Brain specific gravity and CT scan density measurements after human head injury

Systematic Review and Dosage Analysis: Hyperbaric Oxygen Therapy Efficacy in Mild Traumatic Brain Injury Persistent Postconcussion Syndrome

Background

Mild traumatic brain injury results in over 15% of patients progressing to Persistent Postconcussion Syndrome, a condition with significant consequences and limited treatment options. Hyperbaric oxygen therapy has been applied to Persistent Postconcussion Syndrome with conflicting results based on its historical understanding/definition as a disease-specific therapy. This is a systematic review of the evidence for hyperbaric oxygen therapy (HBOT) in Persistent Postconcussion Syndrome using a dose-analysis that is based on the scientific definition of hyperbaric oxygen therapy as a dual-component drug composed of increased barometric pressure and hyperoxia.

Methods

In this review, PubMed, CINAHL, and the Cochrane Systematic Review Database were searched from August 8–22, 2021 for all adult clinical studies published in English on hyperbaric oxygen therapy in mild traumatic brain injury Persistent Postconcussion Syndrome (symptoms present at least 3 months). Randomized trials and studies with symptomatic and/or cognitive outcomes were selected for final analysis. Randomized trials included those with no-treatment control groups or control groups defined by either the historical or scientific definition. Studies were analyzed according to the dose of oxygen and barometric pressure and classified as Levels 1–5 based on significant immediate post-treatment symptoms or cognitive outcomes compared to control groups. Levels of evidence classifications were made according to the Centre for Evidence-Based Medicine and a practice recommendation according to the American Society of Plastic Surgeons. Methodologic quality and bias were assessed according to the PEDro Scale.

Results

Eleven studies were included: six randomized trials, one case-controlled study, one case series, and three case reports. Whether analyzed by oxygen, pressure, or composite oxygen and pressure dose of hyperbaric therapy statistically significant symptomatic and cognitive improvements or cognitive improvements alone were achieved for patients treated with 40 HBOTS at 1.5 atmospheres absolute (ATA) (four randomized trials). Symptoms were also improved with 30 treatments at 1.3 ATA air (one study), positive and negative results were obtained at 1.2 ATA air (one positive and one negative study), and negative results in one study at 2.4 ATA oxygen. All studies involved <75 subjects/study. Minimal bias was present in four randomized trials and greater bias in 2.

Conclusion

In multiple randomized and randomized controlled studies HBOT at 1.5 ATA oxygen demonstrated statistically significant symptomatic and cognitive or cognitive improvements alone in patients with mild traumatic brain injury Persistent Postconcussion Syndrome. Positive and negative results occurred at lower and higher doses of oxygen and pressure. Increased pressure within a narrow range appears to be the more important effect than increased oxygen which is effective over a broad range. Improvements were greater when patients had comorbid Post Traumatic Stress Disorder. Despite small sample sizes, the 1.5 ATA HBOT studies meet the Centre for Evidence-Based Medicine Level 1 criteria and an American Society of Plastic Surgeons Class A Recommendation for HBOT treatment of mild traumatic brain injury persistent postconcussion syndrome.

Head computed tomographic measurement as a predictor of outcome in patients with subdural hematoma with cerebral edema

BACKGROUND

The ability to predict outcome in patients with cerebral edema is important because it can influence treatment strategy. We evaluated whether differences in head computed tomographic (CT) measurements in Hounsfield units (HU) of white matter and gray matter can be used as a predictor of outcome in patients with subdural hematoma with cerebral edema.

METHODS

We evaluated 34 patients who had subdural hematoma with cerebral edema following acute closed head trauma and had undergone head CT within a few hours of admission. We divided them into the survival (n = 24) group and death (n = 10) group, and measured the HU of white matter and gray matter at injury and non-injury sites.

RESULTS

There were no significant differences in operation time or blood loss during surgery between the two groups. Only the HU of white matter in the injury site of patients in the death group were decreased significantly. A cut-off value of 31.5 for HU of white matter showed 80.0 % sensitivity and 99.9 % specificity for death; the area under the curve was 0.91.

