Somatosensory evoked potentials with a unilateral migration disorder of the cerebrum

Transcranial electrical stimulation can be used for clinical investigations of the central nervous system and for monitoring of motor nerve tracts during surgical operations. We wished to reduce the pain involved with the transcranial electrical stimulation and to improve the usefulness of the method for monitoring during surgical operations. A dedicated transcranial electrical stimulator was designed having special features to reduce the pain sensation and the nerve blocking effect of anaesthetics. It provides constant current and constant voltage stimulation pulses with very short duration and high amplitude. The pulse length is adjustable in the range of 15 to 125 microseconds, while the maximum amplitude is 100 V and 1 A for voltage and current stimulation modes, respectively. Special features included high-repetition-rate pulse trains (50-2000 pulses s-1) and a three-electrode stimulation configuration. We suggest that the electrical transcranial stimulation has the potential to be a relatively painless method for routine clinical investigations and a reliable method for monitoring during surgery.     

Peculiarity of soleus motor potentials evoked by transcranial magnetic stimulation and electrical stimulation of tibial nerve

Fas (Apo-1/CD95) ligand (FasL) is a cytotoxic molecule used by T lymphocytes and natural killer cells for target-cell killing and by nonmalignant and malignant cells in the suppression of immune responses. In this study, FasL expression in B- and T-cell non-Hodgkin's lymphomas was investigated by paraffin immunohistochemical analysis. FasL expression was found to be weak in nonaggressive lymphomas (chronic lymphocytic leukemia/small lymphocytic lymphoma, lymphoplasmacytoid lymphoma, Grade 1 follicular center cell lymphoma) and mantle cell lymphoma but strong in aggressive B-cell lymphomas (diffuse large B-cell lymphoma, Burkitt's-lymphoma). Precursor B-lymphoblastic lymphomas were more heterogeneous, with expression varying from weak to strong. In T-cell lymphomas (anaplastic large-cell lymphoma; peripheral T-cell lymphoma, unspecified), strong FasL expression was observed. Apparently, FasL expression is not limited to neoplasms derived from T cells or natural killer cells, and it might play a supporting role in the progression of non-Hodgkin's lymphomas.     

Effects of anesthetics on somatosensory evoked potentials by median nerve stimulation in human--analyses after single administration in volunteers

In the present study, effects of midazolam, thiopental sodium, propofol, and nitrous oxide upon SEP in a clinically used dose were investigated on 24 male volunteers. In addition, antagonistic actions of flumazenil and naloxone against effects of midazolam and nitrous oxide, respectively, on SEP were studied. Midazolam had no effect on latencies of N 20 and P 25, but increased latency of P 45 and attenuated P 100 amplitude. Flumazenil reversed these effects of midazolam of P 45 latency and P 100 amplitude to their control values. While thiopental sodium and propofol suppressed P 100 amplitude, they had no effect on N 20, P 25, P 45 latencies. Nitrous oxide elongated latencies of N 20, P 25, P 45 and decreased P 100 amplitude. Naloxone reversed the effects of nitrous oxide on N 20 and P 25 latencies without affecting increased P 45 latency and attenuated P 100 amplitude. These results suggest that midazolam might have an analgesic action of suppressing cortical sensory neurons, whereas thiopental sodium and propofol have no effect on neurons in the primary sensory cortex. The finding that naloxone antagonized the increased latencies of N 20 and P 25 by nitrous oxide could be explained by the analgesic action of nitrous oxide that could be mediated by opioid receptors. The results also indicate that electrical activities of the cortical neurons in the associated area are more susceptible to psychotropic agents than those in the primary sensory cortex. The effects of anesthetics on SEP appear to reflect their characteristics of functioning mechanisms on cortical neurons. Analysis of SEP is, therefore, useful for the assessment of the mechanism and the acting site of anesthetics in the sensory cortex.     

One-week test-retest reliability of spinal and cortical somatosensory evoked potentials by tibial nerve stimulation

Spinal (Th12) and cortical somatosensory evoked potentials by right and left posterior tibial nerve stimulation at the ankle were performed in 20 healthy volunteers (10 females and 10 males) aged 23-50 years. The procedure was repeated after one week to assess the reliability of the parameters and to establish upper normal variability limits. Reliability was measured by the intraclass correlation coefficient and was excellent for all absolute latencies and at least good for amplitudes and for the spinal-cortical conduction time. Upper variability limits were calculated using a method based on the within-subject mean square, which can be also applied in the case of more than two repetitions.     

