Surgical Treatment of Parkinson's Disease
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SpecialSectionSection Feature Surgical treatment of Parkinson’s Disease he surgical treatment of movement disorders is Authors Lesions in the thalamus more reliably abolished Tover a century old but went into a steep decline in tremor, so that by the late 1950s this had become the the 1970's with the introduction of effective drug preferred target, particularly the ventrointermediate therapies such as levo-dopa. However, about a decade (Vim) nucleus. ago Laitinen reported on the success of pallidotomy for Interest in stereotactic surgery for Parkinson’s the treatment of advanced Parkinson’s disease, which disease all but disappeared following the introduction led to a resurgence of interest in functional of levodopa in 1968. However, the increasing neurosurgery for movement disorders. This coupled to numbers of PD patients with dyskinesias and motor an increased understanding of the underlying neural fluctuations that ensued prompted pursuit of a mechanisms and circuitry involved in basal ganglia surgical solution. Interest in Pallidotomy was renewed disorders with improved surgical techniques and the in the 1980s, and by the mid 1990s its effectiveness had been confirmed by many groups, particularly in development of deep brain stimulation (DBS) Professor Aziz studied technology has paved the way for major advances in physiology at University College the alleviation of levodopa induced dyskinesias. the treatment of Parkinson’s Disease (PD). London graduating in 1978. Unpredictable results with the transplantation of foetal During this time he developed dopamine cells and adrenal medullary grafts into the his keen interest in the role of the striatum, furthered the cause in favour of lesional HISTORICAL BACKGROUND basal ganglia in movement Surgery for PD has passed through several phases disorders. He studied medicine surgery but concern remained regarding high during its evolution, of which three major stages can at King’s College London (1978- complication rates, particularly following bilateral be identified - (1) Non-basal ganglia procedures, (2) 1983) and obtained his surgical procedures. fellowship in 1987 following Open basal ganglia procedures and (3) Stereotactic which he has pursued a career in basal ganglia procedures. neurosurgery. He is currently a DEEP BRAIN STIMULATION (DBS) The recognition that in some cases of stroke, consultant neurosurgeon at the By the 1960s, the use of intraoperative stimulation of contralateral loss of tremor occurred, prompted Radcliffe Infirmary, Oxford and brain targets in preparation for ablative surgery had Charing Cross Hospital, London. Horsley in 1909 to perform excision of the motor He is an expert in functional established the concept that high frequency Vim cortex in a case of athetosis with good effect. However, neurosurgery and has a special stimulation suppressed tremor. This technique was at least two decades passed before this work was interest in the surgical treatment initially used to identify the optimal site for thalamic extended to patients with PD by surgeons such as of movement disorders including lesioning. However by the late 1970s and early 1980s, Bucy (1939). Tremor was reduced with some dystonia. therapeutic rather than diagnostic uses of DBS for PD hemiparesis but the technique was not adopted widely were occurring. High frequency electrical DBS is as identification of the motor strip was difficult, rigidity thought to work by providing an adjustable inhibitory and akinesia remained and post-operative epilepsy effect on the target site. It has the advantages over was a common problem. lesional surgery of being reversible, adaptable and At around this time other procedures which were avoids concern about the adverse cognitive and explored including cervical dorsal rhizotomy, cord bulbar effects observed following bilateral lesions. section, cerebellar dentatectomy and bilateral cortico- Though effective, DBS requires careful postoperative spinal tractotomies but all were later discarded because adjustment, averaging 40 hours of adjustment for of their ineffectiveness. optimum benefit and maintenance of effect in certain In the 1940s and 1950s Meyers focused attention on patient groups. The replacement of equipment when the basal ganglia and reported a 60% improvement in Mr. John Yianni trained at hardware failure occurs (wires moving, breaking or University College London, rigidity and tremor following the combined section of qualifying in 1996. He completed becoming infected) is a further consideration with pallido-fugal fibres, resection of the caudate head and his basic surgical training in estimates in the region of 20%. The stimulation battery anterior capsulotomy. Subsequently an anecdotal