Differential brain area vulnerability to long-term subcortical excitotoxic lesions

To investigate the long-term effects of excitatory amino acid microinjections into the basal forebrain and its correlation with a possible Ca2+ imbalance associated with the excitotoxic process, ibotenic acid, mainly an N-methyl-D-aspartate receptor agonist, and quisqualic acid, an agonist of non-N-methyl-D-aspartate receptors, were injected into two regions rich in cholinergic neurons, namely the medial septal nucleus and the ventral globus pallidus. Within the globus pallidus but not within the medial septal nucleus, 13 days and one year postlesion, nerve cell death was associated with the appearance of calcium deposits within the large putative GABAergic pallidal neurons, being more pronounced in ibotenic acid than quisqualic acid-lesioned rats. An intermediate two month post-lesion study with alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and ibotenic acid microinjections in globus pallidus demonstrated that the AMPA subtype of glutamate receptor may also be involved in this Ca2+ imbalance, together with the N-methyl-D-aspartate and metabotropic subtype receptors. Quisqualic acid lesions in globus pallidus and medial septum were associated with a substantial disappearance of cholinergic cell bodies and their nerve terminal networks within the cerebral cortex and hippocampal formation respectively, as assessed by choline acetyltransferase and acetylcholine esterase immunocytochemistry. Ibotenic acid lesions resulted in a lower reduction of cholinergic markers. One year after septal lesions induced either by ibotenic or quisqualic acid, a marked atrophy of the entire dorsolateral septal nucleus was observed. Our results support the hypothesis that brief and intense glutamate exposure can induce long-term neurodegenerative processes and give evidence that long-term excitotoxic lesions of the two areas studied result in marked differences in neuronal damage, including intracellular calcium deposits which do not correlate with the cholinergic deficits produced by multiple glutamate receptor subtypes.

Glutamate receptors in alcohol withdrawal-induced neurotoxicity

Chronic ethanol ingestion results in an "up-regulation" of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor in mouse brain. This increase in receptors is associated with ethanol withdrawal seizures, which can be attenuated by NMDA receptor antagonists. Chronic exposure to ethanol (3 days) of rat cerebellar granule cells in primary culture also produces an increase in NMDA receptor number and function, which leads to enhanced susceptibility to glutamate-induced neurotoxicity. Antagonists acting at various sites on the NMDA receptor can block glutamate excitotoxicity in both control and ethanol-exposed cells. These results suggest the possibility of developing agents that will ameliorate ethanol withdrawal seizures as well as withdrawal-induced neuronal damage. In addition, acute (2 hr) or chronic (3 day) exposure of cerebellar granule cells to ganglioside GM1 protects control and ethanol-treated cells against glutamate neurotoxicity. However, while the acute GM1 treatment does not interfere with the initial response to glutamate (increase in intracellular Ca2+), this response is "down-regulated" after chronic ganglioside treatment. These findings suggest that the mechanism by which acute and chronic ganglioside treatments protect against glutamate neurotoxicity may differ. Furthermore, chronic ganglioside treatment during ethanol exposure has the potential to prevent the ethanol-induced up-regulation of NMDA receptors that underlies withdrawal seizures and increased susceptibility to excitotoxicity.

Vigabatrin-induced psychosis--management problems

A 22-year-old patient with partial seizures developed schizophreniform psychosis following the introduction of vigabatrin. She stopped her anticonvulsant medication as a consequence of her persecutory delusions. She subsequently suffered status epilepticus with severe brain damage. It is essential to outline a management plan for patients to detect and treat vigabatrin-induced psychosis.

Neurological sequelae following carbon monoxide poisoning clinical course and outcome according to the clinical types and brain computed tomography scan findings

