Abnormal activity in the globus pallidus in off-period dystonia

Subthalamic oscillatory activity in parkinsonian patients with off-period dystonia

OBJECTIVES

The study was aimed to explore oscillatory activity in the subthalamic nucleus (STN) in Parkinson's disease (PD) with off-period dystonia, a type of levodopa-induced dyskinesias (LID).

METHODS

Eighteen patients with PD who underwent STN DBS were studied. Nine patients had dyskinesia defined as the LID group and nine patients who did not present any sign of dyskinesia were defined as the control group. Microelectrode recordings in the STN together with electromyogram (EMG) were recorded. Spectral and coherence analyses were performed to study the neuronal oscillations in relation to limb muscles.

RESULTS

Two hundred and fifteen neurons were identified. There were 39 neurons with tremor-frequency band (4-7 Hz) oscillation, 57 neurons with β-frequency band (12-30 Hz, β-FB) oscillation and 100 neurons without oscillation, and 19 neurons with very low-frequency band oscillation at a mean peak power of 1.2 ± 0.5 Hz (LFB). These LFB oscillatory neurons (n = 15) were frequently significantly coherent with EMG of off-period dystonia. Notably, 89% (n = 17) neurons with LFB oscillation were found in the patients in the off-dystonia group. The age at onset of PD, duration of PD, and levodopa equivalent dose daily consumption were statistically different between two groups (P < 0.05).

CONCLUSIONS

Subthalamic LFB oscillatory neurons seem to play an important role in the genesis of off-period dystonia in advanced PD. Clinical and demographic analyses confirmed that the earlier age at onset of PD, longer duration of PD, and levodopa exposure are important risk factors in the development of the type of LID.

Facing the unique challenges of dyskinesias in Parkinson’s disease

Dyskinesia is among the most challenging complications of levodopa and dopaminergic drug therapy in advanced Parkinson’s disease. This symptom has a negative impact on the quality of life of patients with Parkinson’s disease and is hard to manage. Current advances in our understanding of the diverse phenomenology and complicated pathophysiology of dyskinesia have led to a number of novel strategies aimed at better control of this complication. Further insight has been gained from focusing on the characteristics of the rating scale used for assessment of dyskinesia and from the inherent susceptibility of dyskinesia to placebo effect. Here, we will briefly review the phenomenology, pathophysiology and the treatment of dyskinesia in Parkinson’s disease.

Alleviation of off-period dystonia in Parkinson disease by a microlesion following subthalamic implantation

Object

A collision/implantation or microlesion effect is commonly described after subthalamic nucleus (STN) implantation for high-frequency stimulation, and this is presumed to reflect disruption of cells and/or fibers. Off-period dystonia, a frequent cause of disability in patients with advanced Parkinson disease, can lead to the need for surgical treatment. The authors assessed the early effect of this microlesion on off-period dystonia.

Methods

The authors assessed 30 consecutive patients with the advanced levodopa-responsive form of Parkinson disease. The patients' symptoms were Hoehn and Yahr Scale score ≥ 3, the mean duration of their disease was 11.4 ± 3.5 years, and they had undergone bilateral implantation of electrodes within the STN for high-frequency stimulation between February 2004 and December 2006. The microlesion effect was defined by the clinical improvement (Unified Parkinson's Disease Rating Scale [UPDRS] Part III score, UPDRS Part IV, item 35) assessed the morning of the 3rd day following STN implantation, after at least a 12-hour withdrawal of dopaminergic treatment and before the programmable pulse generator was switched on (off-drug/off-stimulation mode).

Results

Compared with baseline (off state), the microlesion effect improved the motor score (UPDRS Part III) by 27%. Subscores for tremor, rigidity, and bradykinesia respectively improved by 42, 37, and 25%. Nineteen patients (63%) suffered from off-period dystonia before surgery. Twelve (41%) reported complete relief of their symptoms in the immediate postoperative period and remained free of painful off-period dystonia throughout the 6-month follow-up period.

