Gait is associated with an increase in tonic firing of the sub-cuneiform nucleus neurons

In animals, the pedunculopontine (PPN) and the sub-cuneiform (SCU) nuclei located in the upper brainstem are involved during the processing of gait. Similar functional nuclei are suspected in humans but their role in gait is unclear. Here we show that, using extra-cellular recordings of the PPN/SCU region obtained in two parkinsonian patients, the SCU neurons increased their firing rate without modifying their firing pattern during mimicked steps. We conclude that SCU neurons are activated during gait processes.

Historical underpinnings of the term essential tremor in the late 19th century

BACKGROUND

The term essential tremor has been in regular use since the second half of the 20th century. To modern neurologists, the word "essential" may seem cryptic. The historical underpinnings of this term have not been examined.

OBJECTIVES

To bring to attention early medical reports using the term essential tremor and examine the characteristics of the disorder that contributed to the proposed use of the term.

METHODS

Review of 19th and early 20th century medical literature on essential tremor.

RESULTS

The term tremore semplice essenziale (simple essential tremor) was first used by Burresi (Italy, 1874) to describe an 18-year-old man with severe, isolated action tremor. Several years later, Maragliano (Italy, 1879), Nagy (Austria, 1890), and Raymond (France, 1892) described similar cases and proposed the terms tremore essenziale congenito (essential congenital tremor), essentieller Tremor (essential tremor), and tremblement essentiel héréditaire (hereditary essential tremor) to define the illness. Mirroring contemporaneous views of constitutional and inherited disease, the key ingredients of the disorder were viewed as the constant presence of tremor in the absence of other neurologic signs and its heritable nature. By the early 20th century, the term began to appear in the medical literature with greater frequency.

CONCLUSIONS

Toward the end of the 19th century, several clinicians attempted to provide a nosologic separation for a tremor diathesis that was often familial and occurred in isolation of other neurologic signs. This disorder, which was termed essential tremor, was later recognized as one of the most common neurologic disorders.

Pyramidal tract side effects induced by deep brain stimulation of the subthalamic nucleus

OBJECTIVE

To study the pyramidal tract side effects (PTSEs) induced by the spread of current from the subthalamic nucleus (STN) to the pyramidal tract (PT), in patients with parkinsonism undergoing STN stimulation.

METHODS

14 patients bilaterally implanted with tetrapolar electrodes were assessed. For each side separately, the threshold of adverse effects induced by monopolar stimulation delivered by the chronically used contact was detected. The voltage was progressively increased until the patient experienced discomfort. All the PTSEs induced at 130 Hz (high-frequency stimulation (HFS)) and 2 or 3 Hz (low-frequency stimulation (LFS)) were videotaped. By superimposing the preoperative and postoperative MR images, the minimum distance (R) from the centre of the used contact to the medial border of the PT were measured.

RESULTS

The progressive increase in voltage at HFS induced tonic motor contractions, mainly located in the face, in 27/28 electrodes. LFS induced synchronous rhythmic myoclonus in the same territory. PTSEs induced at threshold voltage by HFS were observed in the upper face at 13/28 electrodes (bilaterally in six cases) and in the contralateral lower face at five electrodes. A positive correlation was found between the stimulus intensity capable of eliciting motor contractions at HFS and R.

CONCLUSIONS

HFS of the STN preferentially activates the corticobulbar tract over the corticospinal tract. Therefore, cranial motor contractions need to be looked for during electrical parameter setting. The positive correlation between the electrical intensity threshold for PTSEs and R reflects the need for millimetre accuracy in electrode positioning.

Multicentre European study of thalamic stimulation for parkinsonian tremor: a 6 year follow-up

AIM

To evaluate the results of ventral intermediate (Vim) thalamic deep brain stimulation (DBS) in patients with tremor predominant Parkinson's disease (PD) at 6 years post surgery.

METHODS

This was a prolonged follow-up study of 38 patients from eight centres who participated in a multicentre study, the 1 year results of which have been published previously. Total scores as well as scores for individual items of the motor part and the disability part of the Unified Parkinson's Disease Rating Scale were used for evaluation.

RESULTS

Tremor was still effectively controlled by DBS and appendicular rigidity and akinesia remained stable compared with baseline. Axial scores (speech, gait and postural instability), however, worsened, and in parallel the initial improvement in activities of daily living scores at the 1 year follow-up had disappeared at 6 years, despite sustained improvement of tremor. Remarkably, neither daily doses of dopaminergic medication nor fluctuations and dyskinesias had changed at 6 years compared with baseline in this particular patient group.

