Ablative brain surgery (also known as brain lesioning) is the surgical ablation by various methods of brain tissue to treat neurological or psychological disorders. The lesions it causes are irreversible. Ablative brain surgery was first introduced by Pierre Flourens (1774-1867), a French physiologist. He removed different parts of the nervous system on animals and observed what effects were caused by the removal of certain parts. For example, if an animal could not move its arm after a certain part was removed, it was assumed that the region would control arm movements. The method of removal of part of the brain was termed "experimental ablation". With the use of experimental ablation, Flourens claimed to find the area of the brain that controlled heart rate and breathing. [1] Ablative brain surgery is also often used as an research tool in neurobiology. For example, by ablating specific brain regions and observing differences in animals subjected to behavioral tests, the functions of the removed areas may be inferred. Experimental ablation is used in research on animals. Such research is considered unethical on humans, but the effects of brain lesions (caused by accidents or diseases) on behavior can be observed to draw conclusions on the functions of different parts of the brain.[2]
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Surgical ablation has been used to treat Parkinson's disease. In the 1990s, the pallidum was a common surgical target. Unilateral pallidotomy improves tremor and dyskinesia on one side of the body (opposite the side of the brain surgery), but bilateral pallidotomy was found to cause irreversible deterioration in speech and cognition. The thalamus is another potential target for treating tremor; in some countries, so is the subthalamic nucleus, although not in the United States due to its severe side effects. Generally, deep brain stimulation surgery (DBS) is considered preferable to ablation because it has the same effect and is adjustable and reversible.[3] However, for patients for whom DBS is not feasible, ablation of the subthalamic nucleus has been shown to be safe and effective.[4] DBS is not suitable for certain patients. Patients who suffer from immunodeficiencies is an example of a situation in which DBS is not a suitable procedure. However, a major reason as to why DBS is not often performed is the cost. Because of its high cost, DBS cannot be performed in regions of the world that are not wealthy. In the case of such circumstances, a permanent lesion in the subthalamic nucleus (STN) is created as it is a more favourable surgical procedure.[5]. The surgical procedure is going to be done on the non-dominant side of the brain, a lesion might be favored to evade numerous pacemaker replacements. More so, patients who gain relief from stimulation devoid of any side effects and need a pacemaker change may have a lesion performed on them in the same position. The stimulation parameters act as a guide for the preferred size of the lesion. [6] In order to identify the part of the brain that is to be destroyed, new techniques such as micro electrode mapping have been developed [7].
Cluster headaches have been treated by ablation of the trigeminal nerve, but have not been very effective. Other surgical treatments for cluster headaches are under investigation.[8]
Ablative psychosurgery continues to be used in a few centres in various countries.[9] In the US there are a few centres including Massachusetts General Hospital that carry out ablative psychosurgical procedures.[10] Belgium,[9] the United Kingdom,[11] and Venezuela[12] are other examples of countries where the technique is still used. In the People's Republic of China, surgical ablation was used to treat psychological and neurological disorders, particularly schizophrenia, but also including clinical depression, obsessive-compulsive disorder, and epilepsy.[13] The official Xinhua News Agency has since reported that China's Ministry of Health has banned the procedure for schizophrenia and severely restricted the practice for other conditions.[14]
Experimental ablation involves the drilling of holes in the skull of an animal and inserting an electrode or a small tube called a cannula into the brain using a stereotaxic apparatus. A brain lesion can be created by conducting electricity through the electrode which damages the targeted area of the brain. likewise, chemicals can be inserted in the cannula which also damages the area of interest. By comparing the prior behavior of the animal to after the lesion, the researcher can predict the function of damaged brain segment.[15] Recently, Lasers have been shown to be effective in ablation of both cerebral and cerebellar tissue. A laser called Er:YAG, for example, allows great precision in location and size of the lesion and causes little to no thermal damage to adjacent tissue.[16]