proposed to involve modulation of the dopamine system – and this seems particularly relevant in the context of Parkinson’s disease and addiction.
DBS potentially has effects on the functional activity of other interconnected brain systems. While it can provide therapeutic relief from symptoms of neurological diseases, it does not treat the underlying pathology.
But it provides both effective and rapid intervention from the effects of debilitating illnesses, restoring activity in deteriorating brain regions and aids understanding of the brain circuits involved in these disorders.