Magnetoencephalographic localization of interictal spike sources. Case report

The reliability of localization of interictal spike sources using magnetoencephalography (MEG) was examined by repeated measurements in a patient with temporal lobe epilepsy. During two preoperative recording sessions, the estimated sources, projected onto magnetic resonance images of the patient's brain, were found to lie less than 1 cm apart within the area subsequently resected. The MEG localization was in close agreement with intraoperative cortical recordings.

Intracranial Hypertension in Relation to Memory Functioning during the First Year after Severe Head Injury

The relationship between intracranial hypertension and residual memory deficit after closed head injury was evaluated using the 6-month and 1-year neurobehavioral outcome data obtained by the Traumatic Coma Data Bank. Intracranial pressure was analyzed using the percentage of time that it exceeded 20 mm Hg and the maximum value recorded during the first 72 hours after injury. Memory measures included recall of word lists, prose recall, and visual memory for designs that were obtained 6 months (n = 149) and 1 year (n = 132) after injury. Intracranial hypertension occurred in more than half of the Traumatic Coma Data Bank cohort who met the criteria for the neurobehavioral follow-up study. Linear regression analysis disclosed an effect of elevated intracranial pressure on some, but not all, measures of memory at 6 months, whereas the results were negative for the 1-year follow-up examination. We conclude that the elevation of intracranial pressure exerts little if any effect on later memory functioning, and that any effect it does have diminishes over 1 year in survivors of severe head injury.

Gender differences in source location for the N100 auditory evoked magnetic field

Auditory evoked magnetic fields were recorded in response to contralateral stimulation over the right hemisphere in 6 adult males and 6 adult females. The data were fit to a model of a current-dipole source in a homogeneous sphere and 5 parameters of the dipole were computed--3 spatial coordinates, orientation, and strength. When average values for the dipole parameters were compared between sexes, it was found that the current source for the N100m is located more than 1 cm posterior in females and is oriented pointing more downward. These findings were replicated in separate measurement sessions. Viewing of individual magnetic resonance images did not reveal a corresponding anatomical disparity in the location of the primary auditory cortex which is assumed to produce the N100m. Therefore, functional organization of the auditory cortex may be different for the sexes.

Neurobehavioral outcome 1 year after severe head injury. Experience of the Traumatic Coma Data Bank

The outcome 1 year after they had sustained a severe head injury was investigated in patients who were admitted to the neurosurgery service at one of four centers participating in the Traumatic Coma Data Bank (TCDB). Of 300 eligible survivors, the quality of recovery 1 year after injury was assessed by at least the Glasgow Outcome Scale (GOS) in 263 patients (87%), whereas complete neuropsychological assessment was performed in 127 (42%) of the eligible survivors. The capacity of the patients to undergo neuropsychological testing 1 year after injury was a criterion of recovery as reflected by a significant relationship to neurological indices of acute injury and the GOS score at the time of hospital discharge. The neurobehavioral data at 1 year after injury were generally comparable across the four samples of patients and characterized by impairment of memory and slowed information processing. In contrast, language and visuospatial ability recovered to within the normal range. The lowest postresuscitation Glasgow Coma Scale (GCS) score and pupillary reactivity were predictive of the 1-year GOS score and neuropsychological performance. The lowest GCS score was especially predictive of neuropsychological performance 1 year postinjury in patients who had at least one nonreactive pupil following resuscitation. Notwithstanding limitations related to the scope of the TCDB and attrition in follow-up material, the results indicate a characteristic pattern of neurobehavioral recovery from severe head injury and encourage the use of neurobehavioral outcome measurements in clinical trials to evaluate interventions for head-injured patients.

Initial CT findings in 753 patients with severe head injury. A report from the NIH Traumatic Coma Data Bank

In this prospective multicenter study, the authors have examined data derived from the initial computerized tomography (CT) scans of 753 patients with severe head injury. When the CT findings were related to abnormal intracranial pressure and to death, the most important characteristics of the scans were: midline shift: compression or obliteration of the mesencephalic cisterns: and the presence of subarachnoid blood. Diffuse hemispheric swelling was also found to be associated with an early episode of either hypoxia or hypotension.

