Gilberto Mastrocola Manzano

The effects of total and REM sleep deprivation on laser-evoked potential threshold and pain perception.

Summary Sleep deprivation increased the laser‐evoked potential threshold and concomitantly exerted a hyperalgesic effect in pain perception. These effects were more evident in total sleep deprivation. ABSTRACT We investigated the effects of total and rapid eye movement (REM) sleep deprivation on the thermal nociceptive threshold and pain perception using the objective laser‐evoked potential (LEP) and the subjective visual analogue scale (VAS). Twenty‐eight male adult volunteers were assigned into Control (CTRL), Total (T‐SD), and REM (REM‐SD) Sleep Deprivation groups. The T‐SD and REM‐SD volunteers were totally or selectively deprived of sleep for 2 and 4 consecutive nights, respectively. Pain parameters were measured daily during the experimental period. Volunteers were stimulated on the back of the hand by blocks of 50 diode laser pulses. Intensities increased between successive blocks, ranging from nonnoxious to noxious levels, and the LEP threshold was identified based on the evoked‐response onset. Both the LEP threshold and VAS ratings were significantly increased after the second night of T‐SD. No significant variations were observed in the REM‐SD group, suggesting a predominant role for slow wave sleep rather than selective REM‐SD in pain perception. Also, for both sleep‐deprived groups, the mean values of the LEP threshold and VAS ratings showed a gradual increase that was proportional to the SD deprivation time, followed by a decrease after 1 night of sleep restoration. These findings demonstrate a hyperalgesic modification to pain perception (as reflected by the augmented VAS) and a concomitant increase in the LEP threshold following T‐SD, an apparently contradictory effect that can be explained by differences in the ways that attention affects these pain measurements.

The role of membranous urethral afferent autonomic innervation in the continence mechanism after nerve sparing radical prostatectomy: a clinical and prospective study

PURPOSE We evaluated the somatic and autonomic innervation of the pelvic floor and rhabdosphincter before and after nerve sparing radical retropubic prostatectomy using neurophysiological tests and correlated findings with clinical parameters and urinary continence. MATERIALS AND METHODS From February 2003 to October 2005, 46 patients with prostate cancer were enrolled in a controlled, prospective study. Patients were evaluated before and 6 months after nerve sparing radical retropubic prostatectomy using the UCLA-PCI urinary function domain and neurophysiological tests, including somatosensory evoked potential, and the pudendo-urethral, pudendo-anal and urethro-anal reflexes. Clinical parameters and urinary continence were correlated with afferent and efferent innervation of the membranous urethra and pelvic floor. We used strict criteria to define urinary continence as complete dryness with no leakage at all, not requiring any pads or diapers and with a UCLA-PCI score of 500. Patients with a sporadic drop of leakage, requiring up to 1 pad daily, were defined as having occasional urinary leakage. RESULTS Two patients were excluded from study due to urethral stricture postoperatively. We evaluated 44 patients within 6 months after surgery. The pudendo-anal and pudendo-urethral reflexes were unchanged postoperatively (p = 0.93 and 0.09, respectively), demonstrating that afferent and efferent pudendal innervation to this pelvic region was not affected by the surgery. Autonomic afferent denervation of the membranous urethral mucosa was found in 34 patients (77.3%), as demonstrated by a postoperative increase in the urethro-anal reflex sensory threshold and urethro-anal reflex latency (p <0.001 and 0.0007, respectively). Six of the 44 patients used pads. One patient with more severe leakage required 3 pads daily and 23 showed urinary leakage, including 5 who needed 1 pad per day and 18 who did not wear pads. Afferent autonomic denervation at the membranous urethral mucosa was found in 91.7% of patients with urinary leakage. Of 10 patients with preserved urethro-anal reflex latency 80% were continent. CONCLUSIONS Sensory and motor pudendal innervation to this specific pelvic region did not change after nerve sparing radical retropubic prostatectomy. Significant autonomic afferent denervation of the membranous urethral mucosa was present in most patients postoperatively. Impaired membranous urethral sensitivity seemed to be associated with urinary incontinence, particularly in patients with occasional urinary leakage. Damage to the afferent autonomic innervation may have a role in the continence mechanism after nerve sparing radical retropubic prostatectomy.

