Conventional SEPs Research Articles

Etching Patterns of Self-Etching Primers in Relation to Shear Bond Strength on Unground Enamel Samples.

It was the intention of the study to evaluate the etching effects of several self-etching primers on unground enamel and their relevance for shear bond strength testing. Seven self-etching primers (Clearfil SE, Futurabond NR, M-Bond, One Coat, Optibond, Transbond SEP+, Xeno III) and a conventional 35% phosphoric gel acid were applied to bovine incisors according to the manufacturer’s instructions. All specimens were analyzed by electron microscopy. A visual four-step grading was used for the characterization of the macroscopic (5000×) and microscopic (20,000×) etching patterns. In addition, shear bond strength for all the products was tested with an Instron 3344 after 1000 thermocycles between 5 °C and 55 °C. Statistical analysis was carried out using Kruskal–Wallis with Dunn’s post-test and Pearson’s correlation coefficient. Very strong etching patterns with well-defined prisms were found for the conventional etching, Transbond SEP+, and to a lesser degree, for Xeno III. Clearfil SE and Futurabond NR revealed moderate etching patterns, and M-Bond, One Coat, and Optibond revealed very weak etching patterns. The bond strength correlated well with the etching patterns. The highest shear strength was obtained with conventional etching and Transbond SEP+, followed by Clearfil SE. Moderate shear bond strengths were found for Xeno III, Futurabond NR, One Coat, and M-Bond, and the lowest were found with Optibond.

Pain-related somatosensory evoked potentials following CO2 laser stimulation in peripheral neuropathies.

Pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation were examined in 30 patients with peripheral neuropathies, and the results were compared with clinical sensory findings. Pain SEP findings showed a significant correlation with the clinical impairment of pain sensation, but not with the impairment of deep sensations. In contrast, conventional electrically-stimulated SEPs (electric SEPs) showed a significant correlation with deep sensations, but not with the impairment of pain sensation. Examinations of both pain SEPs and electric SEPs, therefore, are considered to be very useful to evaluate physiological functions of sensory nerves in patients with peripheral neuropathies.

Motor evoked potential monitoring for the surgery of brain tumours and vascular malformations.

Brain surgery incurs a significant risk of a new motor deficit in lesions within or adjacent to the motor areas and pathways which, for the patient, presents one of the most disabling complications of such operations. It is a major concern of intracranial procedures to delineate and monitor motor regions in order to preserve their structural and functional integrity, while still achieving maximal cytoreduction. The technique of motor evoked potential recording has had to be adapted to intraoperative recording conditions under general anaesthesia, but has been available for clinical use now for almost ten years. This contribution summarizes the current technique and related methods, as well as our clinical experience in some 400 cases of MEP monitoring in supratentorial tumors, lesions in and around the brainstem, and aneurysm surgery. Intraoperative MEP recordings have been shown to reliably reflect an impending new motor deficit. Irreversible MEP deterioration heralds new paresis, and unaltered recordings predict preserved motor function. This is also true in aneurysm surgery where conventional SEP monitoring may yield false-negative results with regard to development of a new motor deficit. Moreover, if MEP deterioration can be reversed, or halted by early surgical intervention, the presence of only a transient motor deficit, or even the lack of a new postoperative deficit, indicates the success of the MEP monitoring method in the prevention of a significant motor impairment. Certain complicated lesions can only be operated on at all because MEP monitoring is available. In conclusion, intraoperative MEP monitoring is a useful aid in brain surgery with which to avoid a new motor deficit without compromise to the surgical result. Controlled prospective studies will be required to verify the clinical value of the method.

Cadmium reactivity in metal-contaminated soils using a coupled stable isotope dilution-sequential extraction procedure.

To better understand the intrinsic reactivity of Cd, four soils having diverse sources of Cd contamination (total Cd: 22-34 mg kg(-1)) were investigated using a stable isotope dilution-sequential extraction procedure (SID-SEP) during a 59-week incubation. Samples were spiked with carrier-free 111Cd and periodically extracted into five operationally defined fractions; the 111Cd:10Cd ratios were measured by inductively coupled plasma-mass spectrometry. The total labile pool of Cd (E value) was calculated as well as the labile Cd within each extracted fraction. Results for three of the soils (Cd sources: natural, sewage sludge, smelter emissions) were quite similar. The overall %E after 2-week equilibration was 35-49% of total soil Cd. Within fraction 2 (sorbed/carbonate), 70-75% of the Cd was isotopically labile, while within fraction 3 (oxidizable) only 35-41% of the Cd was labile within 2 weeks. The fourth (reducible) and fifth (residual) fractions were dominated by nonlabile Cd. Although all E values increased somewhat from 2 to 59 weeks, none of the extracted fractions reached isotopic equilibrium with the soluble/exchangeable Cd extracted during step 1. Because fractions 2 and 3 dominated the native Cd in all three soils, the total labile pool was contributed primarily (85-98%) by these two fractions. A fourth soil (mine spoil-contaminated) was demonstrably different: after 2 weeks, the overall %E was just 13 and, although 82% of the total Cd was present in the oxidizable fraction, just 2% of that was isotopically labile. The nonlability of Cd in this soil could be ascribed to the predominance of inorganic forms, most likely occluded Cd in sphalerite. No single Cd fraction from the SEP nor any combination of fractions showed a good correspondence with the size of the isotopically labile pool. Our results suggest that conventional SEPs may be of limited utility for predicting bioavailability, for example, during ecological risk assessment.