The Children's Orientation and Amnesia Test: relationship to severity of acute head injury and to recovery of memory

The Children's Orientation and Amnesia Test (COAT) was developed to assess cognition serially during the early stage of recovery from traumatic brain injury in children and adolescents. The norms for the COAT, which is composed of 16 items evaluating general orientation, temporal orientation, and memory, were defined from data obtained from 146 children aged 3 to 15 years. In 37 patients with head injuries, the duration of posttraumatic amnesia, as indicated by the number of days COAT scores were in the impaired range, was significantly related to both verbal and nonverbal memory at the baseline and 6 and 12 months after injury. COAT scores were a better predictor of verbal and nonverbal memory performance than the Glasgow Coma Scale score at 6 and 12 months after the injury. This study shows that the COAT has adequate reliability and validity as a measure of the duration of posttraumatic amnesia in children and adolescents.

Mild head injury classification

Inconsistencies across studies concerning outcome after mild head injury may reflect differences in the diagnostic criteria used for selection of patients. Consequently, we compared the neurobehavioral outcome in three groups of consecutively hospitalized patients (aged 16 to 50 years) who sustained a closed head injury (CHI) and had a Glasgow Coma Scale (GCS) score in the 9 to 15 range. These groups included patients with uncomplicated CHI with mild impairment of consciousness as reflected by a GCS score in the 13 to 15 range (n = 78), patients with initially mild impairment of consciousness complicated by brain lesion or depressed skull fracture (n = 77), and patients with moderate CHI (n = 60). Tests of memory, information processing, and verbal fluency were administered within 1 to 3 months after injury, and the Glasgow Outcome Scale was completed at 6 months. Neurobehavioral functioning was impaired in the groups with complicated mild CHI and moderate CHI as compared to the group with uncomplicated mild CHI. Although moderate CHI produced longer durations of impaired consciousness and posttraumatic amnesia than complicated mild head injury, patients in these groups did not differ in neurobehavioral performance. Global outcome at 6 months was better in the patients with mild CHI than in patients with complicated mild and moderate injuries. Analysis of the various complications of mild CHI revealed that the presence of an intracranial lesion was related to more severe neurobehavioral sequelae than injuries complicated by a depressed fracture.

Cerebral metabolic and hormonal activations during hemorrhage in sinoaortic-denervated rats

Denervation of sinoaortic baroreceptors in normovolemic rats selectively increases glucose utilization in the median eminence and pituitary neural lobe and enhances secretion of vasopressin and oxytocin. Hemorrhage in denervated animals increases further glucose metabolism in these structures and stimulates the release of both neurohypophysial hormones with preferentially a greater effect on vasopressin. Similar increases in glucose metabolism in these structures with a greater release of vasopressin are observed in sham-operated animals during hemorrhage. Absence of high-pressure receptors, therefore, does not modify the preferential release of vasopressin during hypovolemia. Hemorrhage also increases glucose utilization in the paraventricular and supraoptic nuclei, area postrema, and subfornical organ in sham-operated and denervated rats but only after a 20% blood reduction. The results indicate that decreased inputs from low-pressure receptors during hemorrhage increase the activity of the hypothalamoneurohypophysial system after small reductions in blood volume and that the activity of this system is tonically inhibited by baroreceptors. The activities of structures responsive to circulating angiotensin II (subfornical organ and area postrema) are stimulated by larger reductions in blood volume and their metabolic activities are not tonically influenced by high-pressure receptors.

