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Biomedical subjects

L P Carter

Publications and source records attributed to L P Carter.

At least 19 recordsLinked to original sources
PubMed1999

Pediatric eighth cranial nerve schwannoma without evidence of neurofibromatosis.

Schwannomas of the eighth cranial nerve are rare in children. We report a 4 10/12 - year-old girl with no evidence of neurofibromatosis who presented with facial droop. Radiographic studies revealed a large cerebellopontine angle tumor. At surgery, the tumor was attached to the eighth cranial nerve and histologically was a schwannoma. This is the youngest reported case of unilateral eighth cranial nerve schwannoma in a patient without the stigmata of neurofibromatosis.

Child, Preschool↗
PubMed1998

ICP-CBF trauma bolt, laboratory evaluation.

Thermal diffusion flowmetry is a continuous quantitative technique of measuring regional cerebral blood flow utilizing a silastic strip probe placed through a craniotomy or craniectomy in the operating room. A new bolt like application of this technology is now available for commercial use and is especially designed for bedside placement in trauma patients. This new trauma bolt is tested in juvenile pigs who are subjected to episodes of hypercapnea to increase cerebral blood flow, and records significant changes in blood flow. Another feature of the trauma bolt is a second port for the placement of an intracranial pressure (ICP) monitor. Placement of the probe and ICP monitor were easier than with the silastic probe and had relatively little complication.

Animals↗
PubMed1997

Cerebral blood flow and temporal lobe epileptogenicity.

Long-term surface cerebral blood flow (CBF) monitoring was performed to test the hypothesis that temporal lobe epileptogenicity is a function of epileptic cortical perfusion. Forty-three bitemporal 2-hour periictal CBF studies were performed in 13 patients. Homotopic regions of temporal cortex maintained interictal epileptic cortical hypoperfusion and nonepileptic normal cortical CBF. At 10 minutes preictus, a statistically significant, sustained increase in CBF was detected on the epileptic temporal lobe. Two minutes preictus, there was approximation of CBF in the epileptic and nonepileptic temporal lobes. Thereafter, electrocorticographic (ECoG) and clinical seizure onset occurred. The linear relationship between CBF in the two hemispheres (epileptic and nonepileptic) was the inverse of normal (y = -0.347x + 62.767, r = 0.470, df = 95, p < 0.05). The data indicated a direct linear correlation between epileptic cortical CBF and seizure interval (frequency-1), a clinical measure of epileptogenicity (r = 0.610, df = 49, p < 0.05). Epileptogenicity was also found to be a logarithmic function of the difference between nonepileptic and epileptic cortical perfusion (r = 0.564, df = 58, t = 5.20, p < 0.05). The results showed that progressive hypoperfusion of the epileptic focus correlated with a decreased seizure interval (increased epileptogenicity). Increased perfusion of the epileptic focus correlated with an increased seizure interval (decreased epileptogenicity). The fact that CBF alterations precede ECoG seizure activity suggests that vasomotor changes may produce electrical and clinical seizure onset.

Adolescent↗
PubMed1996

Thermal diffusion flowmetry.

Continuous monitoring of cerebral blood flow (CBF) has been an area under research to observe immediate changes in blood flow under a wide variety of circumstances. Recently, however, continuous monitoring of blood flow in the trauma cases has provided prognostic and therapeutic help in the management of these patients. Changes in CBF prior to the electrical discharge in the epileptic focus imply that blood flow changes may help in defining the focus. In the neurologically compromised patient, for whatever reason, CBF is an important parameter to follow and may give clues to therapeutic efficacy.

Cerebrovascular Circulation↗
PubMed1995

Response of human epileptic temporal lobe cortical blood flow to hyperventilation.

