Christer Tengvar

Adrenaline-induced hypertension: morphological consequences of the blood-brain barrier disturbance

ABSTRACT— Acute hypertension may transiently open the blood‐brain barrier (BBB). To determine whether such temporary exposure of the brain parenchyma to plasma constituents may lead to permanent morphological alterations, acute hypertension was induced by i.v. adrenaline in conscious rates given Evans blue and horseradish peroxidase as tracers. The brain were perfused in situ 24 h later: 17 of 21 brains showed multifocal sites of extravasation of the tracers and of endogenous plasma albumin, fibrinogen and fibronectin identified by immunohistochemistry. The proteins spread locally in the parenchyma and were taken up by neurons. Within the leaking sites in the cortex, hippocampus, thalamus and basal ganglia some shrunken and grossly distorted acidophilic neurons were present. Focal areas of sponginess were observed in the subpial and subependymal zones. Thus, a transient opening of the BBB may lead to neuronal damage.

An improved Percoll density gradient for measurements of experimental brain edema

SummaryMicrogravimetric methods are very useful for quantitative studies on brain edema. One of the techniques available is based on a gradient made up by NaCl and polyvinyl pyrrolidone-coated silica particles (Percoll). The present study was performed to find a way of minimizing fluid shifts between the gradient and the samples. For this purpose, five Percoll density gradients containing various concentrations of sucrose in isotonic saline were prepared. Equivalent samples of normal mouse brain were then added and their second slow movement (drift) indicating interactions between the tissue and the gradient was followed. A concentration of 0.125 M sucrose eliminated the drift of the samples almost entirely.The capacity of this sucrose-containing gradient to reveal brain edema was then evaluated by comparing the density values obtained with those measured in the traditional bromobenzene-kerosene gradient as described by Nelson et al. (1971). For this purpose, we produced in the mouse an acute cytotoxic edema by triethyltin intoxication and a vasogenic edema by a cortical cryogenic injury. The two gradients showed almost identical results.We conclude, therefore, that the 0.125 M sucrose-containing Percoll gradient is a very good alternative to bromobenzene-kerosene gradients used for brain density determinations. Furthermore, Percoll gradients are very stable and contain only non-toxic ingredients.

Disorders of consciousness: preliminary data supports added value of extended behavioural assessment.

Background: The use of validated behavioural assessment scales in assessment of patients with Disorders of Consciousness (DOC) is well established. However, there is little evidence to guide decisions on total time spent in behavioural assessment. Objective: To assess whether brief behavioural assessment was as effective as extended behavioural assessment in detecting non-vegetative behaviours. Methods: Consecutive patients with suspected DOC were assessed with two standardized instruments: Coma Recovery Scale Revised (CRS-R) and Sensory Modality Assessment and Rehabilitation Technique (SMART). Assessors were blinded to results from the other scale at the point of assessment. Two administrations of CRS-R together took 50–60 minutes (‘brief’ assessment). One complete SMART assessment took 600 minutes (‘extended’ assessment). Patients were classified as being in a vegetative state (VS) or minimally conscious state (MCS)/emerged from minimally conscious state (EMCS), following brief and extended assessment. Results: Ten patients were assessed. Brief and extended assessment yielded the same diagnostic category (VS or MCS) for six patients and different categories for four, with extended assessment detecting higher level behaviours. Conclusions: Brief behavioural assessment was not as effective as extended assessment in detecting non-vegetative behaviours. Total time spent in behavioural assessment is likely important. Further studies and clearer clinical guidance are needed.

Formation of oedema in transected rat sciatic nerve

SummaryThe formation of oedema in peripheral nerves was studied in rats at intervals varying from 6 h to 14 days after transection of the right sciatic nerve. Samples were removed proximal and distal to the injury, and the degree of oedema was determined by a microgravimetric method and by measurements of the water content and of the fascicular area. Distal to the lesion, decreased density values indicating the presence of oedema were observed in samples examined after a survival period of 6 h-14 days. The water content and fascicular area were both increased in samples taken 24 h after the injury. Fourteen days postinjury the water content had increased further. Proximal to the lesion, the water content and the fascicular area were increased in samples examined after a survival period of 24 h. Fourteen days after the injury, the increase in water content was even more pronounced. No changes were detected with the microgravimetric technique 6 and 24 h after the injury. Unexpectedly, animals surviving 14 days showed increased density values. The microgravimetric technique used is a valuable adjunctive method for quantitation of peripheral nerve oedema in the acute phase after a traumatic nerve injury. Later on, loss of axons and of myelin components, together with regenerative phenomena, influence the density values obtained. Quantitative methods for studying chronic peripheral nerve oedema should therefore, be supplemented with other techniques.