Corpus callosal atrophy following closed head injury: detection with magnetic resonance imaging

To investigate evidence for diffuse white matter injury and hemispheric disconnection sequelae after severe closed head injury (CHI), this study evaluates the degree of posttraumatic atrophy of the corpus callosum. Corpus callosal atrophy was quantitatively determined using a digitizer to measure sagittal magnetic resonance images of 32 patients with moderate-to-severe CHI and those of 31 control subjects of similar age. In the CHI patients, measurements were significantly reduced for the areas of the anterior four-fifths, the posterior one-fifth, and the total corpus callosum. Moreover, the minimum width of the callosal body was reduced in the CHI patients as compared to that of control individuals. Indices of corpus callosal atrophy were significantly correlated with the chronicity of injury and the degree of lateral ventricular enlargement. There was no difference in callosal measurements between men and women. Magnetic resonance imaging provides an in vivo determination of corpus callosal atrophy which may reflect the severity of diffuse axonal injury and predict the type and severity of hemispheric disconnection effects.

A randomized, controlled trial of methylprednisolone or naloxone in the treatment of acute spinal-cord injury. Results of the Second National Acute Spinal Cord Injury Study

Studies in animals indicate that methylprednisolone and naloxone are both potentially beneficial in acute spinal-cord injury, but whether any treatment is clinically effective remains uncertain. We evaluated the efficacy and safety of methylprednisolone and naloxone in a multicenter randomized, double-blind, placebo-controlled trial in patients with acute spinal-cord injury, 95 percent of whom were treated within 14 hours of injury. Methylprednisolone was given to 162 patients as a bolus of 30 mg per kilogram of body weight, followed by infusion at 5.4 mg per kilogram per hour for 23 hours. Naloxone was given to 154 patients as a bolus of 5.4 mg per kilogram, followed by infusion at 4.0 mg per kilogram per hour for 23 hours. Placebos were given to 171 patients by bolus and infusion. Motor and sensory functions were assessed by systematic neurological examination on admission and six weeks and six months after injury. After six months the patients who were treated with methylprednisolone within eight hours of their injury had significant improvement as compared with those given placebo in motor function (neurologic change scores of 16.0 and 11.2, respectively; P = 0.03) and sensation to pinprick (change scores of 11.4 and 6.6; P = 0.02) and touch (change scores, 8.9 and 4.3; P = 0.03). Benefit from methylprednisolone was seen in patients whose injuries were initially evaluated as neurologically complete, as well as in those believed to have incomplete lesions. The patients treated with naloxone, or with methylprednisolone more than eight hours after their injury, did not differ in their neurologic outcomes from those given placebo. Mortality and major morbidity were similar in all three groups. We conclude that in patients with acute spinal-cord injury, treatment with methylprednisolone in the dose used in this study improves neurologic recovery when the medication is given in the first eight hours. We also conclude that treatment with naloxone in the dose used in this study does not improve neurologic recovery after acute spinal-cord injury.

Neuromagnetic evidence of a dynamic excitation pattern generating the N100 auditory response

Evoked magnetic field recordings were used to localize multiple sources of the negative component of cortical responses to auditory stimuli. The negative cortical component of the auditory evoked response, often called the N100, has traditionally been of interest due to its sensitivity to both stimulation parameters and cognitive variables. Results indicate that this component appears to reflect spreading activation of adjacent cortical columns within the primary projection area of the temporal lobe, extending anteriorly for about 1 cm following the downward slope of the superior surface of the lobe.

Desmopressin, but not vasopressin, decreases activity of the hypothalamo-neurohypophysial system in Brattleboro rats