Quantitative analysis of EEG background activity in patients with rolandic spikes

OBJECTIVE The aim was to compare the background activity, through quantitative EEG analysis, of patients with rolandic spikes and normal age-matched controls. MATERIAL AND METHODS Twenty-one channel EEG of 23 children with rolandic spikes and 39 normal children, with ages ranging from 7 to 12 years, were submitted to quantitative analysis (FFT) of discharge-free epochs. Patients and controls were divided in groups according to age (7-9 and 10-12 years old). Delta, theta, alpha and beta frequency ranges were compared between groups for all electrode positions. RESULTS Comparing normals, the 7-9 years old group showed power reduction in the alpha and beta ranges. Comparing patients and normal age-matched groups, the patients showed power increase, at all frequency ranges in the 7-9 years old group and at delta and theta frequency ranges in the 10-12 years old group. CONCLUSIONS Our findings agree with recent evidences that these children may differ from normal (besides the eventual occurrence of seizures); but they also suggest that these differences can be related to immaturity and not necessarily related to the epileptiform discharge.

Magnitude squared of coherence to detect imaginary movement

This work investigates the Magnitude Squared of Coherence (MSC) for detection of Event Related Potentials (ERPs) related to left-hand index finger movement. Initially, ERP presence was examined in different brain areas. To accomplish that, 20 EEG channels were used, positioned according to the 10–20 international system. The grand average, resulting from 10 normal subjects showed, as expected, responses at frontal, central, and parietal areas, particularly evident at the central area (C3, C4, Cz). The MSC, applied to movement imagination related EEG signals, detected a consistent response in frequencies around 0.3–1 Hz (delta band), mainly at central area (C3, Cz, and C4). Ability differences in control imagination among subjects produced different detection performance. Some subjects needed up to 45 events for a detectable response, while for some others only 10 events proved sufficient. Some subjects also required two or three experimental sessions in order to achieve detectable responses. For one subject, response detection was not possible at all. However, due to brain plasticity, it is plausible to expect that training sessions (to practice movement imagination) improve signal-noise ratio and lead to better detection using MSC. Results are sufficiently encouraging as to suggest further exploration of MSC for future BCI application.

A brief historical note on the classification of nerve fibers

This is a brief review of the literature focused on the articles that formed the basis for the classification of the nerve fibers. Mention is also made to the origin of the nomenclature of the different motoneurons (alpha, beta and gamma).

Reproducibility in nerve conduction studies and F-wave analysis

OBJECTIVE Reproducibility testing of nerve conduction studies and F-wave latencies in a group of healthy volunteers. METHODS A total of 32 healthy volunteers underwent sensory and motor nerve conduction studies of the ulnar and tibial nerves, including F-waves, elicited by 32 stimuli, repeated in two different days by the same examiner. RESULTS The F-wave latencies showed less variability than the other parameters of conduction studies, and, among them, the F-wave mean latency of the tibial nerve has been the one with the higher reproducibility. CONCLUSIONS F-wave latencies were the parameters with best reproducibility, followed by conduction velocities and amplitudes. SIGNIFICANCE Our data showed that the F-wave mean latency is a parameter with a high reliability, considering the reproducibility, for sequential studies.

The frequency of peripheral neuropathy in a group of HIV positive patients in Brazil

