A Brain Pacemaker?

Deep Brain Stimulation often treats Parkinsons

(RxWiki News) Those with hard-to-treat medical conditions live with a frustrating reality. For some disorders  a surgical treatment called deep brain stimulation (DBS) has delivered relief.

Researchers wonder if DBS may possibly help other resistant conditions too.

In DBS, a medical device often referred to as a brain pacemaker is implanted in the brain. The brain pacemaker sends electrical impulses to specific parts of the brain in order to modify electrical activity in a controlled manner.

"Discuss new treatments with your doctor."

A review recently published online details new applications for DBS. These new applications being considered include loss of balance in Parkinson’s disease, depression, obsessive-compulsive disorder, obesity, substance abuse, epilepsy, and dementia from Alzheimer’s and traumatic brain injury.

DBS as a treatment for neurological illness began in the late 1980’s. How DBS works is still unclear but its proven safety, reversibility and effectiveness make it an excellent candidate for treatment.

DBS is known to improve certain motor symptoms in PD like tremor, rigidity and bradykinesia, the slowness of movement that is the most characteristic clinical feature of PD. DBS has also been shown to limit some of the side effects of PD medications like dykinesias, a movement disorder that results in diminished movement ability and tics.

In some people with severe PD, DBS is preferred to medical management, according to a large randomized controlled trial.

Researchers are keen to investigate the use of DBS on the gait and balance, the two PD symptoms that most often lead to disability. Preliminary studies show positive results for using DBS for the treatment of freezing of gait and falls, but researchers must be cautious as larger controlled trials are necessary to understand the application.

DBS may be changing stereotypes left over from the days of 1960's lobotomies regarding the use of surgery to treat psychiatric disorders. DBS has been trialed effectively and compassionately for treatment resistant depression through targeting of nodes within malfunctioning mood circuits.

The results showed that more than 50 percent responded to the treatment with a large reduction in depression and two patients were in remission at six months. After 3-6 years, 64.3 percent were responding positively with fewer depressive symptoms and there was a remission rate of 42.9 percent.

Most participants had improved social functioning, work related activity and overall quality of life.

There were no neurological or cognitive side effects to the trial, although two patients did develop infection and two committed suicide before the end of the trial. The suicides were not linked to the device or the surgery.

Meticulous controlled trials are still needed before long term use of DBS for depression is ready.

Although Tourette’s syndrome tends to significantly decline after the age of 20, there are some treatment-resistant cases that continue on into adulthood. DBS has been used to treat such cases since 1999.

Four small randomized blind trials of DBS to treat adult Tourette’s syndrome have all resulted in symptom reduction for the participants.

Obsessive-compulsive disorder (OCD), an anxiety disorder that can be functionally disabling, has a history of being treated with neurosurgical procedures with some positive results.

Several randomized, double-blind trials have been completed on the use of DBS to treat OCD. In one trial, a third to a half of all patients were classified as responders.

DBS for OCD has shown to be safe, although neuropsychiatric effects due to stimulation like mania were evident and need to be monitored.

Addiction may be treated using DBS by targeting dopamine release centers in the brain. Four reports of DBS for alcohol dependency resulted in two patients significantly reducing their alcohol intake and two patients abstaining from the substance all together.

DBS has also worked in single patient trials for heroin and tobacco dependency.

One side effect of the patient with tobacco dependency was marked weight loss, suggesting that DBS may also be able to treat obesity and food addiction. It is important to note that other preliminary attempts to use DBS for obesity have had unconvincing results.

Surgical procedures have been used to relieve epilepsy for several decades. Electrical stimulation in the past has shown to relieve epilepsy with varying degrees of success.

Some credit this varying rate of success to not knowing the optimal site of stimulation. Trials have targeted the cerebellum, hippocampus and thalamus. Much work is left to be done in this area.

Alzheimer’s Disease (AD), the most prevalent of neurodegenerative dementias, is characterized by changes to the brain that lead to functional impairment in neural circuits affecting cognition and memory.

A trial of DBS in six patients with AD type dementia showed reversal of the hypometabolism that occurs in AD in 3D brain scans at one month. Changes were sustained up until one year after treatment.

Two of the six patients with AD had improved Mini-Mental Status Exam results and the group showed less of a decline than expected in AD patients with no adverse side effects.

Early attempts at brain stimulation for disorders of consciousness from traumatic brain injury (TBI) were limited in understanding and effectiveness.

Those in a minimally conscious state (MCS) after TBI are aware of the environment and maintain most brain function, but are unable to communicate while those left in a persistent vegetative state (PVS) experience wakefulness without awareness of their environment.

A 26 patient Japanese study included five patients in MCS and 21 patients in PVS. After DBS, eight out of 21 PVS patients recovered the ability to follow verbal commands and four out of five MCS patients were recovered enough for hospital discharge.

This study is controversial as the researchers began DBS before one year after the TBI, a time when some recovery from the TBI is still expected. However, the study identifies the need for follow up trials of DBS for TBI.

Any surgery or implantation comes with a set of inherent risks. In the case of DBS, there are risks of infection, migration or failure to live up to expectation.

While DBS has a history of working safely in movement disorders such as essential tremor and PD, the expansion of the treatment to any other treatment resistant disorder should be approached with care. Investigation into the safety and effectiveness are necessary before neural modulation of non-motor brain circuits can become a common-place procedure.

This study was published in the January edition of Surgical Neurology International and funded by an educational grant from Elekta.

Authors Tejas Sankar, Travis S. Tierney and Clement Hamani are from the Department of Neurosurgery, Toronto Western Hospital, in Toronto, Ontario.

The authors disclose no conflicts of interest.

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Review Date: 
August 13, 2012
Last Updated:
August 23, 2012