Lydia Maria Pereira Giuliano

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).

Pudendal somatosensory evoked potentials in normal women

OBJECTIVE Somatosensory evoked potential (SSEP) is an electrophysiological test used to evaluate sensory innervations in peripheral and central neuropathies. Pudendal SSEP has been studied in dysfunctions related to the lower urinary tract and pelvic floor. Although some authors have already described technical details pertaining to the method, the standardization and the influence of physiological variables in normative values have not yet been established, especially for women. The aim of the study was to describe normal values of the pudendal SSEP and to compare technical details with those described by other authors. MATERIALS AND METHODS The clitoral sensory threshold and pudendal SSEP latency was accomplished in 38 normal volunteers. The results obtained from stimulation performed on each side of the clitoris were compared to ages, body mass index (BMI) and number of pregnancies. RESULTS The values of clitoral sensory threshold and P1 latency with clitoral left stimulation were respectively, 3.64 +/- 1.01 mA and 37.68 +/- 2.60 ms. Results obtained with clitoral right stimulation were 3.84 +/- 1.53 mA and 37.42 +/- 3.12 ms, respectively. There were no correlations between clitoral sensory threshold and P1 latency with age, BMI or height of the volunteers. A significant difference was found in P1 latency between nulliparous women and volunteers who had been previously submitted to cesarean section. CONCLUSIONS The SSEP latency represents an accessible and reproducible method to investigate the afferent pathways from the genitourinary tract. These results could be used as normative values in studies involving genitourinary neuropathies in order to better clarify voiding and sexual dysfunctions in females.

Pudendal nerve latency time in normal women via intravaginal stimulation

INTRODUCTION & OBJECTIVES Studies of motor conduction for the efferent functional assessment of the pudendal nerve in women with pelvic dysfunctions have been conducted through researching distal motor latency times. The transrectal approach has been the classic approach for this electrophysiological examination. The objective of the present study is to verify the viability of the transvaginal approach in performing the exam, to establish normal values for this method and to analyze the influence of age, stature and parity in the latency value of normal women. MATERIALS AND METHODS A total of 23 volunteers without genitourinary pathologies participated in this study. In each, pudendal motor latency was investigated through the transvaginal approach, which was chosen due to patients higher tolerance levels. RESULTS The motor response represented by registering the M-wave was obtained in all volunteers on the right side (100%) and in 13 volunteers on the left side (56.5%). The mean motor latency obtained in the right and left was respectively: 1.99 +/- 0.41 and 1.92 +/- 0.48 milliseconds (ms). There was no difference between the sides (p = 0.66). Latency did not correlate with age, stature or obstetric history. The results obtained in the present study were in agreement with those found by other researchers using the transrectal approach. CONCLUSION The vaginal approach represents an alternative for pudendal nerve distal motor latency time, with similar results to those achieved through the transrectal approach. Normative values obtained herein might serve as a comparative basis for subsequent physiopathological studies.

Electrophysiological evaluation of the pudendal nerve and urethral innervation in female stress urinary incontinence

Introduction and hypothesisAlthough still a matter of debate, stress urinary incontinence (SUI) may be accompanied by damage to urethral and pelvic floor innervations, thus promoting dysfunctions of the urethral support and sphincteric closure mechanisms. The aim of this study was to analyze the pelvic floor and urethral innervations through pelvic electrophysiological tests to identify whether neurological alterations interfere with urinary continence and urethral functional activity.MethodsThis prospective study included 52 women, 33 with clinically and urodynamically proven SUI and 19 continent volunteers matched for age, height, parity, and number of vaginal deliveries by the propensity score method. The patients were divided according to the severity of urinary loss evaluated by measuring abdominal leak point pressure (ALPP). Pudendal nerve terminal motor latency (PNTML), pudendal somatosensory evoked potential (SSEP) latencies, urethral and clitoral sensory thresholds, and urethroanal reflex latency were tested.ResultsSUI and control subjects did not differ in PNTML, SSEP latency, and clitoral sensory thresholds. However, reduced responsiveness to urethral electrosensitivity and prolonged urethroanal reflex latency were detected in most incontinent patients. In addition, urethral electrosensitivity was altered in suspected intrinsic sphincteric dysfunction.ConclusionsUrethral afferent pathways can be altered in women with SUI and may play an important role in evoking intrinsic sphincteric dysfunction.

