Hinnovic » What is deep brain stimulation?

What is deep brain stimulation?

What is deep brain stimulation?In this dossier, Hinnovic explores a complex, delicate, expensive and invasive procedure: deep brain stimulation (DBS). Used to treat severe symptoms of neurodegenerative diseases like Parkinson’s disease, essential tremor and dystonia, and increasingly used in psychiatry to treat conditions such as depression and compulsive disorders, deep brain stimulation may improve patient’s quality of life, but does not cure. It is a last resort procedure for treatment-refractory patients. It is a lifelong treatment, which also requires lifelong monitoring.

 

Deep brain stimulation is a two-step procedure (CADTH, 2010).

Find the brain regions responsible for symptoms during the surgery

Firstly, the surgeon makes a hole in the skull and then inserts a small lead. Targeting brain regions potentially responsible for tremors or the symptoms to be treated, the surgeon sends electric shocks. The patient – who remains conscious throughout the procedure – may thus inform the surgeon about the perceived changes (elimination or significant reduction of tremors).

Installation of electrodes and pulse generators

Once the area is identified, the surgeon fixes the electrodes which are then connected to a pulse generator implanted under the skin, just below the clavicle. The generator will send electrical shocks at a frequency and pace that will be adjusted in the months following the surgery. These electrical pulses are generated by a battery that must be changed every two to five years depending on the energy required to control the symptoms.

 

     
 

The diseases

Parkinson’s disease   (Parkinson Society Canada)

  • Parkinson’s disease is a neurodegenerative disease whose most common symptoms are tremors, slowness in movements, muscular rigidity and balance problems. Other symptoms including fatigue, slow speech, difficulty in writing, stooped posture, constipation and insomnia are also observed. Non-motor symptoms such as depression, difficulty in swallowing, sexual problems and cognitive impairments appear over time.

  • There is no cure. The symptoms are usually treated with medication, physical exercises and therapies such as physiotherapy, occupational and speech therapies.

  • The development of Parkinson’s disease varies from one person to another.

  • It is estimated that it affects about 0.5% of people aged 65 to 74 and 1 to 2% of people over the age of 75 (NICE, 2003).

 

Essential tremor   (Association of people affected by essential tremor)

  • Essential tremor is a neurological disorder that can affect the hands, head, voice or other parts of the body. Its progression is reflected by an increase in the amplitude of tremors and in the number of sites affected.

  • The development of essential tremor takes many years and varies from one person to another.

  • It can affect people of all ages, but two incidence peaks are observed: one around the age of 15, the second around the age of 55.

  • Its origin is often hereditary.

  • No therapy stops or slows down the natural progression of symptoms.

 

Dystonia   (Dystonia-Quebec)

  • Dystonia is a movement disorder characterized by chronic, involuntary and painful spasms. Contractions cause twisting, repetitive movements and abnormal posture.

  • It affects different parts of the body such as legs, arms, neck, face, eyes, vocal cords and sometimes several muscle groups at once.

  • Symptoms are usually chronic, but can also occur occasionally during "attacks" or episodes.

  • It can be inherited or caused by special factors such as trauma, certain medications or other diseases. In most cases, the cause remains unknown.

  • Being the most common movement disorder after Parkinson’s disease and essential tremor, dystonia affects approximately 300,000 individuals in North America.

  • There is neither a treatment that is applicable to all patients, nor a therapy that can benefit the majority of them. The most common treatments (often combined) are medication, injections of botulinum toxin and neurosurgery.

 
     

 

Delicate and complex, deep brain stimulation offers undeniable advantages (CADTH, 2010) :

  • It can be tailored to the patient’s needs;

  • Unlike ablative surgery, it is reversible; the electrodes can be removed if necessary;

  • For patients with Parkinson’s, it can reduce or even eliminate tremors and hence, reduce the use of medication.

  • It improves functioning in daily activities as well as overall quality of life.

 

Like any treatment, deep brain stimulation also has limitations (CADTH, 2010) :

  • The surgical procedure itself involves risks such as haemorrhage, stroke, headache and infection;

  • Some risks are also associated to the technology such as leads migration, device malfunction or failure;

  • Some patients may experience cognitive and behavioural problems or depression following the intervention;

  • DBS does not slow down the progression of Parkinson’s disease, essential tremor or dystonia, nor does it improve other symptoms associated with Parkinson’s disease such as depression or anxiety.

 

How the media portrays DBSDespite these caveats, the media generally portray this intervention in a positive light. The benefits of DBS are often emphasized over its limitations and headlines frequently attribute to DBS broader applications than what it actually accomplishes (Racine et al., 2007). In addition, ethical and social issues regarding resource allocation, informed consent, patient selection, etc. are rarely addressed in the media (Racine et al., 2007). In short, although deep brain stimulation is performed since the 1980s and was officially approved by the Food and Drug Administration (FDA) in 1997 for the treatment of tremors, the public has had little opportunity to get a complete and fair description of DBS.

 

In this dossier, Hinnovic takes stock of this impressive technology. We invite you to read our vignettes on the various ethical and social issues DBS raises and to listen to Ghislaine Mathieu who explains how the Canadian regulatory framework evaluates, approves and monitors high-risk medical devices such as DBS.

 

Happy reading!

Author : Myriam Hivon, Ph.D.

 

REFERENCES

 

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