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At least 343 records · Page 19Linked to original sources
PubMed1993

Comparison of scalp electroencephalogram with subdural electrocorticogram recordings and functional mapping in frontal lobe epilepsy.

We compared the findings of scalp electroencephalogram with subdural electrode array (SEA) recordings in 19 patients with refractory frontal lobe epilepsy. Prolonged scalp interictal recordings localized the epileptogenic zone in 12 patients; seven had no interictal sharp waves. The SEAs showed multifocal interictal sharp waves in all patients. Seven patients with localized seizure onset on scalp recording showed extensive ictal onset on the SEA recording. Five patients with lateralized seizure onset to one hemisphere on scalp recording were found to have ictal onset on SEA restricted to a smaller area. Because of the large epileptogenic zone found on SEA recordings, a complete resection was possible in only five (33%) of the 15 patients who had resections. Eight (53%) of the 15 patients benefited from surgery (mean follow-up, 4.6 years). The SEAs also allowed functional localization in most patients. From these data, we suggest that a localizing scalp electroencephalogram in patients with frontal lobe epilepsy may be misleading because SEA recordings show larger epileptogenic zones than anticipated. Furthermore, we postulate that the larger extensive epileptogenic zone may account for the poorer surgical outcome in patients with frontal lobe epilepsy compared with patients with temporal lobe epilepsy.

Adolescent↗
PubMed2002

Halo scalp ring: a case series and review of the literature.

BACKGROUND: Halo scalp ring is an uncommonly reported alopecia of the scalp that arises perinatally. OBJECTIVES: To describe 5 new cases of halo scalp ring, and to review the literature. SETTING: An outpatient dermatology clinic in an urban area; patients diagnosed in a 2-year period were included in the study. RESULTS: Halo scalp ring is most commonly a temporary, nonscarring alopecia that occurs in patients born to primigravidas. CONCLUSIONS: Halo scalp ring is a distinctive form of alopecia attributed to caput succedaneum. It is underreported and generally has a good prognosis. However, scarring may occur.

Alopecia↗
PubMed1975

Frequency dependence of the transmission of the EEG from cortex to scalp.

Simultaneous recordings of the EEG at subdural and scalp electrodes often show very different activities. Large amplitude activity with maximum power between 15 and 30 c/sec can be often observed on the subdural electrodes together with smaller amplitude lower frequencies, whereas on the scalp only a small part of this high frequency activity is seen and the lower frequencies dominate. The impedance between cortex and scalp has been shown to be similar for low and high EEG frequencies and the high attenuation of the beta activity at scalp electrodes is believed to be due to summation of polyphasic cortical activity. The weighted summation of this polyphasic activity across a limited cortical area (spatial average) is similar to the activity of a non-recursive filter between cortex and scalp and has a low pass characteristic.

Brain↗
PubMed1981

Short latency somatosensory evoked potentials to peroneal nerve stimulation: scalp topography and the effect of different frequency filters.

Short latency SEPs to peroneal nerve stimulation were recorded from the scalp of 22 normal adults. The scalp topography and the effect of different frequency filters on these potentials were investigated. Using a wider bandpass (5-3000 Hz), this response usually consisted of 3 positive potentials (peak latencies 17, 22 and 27 msec) followed by a negative potential (peak latency 34 msec). Using a narrower bandpass (150-3000 Hz), these potentials were fractionated into subcomponents and up to 6 positive potentials were followed by an often bilobed negative potential occurring 4-10 msec earlier than the first negative potential recorded with the wider bandpass filters. The negative potential and the preceding major positive potentials were well defined and stable within and across normal subjects which suggests they will be useful in the clinical evaluation of patients with spinal cord pathology and in monitoring patients during surgery. Certain of these potentials recorded using the wider bandpass were often characterized by progressive differences in their peak latencies over the scalp. Evidence is provided which suggests that this occurred because subcomponents of these potentials, observed in recordings using the narrower bandpass had different scalp distributions. Evoked potentials were also recorded from surface electrodes placed over the spine of some of these subjects. These recordings when combined with the scalp recordings provided information concerning the conduction characteristics of SEPs from cauda equina to cerebral cortex.

Adult↗
PubMed1982

Scalp distribution of human auditory evoked potentials. II. Evidence for overlapping sources and involvement of auditory cortex.

