DYT1 dystonia: Neurophysiological properties of the pallidal activity.

OBJECTIVES: The aim of this paper is to find the differences in the physiology of the pallidal neurons in DYT1 and non-DYT1 dystonia. METHODS: We performed microelectrode recording of the single unit activity in both segments of the globus pallidus during stereotactic implantation of electrodes for deep brain stimulation (DBS). RESULTS: We found a reduced firing rate, reduced burst rate, and increased pause index in both pallidal segments in DYT1. Also, in DYT1 the activity in both pallidal segments was similar, but not so in non-DYT1. CONCLUSION: The results suggest a common pathological focus for both pallidal segments, located in the striatum. We also speculate that strong striatal influence on GPi and GPe overrides other input sources to the pallidal nuclei causing similarity in neuronal activity. SIGNIFICANCE: We found significant differences in neuronal activity between DYT1 and non-DYT1 neurons. Our findings shed light on the pathophysiology of DYT-1 dystonia which can be very different from non-DYT1 dystonia and have other efficient treatment tactics.

Oscillations of pause-burst neurons in the STN correlate with the severity of motor signs in Parkinson's disease.

BACKGROUND: Oscillatory activity in the subthalamic nucleus (STN) in Parkinson's disease (PD) is under extensive study. While rhythmic features of local field potentials are implicated in the manifestation of PD motor signs, less is known about single unit activity (SUA). SUA parameters inside the STN show significant heterogeneity, and various firing patterns may contribute unequally to PD pathophysiology. OBJECTIVES: We searched for correlations between SUA parameters and PD motor signs, taking neuronal activity patterns into account. METHODS: 829 spike trains for STN SUA were recorded during 25 DBS surgeries. We have isolated three firing patterns (tonic, irregular-burst and pause-burst) and, using mixed linear models, examined several spiking parameters and burst descriptors (for the last two patterns) for their correlation with UPDRS-III PD motor signs in the contralateral hemibody. RESULTS: The predominance of pause-burst as opposed to tonic activity was associated with a higher PD motor sign severity UPDRS-III. Spike synchronization in the alpha and beta range correlated positively with bradykinesia scores only for pause-burst neurons, while spike synchrony in the theta frequency (4-8 Hz) in these neurons showed an inverse correlation with bradykinesia scores. Other patterns showed no correlation with PD motor signs. CONCLUSIONS: Our work demonstrates the PD motor state is associated with distinct changes in firing patterns and oscillatory synchronization that can be associated with PD motor sign severity. Here, pause-burst patterns were identified as most informative, potentially reflecting a progressive shift from tonic to burst to rhythmic activity in the alpha and beta frequency bands in the parkinsonian state.

Psychogenic (nociplastic) pain: Current state of diagnosis, treatment options, and potentials of neurosurgical management.

Classification of pain syndromes is quite multifaceted. However, pathogenetic classification by which chronic pain syndromes are usually divided into nociceptive, neuropathic and psychogenic, is crucial in choosing treatment tactics. In modern classifications, psychogenic pain is distinguished from nociceptive pain (associated with direct tissue injury or damage) and neuropathic pain (in which lesion can only be determined morphologically). Mental disorders play a leading role in psychogenic pain. Here, somatic/neurological disorders, if any, are of no pathogenetic significance in the dynamics of pain syndrome. There are certain algorithms (though not yet fully developed) and even guidelines for diagnosing and treating nociceptive and neuropathic pain, whereas psychogenic pain has been and still is almost out of sight for a long time. Despite its considerable prevalence, attitude towards it is still uncertain. Until now, it has no single classification, nor any strategy with regards to diagnosis, treatment and prevention.

Patients selection for psychiatric neurosurgery: pitfalls and considerations.

Neurosurgical interventions (destructive or neuromodulation) are considered as a therapeutic option for patients with treatment resistant mental disorders. However, the issues of indications and contraindications for psychiatric surgery, method and patient selection remain unresolved. This article discusses possible problems and contradictions in the selection of patients, the need for an interdisciplinary team to work to solve the question of the feasibility of using neurosurgical methods. The authors have identified the main problems that increase the risks of selection and lead to a lack of results or low efficiency of neurosurgical intervention, namely: (1) diagnostic errors or inaccuracies; (2) inconclusive data on therapeutic resistance; (3) lack of a common understanding of the goals and desired results among participants in the selection of patients for neurosurgery. Possible predictors of surgical outcome and ethical issues are also discussed. Neurosurgical interventions as a treatment option for psychiatric disorders are not officially approved in most countries. So an appropriate algorithm for patient selection and clear criteria for outcome measures are needed.

Gamma Knife capsulotomy for correction of obsessive-compulsive symptoms in a patient with schizophrenia: Case report.

