Ablative brain surgery

Ablative brain surgery was first introduced by Pierre Flourens (1794–1867), a French physiologist. He removed different parts of the nervous system from 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.

Ablative brain surgery is also often used as a research tool in neurobiology. For example, by ablating specific brain regions and observing differences in animals subjected to behavioral tests, the functions of all the removed areas may be inferred.

Experimental ablation is used in research on animals. Such research is considered unethical on humans due to the irreversible effects and damages caused by the lesion and by the ablation of brain tissues. However, 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.

Uses

Parkinson's disease

Parkinson's disease is a progressive degenerative disease of the basal ganglia, characterized by the loss of dopaminergic cells of the substantia nigra, pars compacta (SNc). 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.

Two other rapidly evolving or potential surgical approaches to Parkinson's disease are deep brain stimulation (DBS) and restorative therapies.

Deep brain stimulation is a surgical treatment involving the implantation of a neurostimulator medical device, sometimes called a 'brain pacemaker', which sends electrical impulses to specific parts of the brain. Generally, deep brain stimulation surgery is considered preferable to ablation because it has the same effect and is adjustable and reversible.

The advent of deep brain stimulation has been an important advance in the treatment of Parkinson's disease. DBS may be employed in the management of medication-refractory tremor or treatment-related motor complications, and may benefit between 4.5% and 20% of patients at some stage of their disease course. DBS at high frequency often has behavioral effects that are similar to those of lesioning.

In Australia, patients with Parkinson's disease are reviewed by specialized DBS teams who assess the likely benefits and risks associated with DBS for each individual. The aim of these guidelines is to assist neurologists and general physicians identify patients who may benefit from referral to a DBS team. Common indications for referral are motor fluctuations and/or dyskinesias that are not adequately controlled with optimised medical therapy, medication-refractory tremor, and intolerance to medical therapy. Early referral for consideration of DBS is recommended as soon as optimised medical therapy fails to offer satisfactory motor control.

The thalamus is another potential target for treating a tremor; in some countries, so is the subthalamic nucleus, although not in the United States due to its severe side effects. Stimulation of portions of the thalamus or lesioning has been used for various psychiatric and neurological conditions, and when practiced for movement disorders the target is in the motor nuclei of the thalamus. Thalamotomy is another surgical option in the treatment of Parkinson's disease. However, rigidity is not fully controlled after successful thalamotomy, it is replaced by hypotonia. Furthermore, significant complications can occur, for example, left ventral-lateral thalamotomy in a right-handed patient results in verbal deterioration while right thalamotomy causes visual-spatial defects. However, for patients for whom DBS is not feasible, ablation of the subthalamic nucleus has been shown to be safe and effective. DBS is not suitable for certain patients. Patients with immunodeficiencies are 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. 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. In order to identify the part of the brain that is to be destroyed, new techniques such as micro electrode mapping have been developed.

Cluster headaches

Cluster headaches occur in cyclical patterns or clusters—which gives the condition of its name. Cluster headache is one of the most painful types of headache. Bouts of frequent cluster headaches may last from weeks to months. Attempts have been made to treat cluster headaches via ablation of the trigeminal nerve, but have not been very effective. Other surgical treatments for cluster headaches are currently under investigation.

Psychiatric disorders

Ablative psychosurgery continues to be used in a few centres in various countries. In the US there are a few centres including Massachusetts General Hospital that carry out ablative psychosurgical procedures. Belgium, the United Kingdom, and Venezuela 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, and obsessive-compulsive disorder. 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. In recent studies, deep brain stimulation (DBS) is beginning to replace ablative brain surgery for severe psychiatric conditions that are generally treatment resistant, such as obsessive-compulsive disorder.