Bilateral long-term surface cortical cerebral blood flow (CBF) and electrocorticographic (ECoG) monitoring were performed in eight patients with complex partial seizures. In each patient, the epileptic temporal lobe was localized using ictal ECoG. Mean seizure interval (frequency-1) off anticonvulsant medication, a clinical measure of epileptogenicity, was 1.0 +/- 0.3 h (range: 0.4 to 2.5 h). During 13 interictal hyperventilation periods, 3.6 +/- 0.6 min in duration, the mean decrease in epileptic and nonepileptic temporal cortical CBF was 13.7 +/- 2.3 versus 6.4 +/- 1.9 ml/(100 g min) (t = 2.230, d.f. = 16, P < 0.05), representing 20.9% and 10.8% reduction from baseline CBF during hyperventilation, respectively. Seizure interval decreased (i.e. frequency increased) with increasing magnitude of seizure focus CBF reduction during hyperventilation. Seizure interval was significantly correlated with epileptic temporal lobe CBF decrease during hyperventilation (R = 0.763, d.f. = 5, P < 0.05). The data suggest that, compared to nonepileptic brain, epileptic temporal lobe is particularly prone to hypoperfusion during hyperventilation. Epileptogenicity is a function of this seizure focus susceptibility to ischemia. The finding of abnormal seizure focus autoregulation during hyperventilation has implication for epileptic focus localization with cerebral blood flow analysis.

Adolescent↗
PubMed1995

Continuous regional cerebral cortical blood flow monitoring in head-injured patients.

Continuous regional cerebral cortical blood flow (rCoBF) was monitored with thermal diffusion flowmetry in 56 severely head-injured patients. Adequate, reliable data were accumulated from 37 patients (21 acute subdural hematomas, 10 cerebral contusions, 4 epidural hematomas, and 2 intracerebral hematomas). The thermal sensor was placed at the time of either craniotomy or burr hole placement. In 15 patients, monitoring was initiated within 8 hours of injury. One-third of the comatose patients monitored within 8 hours had rCoBF measurements of 18 ml per 100 g per minute or less, consistent with previous reports of significant ischemia in the early postinjury period. Initial rCoBF measurements were similar in the patients with Glasgow Coma Scale scores of 3 to 7 and in those with scores of 8 or greater. In patients with poor outcomes, rCoBF measurements did not change significantly from initial measurements; however, in those patients who had better outcomes, final rCoBF measurements were higher than initial rCoBF measurements. The patients who had better outcomes experienced normalization of rCoBF during the period of monitoring, and patients with poor outcomes had markedly reduced final rCoBF. These changes were statistically significant. When management was based strictly upon the intracranial pressure, examples of inappropriate treatment were found. For example, hyperemia and increased intracranial pressure treated with mannitol caused further rCoBF increase, and elevated intracranial pressure with low cerebral blood flow treated with hyperventilation increased the severity of ischemia. In 3 (5%) of 56 patients, wound infections developed. Continuous rCoBF monitoring in head-injured patients offers new therapeutic and prognostic insights into their management.

Adolescent↗
PubMed1995

Influence of a 'brain protector' drug 21-amino steroid on the effects of experimental embolic stroke treated by thrombolysis.

This study was designed to evaluate the effects of tissue-type plasminogen activator (tPA) and 21- amino steroid (U74006F) in experimental embolic stroke in rabbits. The size of infarction from embolism was compared to controls with tPA alone, 21-amino steroid alone, and in combination. The middle cerebral artery of the rabbit was embolized by injecting an arterial ('white') thrombus in the right internal carotid artery. The rabbit treatment was 2 mg kg-1 of tissue-type plasminogen activator and/or 3 mg kg-1 of 21 amino steroid started at 2 h post-embolization. The animals were terminated 4 h post-treatment and brains were examined for evidence of ischemia and/or hemorrhage. Administration of tissue-type plasminogen activator and/or 21-amino steroid in the raw data show that there is a tendency for all treatments to reduce the ischemic volume when compared to the control group, also it is evident the standard deviation of these estimates is rather large when compared to the differences between treatments. The results of the analysis of variance shows that the differences expressed are not statistically significant. (No statistical differences were found between the treatment groups and the control group.) The results show that administration of tissue-type plasminogen activator and/or 21 amino steroid at 2 h post-embolization alone or in simultaneous administration does not significantly reduce the volume of infarction. Further studies need to be addressed in regards to the region of viable brain in the peri-infarct area, in reducing the time to treatment.