The scalp distributions of human auditory evoked potentials (AEPs) between 20 and 250 msec were investigated using non-cephalic reference recordings. AEPs to binaural click stimuli were recorded simultaneously from 20 scalp locations over the right hemisphere in 11 subjects. Computer-generated isovoltage topographic maps at high temporal resolution were used to assess the stability of AEP scalp distributions over time and relate them to major peaks in the AEP wave forms. For potentials between 20 and 60 msec, the results demonstrate a stable scalp distribution of dipolar form that is consistent with sources in primary auditory cortex on the superior temporal plant near the temporoparietal junction. For potentials between 60 and 250 msec, the results demonstrate changes in AEP morphology across electrode locations and changes in scalp distribution over time that lead to two major conclusions. First, AEPs in this latency period are generated by multiple sources which partially overlap in time. Second, one or more regions of auditory cortex contribute significantly to AEPs in this period. Additional data are needed to determine the relative contribution of auditory cortex sources on the superior temporal plane and the lateral temporal surface and to identify AEP sources outside the temporal lobe.

Auditory Cortex↗
PubMed1984

Spine and scalp somatosensory evoked potentials in normal subjects and patients with spinal cord disease: evaluation of afferent transmission.

Spine and scalp somatosensory evoked potentials (SEPs) to peroneal nerve stimulation were recorded from 20 normal subjects using 1 restricted and 3 open frequency filter bandpasses. Spine to spine and spine to scalp propagation velocities were calculated. Of those recording parameters investigated, optimal recordings were obtained using an open bandpass (5-1500 or 30-1500 Hz) and recording from 3 surface spine bipolar channels and 1 scalp bipolar channel. This method was then investigated in 40 patients with disease of the spinal cord and peripheral nervous system. Focal spinal cord compressive lesions generally resulted in slowing of spine to spine and spine to scalp propagation velocities. Diffuse or multifocal lesions of the spinal cord generally resulted in the absence of scalp responses. Although there was no consistent correlation of the SEP findings with the sensory exam, there was a correlation of the SEP findings with the clinical prognosis.

Adult↗
PubMed1998

A simple method of scalp localization using multiplanar reconstruction of MR images.

BACKGROUND: Image-based scalp localization methods currently used are complex and not standardized. The authors have developed a simple yet accurate method for craniotomy localization using multiplanar reconstruction (MPR) algorithms. METHODS: In this method, the goal is to localize a projected point (defined as T) of the center of the lesion on the scalp. An oblique coronal plane is reformatted using a patient's magnetic resonance (MR) images with MPR algorithms to include both the center of the lesion and bilateral external auditory meati. Then the distance between T and the ipsilateral external auditory meatus or sagittal suture (defined as S) is measured along the scalp contour in the plane. The distance between the bregma and S is also measured. These distances are used for scalp localization, using a tape measure in the operating room. RESULTS: We have had successful scalp localization in six clinical cases. It took about 3 min to measure each distance on the MR console. CONCLUSION: This method for craniotomy planning using MPR algorithms is simple and sufficiently accurate.

Craniotomy↗
PubMed2003

Focal magnetoencephalographic spikes in the superior temporal plane undetected by scalp EEG.

Temporal lobe spikes were detected by magnetoencephalography (MEG), but not by standard scalp electroencephalography (EEG), in a patient with intractable complex partial seizures. Simultaneous recording of scalp EEG and MEG revealed 2 different types of spike discharges: sporadic single spikes detected by both EEG and MEG which were localised diffusely in the right temporal lobe; and rhythmic MEG spike discharges that were not detected by scalp EEG, focally localised in the posterior part of the superior temporal plane. The tangential current orientation to the scalp may explain the different sensitivity of scalp EEG and MEG to rhythmic discharges. This study shows the unique sensitivity of MEG to epileptic activity in the superior temporal plane.

Adult↗
PubMed2001

Frontal lobe seizure propagation: scalp and subdural EEG studies.

PURPOSE: To study propagation properties of focally originating frontal lobe seizures: principally direction and promptness of ictal spread. METHOD: Forty-eight scalp EEG-recorded and 17 subdurally recorded seizures in two separate groups of patients were visually scrutinized. RESULTS: Initial propagation was directed more commonly to contiguous frontal cortex than to the opposite hemisphere in both studies: 58% and 86% for scalp and subdural recordings, respectively. Eighteen (38%) of scalp EEG seizures propagated within 5-10 s of apparent onset, whereas 16 (33%) did so after 11-20 s; no evidence of propagation could be discerned in the remaining 14 (29%). Of subdurally recorded attacks, only four (24%) propagated in the first 4 s; six (35%) did so after a delay of 5-10 s; six (35%) either failed to propagate or did so after > or =20-s latency. Latency to initial propagation was between 5 and 20 s in 41 (63%) of the 65 seizures in both studies. Ictal activity remained within the frontal lobe of origin for > or =10 s in 39 (81%) of scalp-recorded seizures and 11 (65%) of subdural seizures. It remained so confined for > or =15 s in 26 (54%) and nine (53%), respectively. Twenty-four (50%) of scalp-recorded seizures displayed evidence of opposite hemisphere (bisynchronous or other contralateral) involvement, occurring 5-10 s after onset in eight (17%) seizures and 10-20 s after onset in 16 (33%). Similarly, the subdural study documented spread to the opposite hemisphere in 11 (65%) of seizures with a latency ranging from 1 to 45 s. CONCLUSIONS: Frontal lobe seizures in this study propagated less promptly than reputed, and initial spread occurred more commonly to the frontal lobe of origin than to the opposite hemisphere. Such properties underlie the good lateralizing value of clinical semiology of frontal lobe seizures.

