Neurosurgery for mental disorder NMD

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Neurosurgery for mental disorder (NMD) is rarely undertaken; between 1984 and 1994, a total of only 20 operations per year in the UK (CRAG Working Group, 1996) were done. Even fewer operations per year are done now. Therefore, for practical purposes, this form of treatment has effectively ceased, although it was common up until 40 years ago.

The only contemporary indications for such treatment are severe mood disorder or obsessive compulsive disorder (OCD), when the patient wants the operation, when all other reasonable treatments have repeatedly failed, and the patient remains ill but competent to provide informed consent (CRAG Working Group, 1996). For example, under Section 97 of the Mental Health (Scotland) Act, independent certification by the Mental Welfare Commission of a patient's ability to consent and the appropriateness of treatment is required.

Modern NMD operations comprise subcaudate tractotomy, anterior cingulotomy, limbic leucotomy and anterior capsulotomy (CRAG Working Group, 1996). Operations such as amygdalotomy and hypothalamotomy are no longer practised (CRAG Working Group, 1996).

EARLY HISTORY OF NMD

NMD was originally developed because of a need to treat intractable psychotic disorders at a time when there were no effective treatments (Malhi & Bartlett, 2000). Fulton and Jacobsen, while investigating primate frontal lobe function, discovered that bilateral removal of the orbitofrontal cortex subdued the animals, making them appear less anxious (Fulton &

Jacobsen, 1935). Soon afterwards, Lima operated on humans (Fenton, 1999), and Freeman and Watts (Freeman et al., 1978) began 'psychosurgery' in the USA, devising the standard prefrontal leucotomy. Subsequently, 40000 patients in the USA and 12000 patients in the UK were operated on until the mid-1950s (Malhi & Bartlett, 2000).

At this point, the number of such operations declined because of the development of the first effective drug treatments and reports of a 'post-lobotomy syndrome' (Malhi & Bartlett, 2000). The operations to date had employed relatively crude 'freehand' methods, reflecting neurosurgical practice at the time.

RECENT HISTORY OF NMD

It became apparent that the existing operations lesioned very variable brain regions and that there was considerable variability in clinical outcome. An early consensus arose that patients with mood disorders and OCD appeared to benefit most (Knight, 1964), regardless of operation type.

In such patients, it was claimed that lesions confined to the white-matter tracts deep to the orbitomedial prefrontal cortex had minimal effect on intellect and personality while benefit with regard to illness recovery was maintained (Knight, 1964). A stereotactic operative procedure designed to make reproducible lesions in this brain area was then devised (Knight, 1964). Subsequent post-mortem studies of lesion location confirmed this reproducibility (Newcombe, 1975).

The new procedure was termed 'stereotactic subcaudate tractotomy' (SST) and became by far the most common modern NMD used in the UK over the next 40 years (CRAG Working Group, 1996). In other countries, two other stereotactic operations were developed: cingulotomy and anterior capsulotomy (CRAG Working Group, 1996). The combination of what was essentially SST and cingulotomy was termed 'limbic leucotomy' (Richardson, 1973).

STEREOTACTIC SUBCAUDATE TRACTOTOMY (SST)

For the first few decades following the introduction of SST, large patient follow-up studies indicated a significant improvement in 40-60% of otherwise treatment-refractory patients (Bridges et al., 1994; Goktepe et al., 1975). No operative mortality was reported, and there appeared to be minimal effects on personality, with an epilepsy rate of a few per cent. A substantial reduction in completed suicide rate in comparison to untreated depressive illness was noted. These outcome studies have been strongly criticised because of a number of limitations (Cawley & Tarish, 1994). Constructive recommendations for future study have been made (CRAG Working Group, 1996).

CINGULOTOMY AND ANTERIOR CAPSULOTOMY

Lack of space prevents much comment on these other procedures. However, discussion of operative technique and clinical outcome is available (Ballantyne et al., 1987; Meyerson & Mindus, 1988; Richardson, 1973). It should be noted that the location of the cingulotomy lesion was deliberately variable (Richardson, 1973) though not necessarily for a good reason.

SST AC

V

VP

DMT

W

X White-matter tract damage

Figure 7.4 Limbic cortical basal ganglia re-entrant loop with superimposed lesion locations. PC: posterior cingulate; SAC: subgenual anterior cingulate; MOFC: medial or-bitofrontal cortex; CAC: caudal anterior cingulate; VLA: ventrolateral nucleus of the amygdala; VS: ventral striatum; VP: ventral pallidum; DMT: dorsomedial thalamic nucleus; SST: stereotactic subcaudate tractotomy; C: cingulotomy; AC: anterior capsulotomy. Limbic loop circuitry based on Alexander et al., 1990; Price, 1999. Lesion locations derived from Ballantyne et al., 1987; Knight, 1964; Meyerson & Mindus, 1988; Richardson, 1973. Cingulotomy lesion location is very variable and often deep to caudal anterior cingulate

Moreover, conventional anterior capsulotomy does not attempt to avoid damage to fibres passing to the dorsolateral cortex (Meyerson & Mindus, 1988), a fact which might account for reports of significant postoperative apathy and weight gain (Meyerson & Mindus, 1988) with this procedure.

NMD LESION LOCATIONS

Anatomically, the prefrontal cortex is now recognised as being organised into five parallel cortical basal-ganglia re-entrant loops (Alexander et al., 1990), providing the substrate for motor (skeletomotor and oculomotor), cognitive (dorsolateral) and emotional (orbitofrontal and anterior cingulate) function. The orbitofrontal and anterior cingulate loop is also known as the 'limbic' loop, and considerable evidence links this brain region with emotion and mood (Alexander et al., 1990).

Figure 7.4 shows the limbic loop with lesion locations for the various NMD procedures superimposed. Clearly, these operations would be expected to cause marked disruption of function in this particular loop. It has been argued that these loops comprise functional units (Alexander et al., 1990), and lesions anywhere within such a unit may cause similar clinical syndromes (Megga & Cummings, 1994). This might begin to explain why apparently different NMD procedures have similar reported effects, though, clearly, this does not suggest a mechanism of action.

NATIONAL AND INTERNATIONAL AVAILABILITY OF NMD

NMD has always been a controversial treatment and lack of space prevents detailed discussion of evidence for its efficacy and safety versus adverse outcome, or the limitations of that knowledge. The CRAG Working Group for Mental Illness investigated this issue for the NMD procedures of interest here, and their report constitutes the largest and most recent enquiry into NMD in the UK (CRAG Working Group, 1996). They concluded that 'Subject to existing and recommended additional safeguards and procedures, neurosurgery for mental disorder should continue to be available in Scotland, but only as a treatment for intractable obsessive compulsive disorder and affective disorders (e.g. major depressive illness).' Dundee is currently the only centre in the UK practising NMD. Most other countries still allow NMD, though with variable safeguards on its use (Malhi & Bridges, 1997).

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