Sensations and reaction times evoked by electrical sinusoidal stimulation

OBJECTIVE To determine whether 5 Hz and 2000 Hz sinusoidal electric currents evoke different sensations and to indirectly evaluate which peripheral nerve fibers are stimulated by these different frequencies. METHODS One hundred and fifty subjects chose three among eight descriptors of sensations evoked by 5 Hz and 2000 Hz currents and the results were submitted to factor analysis. In 20 subjects, reaction times to 5, 250 and 2000 Hz currents were determined at 1.1 x ST and reaction times to 5 Hz currents were also determined at 2 x ST. RESULTS Responses were grouped in four factors: Factor 1, which loaded mainly in descriptors related to tweezers stimulation, was higher than the other factors during 2000 Hz stimulation at 1.5 x ST. Factor 2, which loaded mainly in descriptors related to needle stimulation, was higher than the other factors during 5 Hz stimulation. Factor 1 increased and Factor 2 decreased with an increase in 5 Hz intensity from 1.5 to 4x ST. Reaction times measured from the fastest responses were significantly different: 0.57 s (0.16 to 1.60), 0.34 s (0.12 to 0.71) and 0.22s (0.08 to 0.35) for 5, 250 and 2000 Hz, respectively, and 0.22s (0.11 to 0.34) for 5 Hz at 2 x ST. CONCLUSIONS Sinusoidal electrical stimulation of 5 Hz and 2000 Hz evoke different sensations. At juxta-threshold intensities, RT measurements suggest that 2000 Hz stimulates Abeta-fibers, 250 Hz Abeta- or A partial differential-fibers, 5 Hz Abeta-, A partial differential- or C-fibers. The fiber type, which was initially stimulated by the lower frequencies, depended on inter-individual differences.

Perceptions and electric senoidal current stimulation

OBJECTIVE To analyze the relationship between perceptions and electrical senoidal current stimulation (ESCS). METHOD The study population comprise 100 healthy volunteers. ESCS of 5 Hz and 2 kHz were applied to the left index finger at one and 1.5 sensory threshold. Following each stimulus train a list of eight words (four related to thin fiber sensations and four related to thick fiber sensations) was presented to the subjects who were asked to choose the three words closer to the experienced sensation. Each chosen word was given a score 1; final results were obtained by the sum of the scores for the words related to thin and thick fiber systems for each situation. RESULTS For 5 Hz ESCS at one and 1.5 sensory threshold thin fibers had significantly higher scores than thick fibers; for 2 kHz ESCS, thick fibers had significantly higher scores. CONCLUSION These results show that there is a relation between different sensations and ESCS of different frequencies.

Reflexo pudendo-anal em mulheres normais

The pudendo-anal reflex was studied in a sample of 31 normal women. Responses were obtained after bilateral independent stimulation of the clitoris, with surface recordings from both sides of the external anal sphincter. Reponses were elicited with double-pulses of 0,2 ms duration with a interstimulus interval of 5 ms, frequency of stimulation was lower than 0,5 Hz. A minimal of four responses were recorded after supramaximal stimulation. In one volunteer no response was recorded after unilateral stimulation. Latencies of the responses from the right and left sides of the anal sfincter after right and left stimulation were 36.35±6.37, 36.28±6.23, 35.88±4.68, 36.44±4.45ms, respectively. No relation was detected between latencies and age, body mass index and parity (considering either total parity or vaginal delivery only). In 12% of the recordings uncertainty was introduced in the latency measurements related to a poor signal-noise ratio.