Brain Mapping↗
PubMed1991

Potentials evoked in human and monkey cerebral cortex by stimulation of the median nerve. A review of scalp and intracranial recordings.

Somatosensory evoked potentials (SEPs) are generated in afferent pathways, subcortical structures and various regions of cerebellar and cerebral cortex by stimulation of somatic receptors or electrical stimulation of peripheral nerves. This review summarizes current knowledge of SEPs generated in cerebral cortex by stimulation of the median nerve, the most common form of stimulation for human research and clinical investigations. Major sources of data for the review are intracranial recordings obtained from patients during diagnostic or neurosurgical procedures, and similar recordings in monkeys. Short-latency cortical SEPs in the 20-40 ms latency range consist of P20 and N30, recorded from motor cortex and frontal scalp; P25 and N35, recorded from cortex near the central sulcus and central scalp; and N20 and P30, recorded from somatosensory cortex and parietal scalp. Several lines of evidence including cortical surface and intracerebral recordings, neuromagnetic recordings and lesion studies in humans and monkeys, strongly support the conclusion that these potentials are generated in contralateral somatosensory cortex in areas 3b and 1, in contrast to the conclusion of many previous studies that SEPs recorded from the frontal scalp are generated in motor cortex and other frontal lobe areas. These potentials are primarily mediated by cutaneous afferents of the dorsal column-medial lemniscal system; the contribution of muscle afferents has not been completely resolved but appears to be small. There is currently no evidence that short-latency SEPs are generated in cortex other than primary somatosensory cortex. Recordings from the vicinity of the second somatosensory area, from the supplementary motor and sensory areas and from surface cortex other than sensorimotor cortex have not detected reliable short-latency activity, although some of these regions generate long-latency potentials. Consequently, short-latency SEPs recorded from the scalp are similar to those recorded from the surface of sensorimotor cortex. Old World monkeys such as Macaca mulatta and M. fascicularis provide an excellent model for human short-latency SEPs. All the potentials described above in humans have corresponding monkey analogues, with similar distributions over the cortical surface. The squirrel monkey, a New World species, exhibits the same potentials, but due to the different morphology of sensorimotor cortex, the surface distribution of SEPs is quite different.

Afferent Pathways↗
PubMed1993

Scalp-recorded ictal patterns in focal epilepsy.

Scalp-recorded focal EEG seizure patterns are usually expressed as rhythmic metamorphic evolving patterns (with or without epileptiform morphology) that progress through two or more ictal phases into a postictal change. Such patterns are almost invariably seen in temporal complex partial seizures but less often detected in frontal complex partial seizures and least of all in simple partial seizures. The failure of scalp recordings to detect activity from a focal seizure can usually be explained by the seizure's distant location, limited extent, or disadvantageous orientation with respect to scalp electrodes. The elimination of these disadvantages with properly implanted electrodes explains why these recordings are able to detect seizure discharges missed by scalp electrodes. Although the lateralization of a scalp-recorded seizure can be misleading, it usually accurately identifies the focus when it remains well-lateralized throughout its various ictal phases and into the postictal state.

Cerebral Cortex↗
PubMedDate not supplied

Scalp and limbic P3 event-related potentials in the assessment of patients with temporal lobe epilepsy.

Auditory oddball scalp and limbic P3s were recorded from 18 patients with unilateral temporal lobe epilepsy (TLE) prior to seizure surgery. Limbic P3s were unilaterally absent ipsilateral to the seizure focus and were present in the nonepileptogenic temporal lobe in all 18 cases studied. Scalp P3s, recorded from C3 and C4, on the other hand, were elicited bilaterally and there was no significant difference in amplitude or latency between the epileptogenic and nonepileptogenic sides. These data concur with studies of scalp P3 performed following surgery and suggest that the assessment of the contribution of limbic P3 to scalp P3 may be masked by volume conduction effects and other generators of P3. We conclude that the P3 recorded from central scalp sites, unlike its limbic counterpart, offers little clinical information in the presurgical assessment of patients with TLE.

