Psychosurgery is a field of surgery which consists of stereotactic operations on the brain aimed at altering abnormal physiology by severing certain connections between the frontal lobe and the rest of the brain, including the cortex, the nuclei or other brain pathways, which may appear to function normally or abnormally, in order to reduce mental and/or physical suffering in otherwise untreatable patients.
While it was introduced by Moniz in 1936, its popularity and applications boomed for a brief period, only to collapse like a deflated balloon within a few decades. The primary cause of this wane in the practice of psychotherapy was the inappropriate and nonselective use of the operation for all kinds of indications, without regard to the evidence for a good outcome. The lack of accurate diagnostic criteria for many psychiatric disorders, coupled with poor recording and regulation, led to the rise of immense controversy surrounding this field.
Psychosurgery currently refers to operations of the frontal lobe, because no other part of the brain has been found to be sensitive to surgery in such a way as to produce an improvement in affective and anxiety disorders. The only possible exception is resection of the postcentral cortex to relieve the intractable pain in some cases of phantom limb. Recently, interest has been shown in creating lesions in the thalamus and hypothalamus, but the results are far from being translated to the stage of clinical practice.
Operations on the frontal lobe may use various approaches, namely, from the top as Moniz did, laterally, or through the orbit from the inferior aspect. The frontal lobe is the most anterior part of the brain and lies behind the forehead. It ends at the Rolandic fissure behind and the sylvian fissure below. The most posterior parts have to do with the regulation of muscular and visceral functions and should be left untouched for fear of severe disability and even death if they are encroached upon during the operation. For the rest, the frontal lobe has the same structure and so accuracy of lesion location is somewhat flexible, but not the depth of the lesions produced during the operation.
The aim of the operation is to sever some vital connections between this part of the brain and the rest. These include the fronto-thalamic pathways, upon which the cells in the medial nucleus (of the thalamus) depend for survival in a one-on-one manner. Within the nucleus the cells project to the orbit, the frontal pole and the convexity of the frontal lobe, from medial to lateral, respectively. The neurons in the frontal lobe project to the internal capsule and the peduncle, and indirectly to the basal ganglia for the most part. While other frontal lobe-cortical connections do exist, the only important pathway for the purpose of psychosurgery is this pathway. Thus, cutting this pathway at thalamic level (thalamotomy) or during its course (frontal lobotomy), or at its end (topectomy, lobectomy or cortical undercutting) is the aim of psychosurgery.
The goal of surgery has not changed over the decades, but the technique has been highly refined and altered to make the lesions very reliable as to location, using modern imaging techniques and stereotactic surgery. The most recent trend is to forego surgery in favor of non-ablative techniques, namely, deep brain stimulation (DBS) for the same conditions that psychosurgery was indicated in. These include depression and obsessive-compulsive disorder (OCD) resistant to other therapies.
Frontal lobotomy is carried out by the closed (or precision) and the open methods. The open method uses trephine holes to gain access to the frontal lobe close to the coronal suture, preferably from the frontal pole. The cortex at the thalamofrontal radiation is incised using a leucotome or by suction-cautery, and iodized oil is instilled into the incisions finally for X-ray verification of the accurate placement of the lesions. The mortality is about 3%, due mainly to hemorrhage or infection.
Topectomy uses a little larger opening, to resect symmetrical areas of the frontal cortex which are carefully plotted.
Cortical undercutting refers to cutting under the cortex rather than lifting it off, thus limiting blood loss since cerebral arteries travel inwards from the surface of the brain. Described way back in 1949 by Scoville, it makes lesions in Brodmann areas 9 and 10, the cingulate gyrus, and the orbital surface of the frontal lobe, all of which are associated with emotions. This was modified in 1955, by Knight, to restricted orbital undercutting. Lateral dissection was cut short to avoid destroying unnecessary fibers and to avoid extreme personality alterations postoperatively. The improvement in OCD and other psychiatric disorders following this procedure is of the order of 70% to 85%.
All these techniques carry a mortality of 3% or more depending upon operator experience, and a significant risk of epilepsy postoperatively, though this tends to be controlled in about a year.
The transorbital route is simple and suited to poor-risk patients, since it requires no opening of the skull. Instead it uses a pointed tool pushed right through the orbital bone at the back of the socket along the top of the frontal lobe towards the coronal suture, the tool being manipulated to destroy much of the thalamofrontal pathways. This is not otherwise used due to its blind nature and lower effectiveness in psychiatric disorders.
These techniques are being replaced by stereotactic gamma-knife surgery.
Modern stereotactic psychosurgery depends upon four procedures:
- anterior cingulotomy
- subcaudate tractotomy
- limbic leucotomy
- anterior capsulotomy
Since all these techniques cause lesions of the limbic system or adjoining structures, this type of surgery may also be called limbic system surgery. All are comparable in their results and are relatively safe.
- Cingulotomy or anterior cingulotomy refers to placing stereotactic lesions in the anterior cingulate to sever the cingulum bundle. Placing anterior lesions and having a lower total volume of lesions are associated with better outcomes. With significant improvement in symptoms and very few cognitive ill-effects, this procedure shows promise in refractory OCD cases.
Cingulotomy coupled with anterior capsulotomy on both sides can reduce aggressiveness and improve the general state of the patient, with apparently few complications.
- Stereotactic subcaudate tractotomy (SCT) was described by Knight in 1964. It focuses on the destruction of bifrontal pathways in front of the caudate nucleus using radioactive Yttrium implants, connecting the fibers from the frontal cortex and the amygdala to the hypothalamus, to modulate the intensity of emotional reactions. Cognitive deficits were not observed, but memory loss does occur, and some tasks are performed poorly. However, these are transient and thought to be due to postoperative frontal lobe edema than subcaudate damage. The response rates range from 70% to 100%.
- Limbic leucotomy was described in 1973 by Kelly and Richardson. In this stereotactic technique, cingulotomy is paired with SCT to make use of the effects on the autonomic nervous system and the patient’s responses. The improvement was seen in up to 80% of patients.
- Anterior capsulotomy consists of making lesions in the anterior part of the internal capsule. It was introduced by Lars Leksell in Sweden to interrupt the fronto-thalamic radiation. He reported a 78% improvement in symptoms of intractable OCD.
The results of these procedures have been described as excellent in several smaller studies on patients with pharmacoresistant affective disorders or OCD. More than half of treated patients appear to score much higher across the scale of wellbeing and task performance. In OCD, cingulotomy, subcaudate tractotomy, limbic leucotomy, and capsulotomy achieve good results in 56%, 50%, 61% and 67% respectively. In the case of affective disorders, the corresponding rates were 65%, 68%, 78% and 55% respectively. Overall, it is suggested that anterior capsulotomy or limbic leucotomy may be preferred in OCD, while cingulotomy has the lowest rate of adverse effects.>
The similarity of effect rates suggests that these operations are not specific in their benefits and may therefore be used across the spectrum of mental disorder with predictably high rates of success in cases which remain intractable despite adequate and appropriate medical therapy. To quote one study, even by the strictest standards, one-fourth to one-half of patients with intractable OCD benefit from these, and if more general criteria are substituted, this improvement is measurably and significantly present in 50% to 70% of patients.