The treatment of mental illnesses that are resistant to conservative therapy poses a serious problem. Surgical methods with proven efficacy have been proposed for only a small group of psychiatric diseases, while in practice non-classical clinical situations are seen rather often. A 36-year-old man with a 18-year history of "schizophrenia with a predominant obsessive-compulsive syndrome" was referred to the Burdenko National Medical Research Center of Neurosurgery for consideration of neurosurgical treatment. Based on results of longitudinal independent evaluations of the patient in several specialized clinical centers the disease was considered resistant to medical therapy. Radiosurgical procedure was performed by means of Leksell Gamma Knife Perfexion™ (Elekta AB; Stockholm, Sweden). Ventral portion of the anterior limb of internal capsule was targeted with two 4-mm isocenters on each side, with prescription dose at 50% isodose line of 80 Gy and a maximal dose of 160 Gy. No obvious complications or side effects were noted during 13-month follow-up after radiosurgery. Gradual clinical improvement was observed with 25% reduction of the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score at 13 months after treatment. Similarly, the Hospital Anxiety and Depression Scale (HADS) anxiety and depression scores decreased by 24% and 58%, respectively. This is the first published case of radiosurgical treatment of a psychiatric disorder in Russia. It demonstrates the potential efficacy of Gamma Knife capsulotomy for non-classical forms of obsessive-compulsive disorder comorbid with schizophrenia. Nevertheless, definitive conclusions about the reliability of this radiosurgical indication can only be made based on the results of larger studies.

Neurosurgical management of Tourette syndrome: A literature review and analysis of a case series treated with deep brain stimulation.

Tourette syndrome (TS) is a heterogeneous disorder, which clinical presentation includes both multiple motor and vocal tics and commonly associated psychiatric conditions (obsessive-compulsive disorder, attention deficit hyperactivity disorder, depression, anxiety, etc.). Treatment options primarily consist of non-pharmacological interventions (habit reversal training, relaxation techniques, cognitive behavioral therapy, and social rehabilitation) and pharmacotherapy. In case of the intractable forms, neurosurgical treatment may be considered, primarily deep brain stimulation (DBS). DBS appear to be effective in medically intractable TS patients, although, the preferential brain target is still not defined. The majority of studies describe small number of cases and the issues of appropriate patient selection and ethics remain to be clarified. In this article, we review the main points in management of TS, discuss possible indications and contraindications for neurosurgical treatment, and analyze our experience of DBS in a case series of refractory TS patients with the focus on target selection and individual outcomes.

Is there a single beta oscillation band interfering with movement in Parkinson's disease?

Beta oscillations in basal ganglia are considered to contribute to motor dysfunction in Parkinson's disease (PD). However, there is a high variety in frequency borders for beta oscillations between studies, which complicates the comparison and interpretation of results. Here we aimed to study the homogeneity of oscillations in the broad "beta" range (8-30 Hz) and their implication to motor functioning in PD. For this purpose, we recorded local field potentials (LFP) in the subthalamic nucleus (STN) during 34 deep brain stimulation surgeries. We identified spectral features of LFP recordings in the range 8-30 Hz to search for candidate sub-regions of stable oscillations and assessed their association with clinical scores on the contralateral side of the body and sensitivity to motor tests. Lower frequency oscillations (8-16 Hz) had a significant positive association with bradykinesia score. During voluntary movements, we observed a significant increase in LFP power in the 12-16 Hz range and a decrease in the 18-26 Hz range. We may conclude that the 8-30 Hz oscillation range includes oscillations with different functional features-sensitivity and responsiveness to movement, and clinical symptoms, which should be taken into account in further studies of beta oscillations association with PD pathophysiology. These data assume the coexistence of several frequency domains within beta range that are modulated in different ways under dopaminergic regulation and motor processing in human STN.

Voluntary movements cause beta oscillations increase and broadband slope decrease in the subthalamic nucleus of parkinsonian patients.

Periodic features of local field potentials (LFP) are extensively studied to establish the pathophysiological features contributing to Parkinson's disease (PD). Pathological LFP synchronization in the subthalamic nucleus (STN) was assumed to link with motor signs of PD. Commonly, the association between oscillations and clinical signs is studied while the patients are at rest. However, changes in LFPs during movement may reflect particular traits of motor processing in the basal ganglia under PD. Recently, the aperiodic 1/f broadband component of LFP spectra has attracted the attention of researchers because it may provide meaningful information about the neural activity in the brain. Here, we compared LFP signals in the STN of parkinsonian patients at rest and during hand movements occasionally followed by leg movements using two approaches, one of which accounts for the aperiodic features of LFP spectra. Using both methods, a significant increase was observed in synchronization in the low beta range during sequent leg but not hand movements. For either movement, there was a significant increase in gamma range synchronization using uncorrected power spectra and a significant decrease in the slope of the aperiodic component for the 1/f-corrected method. These findings may support the claim that the 1/f slope possibly reflects the excitatory/inhibitory projections ratio in the recording site. Only the difference in the slope correlated significantly with motor signs of PD. These data show that the slope of aperiodic component may be a useful measure that is sensitive to the specific state and its changes in the brain.