Horseradish peroxidase histochemistry. A comparison between various methods used for identifying neurons labeled by retrograde axonal transport.

Horseradish (HRP) histochemistry is widely used in neuroanatomical and neuropathological research. In this study the sensitivity of 6 methods commonly used for demonstration of HRP were compared mainly by observation on retrogradely labeled hypoglossal neurons found after injection of HRP into the tongue of adult mice. For this purpose groups of equivalent sections were obtained from the brainstem of each mouse. In one series, 3 diaminobenzidine techniques (Graham-Karnovsky; Malmgren-Olsson; Streit-Reubi), and Mesulams tetramethyl benzidine procedure were compared. In a second series the groups of sections were incubated with DAB (Graham-Karnovsky; Malmgren-Olsson), p-phenylene diamine (Hanker) or TMB (Mesulam; Hardy-Heimer). All the new methods (Streit-Reubi; Malmgren-Olsson; Hanker, Mesulam; Hardy-Heimer) revealed many more labeled neurons per section than the original Graham-Karnovsky technique and Mesulams TMB procedure was in this regard superior to all of the other tested methods. Particularly in sections from the tongue, disturbing precipitates were often obtained with the TMB methods and they are not as well suited as the new DAB procedures for observations on fine details at the light microscopical level. The new DAB methods (Streit-Reubi; Malmgren-Olsson), apart from their high sensitivity, can very well be used for electron microscopy also. Mesulams TMB procedure should therefore be the method of choice in studies on retrogradely labeled neurons if highest possible sensitivity is needed. For studies on fine details in such neurons, i.e. when highest possible resolution is required, any one of the new DAB procedures should be chosen. Due to their lower tendency to form artefactual precipitates, they can be recommended for other HRP applications as well, such as vascular permeability studies, observations on vasogenic edema and perineurial permeability.

Vascular permeability in acute triethyltin‐induced brain edema studied with FITC‐dextrans, sodium fluorescein and horseradish peroxidase as tracers

ABSTRACT— In golden hamsters, a study was made on the vascular permeability changes which might take place during the formation of triethyltin (TET)‐induced brain edema. For this purpose, the animals received a single intravenous (i.v.) injection of TET sulphate (5–10 mg/kg b.wt) and groups of animals were studied 4 to 24 h thereafter.

Distribution of exudated FITC-dextrans in experimental vasogenic brain edema produced by a focal cryogenic injury

SummaryMice were subjected to cortical cryogenic brain injury, and FITC-dextrans (mol. wt. 20,000 or 150,000) were injected intravenously (i.v.). After a survival period of 4 h the distribution of the FITC-dextrans was determined by a histotechnical procedure described recently (Hultström et al. 1982a). This technique is based on freeze-drying and vapor fixation to immobilize the tracer and to provide tissue fixation.In and around the cryogenic injury both tracers leaked out of the cortical and the leptomeningeal vessels and spread into the brain parenchyma. They were seen as multiple, closely apposed droplets of fluorescent material best recognized by fluorescence microscopy under high magnification. The tracers were also taken up by neuronal perikarya and in glial cell nuclei of, presumably, astrocytic origin.Our study shows that the FITC-dextran technique can be used for experimental studies on the vasogenic form of brain edema. The patterns formed by the extravasated tracers have qualitative similarities to those produced by other more commonly used tracers, such as fluorochrome-labeled serum proteins and peroxidase.