CONCLUSION

This study confirms that patients with tremor dominant PD who do not present with fluctuations and dyskinesias may have a relatively benign progression of the disease. Vim DBS, although having no effect on akinesia and rigidity, is a relatively lenient surgical procedure and may still have a place for long term symptomatic control of PD tremor in selected patients.

Effects of subthalamic nucleus stimulation and levodopa on freezing of gait in Parkinson disease

OBJECTIVE

We studied the effects of subthalamic nucleus (STN) stimulation vs levodopa on freezing of gait (FOG) and gait impairments in a large consecutive series of patients with Parkinson disease with bilateral STN stimulation.

METHODS

One hundred twenty-three patients performed the Stand Walk Sit Test before and 1 year after surgery both off and on levodopa and off and on stimulation.

RESULTS

Before surgery, 25 patients displayed FOG episodes and 48 were unable to complete the Stand Walk Sit Test when off levodopa. Both symptoms were alleviated by levodopa. After surgery, STN stimulation reproduced the improvement induced by levodopa before surgery in all but two patients with FOG and five others unable to walk. In 11 patients, FOG or inability to perform the test first occurred after surgery. In all patients but those experiencing FOG during the Stand Walk Sit Test before surgery, the benefit of STN stimulation did not reach that of levodopa before surgery. In patients with FOG before surgery, the effect of STN stimulation did not differ from that of levodopa either before or after surgery.

CONCLUSIONS

Overall, subthalamic nucleus stimulation improved levodopa-responsive freezing of gait in most patients, although it was not always as effective as levodopa to improve gait impairments. In addition, surgery can induce gait problems in some patients.

Deep brain stimulation in the subthalamic area is more effective than nucleus ventralis intermedius stimulation for bilateral intention tremor

BACKGROUND

The ventro-lateral thalamus is the stereotactic target of choice for severe intention tremor. Nevertheless, the optimal target area has remained controversial, and targeting of the subthalamic area has been suggested to be superior.

PATIENTS AND METHODS

Eleven patients with disabling intention tremor of different etiology (essential tremor (n = 8), multiple sclerosis (n = 2) and one with, spinocerebellar ataxia) were implanted bilaterally with DBS electrodes targeted to the ventro-lateral thalamus using micro-recording and micro-stimulation. Among five tracks explored in parallel optimal tracks were chosen for permanent electrode implantation. Postoperative tremor suppression elicited by individual electrode contacts was quantified using a lateralised tremor rating scale at least 3 months (in most patients >1 year) after implantation. The position of electrode contacts was determined retrospectively from stereotactic X-ray exams and by correlation of pre- and postoperative MRI.

RESULTS

In all patients, DBS suppressed intention tremor markedly. On average, tremor on the left and right side of the body was improved by 68% (+/-19; standard deviation) and 73% (+/-21), respectively. In most patients, distal electrode contacts located in the subthalamic area proved to be more effective than proximal contacts in the ventro-lateral thalamus. In stereotactic coordinates, the optimal site was located 12.7 mm (+/-1.4; mean +/- standard deviation) lateral, 7.0 (+/-1.6) mm posterior, and 1.5 (+/-2.0) mm ventral to the mid-commissural point. In general, the best contacts could be selected for permanent stimulation. Nevertheless, in some instances, more proximal contacts had to be chosen because of adverse effects (paraesthesiae, dysarthria, gait ataxia) which were more pronounced with bilateral stimulation resulting in slightly less tremor suppression on the left and right side of body (63 +/- 18 and 68 +/- 19%, respectively).

CONCLUSION

Direct comparison of different stimulation sites in individual patients revealed that DBS in the subthalamic area is more effective in suppressing pharmacoresistant intention tremor than the ventro-lateral thalamus proper. Anatomical structures possibly involved in tremor suppression include cerebello-thalamic projections, the prelemniscal radiation, and the zona incerta.

Is there a role for physiotherapy during deep brain stimulation surgery in patients with Parkinson's disease?

In our center, a physiotherapist is present in the operative room to bring relief to the Parkinsonian patient during subthalamic nucleus stimulation surgery under local anesthesia. This study searched to determine the causes of pain and suffering during bilateral electrode implantation and to assess the role of physiotherapy. Ninety-two consecutive patients operated on between 2001 and 2004 were included in this retrospective study. A questionnaire with eight items was developed and mailed to the patients. Seventy-five responses to questionnaires were available. All patients except one experienced physical pain and psychological suffering, alleviated by physiotherapy. These preliminary results need to be confirmed in a prospective randomized study.

