Timeline of Neurosurgical Treatments
History of Neurosurgery with Movement Disorders
Contributions of Neurosurgeons to Surgery for Movement Disorders (prior to neuromodulation)
Movement Disorders, especially Parkinson's disease, were considered as surgical diseases until the introduction of L-Dopa (1). Parkinson's disease was the most common indication for surgery although other dyskinesias were operated on as well. Neurosurgeons have shown an exceptional skill of anatomical and physiological knowledge, even in the very early era, and the courage of some of them together with serendipity and careful observation and analysis of their patients, have paved the way to the modern surgery that we know today.
Peripheral and spinal procedures
In 1912, René Leriche reported on two parkinsonian patients in whom the sensory roots of the 5th, 6th and 8th cervical nerves had been cut (2). The results were questionable. In 1930, Pollock and Davis performed a more extensive rhizotomy in one patient (3). The rigidity of the affected arm was effectively abolished which might indicate that the spinal reflex is involved in muscular rigidity. The parkinsonian tremor, however, changed in quality and was replaced by an irregular tremor, sometimes fast, sometimes slow. The loss of sensation in the arm provoked slow and jerky movements.
In 1926, Urechia performed cervical sympathectomy on six patients (4). This approach became popular until 1949 when Gardner and Williams found no objective improvement (5).
Puusepp reported on surgical interruption of Burdach's fibers in the posterior column. He found a slight diminution of rigidity whereas the tremor remained unchanged (6). Lateral pyramidal tractotomy at C2 cervical level, even called pyramidotomy, was reported by Putnam in 1933 for the treatment of athetosis and dystonia (7) and in 1940 for treatment of parkinsonism (8). This approach was later widely used in parkinsonian patients by Ebin (9) and Oliver (10). The results were poor. Tremor diminished in 23%, and paralysis was a rule. The reduction of the symptoms was proportional to the degree of paralysis. Tremor recurred in patients in whom the paralysis improved with time. Oliver continued with interruption of all lateral tracts of one cord hemisphere which resulted in ipsilateral hemiparalysis, contralateral loss of pain and temperature sense and a Horner syndrome (11). The parkinsonian symptoms in his 14 patients were reported to have improved.
Open dentatotomy was tried in one patient with post-encephalitic parkinsonism by Delmas-Marsalet and Van Bogaert in 1935. The patient lived for nine days during which his rigidity was ameliorated while the tremor did not change (12).
In 1949 Walker described mesencephalic pedunculotomy for the treatment of hemiballism (13). This procedure was extended to the treatment of Parkinson's disease by Walker and others. Incisions were made at various depths in the peduncle (14, 15). The tremor relief was proportional to the severity of the hemiparesis whereas rigidity always remained unaffected. According to Walker, a compromise between paralysis and freedom of tremor was what best could be expected of pedunculotomy. In 1956 Cooper no longer found justification for this procedure or any other surgery on the pyramidal tract in parkinsonism 16, However, pedunculotomy was still occasionaly used for dyskinesias such as choreoathetosis and dystonia in infantile cerebral palsy (17).
Already in 1890, Sir Victor Horsley had performed a successful resection of the precentral cortex in a boy with hemiathetosis (18). Bucy in 1939 19 and Klemme in 1940 20 performed subpial resection of the premotor cortex area 6 and the motor cortex area 4 in patients with tremor and other dyskinesias. Surgery caused various degrees of hemiparesis, sometimes spasticity, and not seldom epileptic seizures. The relief of tremor was not accompanied by any effect on the rigidity. However, the handicap felt by the patient after surgery was experienced as less disabling than the previous tremor. In Bucy's opinion, it was impossible to abolish tremor without destruction of some part of the cortico-spinal system.
Operation on the internal capsule
Browder reported on interruption of the anterior internal capsule. His approach was transventricular and it included partial removal of the head of the caudate nucleus (21). Surgery was done under local anesthesia. The internal capsule was cut incrementally until the tremor resolved. Also this operation led to hemiparesis and was soon abandoned.