Effects of the noradrenaline neurotoxinN-2-chloroethyl-N-ethyl-2-bromo-benzylamine hydrochloride (DSP4) on the blood-brain barrier

SummaryCerebral microvessels receive a noradrenergic innervation originating from the locus coeruleus. Previously, many studies have tried to elucidate the role of the central noradrenergic innervation on the blood-brain barrier (BBB). Many of them are based on chemical destruction of the innervation by local injection of 6-hydroxydopamine (6-OHDA) or physical injury to the locus coeruleus. Such methods are not selective and the results reported are contradictory. We have treated mice with a single i. p. injection of the compound,N-2-chloroethyl-N-ethyl-2-bromobenzylamine hydrochloride (DSP4). This substance induces a selective noradrenaline depletion and, unlike 6-OHDA, it can pass into the brain afer an i. p. injection. The animals were allowed to survive for 6 h to 60 days and the BBB was investigated with i.v.-injected horseradish peroxidase (HRP). Brain density values were also determined to find out if edema developed. The light microscopic distribution of HRP in the brain of DSP4-treated animals did not differ from that in control mice, i.e., there were no signs of increased BBB permeability to this protein tracer caused by DSP4. Density determinations revealed statistically significant reduced values in cerebrum (P<0.005) and rhombencephalon (cerebellum) (P<0.0005) of animals given 100 mg/kg body wt. of DSP4 indicating development of edema. A minor drop in density of the rhombencephalon (cerebellum) (P<0.05 at 48 h) and of the cerebrum (statistically not significant) appeared when 50 mg/kg body wt. of DSP4 was injected. Our findings indicate that the BBB to proteins maintains its function but that edema, likely composed of an ultrafiltrate from the blood, will develop after an injection of DSP4. In view of its selective degenerative action on the noradrenergic central neurons, this kind of brain edema is probably a direct consequence of abnormal noradrenergic innervation of the cerebral blood vessels. Our observations are thus in line with the assumption that the noradrenergic innervation influences endothelial permeability in the central nervous system. Alternative pathogenetic mechanisms are discussed.Cerebral microvessels receive a noradrenergic innervation originating from the locus coeruleus. Previously, many studies have tried to elucidate the role of the central noradrenergic innervation on the blood-brain barrier (BBB). Many of them are based on chemical destruction of the innervation by local injection of 6-hydroxydopamine (6-OHDA) or physical injury to the locus coeruleus. Such methods are not selective and the results reported are contradictory. We have treated mice with a single i.p. injection of the compound, N-2-chloroethyl-N-ethyl-2-bromo-benzylamine hydrochloride (DSP4). This substance induces a selective noradrenaline depletion and, unlike 6-OHDA, it can pass into the brain after an i.p. injection. The animals were allowed to survive for 6 h to 60 days and the BBB was investigated with i.v.-injected horseradish peroxidase (HRP). Brain density values were also determined to find out of edema developed. The light microscopic distribution of HRP in the brain of DSP4-treated animals did not differ from that in control mice, i.e., there were no signs of increased BBB permeability to this protein tracer caused by DSP4. Density determinations revealed statistically significant reduced values in cerebrum (P less than 0.005) and rhombencephalon (cerebellum) (P less than 0.0005) of animals given 100 mg/kg body wt. of DSP4 indicating development of edema. A minor drop in density of the rhombencephalon (cerebellum) (P less than 0.05 at 48 h) and of the cerebrum (statistically not significant) appeared when 50 mg/kg body wt. of DSP4 was injected.(ABSTRACT TRUNCATED AT 250 WORDS)

Disorders of Consciousness: Recommendations Are Welcome but Further Guidance is Needed

