9 Surgical Management of Parkinson’s Disease and Other Movement Disorders
Mrs R Mitchell
Consultant Neurosurgeon, QueenElizabethHospital, Birmingham
History of Movement Disorder Surgery
The surgical management of Parkinson’s disease is best understood from a historical perspective, the work of the early movement disorder surgeons contributing to the understanding of the motor pathways.
Sir Victor Horsley was the first surgeon to be appointed to the National Hospital for Nervous Diseases, in London. He published a paper in 19091 on successfully excising the pre-central gyrus of the cortex in a young man who had violent involuntary movements of the right arm.
Surgeons at that time concentrated on removing areas of the brain trying to improve movement disorders. Some of these procedures were labelled as successful but the mortality and morbidity rates were high.2 Pyramidal tractotomies were carried out by Putnam and Walker.3 Using a sub-temporal approach the lateral two thirds of the cerebral peduncle was sectioned using stimulation to define the appropriate tract and check the completeness of the procedure. Walker commented that pedunculotomy yielded a compromise between paralysis and freedom from tremor. These operations contributed to the basic knowledge of the motor pathway but tremor was only lessened by sacrificing motor power, rendering patients hemiplegic and epileptic.
Once the importance of the basal ganglia in motor control was recognised surgeons tried direct transventricular surgery to alleviate Parkinson’s disease.4by lesioning the caudate nucleus, anterior limb of the internal capsule and the pallidofugal fibres. Mortality rates remained high (15.7%) but this work inspired Fenelon5and Guiot6 to coagulate the fibres leaving the globus pallidus( ansa lenticularis) and report a 72% benefit to tremor and rigidity.
In 1952 Irving Cooper 7 an American neurosurgeon interested in the mechanisms and management of Parkinsonism, was performing a left cerebral pedunculotomy for a patient with post encephalitic tremor and rigidity. He performed a sub-temporal craniectomy and elevated the temporal lobe to expose the edge of the tentorium and the arachnoid of the basal cisterns. Adhesions were dense, as was apparently common in post encephalitic cases, consequently a sharp hook was used to open the arachnoid of the interpeduncular cisterns and during this manoeuvre a small artery was torn and bled profusely. Cooper resected the infratemporal gyrus to visualise the vessel and occluded it with silver clips. The operation was abandoned and the peduncle left intact. Post operative angiography indicated that it was the anterior choroidal artery which had been occluded and amazingly the patient awoke relieved of tremor and rigidity on the right side with no motor or sensory deficits.
Recognising the significance of what had occurred Cooper commenced a programme of anterior choroidal artery ligation for patients with severe Parkinson’s disease. The anterior choroidal artery originates from the internal carotid artery a few millimetres above the origin of the posterior communicating artery and supplies principally the globus pallidus and the ventrolateral nuclei of the thalamus. Between 1952 and 1955 Cooper carried out at least 50 operations to occlude the anterior choroidal artery for parkinsonian tremor and rigidity. The procedure was commonly carried out under local anaesthetic with barbiturate sedation. The main advance here was that paralysis was avoided but mortality remained at 10%.
Cooper sought to make the surgical procedures safer and realising that the anterior choroidal artery supplied the medial globus pallidum and lateral thalamus he progressed onto what he described as a “diagnostic intracerebral nerve block”, the injection of procaine and then alcohol into the medial segment of the globus pallidus. Balloon inflation replaced the procaine injection with time, as a way of producing initially reversible lesions to check that the site was correct. Radio-opaque markers were placed on the skull and pneumoencephalography was performed prior to surgery to determine the trajectory of the injection, which was carried out under local anaesthesia. A chair was designed with X-ray cassette holders attached and a simple frame with a cannula holder was applied to the patients head to facilitate and standardise the procedure.
Chemopallidectomy was carried out between 1954 and 1958, followed more successfully by cryothalamotomy from 1957 and significantly mortality dropped to 2%.8
Stereotactic Surgery
In association with Clarke, Sir Victor Horsley developed an animal stereotactic frame9 which was used to examine the relationship of neuroanatomy to function in animals. They conceived the idea of relating a surgical target to a zero point inside the brain. They divided the head with 3 planes: horizontal, frontal and sagittal. The centre of the external auditory meatus and the centre of the lower margin of the orbit on both sides defined the basal plane, the horizontal plane being taken as 10mm above, to make it more central and close to the” important structures of the brain”. The frontal plane was perpendicular to the horizontal, bisecting the auditory meatus as zero. The sagittal plane in the midline of the skull. Horsley and Clarke mounted a hacksaw on a frame and cut slices of frozen heads 1 or 2 mm thick in all three planes. They worked with macaque monkeys and placed glass grids over the sections to determine surgical targets.
