Raina Pang
Dec 2, 2011
Featured

Examining the effectiveness of deep brain stimulation in treating Alzheimer’s disease

Alzheimer’s disease, the most common form of dementia, causes problems with thinking, memory and behavior. Individuals with Alzheimer’s experience confusion, memory loss, irritability, mood swings and trouble with language. Those closest to Alzheimer’s patients feel hopelessness and may suffer from the burden of caregiving.

 

The ramifications of this disease extend beyond patients and their families, affecting everyone through increased healthcare costs. The social burden will only increase as the prevalence of Alzheimer’s rises with an aging population. Because the costs associated with caring for patients increases with disease severity, treatments that reduce the need for care giving will reduce associated costs.

 

Despite intensive study, current treatment options offer minimal changes in disease progression and focus on palliative care. The five FDA approved drugs for Alzheimer’s are limited in the number of people they reach, only about half of patients, and their length of effectiveness, generally less than a year. Deep brain stimulation offers another treatment option for neurodegenerative diseases. Recently, Andres Lozano at Toronto Western Hospital applied deep brain stimulation in treating Alzheimer’s disease. Although quite preliminary, these studies show that deep brain stimulation can improve dysregulated circuit function, which results in improved behavioral symptoms for some patients. 

 

Deep brain stimulation appears effective in other neurological diseases such as Parkinson’s disease and depression. Similar to a pacemakers role in heart regulation, deep brain stimulation involves the implantation of a device that sends electrical currents to the brain. These pulses alter the neural activation. After implantation, the device can be calibrated and is reversible.

 

The neural circuits dysregulated in the specific disease become the targets for deep brain stimulation. In Alzheimer’s disease, the areas targeted include circuits involved in resting state and memory. Pilot studies show minimal adverse effects, increased brain glucose consumption and improvement in some patients. These factors make deep brain stimulation cautiously promising for Alzheimer’s disease.

 

The lack of effective treatment options lowers the threshold for the promise of new treatments. Current treatments for Alzheimer’s only mask symptoms for up to a year. This means that for a new treatment to be considered “successful” it only needs to provide minimal improvements, i.e. some change is greater than none.

 

Deep brain stimulation appears to improve dysregulated neural circuitry, but the behavioral effects remain inconsistent. While it is still unclear which aspects of the treatment result in better behavioral response, the intactness of the circuit appears to be one factor. Deep brain stimulation works better when it starts with a relatively intact circuit, but this is not the only factor as one relatively severe patient showed promising results.

 

Inability, or reduced ability, to treat later stage Alzheimer’s is a unifying theme in Alzheimer’s treatment and deep brain stimulation appears to follow this trend. The dismissal of early symptoms of Alzheimer’s greatly hinders treatment options. Because efficacy of treatment tends to decline the more severe the disease is, development of techniques allowing early diagnosis of Alzheimer’s need to be prioritized. Indeed numerous imaging techniques seem promising in diagnosing and treating Alzheimer’s.   

 

While deep brain stimulation appears to alter dysregulated circuits in Alzheimer’s disease, current studies are far from definitive. The small sample, lack of controls and ‘hit or miss’ success rate imply that this technology is not ready for mainstream marketing. However, the minimal adverse effects and the adjustable and reversible nature of this procedure justify further testing.

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