Somatosensory evoked potentials in rheumatoid polyarthritis with radiologic involvement of the cervical spine

Somatosensory evoked potentials (SEP) have been recorded in 11 patients with cervical spine involvement, with or without signs of myelopathy due to rheumatoid arthritis (RA). In three patients, SEP have been recorded both before and after cervical spine surgery. In seven cases, the P14 (particularly the P9/P14 amplitude ratio) or P30 potentials were abnormal, whereas other potentials and conduction times were less often modified. Vertebral luxation sites that were predominantly observed at the upper cervical level account for these findings, thus supporting the diagnostic utility of P14 and P30 potentials which respectively take origin in the lower brain stem, close to or into the nuclei cuneatus and gracilis. Postoperative SEP were strongly correlated with the surgical outcome. SEP could be abnormal in the absence of overt clinical myelopathy or vertebral luxations, thus revealing infraclinical damage to the somatosensory pathways. This suggests that SEP recording is useful to discriminate RA patients with upper cervical cord dysfunction from those in whom vertebral lesion proves to have no direct impact on somatosensory conduction.     

Usefulness of trigeminal somatosensory evoked potentials to detect subclinical trigeminal impairment in multiple sclerosis patients

Trigeminal somatosensory evoked potentials (TSEPs) by surface electric pulse stimulation were recorded in 30 normal subjects and in 70 multiple sclerosis (MS) patients, 13 of whom presenting clinical trigeminal impairment. We observed significant prolongation of all TSEPs parameters in MS group. TSEPs were abnormal in 45 patients (64.3%). Clinical and neurophysiological data agreed in 36 patients (51%) on 84 sides (60%). TSEPs were able to detect clinically silent lesions 54 times. TSEPs recording proves to be an additional useful test in MS multimodal evoked potential protocols.     

Effect of simultaneous bilateral tibial nerve stimulation on somatosensory evoked potentials (SEP) in dogs

Since somatosensory evoked potentials (SEP) by hindlimb nerve stimulation are known to ascend bilaterally in the spinal cord, it was investigated whether or not simultaneous bilateral stimulation causes facilitation or inhibition of the stimuli. In an experiment using 36 adult Beagle dogs, the difference between simultaneous bilateral stimulation and unilateral stimulation was studied as to latencies and amplitudes. No significant difference was noted. However, the detection of far-field potentials by bilateral stimulation was not effective in which case far-field potentials did not recorded by unilateral stimulation. It was therefore confirmed that simultaneous bilateral stimulation does not cause facilitation or inhibition in the relay pathways, and does not affect the latency.     

The cortical representation of somatosensory evoked potentials of the phrenic nerve

Parasitic third-stage larvae of the sheep abomasal nematode Haemonchus contortus develop and molt in vitro to the fourth stage (L4) in 48-72 hr, at which time they begin feeding. Coincident with the third molt, larvae begin to secrete significant amounts of protein into culture fluids, including a zinc metalloproteinase. This culture-derived zinc metalloproteinase differs from a previously described metalloproteinase from infective third-stage larvae (L3[2M]), which mediates the ecdysis process. These differences include time of expression, molecular mass, and substrate specificity. The purified proteinase, from cultures of L4, has a molecular weight of approximately 46 kDa, functions as an endopeptidase, and digests several native proteins of host origin including fibrinogen and fibronectin.     

LTP of spinal A beta and C-fibre evoked responses after electrical sciatic nerve stimulation

Plasticity in the central nervous system may play an important role in clinical pain. The present study shows that long-term potentiation (LTP) may be induced in single wide dynamic range (WDR) neurons in the dorsal horn after high-frequency stimulation of the sciatic nerve in intact urethane anaesthetized rats. Extracellular recordings of firing responses after single pulse stimuli were made. The high-frequency conditioning stimulus increased the A beta- and C-fibre-mediated firing responses to single pulse stimuli by 60 and 130%, respectively, for more than 6 h. This finding supports a role for WDR neurons in 'nociceptive memory' in the dorsal horn. The model presented here may be an important tool for further investigations of mechanisms of plasticity within the dorsal horn.     