The prognosis for patients who survive carbon monoxide (CO) poisoning is uncertain, particularly in those who develop persistent neurological complications after recovery from the initial coma. Thirty-one patients with the sequelae of CO poisoning, followed for a year, are described. Eight had a progressive course, and 23 had a delayed relapse after an initial recovery period of approximately 20 days (range, 1-36 days). Those with a progressive course developed a persistent akinetic-mute state, and four of the eight died. Those with the delayed relapsing course either developed a parkinsonian state with behavioral and cognitive impairment but could walk (nine cases), or progressed further to an akinetic-mute state, and were bed-bound (14 cases); the deterioration to either condition occurred rapidly over a few days to a week. Fourteen of the patients with the delayed relapses (61%) subsequently improved, but three (13%) died. Those with a progressive course without initial recovery were younger (mean age, 37.0 years) than those with a delayed relapsing course (55.2 years; p < 0.01). The mean duration of their initial coma (9.8 days) was longer than that in delayed relapsing cases (2.0 days; p < 0.01). The mean initial CO hemoglobin level was not different in the two groups. Brain computed tomography (CT) scans were obtained at the onset of sequelae in both groups. Ten patients had a normal CT scan, 13 had white matter low-density lesions, and four had globus pallidus low-density lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation between conditioned taste aversion and radial maze learning following seizure-induced multifocal brain damage: quantitative tests of serial vs. parallel circuit models of memory

Multivariate analyses between conditioned taste aversion (CTA) and radial maze acquisition (RMA) scores and percentages of neuronal dropout within thalamic and telencephalic structures were completed for rats in which overt seizures had been evoked following a single systemic injection of lithium/pilocarpine. Despite multifocal damage, only the amount of damage within the hippocampus (CA1) and the basolateral amygdala was most strongly associated with attenuated CTA, whereas damage within the mediodorsal thalamus was primarily associated with RMA. There was no significant correlation between CTA or RMA. Multiple regression analyses for specific Paxinos and Watson structures and their traditional aggregates supported more precise delineation of neuronal substrates of learning/memory and a multimodal (parallel) model for these processes.

Severe deterioration in cognitive function and personality in five patients with long-standing diabetes: a complication of diabetes or a consequence of treatment?

Changes in mood, personality, and social function were examined in a group of five Type 1 diabetic patients, aged 50 to 66 years, with duration of diabetes from 24 to 47 years. Information on medical history was obtained from their carers and hospital records. All patients had experienced multiple episodes of severe hypoglycaemia and had impaired awareness of hypoglycaemia. Cerebral dysfunction predated the development of minimal diabetic complications and had been apparent for between 1 and 17 years. The carers assessed the pre-morbid and present behaviour and personality of the patients using standard questionnaires. Significant deteriorations were demonstrated in cognitive (p = 0.04) and social functions (p = 0.04), compared with assessment of pre-morbid function. Patients had tended to become more neurotic (p = 0.08) and less extravert (p = 0.07). All of the patients and three of the carers recorded scores suggestive of psychiatric morbidity on the General Health Questionnaire. The patients had experienced loss of employment and the carers described a reduction in the patients' social interactions. Although the aetiology of their cerebral dysfunction can not be definitely ascertained this case series emphasizes the need for long-term prospective studies in patients with diabetes of long duration to assess the impact of the disorder on cognitive and social abilities particularly where there is evidence of cerebral dysfunction. The need for professional support for the carers of such patients should be recognized.

Childhood lead poisoning

Substantial changes in the toxicology and epidemiology of lead have resulted in revisions in the definition of toxicity, and have altered estimates of the numbers of children at risk. As observational studies have increased their sample size, improved the sensitivity of their measurements, and polished epidemiological designs, concentrations of lead once thought to be harmless have been shown to have deleterious neurobehavioral consequences. Prevalence rates have changed in correspondence. Public policy has shifted from case finding to emphasizing primary prevention, the only appropriate strategy for this group of children. It is possible that the rate of the disease could be driven close to zero within two decades.

Neuropsychological toxicology of methylene diphenyl diisocyanate: a report of five cases

The neuropsychological functioning of five men suffering alleged physical, cognitive and behavioural changes following exposure to methylene diphenyl diisocyanate (MDI), an industrial chemical, was investigated in the present study. At the time of assessment, four of the five patients remained symptomatic despite having no contact with MDI for periods ranging from 5 to 9 months. All patients reported experiencing subjective symptoms consisting of respiratory distress, headaches, depression, irritability, forgetfulness, decreased calculating ability, word-finding problems and reduced concentration. While the pattern of neuropsychological deficits varied among the patients, common findings for the group included intact psychomotor, psychosensory, visuographic and language functions accompanied by deceased concentration, mental efficiency, rate of information processing, learning ability and abstract reasoning. All five patients also revealed significant emotional distress on an objective personality measure. In general, the neuropsychological test data support the presence of behavioural and cognitive correlates of CNS injury following exposure to MDI.