Surgery on the basal ganglia
In 1939 Russel Meyers pioneered a new approach to surgical treatment of Parkinson's disease. In the beginning, he resected the head of the caudate nucleus in one patient. Surgery resulted in a long lasting relief of tremor and rigidity (22). Later on Meyers moved towards resection of various parts of the basal ganglia including the head of the nucleus caudatus and the anterior limb of the internal capsule. A complete tremor relief was reported in 20% of the patients and improvement in further 40%. Meyers found soon that the best results were obtained by transventricular approach to, and incision of, the pallidothalamic fibers at the level of the ansa lenticularis. This was the first time that it was proven that tremor and rigidity could be relieved without involvement of the corticospinal tract. Meyers had an operative mortality close to 16% and he warned against adopting this method for general use (23).
The experience of Meyers encouraged the French neurosurgeons Fénelon and Guiot to use a specially designed leucotome and to conduct free hand electro-coagulation of the ansa lenticularis at open craniotomy. Fénelon experimented with subfrontal, transtemporal and transfontal approaches. This latter route provided amelioration of both rigidity and tremor in 72% of his 11 patients (24). Guiot used a subfrontal approach and reported excellent results in 42.5% of his 47 patients (25). The techniques of Fénelon and Guiot were considered to be less traumatic.
Ligation of anterior choroidal artery
In October 1951 (26), Cooper operated on a parkinsonian patient in whom he intended to perform pedunculotomy through a subtemporal approach. During dissection of dense adhesions due to previous encephalitis, an artery was torn and Cooper had to ligate it. The surgery was then interrupted without cutting the cerebral peduncle. Postoperatively, the patient was free from tremor and rigidity in the contralateral extremities, while motor and sensory functions had remained intact. Arteriography showed that the anterior choroidal artery could not be visualized. Anatomical studies revealed that the anterior choroidal artery irrigates, among other structures, the medial and intermediate segments of the globus pallidus. During the following years Cooper operated on more than 50 patients with this technique. The mortality was 10% and the results were encouraging with an overall improvement in 65% of the patients. Rigidity, tremor, gait, handwriting, general disability, and in few cases speech were reported to have improved. Cooper recommended this technique for parkinsonian patients below the age of 55. The benefit of this surgery was confirmed by more than 25 neurosurgeons 16. This finding indicated that the medial pallidum played an important role for parkinsonian tremor and rigidity. Consequently, Cooper later on chose the medial pallidum as his primary target in the treatment of Parkinson's disease.
Thus, the experiences of Meyers, Fénelon and Guiot on the beneficial effect of surgery on the pallidum and the ansa lenticularis, and the experience of Cooper on the ischemic pallidotomy contributed to the implementation and spread of the newly born human stereotactic technique in the treatment of Parkinson's disease and other dyskinesias.
Stereotactic era: Ablative surgery
The first stereotactic surgery for motor disorder was published in 1950 by both Talairach et al (27) and Spiegel and Wycis (28). In the next few years, the stereotactic methodology made its definite breakthrough in the treatment of Parkinson's disease to the extent that "stereotactic surgery" became almost synonymous with parkinsonian surgery (29). In the beginning the lesions were aimed at the pallidum and the ansa lenticularis (30, 31, 32, 33, 34).
Pallidotomy and pallidoansotomy
In June 1952 Narabayashi in Japan, and in July 1953 Cooper in the United States, independently of each other, performed pallidotomy using chemical agents. Following stereotactic injection of procain oil into the pallidum of parkinsonian patients, Narabayashi stated that this procedure was slightly more efective against rigidity than tremor (35). Cooper's pallidectomy provided lasting relief of tremor and rigidity in 70% of the patients (16).