Nonlinear analysis of visual evoked potentials elicited by color stimulation

The relationship between chromatically modulated stimuli and visual evoked potentials (VEPs) was considered. VEPs of normal subjects elicited by chromatically modulated stimuli were measured under several color adaptations, and their binary kernels were estimated. Up to the second-order, binary kernels obtained from VEPs were so characteristic that the VEP-chromatic modulation system showed second-order nonlinearity. First-order binary kernels depended on the color of the stimulus and adaptation, whereas second-order kernels showed almost no difference. This result indicates that the waveforms of first-order binary kernels reflect perceived color (hue). This supports the suggestion that kernels of VEPs include color responses, and could be used as a probe with which to examine the color visual system.     

The origins of the subcortical component of the median nerve somatosensory evoked potentials

Short latency median nerve somatosensory evoked potentials (SEPs) were studied in two patients presenting with well localized unilateral pontine lesions producing hemisensory deficits. Both the early subcortical (N11-N13) and the later cortical component (N19-P22) of the SEP were abnormal in the patient whose lesion involved the medial lemniscus, while they remained unaffected in a second case of lateral inferior pontine infarction in which the medial lemniscus was spread. These results suggest that the N11-N13 component of the scalp recorded SEP emanates from the brain stem medial lemniscal pathway.     

Spinal trigeminal tractotomy and nociceptive reactions evoked by tooth pulp stimulation in the cat

The effect of transection of the descending root of the spinal trigeminal tract on nociceptive and aversive reactions evoked by stimulation of the tooth pulp nerve was studied in cats. The transection was performed 1-1.5 mm caudally to the obex. 1. The nociceptive reaction, characterized by wide opening of the jaw, dorsiflexion and rotation of the head and by signs of affective behaviour, remained unchanged after transection of the descending root of the trigeminal nerve (n = 6). 2. The instrumental escape reaction was elaborated in three cats before transection of the descending root of the trigeminal nerve and in three cats after transection. The escape reaction was retained after transection of the descending root and the speed of learning to escape the tooth pulp stimulation did not significantly differ in these two groups of animals. 3. It is to be concluded that the transection of the descending root of the spinal trigeminal tract in the cat does not result in dental analgesia.     

Normal postexercise facilitation and depression of motor evoked potentials in postpolio patients

We studied the effects of exercise on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation in healthy subjects and postpolio patients. Subjects performed repeated sets of isometric exercise until the muscle fatigued. In both groups, the mean MEP amplitude immediately after each exercise set was approximately twice that of the baseline amplitude, indicating similar postexercise facilitation, and after fatigue was approximately half that of the baseline amplitude, indicating similar postexercise depression. We conclude that the intracortical component of central fatigue is normal in postpolio patients.     

Electrical stimulation of the trigeminal nerve root for the treatment of chronic facial pain

BACKGROUND: Alterations of the p53 gene are involved in the development of diverse human malignancies, but their incidence and clinicopathologic features are still not well characterized for endometrial carcinoma. METHODS: To investigate the clinicopathologic significance of p53, mutations and loss of heterozygosity (LOH) in endometrial carcinoma in 92 patients with this disease were examined. RESULTS: Mutations of p53 were detected in 20 (22%) of the 92 patients with carcinoma, and LOH was detected in 23 (32%) of the 72 patients in whom heterozygosity of the gene was available. There was a significant correlation between the occurrence of mutation and LOH. Mutations and LOH were more frequent in patients with Grade 3 tumors than in those with Grades 1 and 2 tumors (P = 0.0498, P = 0.0051, respectively). Patients with LOH had a poorer postoperative survival than those without LOH (P = 0.0022, log-rank test), and patients with both LOH and mutation showed the worst prognosis (P < 0.0001, log rank test). Loss of heterozygosity of the p53 gene showed a significant relation to prognosis that was independent of tumor stage, histologic grade, and muscular invasion. CONCLUSIONS: Mutation and LOH of the p53 gene are prognostic indicators in patients with endometrial carcinoma, suggesting that alterations of p53 may play an important role in the development of this cancer.     