Conclusions

The author postulated that off-period dystonia alleviation may reflect both a microsubthalamotomy and micropallidotomy effect. They hypothesize, moreover, that the microlesion could play a role in the 6-month postoperative outcome.

Deep brain stimulation in the globus pallidus to treat dystonia: electrophysiological characteristics and 2 years' follow-up in 10 patients

Deep brain stimulation (DBS) was applied in the internal segment of the globus pallidus (GPi) to treat dystonia in 10 patients. One year after surgery the Burke-Fahn-Marsden movement scores were significantly lower than preoperative values (P=0.01). Two years after surgery the mean decrease reached 65% (P=0.001) with no motor symptoms worsening. Single unity activity was recorded in the operating room: GPi cells discharged with tonic (n=19; 29%), irregular (n=32; 48%), or burst-like activity (n=15; 23%) and fired with a mean discharge rate of 39 Hz+/-22. Some neurons demonstrated an oscillatory activity with periods lasting several seconds. Pairs of pallidal cells (n=8) recorded simultaneously displayed discharge synchronization. Movement modulated 64.4% of the cells tested, with increases in firing in 89% of cells and decreases in firing in 10% of cells. GPi cells responded to flexion and extension movements and to several passive manipulations indicating an important sensory role in dystonia. GPi neurons fired in advance of the electromyography (EMG) when the surface EMG was recorded simultaneously with the neuronal activity. Spectral analysis of the co-contracting muscles during dystonia demonstrated prominent high peaks at a low frequency band (20 Hz) during involuntary and voluntary movements. The high amplitude EMG profile recorded at rest diminished to very low values with GPi stimulation, allowing an ease of voluntary contractions. We conclude that DBS in the GPi is a reliable surgical technique for dystonia. GPi cells discharge with distinct electrophysiological characteristics that may explain some of the symptoms in dystonia. EMG recording in the operating room helps to determine which DBS contacts produce the best benefit.

Motor fluctuations and dyskinesias in Parkinson's disease: clinical manifestations

Fluctuations in the symptoms of Parkinson's disease (PD), such as wearing-off and on-off effects, and dyskinesias are related to a variety of factors, including duration and dosage of levodopa, age at onset, stress, sleep, food intake, and other pharmacokinetic and pharmacodynamic mechanisms. The majority of patients, particularly those with young onset of PD, experience these levodopa-related adverse effects after a few years of treatment. Assessment of these motor complications is difficult because of the marked clinical variability between and within patients. Daily diaries have been used in clinical trials designed to assess the effects of various pharmacological and surgical interventions on motor fluctuations and dyskinesias. The most common type of dyskinesia, called "peak-dose dyskinesia", usually consists of stereotypical choreic or ballistic movements involving the head, trunk, and limbs, and occasionally, the respiratory muscles, whereas tremor and punding are less-common complications. Dystonia is also typically seen in patients with diphasic dyskinesia and wearing-off effect. Recognition of the full spectrum of clinical phenomenology of levodopa-related motor complications is essential for their treatment and prevention.

Spontaneous pallidal neuronal activity in human dystonia: comparison with Parkinson's disease and normal macaque

Dystonia is a movement disorder defined by sustained muscle contractions, causing twisting and repetitive movements and abnormal postures. To understand the abnormalities in pallidal discharge in dystonia, we have analyzed the spontaneous activity of 453 neurons sampled from the internal or external pallidum (GPi or GPe) of 22 patients with dystonia, 140 neurons from 11 patients with Parkinson's disease (PD), and 157 neurons from two normal non-human primates (NHPs; Macacca mulatta). All recordings were performed without systemic sedation. Mean GPi discharge rate in dystonia was 55.3 +/- 1.3 (SE) Hz. This was significantly lower than in the normal NHPs (82.5 +/-2.5 Hz) and lower than in PD patients (95.2 +/- 2.3 Hz). Mean GPe discharge rate in dystonia (54.0 +/- 1.9 Hz) was lower than in the normal NHPs (69.7 +/- 3.3 Hz) and was indistinguishable from that in PD patients (56.6 +/- 3.5 Hz). Mean GPi discharge rate was inversely correlated with dystonia severity. GPi showed increased oscillatory activity in the 2- to 10-Hz range and increased bursting activity in both dystonia and PD as compared with the normal NHPs. Because the abnormalities in discharge patterns were similar in dystonia compared with PD, we suggest that bursting and oscillatory activity superimposed on a high background discharge rate are associated with parkinsonism, whereas similar bursting and oscillations superimposed on a lower discharge rate are associated with dystonia. Our findings are most consistent with a model of dystonia pathophysiology in which the two striatal cell populations contributing to the direct and indirect intrinsic pathways of the basal ganglia both have increased spontaneous activity.

