9 Surgical Management of Parkinson’s Disease and Other Movement
Disorders
Mrs R Mitchell
Consultant Neurosurgeon, Queen Elizabeth Hospital, 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.4 by lesioning the caudate nucleus, anterior
limb of the internal capsule and the pallidofugal fibres. Mortality rates remained high (15.7%) but this
work inspired Fenelon5 and 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 Wycis10 are 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 over activity 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. PD
SURG reported good 1 year 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 could be 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.
a. Localisation of the target with scanning,
b. Insertion of the electrodes,
c. 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.25 The 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 scan31 and 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 continues but 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.
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