Definition and Overview
A thalamotomy, also known as thalamus lesion surgery, is a surgical procedure used to destroy a portion of the thalamus, a tiny part of the brain that controls involuntary muscle movements so the patient’s tendency to experience such is restricted.
Due to its ability to control involuntary tremors and muscle spasms, the procedure is sometimes used in the treatment of Parkinson’s disease and management of its symptoms. However, it is less commonly used, with more doctors prescribing either a pallidotomy, which is similar to a thalamotomy in concept but is able to control more symptoms, or deep brain stimulation, which is associated with fewer risks.
Who Should Undergo and Expected Results
A thalamotomy is used in the treatment and management of:
Parkinson’s disease – This is a neurological condition characterised by tremors, rigidity, muscle stiffness, and slowed, imprecise, or uncontrolled movements. These symptoms are caused by the degeneration of the basal ganglia of the brain, which leads to the decreased production of dopamine. The disease develops gradually, but progresses in stages as a greater part of the brain becomes damaged. In the long run, it can cause various complications, such as depression and insomnia.
Essential tremor – This is a neurological disorder characterised by involuntary, uncontrollable, and usually rhythmic tremors or shaking of any part of the body. The tremors most commonly affect the hands, and can be so severe that it prevents a person from performing even simple tasks such as drinking, eating, or writing. The tremors tend to progress over time, especially when aggravated by stress, fatigue, extreme temperatures, and excessive caffeine consumption. Although it causes similar involuntary body movements, this disorder is distinct from Parkinson’s disease.
Although less commonly used than other surgical alternatives, thalamotomy is preferred in certain cases, such as when the patient is no more than 65 years old and has normal intellectual function and memory. It is also used specifically for patients whose main symptoms involve involuntary body movements.
However, the procedure is usually not the first form of treatment. Patients diagnosed with Parkinson’s are first given levodopa, the primary drug used to treat the disease. Surgical intervention is considered when the efficacy of the drug begins to fade, a common occurrence among long-term users of the drug, or when the patient’s tremors do not improve despite the use of medication.
It is important to note that the effects of the procedure are only on the side of the brain opposite to where the surgery was performed. Thus, the surgical side of the brain is determined by which side of the body is experiencing symptoms such as tremors. If a person has tremors in the left side of the body, then he has to undergo a thalamotomy on the right side of the body. This means that if the patient’s tremors affect both left and right sides of the body, then he has to undergo the surgery twice.
A thalamotomy can produce immediate results. However, in spite of this effectiveness, the procedure is not often performed since its effects can also be achieved using a pallidotomy, which can improve other Parkinson’s symptoms such as bradykinesia, walking issues, and speech issues.
How Does the Procedure Work?
Before a thalamotomy is performed, the patient first undergoes a series of brain imaging scans, usually an MRI or a CT scan, to determine the precise location in the brain that will be operated on.
On the scheduled date of surgery, the patient first receives local anaesthesia, which effectively numbs the skull. General anaesthesia is not used for thalamotomy as it is important for the patient to stay awake throughout the procedure so that the surgeon can observe any unusual sensory changes that may indicate a complication.
Once the anaesthetics take effect, the surgeon begins the procedure by drilling a hole through the skull where a probe is inserted and guided towards the thalamus. Once there, the surgeon will inject liquid nitrogen, a very cold substance that effectively destroys the targeted brain tissues. This is just one of the different ways surgeons use to create a lesion on the thalamus. Another method is to heat an electrode probe by up to almost 200 degrees Fahrenheit to burn the brain cells. Once the thalamus is successfully scarred, the surgeon will immediately close the wound.
It is now also possible to perform the procedure in a non-invasive manner using ultrasound waves that are focused directly on the thalamus, causing it to gradually heat up and ablate the targeted tissue. This procedure can destroy cells in the thalamus without drilling a hole through the skull.
The recovery period following a successful thalamotomy may take up to six weeks. Patients are advised to stay in the hospital for two days after the procedure for continuous monitoring before being discharged.
Possible Risks and Complications
A thalamotomy, like any other brain surgery, is a major operation accompanied by a number of potential risks, some of which are serious and may cause permanent complications. The risk is greater when the patient undergoes a thalamus lesion surgery twice or once in both sides of the brain. It is also important for patients to understand that a thalamotomy is a permanent procedure, which causes lasting and irreversible damage to the targeted brain cells.
The most common risks and complications associated with this procedure include:
- Speech problems
Some studies also link the procedure with at least one occurrence of multiple system atrophy.
Clarke CE, Moore AP (2007). Parkinson's disease, search date November 2006. BMJ Clinical Evidence. Available online: http://www.clinicalevidence.com