Acute and chronic neuropsychological consequences of mercury vapor poisoning in two early adolescents

Mercury is an extremely toxic heavy metal that can devastate the central nervous system. The neuropsychological consequences of mercury vapor intoxication have been studied primarily in adults. We present two adolescent half-siblings, ages 13 and 15, who were unintentionally exposed to concentrated mercury vapor for 3 months. Both children participated in neuropsychological evaluations shortly after being diagnosed with mercury toxicity, and again 1 year later. Results from the initial assessments documented functional deficits consistent with diffuse encephalopathy. Upon follow-up, neuropsychological functioning had improved, but deficits remained in visuoperceptual and constructional skills, nonverbal memory, and conceptual abstraction. The deficits persisted despite removal from exposure, return of urinary and blood mercury to acceptable levels, and resolution of neuropsychiatric symptoms. The deficits were similar to, but more severe than, those found in adults suffering from mercury vapor intoxication. The results suggest that the developing brain may be especially vulnerable to mercury vapor toxicity.

A screening algorithm to identify clinically significant changes in neuropsychological functions in the Diabetes Control and Complications Trial. DCCT Research Group

Neuropsychological (NP) evaluations provide an accepted means of monitoring safety in multi-center long-term medical trials. However, using neuropsychologists to review test protocols and rate level of clinical impairment can be a costly and logistically complex undertaking. To facilitate that process, the DCCT Research Group developed a computerized screening strategy that utilized statistical models to identify individuals with possible cognitive deterioration. Two hundred and eight subjects with insulin-dependent diabetes mellitus were assessed twice, 2 years apart, with an extensive battery of NP tests, and the results were rated by expert clinicians. Multiple logistic regression was used to develop a statistical model to predict clinically significant NP worsening (as determined by clinical raters) on the basis of changes in scores (year 2--baseline) derived from the actual tests. A subsequent performance evaluation with an additional 1087 subjects demonstrated that the computerized algorithm was highly successful in identifying individuals with significantly worsened NP performance. Despite a high false positive rate, the algorithm can achieve an 80-90% reduction in the number of cases requiring evaluation by expert neuropsychologists.

Attempted suicide using insulin by a non diabetic: a case study demonstrating the acute and chronic consequences of profound hypoglycemia

This paper describes the case of a non diabetic physician with a prior psychiatric history in which there was overwhelming biochemical and clinical evidence that he had attempted suicide by injecting himself with an overdose of insulin. He was extensively monitored from the time of his admission to hospital in a coma, until he fully recovered consciousness 30 days later and during the next eight months of his rehabilitation. This case attests to the high level of morbidity which might follow profound hypoglycemia. It also illustrates some putative psychodynamics of suicidal behaviour--notably ambivalence and denial (at the time of writing, the patient never acknowledged that he had overdosed with insulin). A selective review on some of the more recent literature on the neuropathological effects of insulin overdose and profound hypoglycemia is presented.

Neurologic sequelae after treatment of severe hyponatremia: a multicenter perspective

Severe, symptomatic hyponatremia is often treated urgently to increase the serum sodium to 120 to 130 mmol/L. Recently, this approach has been challenged by evidence linking "rapid correction" (> 12 mmol/L per day) to demyelinating brain lesions. However, the relative risks of persistent, severe hyponatremia and iatrogenic injury have not been well quantified. Data were sought on patients with serum sodium levels < or = 105 mmol/L from the membership of the American Society of Nephrology. Respondents were given a report form asking specific questions regarding the cause of hyponatremia, presenting symptoms, rate of correction, and neurologic sequelae. Data on 56 patients were analyzed. Fourteen developed posttherapeutic complications (10 permanent, 4 transient) after correction to a serum sodium > 120 mmol/L. Eleven of these 14 patients (including 3 with documented central pontine myelinolysis) had a biphasic course in which neurologic findings initially improved and then worsened on the second to sixth day. Posttherapeutic complications were not explained by age, sex, alcoholism, presenting symptoms, or hypoxic episodes. Increased chronicity of hyponatremia and a high rate of correction in the first 48 h of treatment were significantly associated with complications. No neurologic complications were observed among patients corrected by < 12 mmol/L per 24 h or by < 18 mmol/L per 48 h or in whom the average rate of correction to a serum sodium of 120 mmol/L was < or = 0.55 mmol/L per hour. It was concluded that patients with severe chronic hyponatremia are most likely to avoid neurologic complications when their electrolyte disturbance is corrected slowly.