The pituitary neural lobe of homozygous Brattleboro rats has high rates of glucose utilization not affected by chronic treatment with exogenous vasopressin, despite attenuation of polydipsia and polyuria. We evaluated whether this effect may result from the inability of vasopressin to affect the hypothalamo-neurohypophysial metabolism or from the development of resistance to chronic vasopressin treatment. We used the [14C]deoxyglucose method to compare 28-h effects of vasopressin treatment (5 U/kg, i.m., twice a day) with that of desmopressin (100 micrograms/kg, i.p., once a day), a long-lasting antidiuretic hormone, on glucose utilization of the hypothalamo-neurohypophysial system and related structures in conscious homozygous Brattleboro rats. Vasopressin and desmopressin reduced water intake, plasma osmolality and plasma Na+ concentration similarly. Vasopressin decreased glucose utilization in the supraoptic nucleus, subfornical organ and median preoptic nucleus, but did not alter activity in the paraventricular nucleus and neural lobe. Desmopressin decreased glucose utilization in all these structures. The results indicate that desmopressin has a more potent inhibitory action on the hypothalamo-neurohypophysial system than vasopressin over this short duration of treatment. The lack of response in the neural lobe from chronic treatment with vasopressin seems to be due to its inability to affect the paraventricular nucleus metabolism. The maintenance of metabolic activity in the paraventricular nucleus of vasopressin-treated Brattleboro rats suggests that this structure contributes importantly to the metabolism of neural lobe.

Assessment of a superparamagnetic iron oxide (AMI-25) as a brain contrast agent

We have applied a superparamagnetic iron oxide formulation (AMI-25, Advanced Magnetics, Inc., Cambridge, MA) to image the cerebral vasculature. Contrast-enhanced images of normal anesthetized rats demonstrated excellent gray/white matter differentiation, consistent with known differences in blood perfusion, and cerebrospinal fluid spaces were clearly seen. Alterations in normal perfusion patterns due to barbiturate anesthesia and ischemia were clearly visible. We propose the use of this agent as an adjunct to MRI for the imaging of conditions with perfusion abnormalities.

Behavioral changes after closed head injury in children

This study provides a longitudinal follow-up of the behavioral adjustment of 45 children with mild, moderate, and severe closed head injuries. Two measures of behavioral adjustment, the Child Behavior Checklist (CBCL) and the Vineland Adaptive Behavior Scales (VABS), were obtained from a parent at the time of injury and at 6 and 12 months postinjury. The severely injured children obtained significantly poorer VABS scores than children with mild and moderate injuries over the year-long follow-up. In addition, on the CBCL, severely injured children had more school problems and engaged in fewer social activities than mild and moderately injured children. These results show that severe head injury in children was associated with declines in adaptive functioning, whereas scores for children with mild and moderate injuries did not differ, nor did they deviate from average levels at any follow-up interval.

Source localization of two evoked magnetic field components using two alternative procedures

The purpose of this study was to compare the relative efficacy of two methods in assessing the location of the sources of the N100 and P200 components of evoked magnetic fields (EMFs) to transient tone stimuli. EMFs to left ear stimulation, containing both components, were recorded over the right hemisphere of six normal subjects. The magnetic scalp distributions calculated at several adjacent time points, covering the duration of each component's peak, were used to estimate the source parameters of each component. Good estimates of the source of both components were obtained from all magnetic field distributions. The averaged spatial parameters derived from all distributions of each component as well as the parameters derived from the distribution that gave the best source estimate for each component were projected onto magnetic resonance images of subject's head. It was found that the source of each component is located on the superior surface of the temporal lobe and that the source of the P200 component is anterior to the N100 source in all subjects using both procedures.

Localization of auditory response sources using magnetoencephalography and magnetic resonance imaging

Magnetoencephalography offers the possibility of localizing accurately and noninvasively the source of intracranial currents associated with normal and abnormal brain activity. The purpose of this study was to assess the validity and across-subject reliability of localization of cortical sources responding to ipsilateral and contralateral auditory stimulation. Magnetic evoked fields to both stimulation conditions were measured in eight consecutive normal subjects, and the cortical sources of these fields were estimated on the basis of these measurements. Subsequent projection of the source location coordinates onto magnetic resonance images showed that in all subjects the sources were accurately estimated to fall in the vicinity of the auditory cortex and that two separate sources may account for the response to ipsilateral and contralateral stimulation.