DISCUSSION

Our results are more evidence of the support of neurogenic edema in trauma rather than an important clinical tool at this stage. However, HU values in WM may be one factor in the decision-making process that affects patient outcome. Changing the treatment strategy in patients with a low HU value in the WM at the injury site may bring about an improvement in patient outcome.

CONCLUSION

Measurement in HU of white matter at the injury site might be useful as a predictor of outcome in patients with subdural hematoma with cerebral edema.

Biomechanics of subdural hemorrhage in American football: review of the literature in response to rise in incidence

The number of catastrophic head injuries recorded during the 2011 football season was the highest since data collection began in 1984--the vast majority of these cases were secondary to subdural hemorrhage (SDH). The incidence of catastrophic head injury continues to rise: the average yearly incidence from 2008 to 2012 was 238% that of the average yearly incidence from 1998 to 2002. Greater than 95% of the football players who suffered catastrophic head injury during this period were age 18 or younger. Currently, the helmet industry utilizes a standard based on data obtained at Wayne State University approximately 50 years ago that seeks to limit severity index--a surrogate marker of translational acceleration. In this manuscript, we utilize a focused review of the literature to better characterize the biomechanical factors associated with SDH following collisions in American football and discuss these data in the context of current helmet standard. Review of the literature indicates the rotational acceleration (RA) threshold above which the risk of SDH becomes appreciable is approximately 5,000 rad/s(2). This value is not infrequently surmounted in typical high school football games. In contrast, translational accelerations (TAs) experienced during even elite-level impacts in football are not of sufficient magnitude to result in SDH. This information raises important questions about the current helmet standard--in which the sole objective is limitation of TA. Further studies will be necessary to better define whether helmet constructs and quality assurance standards designed to limit RA will also help to decrease the risk of catastrophic head injury in American football.

Computed tomography-estimated specific gravity at hospital admission predicts 6-month outcome in mild-to-moderate traumatic brain injury patients admitted to the intensive care unit

BACKGROUND

It is clear that patients with a severe traumatic brain injury (TBI) develop secondary, potentially lethal neurological deterioration. However, it is difficult to predict which patients with mild-to-moderate TBI (MM-TBI), even after intensive care unit (ICU) admission, will experience poor outcome at 6 months. Standard computed tomography (CT) imaging scans provide information that can be used to estimate specific gravity (eSG). We have previously demonstrated that higher eSG measurements in the standard CT reading were associated with poor outcomes after severe TBI. The aim of this study was to determine whether eSG of the intracranial content predicts 6-month outcome in MM-TBI.

METHODS

We analyzed admission clinical and CT scan data (including eSG) of 66 patients with MM-TBI subsequently admitted to our neurosurgical ICU. Primary outcome was defined as a Glasgow Outcome Scale score of 1 to 3 after 6 months. Discriminating power (area under the receiver operating characteristic curve [ROC-AUC], 95% confidence interval) of eSG to predict 6-month poor outcome was calculated. The correlation of eSG with the main ICU characteristics was then compared.

RESULTS

Univariate and stepwise multivariate analyses showed an independent association between eSG and 6-month poor outcome (P = 0.001). ROC-AUC of eSG for the prediction of 6-month outcomes was 0.87 (confidence interval: 0.77-0.96). Admission eSG values were correlated with the main ICU characteristics, specifically 14-day mortality (P = 0.004), length of mechanical ventilation (P = 0.01), length of ICU stay (P = 0.045), and ICU procedures such as intracranial pressure monitoring (P < 0.001).

CONCLUSIONS

In this MM-TBI cohort admitted to the ICU, eSG of routine CT scans was correlated with mortality, ICU severity, and predicted 6-month poor outcome. An external validation with studies that include the spectrum of TBI severities is warranted to confirm our results.

Does brain swelling increase estimated specific gravity?

