Lesion Therapy

Lesion Therapy is classified by three common surgical procedures in which a tiny, heated probe is inserted into a specific region of the brain to lesion (or destroy) tissue. The three types of lesion therapy are:

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• Pallidotomy: Targets the globus pallidus internus (GPi) and is the most widely used type of lesion therapy for Parkinson's disease. It has been used over the last several decades to help relieve PD motor symptoms.

• Thalamotomy: Targets the ventral intermediate nucleus (VIM) of the thalamus and is used mainly to treat tremor.

• Subthalamotomy: Targets the subthalamic nucleus (STN). It can provide some of the same benefits as pallidotomy.

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Lesion Therapy Benefits

A pallidotomy lesion has the potential to improve bradykinesia (slowness), rigidity (stiffness), tremor, motor fluctuations, dyskinesia, and in very select cases, freezing. It usually does not improve walking, speech or thinking. Pallidotomies, like deep brain stimulation (DBS), are generally only effective in treating PD symptoms that respond to carbidopa/levodopa, with the exception of tremor. Tremor may respond to pallidotomy (and thalamotomy) even if medications don't work.

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Pallidotomy has advantages over DBS - it doesn't require implanted wires, batteries, or electronic programming sessions to fine-tune settings. There are no hardware malfunctions and usually no infections resulting from the initial surgical procedure.

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For those who might have difficulty traveling for DBS programming, or in cases when DBS is too expensive or not available, pallidotomy may be a reasonable choice. Pallidotomy can be as effective as DBS in treating PD symptoms, however, the lesion must be placed in exactly the right spot. Recent studies have shown that the benefits of pallidotomy when the lesion is well-placed can be long-lasting. A misplaced lesion may lead to persistent side effects or incomplete benefits.

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Subthalamotomy has been gaining popularity because it can provide the same types of benefits as pallidotomy. It is performed less frequently than other types of lesion therapy because it requires a high level of precision. There is also an associated risk of developing dyskinesia.

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Lesion Therapy Complications and Risks

Lesions (cuts) in the brain can cause stroke, seizure, bleeding, weakness, numbness, changes in vision or speech and/or stroke-like symptoms. Lesions on both sides of the brain can affect cognition and speech and have additional effects on walking and balance. Traditionally, lesion therapies have been reserved for treatment on one side of the brain.

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Unlike DBS, pallidotomy should not be performed on both sides of the brain in most cases. This is one major limitation of this surgery. Performing two pallidotomies can lead to permanent speech, swallowing and cognitive problems. People with an existing pallidotomy who require a second surgery will usually have DBS on the opposite side of the brain.

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A few subthalamotomy patients have developed a side effect called hemiballism (uncontrollable flinging of one arm and/or leg,) but in most cases it is temporary.

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Despite the benefits, subthalamotomies are still not frequently performed as they carry the risk of lasting adverse effects (unwanted and unexpected medical events) when the lesion is not accurately placed.