Acoustic Stimulation↗
PubMed2004

Bilateral mesial temporal lobe epilepsy: comparison of scalp EEG and hippocampal MRI-T2 relaxometry.

OBJECTIVE: Bilateral hippocampal abnormality is frequent in mesial temporal lobe sclerosis and might affect outcome in epilepsy surgery. The objective of this study was to compare the lateralization of interictal and ictal scalp EEG with MRI T2 relaxometry. MATERIAL AND METHODS: Forty-nine consecutive patients with intractable mesial temporal lobe epilepsy (MTLE) were studied with scalp EEG/video monitoring and MRI T2 relaxometry. RESULTS: Bilateral prolongation of hippocampal T2 time was significantly associated with following bitemporal scalp EEG changes: (i) in ictal EEG left and right temporal EEG seizure onsets in different seizures, or, after regionalized EEG onset, evolution of an independent ictal EEG over the contralateral temporal lobe (left and right temporal asynchronous frequencies or lateralization switch; P = 0.002); (ii) in interictal EEG both left and right temporal interictal slowing (P = 0.007). Bitemporal T2 changes were not, however, associated with bitemporal interictal epileptiform discharges (IED). Lateralization of bilateral asymmetric or unilateral abnormal T2 findings were associated with initial regionalization of the ictal EEG in all but one patient (P < 0.005), with lateralization of IED in all patients (P < 0.005), and with scalp EEG slowing in 28 (82,4%) of 34 patients (P = 0.007). CONCLUSION: Our data suggest that EEG seizure propagation is more closely related to hippocampal T2 abnormalities than IED. Interictal and ictal scalp EEG, including the recognition of ictal propagation patterns, and MRI T2 relaxometry can help to identify patients with bitemporal damage in MTLE. Further studies are needed to estimate the impact of bilateral EEG and MRI abnormal findings on the surgical outcome.

Action Potentials↗
PubMed1997

Inhibition of hair growth by testosterone in the presence of dermal papilla cells from the frontal bald scalp of the postpubertal stumptailed macaque.

Hair-follicle regression in the bald scalps of stumptailed macaques develops after puberty, which corresponds to an elevation of serum testosterone and dihydrotestosterone. Using the cultured cells from the pre- and postpubertal macaques, we examined the role of dermal papilla cells in testosterone-induced inhibition of outer root sheath cell proliferation. Testosterone showed no effects on proliferation of either dermal papilla cells or outer root sheath cells cultured alone. Testosterone-induced inhibition of outer root sheath cell proliferation occurred only in coculture with dermal papilla cells derived from the bald scalps of adult macaques but not with dermal papilla cells from the hairy occipital scalps of adult macaques or the prebald frontal scalps of juvenile macaques. Furthermore, RU 58841, an androgen receptor blocker, antagonized this testosterone-elicited inhibition. Together our data indicate that the inhibitory effect of testosterone on proliferation of epithelial cells is age dependent, and androgen may play an essential role in hair growth either by inducing repressor(s) from dermal papilla cells, which may then inhibit the growth of epithelial cells of the hair follicle, or by inducing growth factor(s) from dermal papilla cells, which, in turn, may trigger the induction of some repressors in epithelial cells, thereby inhibiting the epithelial cell growth. Our animal studies also showed that RU 58841 has a dramatic effect on hair regrowth in the bald frontal scalp of the stumptailed macaque, which may further support our in vitro culture studies showing that antiandrogens can antagonize testosterone-elicited hair growth. In summary, our studies may provide a model for further isolation of androgen-regulated repressor(s)/growth factors, which may help control hair growth and baldness.

Alopecia↗
PubMed1980

Alterations in the electrocardiogram of the fetal lamb as a sign of fetal asphyxia. A comparison between the scalp lead and the precordial lead.

Progressive changes in the ST-T period of the fetal electrocardiogram (FECG) were studied in 18 lamb fetuses, acutely exteriorized and subjected to graded hypoxia. The aim of the study was to compare the bipolar precordial lead (CR-lead) with the unipolar scalp lead, and to correlate the alterations in the FECG to blood-gas and acid-base status. The scalp lead gave less information regarding fetal condition and was more difficult to interpret than the precordial lead. This might be one factor in the controversy regarding the significance of alterations in the FECG during asphyxia and labor, since the scalp lead is used mainly in clinical situations. Our previous results demonstrating progressive changes in the ST-T period of the FECG during hypoxia in experimental animals and showing the same ECG changes in newborn human infants immediately after birth, were registered with the bipolar precordial lead. It is possible that a bipolar scalp lead might give more information regarding the fetal condition than the unipolar scalp lead mainly used in clinical practice.