OBJECTIVE

At the acute phase of traumatic brain injury (TBI), brain swelling contributes substantially to the development of secondary neurological lesions. Elucidating the pathophysiology of brain swelling is crucial to improve TBI management. In a previous study, specific gravity (SG) of the noncontused hemisphere, as estimated by computed tomography (CT), was higher in patients with high Marshall CT scores and severe brain swelling. The aim of this study was to investigate the relationship between estimated specific gravity (eSG) and clinical variable suggestive of brain swelling.

DESIGN

Retrospective study of data from a prospectively established database.

SETTING

Neurology ICU in a teaching hospital in Paris, France.

PARTICIPANTS

We studied 20 patients with severe traumatic brain injury (TBI), 20 patients with high-grade subarachnoid hemorrhage (SAH) presenting similar brain-swelling criteria, 20 patients with low-grade SAH, and 20 healthy controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Estimated brain specific gravity was acquired from CT images obtained at ICU admission. eSG was estimated in the overall intracerebral content and in a region-of-interest composed of white matter and the diencephalon. eSG in the region of interest was significantly higher in the TBI patients than in the high-grade SAH patients (1.0350 +/- 0.0041 vs. 1.0310 +/- 0.0019 g/ml, P < 0.05). eSG was similar in the high-grade SAH, low-grade SAH, and control groups.

CONCLUSIONS

Our findings do not support a causal link between brain swelling and eSG elevation. The eSG increase in severe TBI patients is not due to brain swelling.

Does the brain become heavier or lighter after trauma?

An uncontrolled rise in intracranial pressure is probably the most common cause of death in traumatic brain-injured patients. The intracranial pressure rise is often due to cerebral oedema. Diffusion-weighted imaging has been extensively used to study cerebral oedema formation after trauma in experimental studies. Nevertheless, this technology is difficult to perform at the acute phase, especially in unstable head trauma patients. For these reasons, a safe examination allowing us to better understand the pathophysiology of cerebral oedema formation in such patients would be of great interest. Radiological attenuation is linearly correlated with estimated specific gravity in human tissue. This property gives the opportunity to measure in vivo the volume, weight and specific gravity of any tissue by computed tomography. We recently developed a software package (BrainView) for Windows workstations, providing semi-automatic tools for brain analysis from DICOM images obtained from cerebral computed tomography. In this review, we will discuss the results of the in vivo analysis of brain weight, volume and specific gravity and consider the use of this software as a new technology to improve our knowledge of cerebral oedema formation after trauma and to evaluate the severity of traumatic brain-injured patients.

Computed tomography-estimated specific gravity of noncontused brain areas as a marker of severity in human traumatic brain injury

In this study, we assessed the relationship between brain estimated specific gravity (eSG) and clinical symptoms, therapeutic intensity level, and outcome in human traumatic brain injury (TBI). Brain weight, volume, and eSG of the noncontused hemispheric areas were measured from computed tomography (CT) DICOM images on the initial (5 +/- 6 h) CT of 120 patients with severe TBI. Control values were obtained from 40 healthy patients. The eSG of the noncontused hemispheric areas was significantly higher in TBI patients than in controls. eSG was higher in patients having a Marshall CT classification of 3 or 4 or a low initial Glasgow coma score. Two groups were defined according to the eSG of the noncontused hemispheric areas: less than (n = 83, 69%) or more than (n = 37, 31%) the threshold of normality (defined as 1.96 sd above normal = 1.0355 g/mL). The occurrence of mydriasis, use of osmotherapy at the scene of the accident, and therapeutic intensity level were higher in the increased eSG group. The outcome at intensive care unit discharge was worse in patients with an increased eSG although the difference was no longer significant at 1 yr. eSG determination by CT analysis might be relevant in the early management of TBI.