The design of the Horsley Clarke frame inspired the creation of the majority of human frames which were developed after the Second World War when technology had advanced significantly and air encephalography was used to enable brain structures to be referenced to internal brain landmarks rather than the external bony landmarks of the animal frame.
Spiegel and Wycis10are credited with the first human frame which was originally made to lesion the medial nucleus of the thalamus and replace the psychosurgical procedure of frontal lobotomy. In the first communication about the frame the authors also comment that it can be used for interruption of the spinothalamic tract for pain, for pallidal lesions in involuntary movement disorders, for electrocautery of the Gasserian ganglion in trigeminal neuralgia and to aspirate fluid from pathological cavities such as cystic tumours.
Speigel describes11 how he was initially worried that pallidal lesions would cause hypokinesis so a hyperkinetic Huntingdon’s chorea patient was chosen first for stereotactic pallidotomy in 1948. Surgery decreased the chorea and did not induce rigidity so parkinsonian patients were then accepted for operation.
The 50s and 60s were the heydays of stereotactic surgery for movement disorders all around the world. The mortality rate of this type of surgery was so much lower than the previous operations it is no wonder that this form of surgery was so widespread and there would have been many patients at that time with post encephalitic parkinsonism in whom surgery may have proved helpful.
In 196612 with the availability of levodopa, surgery was suddenly abandoned and perhaps in neurological circles forgotten. Surgery continued to be offered in a few centres,in particular: thalamotomy for tremor.13 A further decade passed and published reports appeared of the complications of long term levodopa therapy.14 At first there was hope for further wonder drugs in the manufacture of levodopa agonists but none have proved as impressive as levodopa itself and there are now a large cohort of patients suffering with levodopa induced dyskinesia and on /off fluctuations. There are still surgeons offering lesioning for Parkinson’s disease, essential and MS tremor, especially in countries with less resources. Technology continued to advance and from air encephalography, oil and then water soluble contrast materials were used for ventriculography. Now the risk of post operative epilepsy is reduced by using CT and MRI scanning. The scans have been used to localise targets in the brain with conventional stereotaxy and more recently with direct visualisation of brain nuclei.
Resurgence of Surgery for Movement Disorders
At the start of the 1990s Laitenen published a much cited paper15 drawing the attention of the neurological and neurosurgical community to the value of pallidotomy in Parkinson’s disease. Levodopa dyskinesias were lessened in patients who underwent this form of surgery and there was what is commonly described as a resurgence of interest in surgery for movement disorders. Suddenly the journals were full of papers on the topic.
The 1990s saw two further developments: deep brain stimulators which had previously only been used in pain patients16 were trialled initially for thalamic stimulation17 and then pallidal stimulation.18 Once more it had been necessary for the technology to advance and the early pain stimulators had external batteries and were prone to migration and fracture. Now batteries are internal and complications such as fracture are rare.
The second development was a better understanding of the pathophysiology of Parkinson’s disease brought about by the consumption of MPTP by unfortunate drug addicts19 and the setting up of animal models of Parkinson’s disease which elucidated that there was overactivity of both the medial segment of the globus pallidus and subthalamic nucleus in Parkinson’s disease.20 This made sense of lesioning the globus pallidus and led on to the further development of subthalamic stimulation.21
Current Status of Surgery for Movement Disorders
Bilateral subthalamic stimulation is currently the operation of choice in Parkinson’s disease. PDSURG reported good 1year results in 201022 Subthalamic stimulation needs to be carried out bilaterally as the main benefit is the reduction in drugs required after surgery and thus the reduction in drug side effects. Stimulation has been adopted in preference to lesioning because of concern at the risk of hemiballismus with STN lesioning and the hope that stimulation couldbe stopped and replaced with other therapies if there were further therapeutic developments. The current criteria for bilateral STN surgery are that the patient has dopa responsive disease and has developed the complications of medical therapy, especially levodopa induced dyskinesia and “on/off” fluctuations. The patients range in age from those with early onset disease in their 40s to the early seventies.