Neuropsychological sequelae of methyl bromide: a case study

Methyl bromide (MB) is a pesticide used primarily as a fumigating agent for homes, storage vehicles and soil. Chronic exposure to MB is known to cause damage to the central nervous system and other organs. Previously published post-mortem studies have also revealed significant brain abnormalities in patients whose deaths were attributed to MB. Only one study to date has examined the neuropsychological effects of this potential neurotoxin. The present case report documents the events surrounding an incident of acute and subacute MB exposure following home fumigation and the neuropsychological after-effects associated with that exposure. Behavioural and cognitive correlates of CNS dysfunction revealed by the neuropsychological testing included impairments in concentration, information processing, learning and memory. Emotional sequelae appeared to be a secondary problem associated with fears over physical well-being and impaired cognition. The cognitive symptomatology did not abate after completion of litigation and award of compensation.

AF64A-induced brain damage and its relation to dementia

Several data obtained in the AF64A-model are of particular relevance for our understanding of the pathogenesis and progression of Alzheimer's disease. The AF64A-induced withdrawal of cholinergic function in the rat hippocampus was associated with reversible functional changes in other neurotransmitters, including noradrenaline, serotonin, somatostatin and glutamate, thereby mimicking changes in Alzheimer's disease. Identical changes in markers for synaptic vesicles were found in Alzheimer's disease and AF64A-model. A study on the role of gender revealed a higher susceptibility to the neurotoxic action of AF64A in female rats. The cholinergic deficit was also responsible for a disinhibition of the negative feedback regulation of glucocorticoids. Increased exposure to glucocorticoids, however, enhanced the vulnerability of hippocampal cholinergic neurons to AF64A. These data indicate that the AF64A-induced cholinergic deficit in the rat brain represents a reliable tool to study several mechanisms possibly involved in Alzheimer's disease.

Possible role of the N-terminus of substance P in kainic acid-induced toxicity in rats

Subcutaneously administered kainic acid (KA) in the rat results in brain damage accompanied by a behavioral response characterized by wet dog shakes (WDS), seizures and brain damage, an effect that is potentiated by opioids. Based on the potentiative effect of the N-terminus of substance P (SP) on the ability of KA to induce behavioral responses in mice, we tested the hypothesis that the N-terminus of SP also plays a role in KA-induced neurotoxicity in rats. Pretreatment i.p. with 1 or 10 nmol of SP(1-7), a major N-terminal metabolite of the undecapeptide SP, 15 min before administration of 12 mg/kg of KA potentiated the incidence of WDS. In contrast, after administration of 1 nmol of [D-Pro2, D-Phe7]SP(1-7) (D-SP(1-7)), the D-isomer of SP(1-7) and a substance P N-terminal antagonist, the intensity of KA-induced WDS was no different from those in either the KA- or saline-injected rats. However, pretreatment with D-SP(1-7) completely blocked the potentiative effect of SP(1-7) on the KA-induced WDS. While the severity of KA-induced lesions was not significantly altered by pretreatment with 1 nmol of SP(1-7), the effect of KA was not significantly different from that in control rats when administered with 1 nmol of D-SP(1-7). These results suggest a possible involvement of endogenous SP N-terminal activity in the effects following subcutaneous (s.c.) administration of KA.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropsychological and emotional sequelae of eosinophilia-myalgia syndrome

