Psychiatric Neurosurgery

Of all the somatic therapies in psychiatric practice today, psychiatric neurosurgery requires the most knowledge about functional neuroanatomy since it is the most radical and irreversible of all interventions. It was only in the last years of the 19th century that rational approaches to psychosurgery were first tried, pursuant to well-publicized clinical cases like Phineas Gage whose frontal lobe lesion in a mining accident showed that frontal lesions could alter a person's personality. In 1894, a Swiss surgeon named Burkhardt performed an operation to selectively destroy the frontal lobes of several psychotic patients in an effort to control their symptoms. Subsequently, Fulton and Jackobsen reported that frontal ablation lessened anxiety in chimpanzees. From these observations, Moniz (1937) argued that by severing the connections between different brain regions, one could force impulses and thoughts to "re-channel" and in effect, coax the brain to "reorganize".

This provisional conclusion about brain organization in the late 1930s launched frontal lobotomy as a treatment for psychiatric disorders. Overcrowded mental asylums and the use of highly morbid convulsive therapy at the time also aided the popularity of lobotomy. Moniz (1937) and Lima's first lesion technique was to inject alcohol in the bilateral frontal lobes of asylum patients. They reported "improvement" in 14 out of 20 subjects. They later developed the leucotomy (a tool to interrupt white matter tracts) and described a rather large surgical target in the frontal lobes. Moniz was the first psychiatrist to receive the Nobel prize in 1949 for his contributions in treating psychosis with leucotomy.

Walter Freeman and James Watts introduced the procedure to the United States. They modified it so the disconnection was carried out through bilateral burr holes placed in the inferior frontal region at the level of the coronal suture. The leucotomy spatula was introduced blindly and swept back and forth. Freeman later devised the so-called ice-pick transorbital leucotomy, performed typically on patients who were postictal from ECT. He inserted a sharp blade under the eyelid through the thin bone into the orbitofrontal lobe. Many of the patients were reported to be improved although a great number of them were observed to have become amotivational and to have lost their capacity to be emotional (McLardy et al., 1949). This crude intervention was zealously promoted by Freeman himself and is likely the source of many of the controversies and stigma surrounding neurosurgery for psychiatric conditions.

Currently, the practice of psychiatric neurosurgery is much more restricted and regulated. Candidates are evaluated by multidisciplinary teams and must meet stringent criteria for severe resistance to conventional multimodal therapies. The majority has either refractory OCD, anxiety, or mood disorders. Treatment of schizophrenia with this modality has fallen out of favor. Current surgical procedures are much more refined and specific in their targets. There are four distinct stereotactic approaches that continue to be used: cingulotomy, subcaudate tracheotomy, limbic leucotomy, and anterior capsulotomy. They are generally performed bilaterally and share similar complication and risks profiles. These include minor symptoms such as headaches, low-grade fever, confusion, and isolated seizures. The most serious complication (intracranial hemorrhages) is rare (0.4 percent in some cases). Mortality directly related to any of the procedures is very rare. Lethargy, personality, cognitive, and behavioral changes are more specific to each intervention.

The aim of a cingulotomy is to lesion the cingulate fasiculus with thermocoagulation approximately 2 to 2.5 cm posterior to the tip of frontal horns, 7 mm lateral to the midline and 1 mm above the ventricular roof. It is the most reported neurosurgical procedure for psychiatric disease in North America and likely the safest. Studies show a range of 30 to 60 percent of significant improvement with affective disorders demonstrating the highest rate of response and OCD the lowest (Tippin et al., 1982).

The goal of a subcaudate tractotomy is to interrupt the fibers from the orbitofrontal cortex to the thalamus. This intervention was designed to minimize cognitive and personality impairments. The target is the substantia innominata (white matter beneath the head of the caudate). The lesion is created with radioactive rods with a half-life of 68 hr. The target area lies at the antero-posterior level of the planum spenoidale, extending from 6 to 18 mm from the midline, being 20 mm long in an antero-posterior direction. Studies have shown significant relief in up to 45 percent of severely ill subjects. Affective disorders are more likely to respond, although OCD symptoms also improve (Hodgkiss et al., 1995).

Limbic leucotomy is a combination of the two previous procedures. Three 6-mm lesions are placed in the posterior inferior medial quadrant of each frontal lobe, along with two lesions in each cingulated gyrus. Results in OCD have shown up to 89 percent improvement up to 16 months postoperatively with improvement in cognitive functions in some patients.

Finally, the aim of anterior capsulotomy is to disconnect fronto-thalamic fibers as they pass through the anterior limb of the internal capsule, between the head of the caudate and putamen. One of the earlier indications for this procedure was schizophrenia, but this has fallen out of favor. Recent reports indicate greatest responses in OCD and depression. Interestingly, a mean 10 percent weight gain is common (Lippitz et al., 1999).

Clinical improvement with all four interventions is progressive over several months. Unfortunately, given the limited use of standardized rating scales across different sites and the open nature of these reports, it is hard to compare results. A recent review (Cos-grove et al., 1995) used the "much improved" clinical outcome measure and found that in OCD capsulotomy was 67 percent effective followed by limbic leucotomy (61 percent), cingulotomy (56 percent), and subcaudate tractotomy (50 percent). In mood disorders, limbic leucotomy was 78 percent effective, subcaudate tractotomy was 68 percent effective, cingulotomy was 65percent effective and finally anterior capsulotomy was 55 percent effective. With the advent of deep brain stimulation, all these areas are potential candidates for neuromodulation with "reversible lesions." Theoretically, one could expect double-blind controlled studies with lead-in sham arms where the implanted wires are not activated.

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