A new method for fast quantitative mapping of absolute water content in vivo

The presence of brain edema, in its various forms, is an accompanying feature of many diseased states. Although the localized occurrence of brain edema may be demonstrated with MRI, the quantitative determination of absolute water content, an aspect that could play an important role in the objective evaluation of the dynamics of brain edema and the monitoring of the efficiency of treatment, is much more demanding. We present a method for the localized and quantitative measurement of absolute water content based on the combination of two fast multi-slice and multi-time point sequences QUTE and TAPIR for mapping the T(2)* and T(1) relaxation times, respectively. Incorporation of corrections for local B(1) field miscalibrations, temperature differences between the subject and a reference probe placed in the FOV, receiver profile inhomogeneities and T(1) saturation effects are included and allow the determination of water content with anatomical resolution and a precision >98%. The method was validated in phantom studies and was applied to the localized in vivo measurement of water content in a group of normal individuals and a patient with brain tumor. The results demonstrate that in vivo measurement of regional absolute water content is possible in clinically relevant measurement times with a statistical and systematic measurement error of <2%.

A quantitative computed tomography assessment of brain weight, volume, and specific gravity in severe head trauma

BACKGROUND

Computed tomography DICOM images analysis allows a quantitative measurement of organ weight, volume and specific gravity in humans.

METHODS

The brain weight, volume and specific gravity of 15 traumatic brain-injury patients (3+/-2 days after trauma) were computed using a specially designed software (BrainView). Data were compared with those obtained from 15 healthy subjects paired for age and overall intracranial volume.

RESULTS

Hemisphere weight were 91 g higher in patients than in controls (1167+/-101 vs 1076+/-112 g; p<0.05). Specific gravity of hemispheres (1.0367+/-0.0017 vs 1.0335+/-0.0012 g/ml; p<0.001), brainstem (1.0302+/-0.0016 vs 1.0277+/-0.0015 g/ml; p<0.001) and cerebellum (1.0396+/-0.0020 vs 1.0375+/-0.0015 g/ml; p<0.05) was significantly higher in traumatic brain injury (TBI) patients than in controls (all p<0.0001 without interaction). This increase in specific gravity was evenly distributed between the hemispheres, the brainstem and the cerebellum, and the grey and white matter. It was more pronounced in the rostral than in the caudal areas of the hemispheres. It was independent of the volume of brain contusion, of the mechanism of head injury, of natremia and of initial Glasgow coma score.

CONCLUSION

Human TBI patients present a diffuse increase in specific gravity. This observation is in sharp opposition with the data derived from the experimental literature.

Comparison of cerebral blood flow in computed tomographic hypodense areas of the brain in head-injured patients

OBJECTIVE

Hypodense lesions identified on computed tomographic (CT) scans are often assumed to indicate ischemia. The purpose of this study was to investigate regional cerebral blood flow (rCBF) in hypodense areas of the brain after severe traumatic brain injury.

METHODS

CBF was measured by stable xenon-enhanced CT scans. Hypodense areas were identified, and rCBF values as well as CT density were averaged for the region.

RESULTS

Thirty (60%) of the 50 patients had a total of 45 hypodense regions, which were associated with either contusion (n = 30) or areas of infarction (n = 15). rCBF in the hypodense regions was variable, ranging from a low of 3.3 to a high of 72.5 ml/100 g/min. The cause of the lesion was the major factor associated with the level of rCBF. Although the average decrease in CT density was similar for the two types of lesions, the average rCBF was significantly lower and the difference in rCBF between the lesion and the contralateral side was greater when the hypodense lesion was associated with a contusion. A critical reduction in rCBF (<20 ml/100 g/min) was found in 19 (63%) of the hypodense regions associated with contusions but in only 4 (27%) of those from areas of infarction.

CONCLUSION

Hypodensity on plain CT scans does not always indicate reduction in CBF. This association was found more commonly when the low-density area was associated with a contusion. In hypodense areas associated with infarction, rCBF was variable and not commonly in the ischemic range at the time the CBF measurement was obtained.

Use of magnetic resonance imaging for in vivo measurements of water content in human brain: method and normal values

OBJECT

The authors present a quantitative in vivo magnetic resonance (MR) imaging method and propose its use for the accurate assessment of brain water in humans.