Effects of the stimulus phase on the air-conducted ocular vestibular evoked myogenic potential in healthy subjects

OBJECTIVE The study aimed to examine the effect of the stimulus phase of air-conducted sound on ocular vestibular evoked myogenic potentials (oVEMPs). METHODS oVEMPs were recorded after air-conducted sounds (500Hz, 4ms duration), presented with initial condensation (positive), rarefaction (negative), and alternant polarities from 12 healthy subjects. RESULTS Most responses showed a bifid n10 peak separated by ∼1.9ms. The most prominent sub-peak after condensation was shorter than the most prominent sub-peak after rarefaction; however, the first sub-peak was shorter after the rarefaction stimuli. When a third sub-peak appeared, it occurred before the most prominent sub-peak after condensation and after the most prominent sub-peak after rarefaction. The latency difference between this third sub-peak and the closest sub-peak was shorter than the difference among the others sub-peaks, in both cases; the oVEMPs after alternating stimuli was an amalgam of the responses to the different stimuli. CONCLUSIONS The findings suggest that the negative to positive change of the stimulus was the main event responsible for the stimulation, and that when a third sub-peak appeared it was related to the initiation or the end of the stimulus. SIGNIFICANCE These findings suggested that the oVEMP response, obtained by air conducted sound, was secondary to stimulation of the same type of afferent vestibular unit, independent of the stimulus polarity.

Expression of praxis induction on cortical excitability in juvenile myoclonic epilepsy.

OBJECTIVE This study aimed to evaluate the effects of praxis induction on sensorimotor cortical and transcallosal excitability in juvenile myoclonic epilepsy (JME). METHODS A total of 36 subjects (18-62years) were included. The JME group was screened by video-electroencephalography neuropsychological protocol and divided into JME without praxis induction [JME-WI (n=12)], JME with praxis-induced seizures or epileptiform discharges [JME-PI (n=10)], and healthy controls (n=14). Motor and somatosensory cortical excitability and transcallosal pathways were evaluated through single-pulse transcranial magnetic stimulation (sTMS) and somatosensory evoked potentials (SEPs). RESULTS Motor and transcallosal excitabilities tested with sTMS were not different in the motor-dominant or non-dominant hemisphere among groups. Significant differences were found in cortical SEP amplitudes in the P27 component of the non-dominant hemisphere (p=0.03, Cohens d=0.98), N35 in the dominant hemisphere (p=0.04, Cohens d=0.96), and P27-35 interpeak amplitude in both somatosensory cortices of the JME-PI group (p=0.03, Cohens d=0.96; p=0.02, Cohens d=1.05) when compared with healthy controls. Giant SEPs were observed in two (16.7%) and five (50%) patients of the JME-WI and JME-PI groups, respectively. Cortical latencies did not reveal differences. CONCLUSIONS Praxis induction was associated with enhanced excitability in the somatosensory cortex of JME patients. SIGNIFICANCE These findings may help clarifying the less favorable therapeutic response in the JME-PI group and indicate identifying praxis induction as an important determinant in differentiating between JME patients.

19. Motor skills were affected by intrauterine somatosensory brain injury that mimics a brachial plexus palsy

cussion-induced rippling of the anterior thigh muscles and biceps brachii. Creatine kinase (CK) values were elevated 3-fold and acetylcholine receptor (AChR) binding antibodies were positive. Nerve conduction studies, including 2 Hz repetitive nerve stimulation were normal. Single fiber electromyography was normal. The needle examination demonstrated small motor unit potentials. Multichannel, intramuscular needle recording of thigh muscles revealed a brief discharge with a frequency of 100 Hz lasting 0.5–1 s. These discharges were much briefer than muscle rippling noted on the skin surface. Muscle biopsy showed an active inflammatory myopathy and reduced sarcolemmal caveolin-3 immunostain in a mosaic pattern. Caveolin-3 gene analysis revealed no mutation. Immunotherapy resulted in resolution of the muscle weakness and rippling and normalization of the CK and AChR antibodies. Conclusion: This case underscores the importance of caveolin-3 in the pathogenesis of iRMD. In addition, the abnormal muscle activity was not completely silent in this patient, suggesting that acquired neuromuscular hyperexcitability consists of a continuum of disorders.