Neuronal activity in the basal ganglia and thalamus in patients with dystonia

OBJECTIVE

To explore the role of abnormal neuronal activity in the basal ganglia and thalamus in the generation of dystonia.

METHODS

Microelectrode recording was performed in the globus pallidus internus (GPi), ventral thalamic nuclear group ventral oral posterior/ventral intermediate, Vop/Vim) and subthalamic nucleus (STN) in patients with primary dystonia (n=11) or secondary dystonia (n=9) during surgery. Electromyogram (EMG) was simultaneously recorded in selected muscle groups. Single unit analysis and cross-correlations were carried out.

RESULTS

Three hundred and sixty-seven neurons were obtained from 29 trajectories (GPi: 13; Vop/Vim: 12; STN: 4), 87% exhibited altered neuronal activity including grouped discharges in GPi (n=79) and STN (n=37), long-lasting neuronal activity (n=70) and rapid neuronal discharge (n=86) in Vop/Vim. There were neurons in Vop, GPi and STN firing at the same frequency as EMG during dystonia (mean: 0.39 Hz, range 0.12-0.84 Hz). Significant correlations between neuronal activity and EMG at the frequency of dystonia were obtained (GPi: r2=0.7 (n=31), Vop/Vim: r2=0.64 (n=18) and STN: r2=0.86 (n=17)).

CONCLUSIONS

Consistent with previous findings of abnormalities observed in Vop/VIM and GPi in relation to dystonia, the present data further show that the altered activity in GPi, specifically in dorsal subregions of GPi, Vop/Vim and STN is likely to be directly involved in the production of dystonic movement. Dystonia-related neuronal activity observed in motor thalamus and basal ganglia nuclei of GPi and STN indicates a critical role of their interactions affecting both indirect and direct pathways in the development of either generalized or focal dystonia.

SIGNIFICANCE

These data support a central role of the basal ganglia in producing dystonic movements.

Clinical-pathological study of levodopa complications

We sought to determine the continued benefit and the pattern of motor complications of long-term levodopa treatment in Parkinson's disease. Patients were evaluated between 1968 and 1996. Only those who had an adequate levodopa trial and in whom autopsy revealed Lewy body Parkinson's disease were included. Total levodopa and mean daily dose were calculated in each case. Dyskinesia, wearing-off and on-off were collectively classified as motor adverse effects and reported as cumulative incidence. Forty-two patients (male, 30; female, 12) with mean 15.9 years of illness and 9.1 years follow-up received on average 500-mg levodopa daily over 9.8 years. Seventeen of 21 patients assessed during the last 18 months of life reported some motor benefit. Adverse effects were seen in 71.4% of patients. The most common was dyskinesia, in 61.9%; wearing-off in 35.7%; and on-off in 16.7% of patients. The earliest adverse effect was dyskinesia and the last to emerge was on-off. Isolated dyskinesia was seen in 35.7% and wearing-off in 7.1% of patients; 15.5% of patients developed dyskinesia after 2.6 years and 31% after 6.4 years on levodopa. We concluded that levodopa benefit declined and adverse effects increased with time. Dyskinesia was the earliest and the most common isolated adverse effect.