METHODS

With this technique, a pure T1-weighted image of a selected brain slice in a patient is generated, and the image is subsequently converted to a pure water image by means of an equation derived from a tissue relaxation model. The image intensity in the resulting water map directly yields absolute measures of water expressed in grams of water per gram of tissue at a given anatomical location. The method has been validated previously in a series of phantom experiments and in an infusion model of brain edema in cats. In this report, the authors evaluate the method by using samples of tissue harvested from patients who underwent surgery for brain tumor removal and apply the technique to a series of normal volunteers, providing average regional brain water content (f(w)) values for a range of tissues. Application of the method in pathological conditions such as head trauma, tumor, and hydrocephalus allows quantification of regional or global increases in f(w) that result from edema.

CONCLUSIONS

It is now possible to obtain accurate brain water measurements with the anatomical resolution of MR imaging. This permits monitoring of the development and resolution of edema in a variety of clinical circumstances, thus enhancing understanding of the underlying pathophysiological processes.

Effects of niravoline (RU 51599), a selective kappa-opioid receptor agonist on intracranial pressure in gradually expanding extradural mass lesion

It has recently been reported that kappa-opioid receptor agonists inhibit antidiuretic hormone secretion and promote water excretion in humans and animals. We investigated the effect of niravoline (RU 51599), a selective kappa-opioid receptor agonist in the treatment of intracranial hypertension. Acute intracranial hypertension was induced in cats by continuous inflation of an extradural balloon with physiological saline at the constant rate of 0.5 ml/h for 3 h. At this point, inflation was discontinued and the balloon remained expanded for an additional hour after which it was deflated. In the post-deflation period, monitoring continued for 1 h. The control group (n = 8) received ringer's lactate solution only, while the treatment group (n = 8) received an intravenous (IV) injection of 1.0 mg/kg of niravoline, every hour at the beginning of balloon inflation, during balloon inflation, in post-inflation, and at deflation time (5 doses). Changes in intracranial pressure (ICP), mean arterial blood pressure (MAP), cerebral perfusion pressure (CPP), electroencephalogram (EEG), blood gases, pupil size, serum electrolytes, and osmolality were measured in both groups. Brain water content was determined in a separate group of cats at the end of a 3-h extradural brain compression. Compared to the untreated group, the niravoline-treated group had a significantly lower ICP and higher CPP at the 2 and 3 h during balloon inflation, in post-inflation, and in post-deflation periods. Brain water content was significantly reduced in niravoline-treated animals. No significant change was observed in serum osmolality throughout the experiment. Our results indicate that the mechanism by which niravoline reduces ICP is partly via a reduction in brain water content. Also, the current findings suggest that in clinical situations in which ICP is elevated due to the pressure of an extradural mass, niravoline may effectively reduce ICP while maintaining adequate CPP until the mass is removed.

Ultrastructural study of brain microvessels in patients with traumatic cerebral contusions

Brain tissue from 11 patients with traumatic cerebral contusions submitted to surgery was studied. Control biopsy specimens were obtained from 5 patients undergoing ventriculo-peritoneal shunts for "communicating" hydrocephalus. After collection, the small fragments were fixed by immersion in glutaraldehyde-osmium and embedded in Epon. Semi-thin sections stained with toluidine blue were observed with the light microscope. Thin sections stained with lead citrate and uranyl acetate were observed using a Jeol electron microscope. In tissues from patients with head trauma a clear space most probably corresponding to fluid accumulation was systematically observed around microvessels. Ultrastructurally endothelial cells from these specimens exhibited signs of marked intracellular oedema, tight junctions being intact. Pinocytotic activity was increased, mainly at the abluminal surface. Swelling of astrocytic perivascular processes and the appearance of macrophagic cells with voluminous lysosomes were also observed. The authors conclude that the oedema of endothelial cells probably represent a central fact in the pathophysiology of traumatic brain oedema and speculate on the putative involvement of stretch-activated receptors in this condition.