tance of repeated assessments 2 is a limitation. Together with the emphasis on “reasonable time” for administration, there is a risk that behaviors inconsistent with vegetative state may continue to be missed. The Recommendations do state that “extended or repeated assessment with a DOC scale is likely to improve diagnostic accuracy.” However, no concrete guidance is given regarding the recommended number of such assessments in clinical practice. “Extended or repeated” may be variously interpreted as anything from 2 assessments on the same day, upward to daily assessments over a number of weeks. A helpful addition to the Recommendations would be a statement of current expert opinion regarding a minimum number of assessments and/or time spent in behavioral assessment before a conclusion can be reached about the patient’s functional level. Most assessment scales (Sensory Modality And Rehabilitation Technique [SMART] 3 excepted) do not, themselves, make a specific recommendation on this point. Indeed, this aspect of SMART is overlooked in the Recommendations, which state somewhat misleadingly that assessment time for SMART is 60 minutes or more. In fact, 10 assessments, each of 60 minutes, are required. A clearer indication of the role of assessment scales in the broader clinical diagnostic process would also be welcome. Even the most recent of previous guidelines 4 on DOC diagnosis are now several years old and predate developments in magnetic resonance imaging and neurophysiologic techniques. The important point in the Recommendations, that current evidence is insufficient to allow a recommendation on the use of these scales for diagnostic classification, is absent from the conclusions in the abstract. 1 It is especially important to highlight this when, for example, the Coma Recovery Scale-Revised (CRS-R) specifically yields a diagnostic classification. Thus, the CRS-R is recommended for patient assessment, but not for diagnosing a patient with a DOC. This somewhat subtle distinction is at risk of being overlooked by clinicians with less experience in assessment of DOC, presumably a group to whom the Recommendations are directed. We join others 5 in a call for a broader update of guidance on diagnosis of DOC, including but not limited to, behavioral assessment.

Diagnosis of Disorders of Consciousness : Evoked Potentials and Behavioural Assessment in clinical practice

Endogenous free radical production by NADPH oxidase 2 contributes to the secondary injury cascade after traumatic brain injury in miceAccepted Abstracts from the International Brain Injury Association’s Ninth World Congress on Brain InjuryObjectives: Studies have shown that occupational therapy interventions for clients with cognitive impairment following acquired brain injury (CIABI) have a positive effect on performance of activities of daily living, although the exact nature of the interventions are not clearly described. A better understanding of current practice is therefore needed to move further in the search for evidence based occupational therapy for clients with CIABI. Research on occupational therapists’ (OTs’) practice can play an important role to explore and describe current practice and furthermore define and evaluate the effectiveness of different components in OT interventions. The aim of this study was to survey Swedish OTs’ practice patterns for clients having CIABI.Methods: The study had a cross-sectional design using a questionnaire developed in two former studies. A stratified random sample was done with 250 OTs each from the following areas: regional care, somatic county care, primary care and municipal eldercare. The questionnaire was sent out using on-line survey software and 462 participants responded. Data is currently analyzed by descriptive and comparative statistics.Results: Preliminary results show that the interventions targeted a wide range of cognitive impairments and its consequences. Interventions were both remedial and compensatory with graded activity as the most common remediating intervention. To compensate for activity limitations prescription, or recommendation, of assistive devices (AD) as well as supporting clients in finding internal strategies were used extensively. The ADs used consisted of both high and low technology devices. Eighty-two percent also included different specific interventions to improve clients’ decreased self-awareness in their practice. A vast majority of the OTs (94%) preferred to use observations in daily activities to assess both activity limitations and cognitive impairment. Almost all participants also used interviews and sixty-two percent used tests on impairment level. To support practice general Occupational Therapy models were widely used while theories focusing on cognitive impairments specifically were used less. The participants’ answers reflected a client-centered attitude with collaborative goal-setting and feedback discussions after each session. Eighty- four percent felt dependent on relatives to reach a successful outcome and most of them worked deliberately to involve relatives in the rehabilitation. The OTs responses were evenly distributed over the spheres of activity. Ninety-two percent of the participants worked in team and the most common diagnoses were stroke and traumatic brain injury. There were some differences in responses between the spheres.Conclusions: Preliminary conclusions are that the OTs practice patterns included interventions targeting most cognitive impairments and their consequences in daily activities. The use of daily activities as a mean was preferred irrespective of whether the interventions were remediative or compensatory. Interventions targeting decreased self-awareness as well as the use of ADs were common. A client-centered approach was dominating including collaboration with relatives.For personalcentered approach was dominating including collaborationwith relatives.Diagnosis of Disorders of Consciousness : Evoked Potentials and Behavioural Assessment in clinical practice