The contralateral effect of antidromic stimulation of the trigeminal nerve on the rabbit eye

The effect on contralateral eyes after injuries to one eye has been called the consensual reaction and has been postulated to be either the consequence of a neural reflex or one achieved by circulating substances. Trigeminal stimulation always causes ipsilateral miosis, ocular hyperemia, intraocular hypertension, and a disruption of the blood-aqueous barrier. Disruption of the blood-aqueous barrier in the contralateral eye after stimulation of the trigeminal nerve always occurs and depends on intact sensory innervation to that globe in rabbits. The disruption is not prevneted by pretreatment of the animals with indomethacin. The phenomenon of disruption of the barrier is sometimes accompanied by an elevation of intraocular pressure in the contralateral eye but not by the other irritative responses. Thus, unilateral stimulation of a sensory nerve, the trigeminal, in the rabbit, can produce ipsilateral contralateral disruption of the blood-aqueous barrier.     

Visual evoked potentials during appetitive behavior after septal lesions in rats.

Analyzed averaged visual evoked responses (VERs) at the cortex to flashes used as probe stimuli during different phases of fixed-ratio barpressing for sucrose, using 5 lesioned and 7 nonlesioned male Holtzman rats. Results reveal changes in late components (including after-discharge responses) of VERs of septal preparations that would suggest enhanced electrophysiological arousal to appetitive conditions. The brain-damaged Ss also displayed heightened electrophysiological reactivity to conditions of frustration instituted by intermittent withholding of reinforcement. These dysfunctions were related to the reduced distractibility to trains of extraneous stimuli shown by septal preparations during appetitive behavior. It is suggested that impairment in inhibitory modulation of arousal mechanisms is related to augmentation in behavioral response tendencies often displayed by septal preparations. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduction of prelimbic inhibitory gating of auditory evoked potentials after fear conditioning.

Inhibitory gating (IG) is a basic central nervous system process for filtering repetitive sensory information. Although IG deficits coincide with cognitive and emotional dysfunction in a variety of neuropsychiatric disorders, limited research has been completed on the basic, functional nature of IG. Persistent IG occurs in rat prelimbic medial prefrontal cortex (mPFC), a crucial site for modulating emotional learning. To investigate the interaction of affect and IG, we recorded local field potentials (LFP) directly from prelimbic mPFC and examined the influence of tone-shock fear conditioning (FC) on IG. Behavioral reactions during IG were observed before and after FC, and increase of orienting response after FC indicated induction of tone-shock association. After FC, some components of LFP response exhibited short-term weakening of IG. On a subsequent day of recording, IG strengthened for all LFP components, but individual components differed in their particular changes. Affective regulation of IG represents an important factor influencing within-subject IG variability, and these results have implications for understanding the role of rapid, implicit neural coding involved in emotional learning and affective disruption in psychiatric disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuralgia of the trigeminal nerve

On the basis of clinical observations of 314 patients with neuralgia of the trigeminal nerve and a number of studies conducted on them (EEG, REG, tomography of the intraorbital canal, a morphological study on neurovascular fascicli removed during the operation of neurotomy and etc.) the authors discuss some problems of the etiology, pathogenesis, clinical picture and treatment of neuralgia of the trigeminal nerve.     

Modulation of cerebral somatosensory evoked potentials arising from tibial and sural nerve stimulation during rhythmic active and passive movements of the human lower limb

The magnitudes of cerebral somatosensory evoked potentials (SEPs), following stimulation of cutaneous or muscle afferents in the upper limb, are reduced during active and passive movements of the fingers. The generalizability of such a movement effect was tested for lower limb events. We measured SEP magnitudes following activation of cutaneous (sural) and mixed (tibial) nerves during the flexion phase of active and passive rhythmic movements of the human lower limb. In eight volunteers, 150 SEPs per condition were recorded from Cz' referenced to Fpz'. Compared to stationary controls, both active and passive movements significantly depressed the early SEP components (P1-N1) [mean values, to 12.8%, 9.9% respectively for tibial nerve and to 29.6%, 25.6% for sural nerve stimulation, p < 0.05]. The attenuation was still observed when only one leg was moved and with stimulation at an earlier point in the flexion phase of movement. Visual fixation did not significantly affect P1-N1 amplitudes, compared to eyes closed. As previously shown, soleus H reflexes with stable M waves were significantly depressed during the movements (p < 0.05). The general construct may be that centripetal flow initiated from somatosensory receptors during limb movement leads to modulation of both spinal and cortical responses following large diameter cutaneous or muscle afferent activation.