Repeated decompressive craniectomy after head injury in children: two successful cases as result of improved neuromonitoring

BACKGROUND Decompressive craniectomy in the treatment of posttraumatic brain swelling is not generally accepted. Until now the efficacy of operative decompressive craniectomy in posttraumatic brain swelling of children appeared more promising. However, the criteria for such procedures remain unclearly defined. METHODS We present two children who had repeated decompressive craniectomy following head injury, in order to control intracranial pressure (ICP) sufficiently. Our indications for performing a decompressive craniectomy in the presence of conservatively uncontrollable raised ICP are: (1) Patient is between the ages of 3 and 35 years. (2) An initial Glasgow Coma Scale (GCS) ranging between 4 and 8. (3) Three criteria have to be fulfilled at the same time: The cerebral perfusion pressure (CPP) has to drop to values of less than 60 mm Hg. It is impossible to control the ICP values (up to 45 mm Hg) conservatively. The diastolic velocity of the transcranial doppler sonography (TCD) has to decrease until only a systolic flow pattern is obtained. (4) No other mass lesion should be detected on cranial computed tomography (CCT) that could account for the rise in pressure. In both cases we performed bifrontal decompressive craniectomies. RESULTS Both patients survived. Seven months after the accident, patient No. 1 was oriented and could walk on her own with a mild right-side hemiparesis. Patient No. 2 could attend school 12 months postinjury. Both patients developed hygromas after the craniectomy. A shunt operation, however, was not necessary. CONCLUSIONS ICP monitoring, together with CCT examination, simultaneous recording of TCD, and systemic parameters, will reveal a patient at risk at a time when impending damage due to uncontrollable ICP may still be prevented. The simultaneous assessment of cerebral blood flow by transcranial doppler (TCD), in this situation, proves most valuable. It improves the guidelines of patient selection for decompressive craniectomy, in the presence of conservatively uncontrollable ICP.

Focal ischemia due to traumatic contusions documented by stable xenon-CT and ultrastructural studies

A traumatic cerebral contusion causes a zone of perifocal neuronal necrosis, the cause of which is not known; the surgical management of these lesions remains controversial. To determine the pathophysiological mechanisms responsible for brain damage after contusions, the authors performed cerebral blood flow (CBF) mapping studies and related these to change in local cerebral blood volume (CBV) and ultrastructure. In 11 severely head injured patients with contusion, CBF and CBV were measured in pericontusional areas using stable xenon-computerized tomography (CT). These studies demonstrated a profound reduction in perilesional CBF (mean 17.5 +/- 4 ml/100 g/min), which was always accompanied by a zone of edema defined by CT density measurements. Mean CBV in these regions was 2.3 +/- 0.4 ml/100 g, a reduction to approximately one-half the value of 4.8 ml/100 g found in the nonedematous regions, and to approximately 35% of the value of 6.0 ml/100 g found in normal volunteers. Ultrastructural analysis of the pericontusional tissue, taken at surgery in four patients with high intracranial pressure showed glial swelling with narrowing of the microvascular lumina due to massive podocytic process swelling. Additionally, some suggestion of vascular occlusion due to erythrocyte and leukocyte stasis was seen. These data support the conclusion that microvascular compromise by compression and/or occlusion is a major event associated with profound perilesional hypoperfusion, which is a uniform finding within edematous pericontusional tissue.

Pathophysiology of brain swelling after acute experimental brain compression and decompression

Global ischemia was created by controlled expansion of an epidural balloon for 25 minutes in Group A (six cats) and for 5 minutes in Group B (six cats). The alterations of intracranial pressure, arteriovenous oxygen content difference, cerebral metabolic rate of oxygen, cerebral blood flow, and electroencephalogram were observed until brain death or 24 hours' survival with normal intracranial pressure. The animals were then killed for brain histological examination. In four other cats, a 2% solution of Evans blue dye (4 mg/kg) was injected intravenously--immediately after deflation--resulting in 25 minutes of global ischemia. Two other cats received 5 minutes of global ischemia. The cats were killed 1 hour later. Abrupt swelling occurred in Group A, and no swelling was found in Group B. A transient absolute hyperemia was found immediately after deflation in both groups. The cerebral blood flow and cerebral metabolic rate of oxygen decreased markedly with low arteriovenous oxygen content difference and flat electroencephalogram in Group A, compared with gradual recovery of cerebral blood flow and cerebral metabolic rate of oxygen with high arteriovenous oxygen content difference and reappearance of electroencephalogram activity in Group B. The extravasation of Evans blue was observed on the compressed cerebral hemisphere, thalamus, hypothalamus, and brain stem in swelling animals and only on the compressed hemisphere in nonswelling animals. Histologically, the damage and congestive dilation of capillary, degeneration, and necrosis of neuronal and glial cell were found prominently on the hypothalamus and brain stem in the swelling group.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional theoretical SAR and temperature distributions created in brain tissue by 915 and 2450 MHz dipole antenna arrays with varying insertion depths