Thalamic stimulation is still offered for essential tremor and occasionally the tremor of multiple sclerosis. Bilateral pallidal stimulation has become established for dystonia.23
Bilateral Subthalamic Stimulation for Parkinson’s disease
It must be emphasized that a whole team of people are needed to look after a surgical patient including a neurologist specialising in the selection and management of surgical cases , a specialist nurse often responsible for stimulation adjustments and the technical support requires in scanning, operation and electrophysiology.
The procedure has three parts.
- Localisation of the target with scanning,
- Insertion of the electrodes,
- Tunnelling of the connecting wires and insertion of the battery box.
It has been our philosophy at the Queen Elizabeth Hospital, Birmingham to make the procedure as minimally distressing for the patient as possible so we have developed a technique whereby the patient is brought down to theatre and the whole procedure is completed under general anaesthetic in one day enabling the patient to be discharged 2-3 days after surgery.24
The three different parts of the surgery can be performed with and without anaesthetic, in some cases weeks apart. There is debate in neurosurgical circles about the variation in technique and about the use of electrophysiology.25The STN nucleus has very characteristic firing and this enables confirmation that the electrode is correctly localised in the STN nucleus on the operating table, the scan localisation cannot currently be carried out “real time”. However some would argue that electrophysiology increases the risk of haemorrhage during the procedure, our compromise has been to limit ourselves to a maximum of three tracks on each side, where some groups would routinely employ five.26
The patients prefer not to be awake during the procedure and in our experience awake testing becomes unreliable as the patient tires and once one track has been tried, there may be a “placement effect”.We have shown that the patients benefit from a shorter procedure and a shorter length of stay in hospital with the general anaesthetic procedure.There have not been an increase in complications and the electrophysiological recording has not deteriorated with the patients under general anaesthetic.27
Following surgery the patients are sent home on their usual medication with the stimulator turned off, they are left for about 4 weeks for any brain swelling to subside. The patients are then brought to the hospital “off” medication and each of the eight electrodes trialled. Stimulation is commenced with one electrode on each side which has a low threshold for improvement in parkinsonian symptoms and a wide range of voltage before any side effects such as muscular pulling or double vision are noted.
The patients have a hand held device and can increase their stimulation gradually over the following weeks whilst decreasing their medication, closely supervised by the specialist nurse. Stability is usually achieved after approximately 6 months with the patient on about half their pre operative medication with an associated reduction in the side effects of the medication and smoother control of the disease process. There are now patients who have undergone stimulation for over 10 years and there does not appear to be a need to increase the voltage of stimulation.28 Battery replacements are required every 5 or more years and there is always the risk of infection, especially at the time of battery replacement. At worse this can lead to removal of the whole system, a major setback for any patient. Long term complications include weight gain; depression has been reported but unlike the weight gain, this has not been significant in our patients.29
Future Prospects
As can been seen from the earliest development of this type of surgery, progress only occurs when there is technological development, we await a new wave of technological advances as there have been no major changes in the last few years. We do now have rechargeable batteries and different stimulator systems available.
We have used modern MRI scanning to confirm the accuracy of our electrode placement.30 Currently the “on table” MRIs are only 0.5 Tesla and are not accurate enough to show the STN,which would reduce the length of operation and the risk of electrophysiology if developed. Frameless surgery is possible but the head still needs to be clamped for the procedure.
There have been PET scan31and other studies of patients with stimulators helping us to understand the pathophysiology of the disease and its treatment, hopefully leading to further treatment options.
Considering other recent experimentation, transplantation was dropped as an option after successfully transplanted patients in the American study developed worse dyskinesias32 and Amgen Inc. halted all clinical trials of GDNF on 1st September 2004 due to safety concerns.33
Stem cell research continuesbut teratomas have been reported and current publications are discussing porcine grafting in some detail.34
We do now have evidence of sustained improvement in mobility with stimulation.29
If you are a patient with Parkinson’s disease today and have already developed side effects of treatment, bilateral STN stimulation is likely to be your best surgical option.
References
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2. Bucy PC Cortical extirpation in the treatment of involuntary movements.Am. J. Surg. 1948; 75:257-263.
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5. Fenelon F Essais de traitement neurochirurgical du syndrome parkinsonien par intervention direct sur les voies extrapyramidales immediatement sous-striopallidales. Rev.Neurol.1950;83:437-440.
6. Guiot G Traitement des movements anormaux par la coagulation pallidale. Rev. Neurol. 1953; 89:578-580.
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20. Mitchell IJ , Clarke CE et al. Neural mechanisms underlying parkinsonian symptoms based upon regional uptake of 2-deoxyglucose in monkeys exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Neuroscience 1989 32:213-26.
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