Animals↗
PubMed1998

Combination of bupivacaine scalp circuit infiltration with general anesthesia to control the hemodynamic response in craniotomy patients.

BACKGROUND: Sudden and overwhelming increases in blood pressure (BP) and heart rate (HR) during incision of the scalp may give rise to morbidity or mortality in patients with intracranial pathology undergoing neurosurgery. A modification of the method proposed by Labat to abate this circumstantiality was applied in a group of patients receiving craniotomy. The modified method was to combine scalp circuit infiltration of local anesthetic with general anesthesia to control the hemodynamic response to craniotomy. METHODS: Twenty-six patients scheduled to undergo craniotomy were randomly divided into two groups. Patients whose conditions or their current medication that might affect the stability of hemodynamics were excluded. In group A patients (N = 16) 25-30 ml of 0.25% bupivacaine was used for scalp circuit infiltration on the operation side, while in those of group B (N = 10) the same volume of 0.9% normal saline was used. After induction, anesthesia was maintained with 0.6% to 1.2% end-tidal isoflurane (ET-Iso) and 50% N2O in oxygen (N2O:O2 = 2 l/min:2 l/min). The end-tidal CO2 was kept within the range of 25-30 mmHg. BP and HR were recorded every five min before incision and then every two min after incision until one hour after induction. ET-Iso was also recorded every two min throughout a period of sixty min. If the BP and HR increased above 20% of the baseline (10 min before incision), thiopental 2.5 mg/kg and fentanyl 2 micrograms/kg were administered. If hypertension became sustained, the isoflurane concentration was adjusted until an acceptable level was obtained. RESULTS: The mean BP during the surgery was 92 +/- 1 mmHg in group A and 92 +/- 7 mmHg in group B. The difference in BP between incision to 6 min after incision was statistically significant (P < 0.05). The mean HR during surgery was 101 +/- 5 beats/min in group B and 91 +/- 2 beats/min in group A, the difference of which was not statistically significant. All of the patients in group B required a deepened anesthesia to keep the BP and HR within the normal range, but no patient in group A had such need. The average concentration of ET-Iso during the 60 min period was 0.95 +/- 0.12% in group B and 0.41 +/- 0.01% in group A, respectively. The difference was statistically significant (P < 0.05). CONCLUSIONS: Our results showed that scalp circuit infiltration with 0.25% bupivacaine significantly improved the cardiovascular stability and reduced the requirement of isoflurane during craniotomy. The routine use of bupivacaine scalp circuit infiltration in patients undergoing craniotomy should be considered.

Adult↗
PubMed2002

[Application of meshed acellular dermis xenograft (pigskin) with scalp thin skin autograft in 15 patients].

OBJECTIVE: To present the clinical application of the meshed acellular dermis xenograft with scalp thin split-thickness skin autograft. METHODS: The meshed acellular dermis xenograft (pigskin) was placed on the granulation or defects after scar resection. Four or five days afterwards, scalp thin split-thickness skin was transplanted. A total of 15 patients with 25 wounds were treated using this technique. The survival rates and quality of the grafts were observed. RESULTS: The survival rate of the meshed acellular dermis xenograft was (96.40 +/- 2.60)% and the scalp thin split-thickness skin autograft was (97.44 +/- 3.50)%. All grafts showed normal skin-alike color and elastic and smooth texture. CONCLUSION: The combined use of meshed acellular dermis xenograft and scalp skin autograft demonstrated an ideal way for the repair of full-thickness skin burn or defects from scar resection. The scalp can provide thin skin graft repeatedly without influence of the hair.

Adolescent↗
PubMed1996

Primary intracranial malignant tumour mistaken for a postburn scalp Marjolin's ulcer.

This report presents an apparent squamous cell carcinoma over a burn scar in the scalp (Marjolin's ulcer) that was resected and soft tissue expanders inserted in the hair-bearing scalp. In the postoperative period the patient developed neurological impairment with a CT scan showing a parasagittal brain tumour infiltrating the skin. The tumour was resected and the resultant skin and cranial defect were covered with an expanded scalp flap. Histological examination showed malignant angioblastic meningioma. The tumour recurred aggressively, leading to the death of the patient. The case is considered very unusual, as a brain tumour does not seem to be a reasonable suspect in the differential diagnosis of a chronic ulcer over a burn-induced scalp scar.

Adult↗