Animals↗
PubMed1994

Contributions of the parietal and frontal lobes to sustained attention and habituation.

The parietal cortex may be important in sustaining attention toward visual stimuli in peripheral space whereas the frontal cortex may mediate selective attention through habituation to peripheral stimuli. To test this hypothesis, patients with focal lesions of either the parietal or frontal cortex or both and normal controls were studied using a paradigm known as Troxler fading. Accordingly, if one fixates on a centrally located stimulus and attends to a stationary stimulus in peripheral vision, the peripheral stimulus quickly fades from awareness (i.e. Troxler fading: Troxler [Verschwinden, unseres, Opthal, Vol. 2, pp. 51-53. Fromann, Jena, 1804]). Movement of the peripheral stimulus on the retina normally prevents Troxler fading. Results indicated that patients with parietal lesions not only reported accelerated Troxler fading but also reported fading of moving peripheral stimuli contralateral to their brain lesion. In contrast, patients with frontal lesions rarely reported Troxler fading. In one patient with a left parietal and a right frontal lobe lesion fading was hemi-spatially dissociated, being accelerated in right hemispace but absent in left hemispace. These observations suggest that the parietal and frontal cortices play complementary roles in attentional processing.

Aged↗
PubMed1994

Surface cortical cerebral blood flow monitoring and single photon emission computed tomography: prognostic factors for selecting temporal lobectomy candidates.

A series of 23 patients with medically intractable temporal lobe epilepsy was studied with surface cortical cerebral blood flow monitoring, single photon emission computed tomography (SPECT) and subdural strip electrocorticographic (ECoG) monitoring for localization of the seizure focus. All patients underwent anterior temporal lobectomy and seizure outcome was determined after a mean of 9 months (range: 3-17 months). Invasive and non-invasive cerebral blood flow (CBF) parameters with prognostic value for seizure-free outcome were: (a) inter-ictal seizure focus with CBF < 65 ml/100 gm-min; (b) inter-ictal seizure focus CBF < or = normal temporal lobe CBF; and (c) concordance of inter-ictal and/or early post-ictal SPECT and ictal ECoG for seizure focus localization. These results should improve prognostic value of invasive and non-invasive cerebral blood flow data for selection of temporal lobectomy candidates.

Adolescent↗
PubMed1994

Long-term surface cortical cerebral blood flow monitoring in temporal lobe epilepsy.

Long-term subdural surface cortical cerebral blood flow (CBF) and electrocorticographic monitoring was performed in 12 patients with complex partial seizures. A total of 40 seizures were analyzed. Baseline CBF values from nonepileptic and epileptic temporal lobe (mean +/- standard error) were 60.0 +/- 1.0 and 50.2 +/- 1.8 ml/100 g per minute, respectively (P < 0.05). In general, clinical seizure onset was preceded by a 20-minute preictal CBF increase from baseline in the epileptic temporal lobe. Peak early postictal CBF values of nonepileptic and epileptic temporal lobes were 57.7 +/- 13.3 and 89.0 +/- 21.7 ml/100 g per minute (P > 0.05) at 5.2 +/- 2.2 and 2.4 +/- 1.0 minutes (P > 0.05) after clinical seizure onset, respectively. Statistically significant differences between nonepileptic and epileptic temporal lobe CBF were detected at 50 minutes (74.0 +/- 14.2 and 37.5 +/- 9.2 ml/100 g per minute, respectively; P < 0.05) and 60 minutes (75.6 +/- 13.6 and 36.1 +/- 8.5 ml/100 g per minute, respectively; P < 0.05) postictal. The data suggest that the optimal times for CBF analysis to differentiate epileptic from nonepileptic temporal lobe are 1) during the interictal period and 2) late (50 to 60 minutes) postictal. The results of this study should improve the understanding of the dynamic cerebral perfusion patterns in the epileptic human brain.