Oxford, obtaining his surgical unit also requires replacement every three to five observation by Cooper (1953) led to a new approach. membership in 1999. years depending on target and parameter settings. Subsequently he joined the In a case of attempted pedunculotomy for Oxford Movement Disorder Occasionally this entails emergency admission parkinsonism, the procedure had to be abandoned Group based at The Radcliffe following dramatic rebound symptoms that have been because of bleeding which was controlled by clipping Infirmary Oxford, where he is observed following acute stimulator failure. DBS the anterior choroidal artery. The patient not only currently clinical research fellow therefore necessitates considerable long-term working towards an MD. His field survived, but had good amelioration of symptoms and of interest includes stereotactic commitment from the team looking after the patient. no deficit despite infarction of the globus pallidus. functional neurosurgery for Consequently there remains a place for “palliative” Procedures such as these led the way for modern movement disorders, in thalamotomy or pallidotomy in certain situations. stereotactic neurosurgery. particular dystonia. Although results following DBS can be impressive, By the early 1950s a small area of the basal ganglia they are dependent on careful patient selection. With was defined as the optimal target in surgery for Parkinsonism, the exception of tremor, successful surgical treatment of comprising the medial pallidum and the ansa lenticularis. The tools Parkinsonian symptoms is reliant upon the presence of a capable of reaching these targets without causing damage along dopaminergic responsive system. “Burned out” cases, with no the approach were available in concept from the late 19th century useful “on” periods, will not respond to surgery. Similarly non- and are described by Harting of Utrecht (1861) who designed the dopa responsive parkinsonian diseases, such as multiple system "kephalograph" to make directed intracranial lesions in the atrophy, will not significantly benefit from surgery. It is crucial that experimental animal and Zernov (1889) who developed the patients with significant cognitive or psychiatric difficulties are “encephalometer”, successfully used to treat superficial brain avoided. lesions. Drug induced hallucinations, postural instability and dysphonia, The breakthrough in the development of human stereotactic particularly in the “on” state are further poor prognostic signs. surgery came in 1947 when Speigel and Wycis, who by extending Although the temptation is to offer surgery because little else can the original frame designed by Horsley and Clarke (1908), be done, it must be considered that surgery carries with it at least introduced the stereo-encephalotome, which used landmarks a 3% risk of significant morbidity or mortality resulting from intra- within the brain, rather than the skull. Parkinsonism could now be cerebral haemorrhage. This makes the trade off between possible treated by thermal lesion or injection of alcohol (chemo- risks and potential benefit not sufficiently favourable to pallidectomy) in the thalamus, ansa lenticularis and pallidum. recommend surgery in these patients. ACNR • VOLUME 2 NUMBER 6 JANUARY/FEBRUARY 2003 21 Special Feature the resultant reduction of medication postoperatively. On stimulation or lesioning of the pallidum or STN, transient dyskinesias may ensue, which are usually a predictor of successful outcome. Unilateral surgery can be offered to patients with very asymmetric disease, but most require bilateral surgery to avoid problems with variable medication requirements on the two sides. Adverse effects are very frequent during electrical stimulation of the subthalamic area and include dystonic symptoms, paraesthesia and oculomotor effects. There is also concern about the Lesional Surgery. Post-operative axial MRI scan of DBS. Coronal MRI scan of a patient following frequency of psychiatric side effects, patient following bilateral pallidotomy for PD. implantation of bilateral electrodes into the GPi. particularly depression that probably arises as a result of the inhibition of STN TARGETS FOR DBS IN TREATMENT OF PARKINSON’S DISEASE limbic areas. As this can occur in the absence of any previous Thalamus history of mental disorder, patients with a history of significant Historically, chronic thalamic stimulation had already been used for depression should not be offered STN surgery, since the observed the treatment of chronic pain. However because the thalamus is the rate of suicide has been high in some series. final common outflow pathway for all tremors, contralateral tremor is reliably suppressed with DBS in the region of Vim. The majority SUMMARY of studies that have evaluated thalamic stimulation have reported In