A neuropatia periferica e complicacao neurologica comum, podendo ocorrer nas fases assintomaticas e sintomaticas da infeccao pelo virus da imunodeficiencia humana (HIV). As sindromes mais comuns sao a polineuropatia distal simetrica, polineuropatia desmielinizante inflamatoria, polirradiculopatia, mononeuropatia, mononeuropatia multipla e neuropatia autonomica. OBJETIVO: Avaliar a frequencia da neuropatia periferica em um grupo de pacientes HIV positivo em Sao Paulo, Brasil. METODO: Em um periodo de 17 meses, foram avaliados clinicamente 49 pacientes HIV positivos. Foram solicitados exames laboratoriais e eletroneuromiografia (ENMG) para todos os pacientes. RESULTADOS: Foi estabelecido o diagnostico clinico de neuropatia periferica em 34 (69,4%) dos 49 pacientes. O sinal neurologico mais comum foi a alteracao da sensibilidade (97,1%). Treze (33,3%) dos 39 pacientes que realizaram a ENMG tiveram o diagnostico de neuropatia periferica, sendo a neuropatia sensitivo-motora axonal o achado mais comum. Nao foram encontradas alteracoes significativas nos exames laboratoriais (42 pacientes realizaram os exames), com excecao de quatro pacientes em que o VDRL foi positivo. CONCLUSAO: A neuropatia periferica foi um achado frequente no grupo de pacientes HIV positivo estudados clinicamente.UNLABELLED Peripheral neuropathy is a common neurological complication occurring in asymptomatic and symptomatic stages of HIV infection. The most common syndromes are distal symmetric polyneuropathy, inflammatory demyelinating polyneuropathy, poliradiculopathy, mononeuropathy, mononeuropathy multiplex and autonomic neuropathy. PURPOSE To evaluate the frequency of peripheral neuropathy in a group of HIV seropositive outpatients in São Paulo, Brazil. METHOD Over a period of 17 months, 49 HIV+ patients where evaluated clinically. Laboratory analysis and electroneuromyography were requested to all patients. RESULTS >Thirty four (69.4%) of the 49 patients had the diagnosis of peripheral neuropathy established on clinical grounds. The most common sign was impairment (97.1%) of sensibility. Thirteen (33.3%) of the 39 that were subjected to electroneuromyography had features of peripheral neuropathy, being a sensitive-motor axonal neuropathy the most common. No abnormalities were found in the laboratory analysis performed in 42 patients, except in four who had VDRL positive. CONCLUSION A peripheral neuropathy was frequently found upon clinical examination in our group of HIV positive individuals.

Flunitrazepam-induced changes in neurophysiological, behavioural, and subjective measures used to assess sedation

INTRODUCTION Certain features of event-related potentials (ERPs), electroencephalographic (EEG), and behavioural measures vary with differing states of alertness and/or sedation. PURPOSE This study was conducted to investigate changes in several measures usually viewed as reflecting states of sedation/sleepiness associated with the use of a range of doses of the hypnotic benzodiazepine (BZD) flunitrazepam (FNZ). METHODS This was a double blind, independent group design study of the effects of acute oral doses of FNZ in young healthy volunteers. Forty-eight subjects were randomly allocated to one of four groups-FNZ (0.6, 0.8, and 1.0 mg) and placebo (PLAC)-and tested prior to treatment and then in a posttreatment session close to the theoretical peak plasma concentration. ERP latencies and amplitudes were measured at midfrontal (Fz), midcentral (Cz), and midparietal (Pz) using a standard auditory oddball paradigm. EEG changes were assessed at Pz. Behavioural measures included the digit-symbol substitution test (DSST), a cancellation task (CT), and subjective ratings of alertness and attentiveness by the subjects (SUB) and the experimenter (EXP). RESULTS FNZ led to psychomotor impairments and decreased alertness and attention; these effects were consistent with previous findings. A progressive, dose-related increase in P3 latency occurred in Fz, Cz, and Pz, and there was an increase in N1 (Fz, Cz) and N2 (Fz). N2-P3 amplitude decreased in Fz. EEG power bands beta 1 increased for the two highest doses, but no significant differences were noted in theta, delta, and alpha bands. P3 latencies, experimenter-rated levels of alertness, and DSST scores differentiated all three doses of FNZ from PLAC. CONCLUSION The most sensitive measures used were P3 latencies of the ERPs (which varied with FNZ dose), DSST, and the experimenter-rated levels of alertness. However, we found no evidence for the assumption that one single phenomenon was reflected in all measures and different mechanisms were probably involved. Further experiments will be needed for more in-depth probing of the finer mechanisms underlying sedation/sleepiness and how they affect behavioural and eletrophysiological measures of the central nervous system (CNS) function.