Surgical therapy for Parkinson's disease

High frequency stimulation (HFS) has become the main alternative to medical treatment, due to its reversibility, adaptability, and low morbidity. Initiated in the thalamus (Vim) for the control of tremor, HFS has been applied to the Pallidum (GPi), and then to the subthalamic nucleus (STN), suggested by experiments in MPTP monkeys. STN-HFS is highly efficient on tremor, rigidity and bradykinesia and is now widely applied. Criteria for success are correct patient selection and precise electrode placement. The best outcome predictor is the response to Levodopa. The mechanisms of action might associate inhibition of cell firing, jamming of neuronal message and exhaustion of synaptic neurotransmitter release. The inhibition of glutamate STN release could be neuroprotective on nigral cells. Animal experiments support this hypothesis, not contradicted by the long-term follow up of patients. Neuroprotection might have considerable impact on the management of PD patient and warrants clinical trials.

Long term effects of bilateral subthalamic nucleus stimulation on cognitive function, mood, and behaviour in Parkinson's disease

BACKGROUND

Long term effects of subthalamic nucleus (STN) stimulation on cognition, mood, and behaviour are unknown.

OBJECTIVE

This study evaluated the cognitive, mood, and behavioural effects of bilateral subthalamic nucleus deep brain stimulation (STN DBS) in patients with Parkinson's disease (PD) followed up for three years.

METHODS

A consecutive series of 77 PD patients was assessed before, one, and three years after surgery. Mean (SD) age at surgery was 55 (8). Seven patients died or were lost for follow up. Neuropsychological assessment included a global cognitive scale, memory, and frontal tests. Depression was evaluated using the Beck depression inventory. Assessment of thought disorders and apathy was based on the unified Parkinson's disease rating scale. Reports of the behavioural changes are mainly based on interviews done by the same neuropsychologist at each follow up.

RESULTS

Only two cognitive variables worsened (category fluency, total score of fluency). Age was a predictor of decline in executive functions. Depression improved whereas apathy and thought disorders worsened. Major behavioural changes were two transient aggressive impulsive episodes, one suicide, four suicide attempts, one permanent apathy, one transient severe depression, four psychoses (one permanent), and five hypomania (one permanent).

CONCLUSIONS

Comparing baseline, one year, and three year postoperative assessments, STN stimulation did not lead to global cognitive deterioration. Apathy scores mildly increased. Depression scores mildly improved. Behavioural changes were comparatively rare and mostly transient. Single case reports show the major synergistic effects of both medication and stimulation on mood and behaviour, illustrating the importance of a correct postoperative management.

La stimulation cérébrale profonde dans la maladie de Parkinson

The present renewal of the surgical treatment of Parkinson's disease, almost abandoned for twenty Years, arises from two main reasons. The first is the better understanding of the functional organization of the basal ganglia. It was demonstrated in animal models of Parkinson's disease that the loss of dopaminergic neurons within the substantia nigra, at the origin of the striatal dopaminergic defect, induces an overactivity of the excitatory glutamatergic subthalamo-internal pallidum pathway. The decrease in this hyperactivity might lead to an improvement in the pakinsonian symptoms. The second reason is the improvement in stereotactic neurosurgery in relation with the progress in neuroimaging techniques and with intraoperative electrophysiological microrecordings and stimulations, which help determine the location of the deep brain targets. In the 1970s chronic deep brain stimulation in humans was applied to the sensory nucleus of the thalamus for the treatment of intractable pain. In 1987, Benabid and colleagues suggested high frequency stimulation of the ventral intermediate nucleus of the thalamus in order to treat drug-resistant tremors and to avoid the adverse effects of thalamotomies. How deep brain stimulation works is not well known but it has been hypothetized that it could change the neuronal activities and thus avoid disease-related abnormal neuronal discharges. Potential candidates for deep brain stimulation are selected according to exclusion and inclusion criteria. Surgery can be applied to patients in good general and mental health, neither depressive nor demented and who are severely disabled despite all available drug therapies but still responsive to levodopa. The first session of surgery consists in the location of the target by ventriculography and/or brain MRI. The electrodes are implanted during the second session. The last session consists in the implantation of the neurostimulator. The ventral intermediate nucleus of the thalamus was the first target in which chronic deep brain stimulation electrodes were implanted in order to alleviate tremor. This technique can be applied bilaterally without the adverse effects of bilateral thalamotomies. Like pallidotomy, internal globus pallidum stimulation has a dramatic beneficial effect on levodopa-induced dyskinesia but its effects on the parkinsonian triad are less constant and opposite motor effects are sometimes observed in relation with the stimulated contact. The inconstant results, perhaps related to the complexity of the structure led to the development of subthalamic nucleus stimulation. The alleviation of motor fluctuations and the improvement in all motor symptoms allows a significant decrease in levodopa daily dose and in levodopa-induced dyskinesia. Presently, deep brain stimulation is a fashionable neurosurgical technique to treat Parkinson's disease. Subthalamic nucleus stimulation seems to be the most suitable target to control the parkinsonian triad and the motor fluctuations. Because of the possible adverse effects it must be reserved for disabled parkinsonian patients. No large randomized study comparing different targets and different neurosurgical techniques has been performed yet. Such studies, including cost benefit studies would be useful to assess the respective value of these different techniques.