Theoretical three-dimensional power deposition and temperature distributions were calculated for interstitial hyperthermia microwave antenna arrays driven at 915 and 2450 MHz in brain tissue. Four dipole antennas were assumed to be placed in a 2 x 2 cm array with varying insertion depths in cylindrical tumour models. The bioheat transfer equation was solved for the three-dimensional steady-state temperature distributions using a finite element method. Homogeneous and non-homogeneous blood flow models were considered. As a basis of comparison of the various temperature distributions, the volume of the tumour heated to greater than or equal to 43 degrees C was calculated. SAR distributions calculated for the 915 MHz antenna arrays in brain tissue were very similar to those calculated for muscle. The 2450 MHz arrays showed similar behaviour to the 915 MHz arrays; however, as the insertion depth increased from slightly less than a full-wavelength there was a single hotspot centred at the antenna junction. For the 2450 MHz arrays, the predicted therapeutic tumour volumes were relatively constant over the entire range of insertion depths considered, and in fact, for most insertion depths considered, the model predicted the 2450 MHz arrays would heat larger therapeutic volumes than the 915 MHz arrays. For the 915 MHz array, at insertion depths between 7.8 and 14.6 cm there was a sharp decrease in the predicted therapeutic volume due to a proximal secondary hotspot in the normal tissue causing overheating. However, when the same size tumour at the same insertion depth was heated with the 2450 MHz array, the hotspot was in the tumour, adding to the volume of tumour that was heated to therapeutic temperatures.

Glial swelling following human cerebral contusion: an ultrastructural study

The ultrastructural features of cerebral contusion seen three hours to 11 days after head injury were studied in 18 patients undergoing surgery. Massive astrocytic swelling ("cytotoxic" oedema) was seen three hours to three days after injury, maximal in perivascular foot processes, and compressing some of the underlying capillaries. The tight junctions were not disrupted. Neuronal damage was most marked three to 11 days after injury. The pathophysiological mechanisms leading to oedema formation and neuronal degeneration are discussed.

Intracerebral haematoma: aetiology and haematoma volume determine the amount and progression of brain oedema

In a study of 182 patients with a traumatic, 'spontaneous', or aneurysmal intracerebral haematoma (ICH) a significant correlation was found between the amount of focal brain oedema seen on computed tomogram (CT) and both the aetiology and the size of the haematoma. Traumatic haematomas were associated with twice the oedema per unit volume of haematoma, and a doubling of median oedema volume on second CT (performed in 18 patients), compared to spontaneous or aneurysmal haematomas.

The time course of vasogenic oedema after focal human head injury--evidence from SPECT mapping of blood brain barrier defects

We have tomographically mapped changes in the blood brain barrier (BBB) (99 mTc Pertechnetate) in 20 patients with acute contusions, and four with acute subdural haematomas in situ. The changes were related to regional CBF, (99 mTc HMPAO SPECT) T2 weighted MRI scans, CT abnormalities and the clinical features. Seventy-five percent of contusions were accompanied by a BBB abnormality, usually a "halo" around the lesion, which was more common in scans made after the second day. All contusions demonstrated "oedema" as a zone of "T2" signal on MRI or a zone of lucency on CT, and all were accompanied by a focal zone of low CBF on SPECT. Early contusional oedema appears to be cytotoxic but in certain cases, delayed blood brain barrier lesions develop, suggesting a vasogenic component.