Behavioral changes after closed head injury in children

This study provides a longitudinal follow-up of the behavioral adjustment of 45 children with mild, moderate, and severe closed head injuries. Two measures of behavioral adjustment, the Child Behavior Checklist (CBCL) and the Vineland Adaptive Behavior Scales (VABS), were obtained from a parent at the time of injury and at 6 and 12 months postinjury. The severely injured children obtained significantly poorer VABS scores than children with mild and moderate injuries over the year-long follow-up. In addition, on the CBCL, severely injured children had more school problems and engaged in fewer social activities than mild and moderately injured children. These results show that severe head injury in children was associated with declines in adaptive functioning, whereas scores for children with mild and moderate injuries did not differ, nor did they deviate from average levels at any follow-up interval.

Spatially Distributed Cortical Excitation Patterns of Auditory Processing during Contralateral and Ipsilateral Stimulation

Utilizing the high spatial and temporal resolution of magnetoencephalography in conjunction with magnetic resonance images, the current study explored the underlying electrical patterns of cortical excitation during both contralateral and ipsilateral auditory stimulation. Instead of studying only the peaks of the N100 component of the evoked magnetic field, a 30-msec window was chosen about the area where the peaks occurred and the intracranial sources generating that component were estimated at successive 5-msec intervals. Results indicated that the sources for both contralateral and ipsilateral conditions were best represented as a continuous movement of activation in an anterior–inferior direction along the superior surface of the temporal lobe. Although the peak magnetic fields of the N100 to contralateral stimulation were of shorter latency and higher amplitude, the generating sources of both had very similar time-dependent movement patterns, and comparisons of source localizations were dependent on the latency at which they were contrasted.

Dichotic listening and manual performance in relation to magnetic resonance imaging after closed head injury

In order to investigate post-traumatic hemispheric disconnection effects, dichotic listening and intermanual tasks were administered to 69 patients who had sustained a closed head injury of varying severity. The manual tasks consisted of naming objects palpated in either hand, transfer of postures from one hand to the other and writing. Consistent with predictions, the degree of ear asymmetry in dichotic listening performance was directly related to the severity of the head injury as reflected by the degree of impaired consciousness. Depth and localisation of parenchymal lesion characterised by magnetic resonance imaging were also related to the degree of ear asymmetry. Parenchymal lesions situated in sites which could potentially interfere with callosal auditory or geniculocortical pathways produced a greater disparity in response to left versus right ear inputs as compared with parenchymal lesions in areas such as the frontal lobes which are purportedly unrelated to asymmetries in dichotic listening performance. The results provide further evidence for the effects of multifocal brain lesions involving the white matter on tasks which require intra and/or interhemispheric integration.

Middle cerebral artery occlusion in rats studied by magnetic resonance imaging

Ischemia due to middle cerebral artery occlusion was studied in 29 rats from 1 to 24 hours after occlusion using magnetic resonance imaging. Images were made before and after the injection of a superparamagnetic iron oxide compound, AMI-25. Subtraction images demonstrated the region of perfusion deficit as early as 1 hour after occlusion, earlier than conventional T2-weighted images. The area of altered perfusion detected by this technique (subtraction imaging after AMI-25 administration) correlated with that demonstrated by iodoantipyrine autoradiography. Since this magnetic resonance technique can be used to serially estimate the location and size of the ischemic area, the technique can be an important adjunct to metabolic studies of focal ischemia using magnetic resonance spectroscopy. The technique may have clinical applications as well.

Duration of impaired consciousness in relation to side of lesion after severe head injury. NIH Traumatic Coma Data Bank Research Group

The relation between hemispheric lateralisation of intracerebral lesion and duration of impaired consciousness was investigated in 43 survivors of severe closed head injury. Duration of impaired consciousness, defined as the time from injury until the obeying of commands, was significantly longer in patients with left hemisphere than right hemisphere lesions. However, the side of intracerebral lesion had no effect on duration of impaired consciousness defined as time from injury until localisation to pain. Use of verbal methods to assess level of consciousness may be responsible for the observation that lesions of the language dominant hemisphere produce greater disturbance of consciousness than similar insults to the right hemisphere.