[Parkinson's disease: deep brain stimulation]

The effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) or the internal pallidum (GPi) on the parkinsonian triad and on levodopa-induced dyskinesias are very similar. The antiakinetic effect of STN DBS seems to be slightly better. On the contrary to pallidal DBS, stimulation of the STN allows to reduce dopaminergic treatment by more than 50p.100 on average. Moreover, the current drain is smaller in STN. Thus, the STN is a low budget target compared to the GPi. STN DBS seems to be as effective on PD tremor as stimulation of the classic thalamic target, the ventral intermediate nucleus (Vim), whereas Vim stimulation has no effect on akinesia and very little on levodopa-induced dyskinesias. Thus, the STN has become the main target nucleus for DBS in PD, which is most often performed bilaterally in one surgical procedure. There is a good correlation of the preoperative response to levodopa and postoperative effects of bilateral STN DBS and this defines the patient population. Given the large patient population, simple guidelines for patient selection are developed. The referring physician can preselect patients based mainly on age (less than 70), absence of dementia and presence of severe disability related to motor fluctuations or dyskinesias. It is the responsibility of the operating centre to determine the levodopa response, to confirm the diagnosis, to rule out contraindications and to make sure that the medical treatment cannot be further optimised. Severe surgical complications with permanent sequels are relatively rare, about 1p.100 per implanted side. The patient selection, the precision of the surgery and the quality of the postoperative follow-up are the three main determinants of success.

Bilateral subthalamic nucleus stimulation improves health-related quality of life in PD

In order to assess the impact of bilateral subthalamic nucleus (STN) stimulation in PD on quality of life, the PD Quality of Life questionnaire was assessed in 60 consecutive patients with PD before surgery and 12 months after surgery. All aspects of quality of life, including motor (+48%), systemic (+34%), emotional (+29%), and social (+63%) dimensions, significantly improved with long-term STN stimulation.

[Parkinson disease: deep cerebral stimulation]

The effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) or the internal pallidum (GPi) on the parkinsonian triad and on levodopa-induced dyskinesias are very similar. The antiakinetic effect of STN DBS seems to be slightly better. On the contrary to pallidal DBS, stimulation of the STN allows to reduce dopaminergic treatment by more than 50 p. 100 on average. Moreover, the current drain is smaller in STN. Thus, the STN is a low budget target compared to the GPi. STN DBS seems to be as effective on PD tremor as stimulation of the classic thalamic target, the ventral intermediate nucleus (Vim), whereas Vim stimulation has no effect on akinesia and very little on levodopa-induced dyskinesias. Thus, the STN has become the main target nucleus for DBS in PD, which is most often performed bilaterally in one surgical procedure. There is a good correlation of the preoperative response to levodopa and postoperative effects of bilateral STN DBS and this defines the patient population. Given the large patient population, simple guidelines for patient selection are developed. The referring physician can preselect patients based mainly on age (less than 70), absence of dementia and presence of severe disability related to motor fluctuations or dyskinesias. It is the responsibility of the operating centre to determine the levodopa response, to confirm the diagnosis, to rule out contraindications and to make sure that the medical treatment cannot be further optimised. Severe surgical complications with permanent sequels are relatively rare, about 1 p. 100 per implanted side. The patient selection, the precision of the surgery and the quality of the postoperative follow-up are the three main determinants of success.