Traumatic brain swelling studied by computerized tomography and densitometry

Two-hundred and fifty-two computerized tomography (CT) scans of 107 patients with head injuries were analyzed. The most frequent consequence of trauma was a diffuse swelling of the brain in 91% of the cases. The severity of brain swelling and its course can be estimated by the compression of (or absence of) the intracranial cerebrospinal fluid space. These observations may be of prognostic value as well. By measurement of the Hounsfield units (HU) in 52 cases the blood or water content in the brain tissues was assessed. An increase in blood content of the tissues (hyperaemia) can account for an increase in Hounsfield values. A decrease in HU suggests brain edema. The density measurements showed that in the first hours and days following head injury, the diffuse brain swelling was caused by severe cerebrovascular congestion in the majority (53%) of the cases. Immediate brain edema without a preceding hyperaemic phase occurs less frequently (32%). Between the 1st and 4th day after injury, edema started to prevail, and between the 5th and 8th day the edematous type of brain swelling was present almost exclusively.

Posttraumatic cerebral hemispheric swelling. Analysis of 55 cases studied with computerized tomography

The authors have analyzed the clinical course and intracranial pressure (ICP) changes in 55 severely head-injured patients presenting with bulk enlargement of one cerebral hemisphere within a few hours after trauma. These patients represent 10.5% of a series of 520 patients with severe head injury studied with computerized tomography (CT). Cerebral hemispheric swelling has the highest mortality rate and the shortest survival period after trauma in all series of severe head injury. In this series, it was associated with an ipsilateral subdural hematoma of variable size in 47 patients (85%) or with a large epidural hematoma in five patients (9%); in three patients (5.4%) it occurred as an isolated lesion. Evacuation of an associated extracerebral hematoma, which was performed within 4 hours after injury in only 20% of cases, scarcely changed the patients' preoperative neurological status. The high incidence of arterial hypotension and/or hypoxemia at admission (47% of cases) and the severity of the clinical presentation (82% of patients scored 5 points or less on the Glasgow Coma Scale, 74% had unilateral or bilateral mydriasis, and 80% had an initial ICP above normal) correlated with a very poor final outcome (87% mortality). Only one of the 11 patients with normal initial ICP continued to have normal pressure throughout the course. High-dose thiopental failed to control severe intracranial hypertension in 24 patients (51%) who had a fulminant, malignant course. A transient decrease in ICP elevation was achieved in 15 patients (31.4%) and definitive control in eight patients (17%), among whom were the seven survivors in this series. In the authors' experience, once ICP is controlled, barbiturate administration should not be discontinued until a control CT scan shows complete disappearance of the mass effect.

Cerebral hemisphere swelling in severe head injury patients

The clinical course and the intracranial pressure (ICP) changes in 66 severe head injury patients presenting bulk enlargement of one cerebral hemisphere within a few hours of trauma have been analyzed. These patients represent 11% of a series of 589 severe head injury cases studied with computerized tomography (CT). Cerebral hemisphere swelling, which was associated with an ipsilateral subdural haematoma of variable extent in 58 patients (88%), or a large epidural haematoma in 5 patients (7%), and occurred as an isolated lesion in 3 patients (4%), carried the highest incidence of uncontrollable intracranial hypertension, the highest mortality rate and the shortest survival period after trauma in the authors' severe head injury series. The high incidence of arterial hypotension and/or hypoxaemia at admission (48% of cases), and the severity of clinical presentation (82%) of patients scored 5 patients or less in the Glasgow Coma Scale, 77% had uni- or bilateral mydriasis and 82% initial ICP above normal limits) correlated with the very poor final outcome (85% mortality). Only one of the 12 patients with normal initial ICP continued to have low pressure throughout the course. High dose thiopental failed to control severe intracranial hypertension in 29 patients (44%) who had a fulminant, malignant course. A transient decrease in ICP elevation was achieved in 17 patients (26%) and a definitive control in 12 patients (18%), among them the 10 survivors in this series. In the authors experience once ICP is controlled, and unless haemodynamic instability compells action to the contrary, barbiturate should not be discontinued until a control CT scan shows complete disappearance of the mass effect.