The pallidum and its output pathways became popular targets among the pioneers of stereotactic surgery. Hence, Spiegel and Wycis, Riechert, Talairach, Guiot, Leksell, Krayenbühl, Bertrand, Gillingham and others recommended various parts of the globus pallidus as surgical target for treatment of parkinsonian patients. With exception of Leksell, most surgeons aimed at the anterior, dorsal and medial part of the globus pallidus. The overall results of pallidotomy were more rewarding for rigidity than for tremor relief (36). However, the group of Leksell reported in 1960 an overall improvement of about 80% of their patients with regard to both tremor, rigidity and bradykinesia (37). The target of Leksell lay at the most ventral part of the postero-lateral pallidum, i.e., completely outside the common pallidal target used by the others. Leksell's target was "rediscovered" by Laitinen and coworkers in 1985 (38).
Based on the anatomical fact that the outflow from the pallidum to the thalamus runs through the fasciculus lenticularis and the ansa lenticularis and that these two bundles together with ascending cerebello-rubro-thalamic pathways converge in the Field H of Forel, Spiegel and Wycis advocated this area as a stereotactic target. Their target lay 6-7 mm lateral from the midline of the third ventricle, 11 mm anterior to the posterior commissure and 2 mm below the level of the intercommissural line (39). The advantage would be that at this level the maximum number of fibers can be interrupted by the smallest lesion (40). Spiegel and Wycis called the procedure campotomy (interruption of campus Foreli) and reported a more consistent improvement of tremor than rigidity, while bradykinesia had not improved (39, 40).
In 1954, Hassler and Riechert introduced ventrolateral thalamotomy as a target of choice for the treatment of Parkinson's disease (41). They noted that the effect of thalamotomy on tremor was better than that of pallidotomy. Even rigidity was relieved, but bradykinesia had remained unaffected. They recommended the anterior part of the ventrolateral thalamus, i.e., the nucleus ventralis oralis anterior, in cases where relief of rigidity was the main goal and the posterior part, the nucleus ventralis oralis posterior in cases where the tremor was the dominating symptom. These recommendations were based on the fact that the pallidothalamic fibres mediating rigidity ended in the ventralis oralis anterior, whereas the dentatothalamic fibers mediating tremor ended in the ventralis oralis posterior. With the introduction of microelectrode techniques, an area of the thalamus, just behind the ventralis oralis posterior, was shown to contain cells which fired in a tremor-synchronous manner (42, 43). This area called nucleus ventralis intermedius became gradually the stereotactic target of choice for the treatment of all tremors, regardless of etiology (44, 45). Besides, the ventrolateral complex of the thalamus became a target of choice in treatment of other movement disorders including athetosis, ballism, chorea and dystonia. However, the results of thalamotomy in these disorders were not as rewarding as in pure tremor.
With the advent of stereotaxis for treatment of movement disorders, there was a radical decrease in surgical mortality. The stereotactic technique proved to be efficient not only in geometrically defining specific targets deep in the brain, but also in making possible to reach them with a probe without causing a major trauma to surrounding structures. The early stereotactic procedures of Spiegel et al. had a mortality of two percent (33). Gradually the mortality decreased and reached already in the 1960's a rate of less than one percent (46, 47). It was also definitely proven that movement disorders could be treated practically without involvment of the corticospinal tract and thus, with very low risk of provoking a hemiparesis. Surveys conducted by many authors on different complications such as hematomas (47, 48), infections (49), and neurological side effects (50, 51, 52), confirmed the safety of stereotactic functional neurosurgery.
After the introduction of L-dopa therapy in the late sixties and early seventies, there was a dramatic decline of stereotactic surgery for Parkinson's disease (1, 45). However, long-term L-dopa therapy caused several side effects and the beneficial effect often decreased. One-and-a-half decades later, a renaissance of stereotactic treatment started again when Laitinen et al re-introduced Leksell's posteroventral pallidotomy for treatment of post-L-Dopa PD (53).