Cortical correlates of response time slowing in older adults: ERP and ERD/ERS analyses during passive ankle movement

OBJECTIVES The response time (RT) to kinesthetic perception has been used as a proprioceptive measurement, for example, in older individuals. However, the RT cannot provide information on impairments at specific stages of the respective sensorimotor processing. In the present study, electroencephalographic (EEG) signals were recorded during passive ankle movement with and without an associated perceptual task of movement detection. The main purpose was to analyze differences between young and older adults both in terms of RT and cortical responses. Putative differences in the latter were expected to point to changes in the processing associated with neural pathways or cortical regions in the older subjects. METHODS The EEG activity of nineteen older (OA, 65-76 years) and 19 young adults (YA, 21-32 years) was recorded during passive ankle movement, without motor voluntary response (NVR, sensory condition), and during a condition with voluntary motor response (VR, with measurement of the RT). Event-related potentials (ERP) and beta event-related desynchronization/synchronization (ERD/ERS) were recorded and analyzed in both experimental conditions. RESULTS The RT in OA was larger than in YA (P<0.0001). EEG analyses showed that the N1 amplitude was larger in the VR than in the NVR condition (P=0.006), whereas no difference for latency was obtained between conditions (P=0.376). Comparisons between the groups revealed attenuated (P=0.019) and delayed (P=0.001) N1 in the OA group, irrespective of the condition (no interaction group vs condition). Only OA showed correlations between RT and N1, with significant correlation for both amplitude (r=-0.603, P=0.006) and latency (r=0.703, P=0.001). The ERD/ERS analyses revealed a task-dependent group effect: in NVR, significant differences were obtained only for the ERS amplitude, which was attenuated in OA (P=0.003). In VR, larger (P=0.004) and delayed (P=0.003) ERD and attenuated (P=0.029) and delayed (P=0.017) ERS peaks were observed in the older group. CONCLUSIONS The results suggest that a larger response time to proprioceptive stimuli in older adults is associated with a weaker and delayed proprioceptive afferent inflow to the cortex. In this scenario, older adults would need a higher cognitive effort (larger ERD) to process the sensory inputs when attempting to properly perform a sensorimotor task. SIGNIFICANCE ERP and ERD/ERS measurements during kinesthetic assessment provide new insights on identification of the origin of sensorimotor slowing in older adults.

A double-dissociation of behavioural and event-related potential effects of two benzodiazepines with similar potencies

This study was designed to explore the role of benzodiazepine affinity to benzodiazepine binding site on acute psychomotor, subjective and memory effects, as well as auditory Event Related Potential (ERP) latencies, in healthy volunteers. Two benzodiazepines with similar affinity to benzodiazepine binding sites, or potency, were compared: the atypical compound lorazepam (2.0 mg), which has been reported to impair priming, and a standard benzodiazepine, flunitrazepam (0.6 mg, 0.8 mg, 1.0 mg). The study followed aplacebo-controlled, double-blind, parallel-group design. Sixty subjects completed a test battery before treatment and at theoretical peak plasma concentration of drugs. Lorazepam and 1.0 mg of flunitrazepam led to comparable alterations on psychomotor, subjective and auditory episodic memory measures. A double-dissociation was found for lorazepam and the equipotent dose of flunitrazepam (1.0 mg): lorazepam was more deleterious than flunitrazepam in time taken to identify fragmented shapes. Lorazepam also impaired direct and indirect stem-completion in comparison to placebo, but this effect was abolished when time to identify shapes was used as a covariate. By contrast, 1.0 mg of flunitrazepam prolonged auditory ERP latencies to a greater extent than lorazepam. High affinity to the benzodiazepine binding sites does not seem to explain the consistent lorazepam-induced impairment of indirect stem-completion. Differences in impairment profile between the benzodiazepines employed may relate to the modality (visual or not) of the tasks used.