Pain-related somatosensory evoked potentials can quantitatively evaluate hypalgesia in Wallenberg's syndrome.

In 6 patients with Wallenberg's syndrome who showed a dissociated loss of pain sense, we recorded pain-related somatosensory evoked potentials following CO2 laser stimulation of the hand dorsum (pain SEPs). Two components, N2 and P2, were recorded by stimulation of the unaffected hand, whereas on the affected side they were absent or decreased in proportion to the severity of hypalgesia which was evaluated by both needle test and CO2 laser stimulation. Latency of either component, if appeared, was longer in the affected hand stimulation than that in the unaffected one. In contrast, N20 of the conventional electrically-stimulated SEPs (electric SEPs) showed no difference between the two sides. It is concluded that, unlike other electrophysiological methods, pain SEPs following CO2 laser stimulation can quantitatively evaluate functional impairment of the spinothalamic tract in Wallenberg's syndrome.

Clinical application of paraspinal somatosensory evoked potentials (PS-SEPs) for the diagnosis of spinal cord lesion.

To evaluate the clinical utility of somatosensory evoked potentials elicited by stimulation of the paraspinal region (PS-SEPs), waveform characteristics and scalp topography were studied in 23 normal controls. PS-SEPs were recorded in 22 patients with spinal lesions, and the relation between the abnormal PS-SEPs and clinico-radiological findings was investigated. 1) The normal control study showed clear waveforms on the scalp elicited by stimulation of the paraspinal region from C7 to the L2 spinous process level, with both bilateral and unilateral stimulation. The latency of PS-SEPs was gradually decreased when stimulation was moved in the caudo-rostral direction. 2) The normal range of spinal conduction time and conduction velocity was wide. The conduction velocity resulting from stimulation of the lumbar region tended to be slower than that from stimulation of the thoracic region, perhaps due to the difference in the length of the peripheral cutaneous nerves. 3) There was no correlation between the height and the latency of PS-SEPs. 4) Amplitudes of PS-SEPs after unilateral stimulation of the C7 and Th5 spinous levels were larger on the scalp contralateral to the side of stimulation. These findings were similar to SEPs elicited by median nerve stimulation. There was no significant amplitude laterality of PS-SEPs when the Th10 and L2 spinous levels were stimulated. Posterior tibial nerve SEPs showed a larger amplitude at the scalp ipsilateral to the side of stimulation than at the contralateral side. All these findings suggest that the cortical generator sites of PS-SEPs elicited by C7 and Th5 stimulation are located near the hand area, and those from Th10 and L2 stimulation are between the hand and the foot area. 5) Unilateral stimulation disclosed a clear laterality of sensory disturbance that was obscure when only bilateral stimulation was employed. PS-SEPs showed a high degree of abnormality when the patient had deep sensory disturbance. Generally, abnormal PS-SEPs were found caudal to the clinical sensory level, and a few cases showed abnormal PS-SEPs rostral to the sensory level. The latter might indicate that PS-SEPs detected subclinical sensory disturbance. It was therefore concluded that PS-SEPs are a useful tool for the objective evaluation of sensory disturbance, especially in cases of thoracic lesion, because conventional SEP studies, utilizing non-cephalic references do not provide clear identification of abnormal sensory levels along the thoracic spinal cord.

Electric Field Driven Separations: Phenomena and Applications

Abstract The efficiency of separation processes can usually be assured either by an energy input or by external forces. The majority of conventional sep- arations applies mechanical or thermal energy in combination with pressure or gravity forces. The ability of superimposed electric fields to improve separation processes has been well known for many years. The familiar industrial applications range from solid-solid separation in the beneficiation of ores in the mining industry, coalescence of “water-in-oil” emulsion in the petroleum industry, to cleaning of exhaust gases from solid particles in various technologies.

