Pedro Schestatsky

Neurophysiologic study of central pain in patients with Parkinson disease

Background: Patients with Parkinson disease (PD) may present with various types of pain. In some instances, no cause can be identified and pain is considered a primary disorder (primary central pain [PCP]). We hypothesized that PCP in patients with PD (PD-PCP) may be due to a dysfunction of pain pathways or the processing of pain inputs in the CNS. Methods: We carried out a psychophysical and neurophysiologic study in 9 patients with PD-PCP, 9 patients with PD without pain (PD-NoP), and 9 healthy control subjects. We assessed the clinical characteristics of pain, performed quantitative sensory testing with thermal probes, and recorded laser-evoked potentials (LEPs) and laser-induced sudomotor skin responses (l-SSRs) in “off” and “on” conditions. Results: In “off” condition, patients with PD-PCP had lower heat pain and laser pinprick thresholds, higher LEP amplitudes, and less habituation of the l-SSR in comparison with PD-NoP patients and control subjects. Abnormalities were more marked in the most affected side. In “on” condition, psychophysical and neurophysiologic differences disappeared or were significantly attenuated. Conclusion: Conduction along peripheral and central pain pathways is normal in patients with Parkinson disease with or without primary central pain. However, apart from signs of hyperalgesia, our patients exhibited lack of habituation of sympathetic sudomotor responses to repetitive pain stimuli, suggesting an abnormal control of the effects of pain inputs on autonomic centers. Abnormalities were attenuated by l-dopa, suggesting that the dysfunction may occur in dopamine-dependent centers regulating both autonomic function and inhibitory modulation of pain inputs.

Classification of methods in transcranial Electrical Stimulation (tES) and evolving strategy from historical approaches to contemporary innovations

Transcranial Electrical Stimulation (tES) encompasses all methods of non-invasive current application to the brain used in research and clinical practice. We present the first comprehensive and technical review, explaining the evolution of tES in both terminology and dosage over the past 100 years of research to present day. Current transcranial Pulsed Current Stimulation (tPCS) approaches such as Cranial Electrotherapy Stimulation (CES) descended from Electrosleep (ES) through Cranial Electro-stimulation Therapy (CET), Transcerebral Electrotherapy (TCET), and NeuroElectric Therapy (NET) while others like Transcutaneous Cranial Electrical Stimulation (TCES) descended from Electroanesthesia (EA) through Limoge, and Interferential Stimulation. Prior to a contemporary resurgence in interest, variations of transcranial Direct Current Stimulation were explored intermittently, including Polarizing current, Galvanic Vestibular Stimulation (GVS), and Transcranial Micropolarization. The development of these approaches alongside Electroconvulsive Therapy (ECT) and pharmacological developments are considered. Both the roots and unique features of contemporary approaches such as transcranial Alternating Current Stimulation (tACS) and transcranial Random Noise Stimulation (tRNS) are discussed. Trends and incremental developments in electrode montage and waveform spanning decades are presented leading to the present day. Commercial devices, seminal conferences, and regulatory decisions are noted. We conclude with six rules on how increasing medical and technological sophistication may now be leveraged for broader success and adoption of tES.

A double-blind, randomized, crossover study of Prosigne versus Botox in patients with blepharospasm and hemifacial spasm

There is a lack of evidence on the clinical efficacy and safety of the recently released Chinese botulinum toxin serotype A (Prosigne) for the treatment of focal dystonias and hemifacial spasm. Determining a more precise role of Prosigne in the treatment of such conditions is of paramount importance, because botulinum toxin type A treatments have a huge economic implication in health services, especially in developing countries. The aim of our study was to compare the efficacy and safety of Prosigne in the treatment of blepharospasm and hemifacial spasm in comparison to Botox. We performed a double-blind, randomized, crossover study enrolling 26 patients. There were no significant differences between Prosigne and Botox regarding subjective global improvement, response onset, efficacy duration, and incidence and severity of adverse events. Our results suggest that Prosigne and Botox are comparable with respect to efficacy and safety for the short-term treatment of blepharospasm and hemifacial spasm.

Simultaneous EEG Monitoring During Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a technique that delivers weak electric currents through the scalp. This constant electric current induces shifts in neuronal membrane excitability, resulting in secondary changes in cortical activity. Although tDCS has most of its neuromodulatory effects on the underlying cortex, tDCS effects can also be observed in distant neural networks. Therefore, concomitant EEG monitoring of the effects of tDCS can provide valuable information on the mechanisms of tDCS. In addition, EEG findings can be an important surrogate marker for the effects of tDCS and thus can be used to optimize its parameters. This combined EEG-tDCS system can also be used for preventive treatment of neurological conditions characterized by abnormal peaks of cortical excitability, such as seizures. Such a system would be the basis of a non-invasive closed-loop device. In this article, we present a novel device that is capable of utilizing tDCS and EEG simultaneously. For that, we describe in a step-by-step fashion the main procedures of the application of this device using schematic figures, tables and video demonstrations. Additionally, we provide a literature review on clinical uses of tDCS and its cortical effects measured by EEG techniques.