Adolescent↗
PubMed1993

Cerebral blood flow (CBF) monitoring in intensive care by thermal diffusion.

Continuous monitoring of cortical blood flow (CoBF) in the intensive care unit is possible with thermal diffusion techniques. The normal brain flow limits have been established when electrical activity ceases and when infarction is likely to occur. With continuous monitoring of CoBF one can see immediate changes in flow and approaching these levels may be anticipated. The thermal diffusion system we have employed is based on the thermal conductivity of cortical tissue. As blood flow increases through the tissue, the conduction of energy away from the flow probe allows the sensor to detect changes in flow. This form of monitoring has been carried out in patients with subarachnoid hemorrhage, resection of cerebral mass lesions, severe craniotrauma, and intractable epilepsy. In subarachnoid hemorrhage, vasospasm can be identified and the efficacy of treatment determined with continuous monitoring of CoBF. During resection of mass lesions, increases in blood flow can be readily detected to document the recovery of brain tissue. Continuous monitoring of CoBF in epilepsy patients is now possible with the implantation of subdural electrodes. The increase in blood flow can be documented and it is apparent that a period of elevation of blood flow is quite short. Therefore, this may be helpful in determining when other forms of CBF determination, such as Single Photon Emission Computed Tomographic (SPECT) scanning should be performed. In patients with cranial trauma, different patterns of CoBF changes are apparent. Some patients may develop increased CoBF prior to elevation of intracranial pressure (ICP); other patients demonstrate a drop in CoBF as a response to increased ICP.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Temperature Regulation↗
PubMed1993

Spinal epidural hematoma in a hemophilic infant.

PURPOSE: Although intracranial hemorrhage remains a leading cause of death in hemophilia, spinal epidural hematoma is seen rarely. Decompressive laminectomy has a high associated morbidity, and recent reports have suggested that patients can be treated conservatively without surgical intervention. PATIENTS AND METHODS: We present a case of spontaneous spinal epidural hematoma diagnosed by MRI scan in a 6-month-old hemophilic infant. Immediate treatment with factor VIII replacement was instituted. RESULTS: There was rapid and complete clinical and radiographic resolution. CONCLUSION: This case shows that selected hemophilic patients with spinal epidural hematoma can be spared surgical decompression by prompt medical attention.

Factor VII↗
PubMed1992

Influence of tissue plasminogen activator and heparin on cerebral ischemia in a rabbit model.

BACKGROUND AND PURPOSE: The aims of this study were to verify that tissue-type plasminogen activator given either 1 or 2 hours after experimental embolic stroke in rabbits diminishes the volume of resulting ischemic brain and to ascertain the effect of the simultaneous administration of heparin. METHODS: We embolized the middle cerebral artery of rabbits by injecting performed autologous arterial ("white") thrombus into one internal carotid artery. Treatment with 2 mg/kg tissue-type plasminogen activator, alone or in combination with heparin, was commenced either 1 or 2 hours after embolization. The animals were killed 5 hours after treatment commenced, and their brains were examined for evidence of ischemia and hemorrhage. RESULTS: Administration of tissue-type plasminogen activator significantly diminished the size of the resulting brain ischemia. Administration of heparin, with or instead of tissue-type plasminogen activator, did not result in a significant decrease in the volume of cerebral ischemia, but it also did not lead to hemorrhagic transformation of the stroke. CONCLUSIONS: In the rabbit model, administration of tissue-type plasminogen activator within 2 hours diminished the volume of brain rendered acutely ischemic by embolic stroke. Since the simultaneous administration of heparin during this same period did not result in any instances of hemorrhagic transformation, tissue-type plasminogen activator may have some place for use in such circumstances to mitigate a tendency to further embolic or thrombotic events.

Analysis of Variance↗