Physiological study of the spinothalamic tract conduction in multiple sclerosis

This is the first paper to study the physiological function of the spinothalamic tract in multiple sclerosis (MS) using pain-related somatosensory evoked potentials (pain SEPs) following CO 2 laser stimulation. Among 12 patients with MS, hand-and foot-stimulated pain SEPs were significantly delayed or absent in 3 and 7, respectively. These results were totally consistent with clinical impairment of pain-temperature sensation. In contrast, the results of conventional electrically-stimulated SEPs were compatible with impairment of vibration sensation. Therefore, the examination of both pain and electric SEPs is very useful to evaluate the physiological function of the ascending spinal tract in patients with MS.

Spatial mapping of SEP in comatose patients: Improved outcome prediction by combined parietal N20 and frontal N30 analysis

The aim of this study is to evaluate whether SEP spatial mapping can improve outcome prediction in comparison to the conventional SEP recordings. Twenty patients comatose as a result of head injury or cerebral vascular disorders were submitted to 19-channel SEP mapping from median nerve stimulation. SEP recording were performed within the 4th hospital day in 18 cases and over one month from the insult in the remaining two. Nine patients (45%) showed a good recovery or a mild disability, 3 (15%) a severe disability and the rest (40%) died or remained in a vegetative state. Five patients (28%) had bilaterally normal SEP, 5 (28%) the absence of both parietal N20 and frontal N30, while the others (44%) had a dissociation N20/N30 (namely, preserved N20 with absent N30). The SEP mapping was significantly related to the outcome (P = 0.0087) and improved the outcome prediction in comparison to the conventional SEP recordings, allowing to check the presence of frontal N30: in patients with bilaterally present N20 the outcome appeared to depend upon the N30. SEP mapping proved to be a far superior prognostic indicator than the Glasgow Coma Scale. In 3 patients with midline shift on CT scan an abnormal spatial distribution of N20 was disclosed by SEP mapping. Our preliminary results suggest that SEP mapping may improve the assessment of comatose patients in comparison to the use of parietal derivations only.

CO2 laser-induced pain-related somatosensory evoked potentials in peripheral neuropathies: correlation between electrophysiological and histopathological findings.

Pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation as well as conventional electrically stimulated SEPs (electric SEPs) were examined in 10 patients with peripheral neuropathies in whom the histopathological examination of the sural nerve was done. Results of pain SEPs showed a positive relationship with clinical impairment of pain sensation and densities of small myelinated fibers of the sural nerve. In contrast, results of electric SEPs showed a positive relationship with clinical impairment of deep and tactile sensations and with densities of large myelinated fibers of the sural nerve. Therefore, pain SEPs are considered to be generated by ascending signals mediated through nociceptive receptors and A delta fibers. The pain SEP is only one noninvasive and objective method currently available to investigate a physiological condition of the sensory pathway responsible for pain sense, and is especially useful when combined with the conventional electric SEPs.

PAIN-RELATED SOMATOSENSORY EVOKED POTENTIALS IN SYRINGOMYELIA

Pain-related somatosensory evoked potentials following CO2 laser stimulation (pain SEPs) and conventional electrically-stimulated SEPs (electric SEPs) were examined in 8 patients with syringomyelia who showed various forms of dissociated sensory loss. Unlike clinical examination using a pin or needle, pain SEP is considered to be an objective and quantitative test to investigate functions of peripheral and central sensory pathways responsible for pain-temperature sensation (A delta fibres and the spinothalamic tract). Pain SEPs were abnormal in all patients. The results were generally compatible with the degree of a clinical impairment of pain-temperature sensation. Subclinical abnormality was detected in 3 patients. Electric median nerve SEPs using the scalp reference (Fz) were normal in 6 out of 8 patients. However, anterior and posterior cervical responses using a noncephalic reference were absent or small in 7 patients. Electric SEPs following tibial nerve stimulation were normal in 7 patients. These findings suggest that the function of the ascending fibres through the dorsal columns is intact in most patients, whereas the dorsal horn, where a fixed cervical potential is generated, is impaired. Pain SEPs combined with electric SEPs therefore appear to be extremely useful for investigating physiological function in the sensory pathways in patients who show 'dissociated sensory loss' such as in syringomyelia.

Pain-related somatosensory evoked potentials in cortical reflex myoclonus.

To elucidate the sensitivity to pain stimuli in patients with cortical reflex myoclonus, pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation and conventional electrically-stimulated SEPs (electric SEPs) were compared in four patients with cortical reflex myoclonus. The P25 peak of electric SEPs was considerably enhanced but the P320 potential of pain SEPs was of normal amplitude in all patients. After medication, myoclonus was reduced and the amplitude of P25 was decreased, but P320 showed no change. In our previous study of the scalp distribution in normal subjects, a subcortical site, probably the thalamus, was considered to be the generator source of P320. Because most pain stimuli do not reach the cortex, patients with cortical reflex myoclonus are not sensitive to pain stimuli and P320 in pain SEPs is not enhanced.