Hyperhidrosis in Parkinson's disease

We studied the sudomotor skin response (SSR) in patients with Parkinsons disease with and without symptomatic hyperhidrosis. The study was carried out in 13 patients who complained of excessive sweating and in 37 patients who did not have excessive sweating. Patients were matched for age, sex, degree of impairment, duration of the disease, and number and severity of autonomic disturbances. Excessive sweating involved mainly the face, head, and trunk. The SSR was recorded from the palm of the hands to electrical stimulation of the median nerve at the wrist. We analyzed onset latency, peak to peak amplitude, and waveform. Patients with hyperhidrosis had more often absent responses (χ2 = 5.292; P = 0.021), their responses were of lower mean amplitude (analysis of variance [ANOVA]; F[2,101] = 11.678; P < 0.001), and they had a reduced number of responses with a predominantly negative component (χ2 = 8.493; P = 0.004) than patients who did not complain of sweating disturbances. Our results indicate that excessive sweating in Parkinsons disease concurs with decreased activation of sweat glands in the palms of the hands and suggests that axial hyperhidrosis could be a compensatory phenomenon for reduced sympathetic function in the extremities.

Non-invasive brain stimulation and the autonomic nervous system

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are non-invasive methods of brain stimulation (NIBS) that can induce significant effects on cortical and subcortical neural networks. Both methods are relatively safe if appropriate guidelines are followed, and both can exert neuromodulatory effects that may be applied to the investigation of the autonomic nervous system (ANS). In addition, ANS measures can shed important light onto the neurobiologic mechanisms of NIBS. Here we present a systematic review on studies testing NIBS and ANS simultaneously. We structure our findings into four broad (not mutually exclusive) categories: (i) studies in which ANS function was modified by NIBS versus those in which it was not; (ii) studies in which NIBS was used to understand ANS function, (iii) studies in which ANS was used to understand NIBS mechanisms and (iv) NIBS/ANS studies conducted in healthy subjects versus those in patients with neuropsychiatric diseases. Forty-four articles were identified and no conclusive evidence of the effects of NIBS on ANS was observed, mainly because of the heterogeneity of included studies. Based on a comprehensive summary of this literature we propose how NIBS might be further developed to enhance our understanding of the cortical mechanisms of autonomic regulation and perhaps to modulate autonomic activity for therapeutic purposes.

Validation of a Brazilian quantitative sensory testing (QST) device for the diagnosis of small fiber neuropathies.

Quantitative sensory testing (QST) is defined as the determination of thresholds for sensory perception under controlled stimulus. Our aim was to validate a new QST device for Brazilian sample. In 20 healthy adults, thermoalgesic thresholds were assessed using a QST prototype (Heat Pain Stimulator-1.1.10; Brazil). A 30 × 30 mm(2) thermode with a 1°C/s stimulus change rate were applied. Thresholds of three consecutive stimuli were averaged in two different sessions separated by at least two weeks. Additionally long thermal heat pain stimulus was performed. To evaluate the consistency of our method we also analyzed 11 patients with small fiber neuropathy. Results showed good reproducibility of thermal perception thresholds in normal individuals and plausible abnormal thresholds in patients. We conclude that our QST device is reliable when analyzing the nociceptive pathway in controls and patients.

Brazilian Portuguese Validation of the Leeds Assessment of Neuropathic Symptoms and Signs for Patients with Chronic Pain

BACKGROUND Neuropathic pain (NP) is a very frequent and unrecognized condition in clinical practice. Therefore, it is important to have a reliable instrument to assess pain subtypes in various cultures. The Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) has been widely used and validated in many countries. Up to now, there has been no reliability study of this instrument in Brazil. METHODS The scores of the Brazilian Portuguese version of the LANSS were studied in a sample of 90 chronic pain outpatients from southern Brazil. LANSS was translated into Portuguese and then back translated to English. Intraclass correlation coefficient (ICC) and internal consistency (IC) were estimated. The intensity of pain complaints, other demographic data, and LANSS scores distribution according to pain subtypes (nociceptive, neuropathic, and mixed) were also evaluated. RESULTS The Brazilian Portuguese version of the LANSS showed good ICC (r = 0.97) and IC (Cronbachs α = 0.67 for total LANSS score). Patients with NP provided significant higher LANSS scores (19.1 ± 3.3) in comparison with those with nociceptive (7.3 ± 4.5) and mixed (13.9 ± 3.7) types of pain. CONCLUSIONS This LANSS version was found to be a reliable instrument for the evaluation of pain complaints due to a variety of causes. The profile of pain scores was similar to that observed in other countries.

What do general neurologists need to know about neuropathic pain

Neuropathic pain (NP) is defined as pain caused by lesion or dysfunction of the somatosensory system, as a result of abnormal activation of the nociceptive pathway (small fibers and spinothalamic tracts). The most common causes of this syndrome are the following: diabetes, post-herpetic neuralgia, trigeminal neuralgia, stroke, multiple sclerosis, spinal cord injury, HIV infection, cancer. In the last few years, the NP has been receiving special attention for two main reasons: (1) therapeutical refractoriness of a variety of pain syndromes with predominant neuropathic characteristics and (2) the development of diagnostic tools for neuropathic pain complaints. The present review article provides relevant information on the understanding and recognition of NP, as well as evidence-based therapeutic approaches.

Pain–autonomic interaction after work-induced sleep restriction

Poor sleep is commonly associated with alterations in pain perception. However, there is a lack of studies that address work‐associated sleep restriction (SR) and changes in non‐nociceptive perception and autonomic responses after work‐induced SR.