In recent years there has been an increasing number of cases presenting with a newly recognized multiple systemic disorder, Eosinophilia-Myalgia Syndrome (EMS), in the United States. This report documents demographic data and scores from intelligence, memory, neuropsychological, and achievement testing from eight patients, and Minnesota Multiphasic Personality Inventory-2 (MMPI-2) profiles obtained by nine patients, all of whom were referred to a doctoral level neuropsychologist in private practice. Intelligence scores revealed a Full Scale Mean IQ of 90.6, with a Verbal IQ Mean of 92.3, and a Performance IQ Mean of 90.9 for the Wechsler Adult Intelligence Scale--Revised. For the Wechsler Memory Scale, the patients earned a mean Memory Quotient of 80.5. On the Halstead-Reitan Neuropsychological Test Battery, the patients earned a mean Impairment Index of .82, and Achievement Test scores on the Wide Range Achievement Test--Revised ranged from a grade level of 4th grade to a grade level of above 12th grade for reading, and from a grade level of 5th grade to a grade level of above 12th grade for arithmetic. Both the modal and mean MMPI-2 profiles had 2-3/3-2 two point codes suggesting feelings of depression, tension, nervousness, fatigue, helplessness, somatic complaints and overcontrol. In all, the neuropsychological, intellectual, memory and achievement test scores suggested a pattern of moderate to severe impairment and the MMPI-2 test scores suggested a pattern of moderate emotional disturbance.

Selective excitotoxic pathology in the rat hippocampus

The pattern of cell loss and neuronal degeneration resulting from multiple microinjections of N-methyl-D-aspartate (NMDA), ibotenate (IBO), quisqualate (QUIS), and kainate (KA) into hippocampus was studied, together with the protection provided by the NMDA antagonist 3-(+/-)-2-carboxypiperazin-4-yl-propyl-1-phosphonate (CPP). Histological evaluation was carried out after 7 days of survival. NMDA and IBO resulted in an extensive loss of all cells in the hippocampus including dentate gyrus, hilar cells, and CA3-CA1 pyramidal cells, but there was an absence of damage to areas and structures outside hippocampus. After QUIS and KA injections the hippocampal damage was limited to hilar cells in the dentate gyrus, CA3 pyramidal cells, and partial loss of CA1 cells; there was extensive extrahippocampal damage including entorhinal cortex, amygdala, layers III, V, and VI of ventral neocortex, olfactory areas, and various thalamic nuclei. CPP provided almost complete protection from the effects of intrahippocampal injections of NMDA and IBO, but did not affect the hippocampal cell loss found after QUIS and KA (with the exception of minor protection of some CA1 cells). CPP protected most extrahippocampal sites from the damage resulting from QUIS and KA, indicating that such excitotoxic cell death is indirect and involves NMDA receptor activation by an endogenous agent. The use of multiple microinjections as opposed to single injections allows a clearer interpretation of selective excitotoxic vulnerability.

Computed axial brain tomograms in long-term benzodiazepine users

Computed axial brain tomograms were recorded in four groups of subjects: (a) subjects who had never taken benzodiazepines (n = 25); (b) subjects who had taken them in the past for less than a year (n = 9); (c) patients currently taking benzodiazepines (n = 30); and (d) patients who had taken benzodiazepines in the past for at least a year and who had been withdrawn from medication for at least 6 months (n = 17). Ventricle-to-brain ratios and tissue absorption to X-rays were computed. No overall differences were found between the main groups. However, a few brain regions differed in density between nonusers and heavy users, particularly those taking lorazepam.

Environmental neurotoxicity of chemicals and radiation

Epidemiologic and societal concerns continue to stimulate studies in the field of environmental neurotoxicology. Although the role of heavy metals, aluminum, and iron are unclear in the etiology of human neurodegenerative disorders, these toxins have provided fertile ground for in vivo and in vitro experimental studies to elucidate their role in neurotoxic injury. Experimental models of clinical syndromes are discussed with special relevance to developmental neurotoxicology. Cycloleucine, tellurium, and 1,3-dinitrobenzene provide models of subacute combined degeneration, primary peripheral nerve demyelination, and thiamine deficiency-like lesions, respectively. Increasing attention is being given to irradiation neurotoxicity, especially in the developing or young central nervous system. A fuller understanding of the pathogenesis of low-dose irradiation injury allows for a clearer understanding of its neurobiology and also provides a more rational approach to understanding an interventional therapy associated with brain irradiation for childhood neoplasia.

Experimental seizure-induced brain damage: electrophysiological, metabolic and pathological correlation

Limbic seizures elicited by an intra-amygdaloid KA injection is the only and unique model which can produce unilateral hippocampal degenerative lesions and atrophy. This model is important not only to investigate neurophysiological epileptogenesis but also to study the causative process of human mesial temporal sclerosis observed in patients with intractable complex partial seizure.