[Cocaine-induced acute CNS diseases]

Drug-associated/-induced neurological complications are well known in the literature. Cocaine is of major interest due to its widespread use. On the basis of a case report, we discuss the broad spectrum of medical and, in particular, neurological complications. The risk of cerebrovascular damage and epileptic seizures is indicated. The pathophysiological mechanisms of cerebrovascular complications are not well understood.

[Polyneuropathy and encephalopathy caused by organic solvents and mixed solvent solutions. Occupational medicine and neurologic aspects of a new occupational disease]

Solvent induced polyneuropathy and encephalopathy have been acknowledged quite recently as occupational diseases in Germany. For compensation first of all the diagnosis has to be proven. For differential diagnosis other known causes as well as non-organic mental diseases must be taken into consideration. The causality between proven exposures and diagnosed disease has at least to be probable. To evaluate causation extensive experience of the experts is needed. In this context scientific criteria regarding neurotoxicity of the solvent, duration of exposure, individual aspects of non-occupational influences, time course of the disease are important within a through synoptic evaluation. Possibilities and limitations of sensitive diagnostic measures such as neurographic, neuropsychologic and neuroimaging examinations are discussed. The prognosis of toxic polyneuropathy and encephalopathy is in general favorable if exposure has stopped. Additionally, adequate therapy and rehabilitation measures are supportive for a good prognosis.

[Brain damage caused by hypotensive anesthesia? Both the anesthetic technique and the anesthetic agent must be chosen with care]

During the fifty years since hypotensive anaesthesia, induced hypotension to minimise intraoperative blood loss, became an established routine, there have been few reports of associated cerebral complications. However, evidence of disturbed cerebral function among patients undergoing orthognathic surgery under induced hypotension was obtained in a recent study where the level of adenylate kinase activity in cerebrospinal fluid was used as a highly sensitive biochemical marker of brain cell injury. Moreover, psychometric tests revealed persistent postoperative mental deterioration. The underlying cause of brain cell injury seems to be complex, and as in all likelihood it is not hypotension per se that is responsible, the effect of the anaesthetic agents used (isoflurane and propofol) has to be considered. It was also noted that hypotension did not improve the clinical outcome of orthognathic surgery, as compared with comparable operations performed under normotension.

Inhibition of iron-dependent and ischemia-induced brain damage by the alpha-tocopherol analogue MDL 74,722

Free radical-induced lipid peroxidation is an important factor in the pathogenesis of ischemic brain damage. We studied the effects of the alpha-tocopherol analogue MDL 74,722 on iron-dependent lipid peroxidation and infarct volume after transient focal cerebral ischemia. The effects of MDL 74,722 on iron-induced lipid peroxidation were tested in cerebellar granule cell cultures by means of a thiobarbituric acid reactive substances (TBARS) assay. The absorbance resulting from mitochondrial reduction of 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) was taken as a measure of cell viability. Besides, in male Wistar rats the left middle cerebral artery (MCA) was occluded for 3 h by means of an intraluminal filament. Rats were treated with vehicle (n = 19) or MDL 74,722 (n = 17), administered intravenously for 3 h in a dose of 2 mg/(kg.h), starting 105 min after MCA occlusion. Infarct volume was measured in coronal brain sections stained with hematoxylin and eosin. In cerebellar granule cell cultures, MDL 74,722 resulted in a dose-dependent inhibition of TBARS formation and prevention of cell toxicity. The compound reduced infarct volume after transient occlusion of the MCA in rats by 49%. It is concluded that MDL 74,722 is a potent inhibitor of lipid peroxidation and reduces infarct volume by about one half, even when treatment is delayed. This contributes to its potential clinical usefulness.

Selective vulnerability of the developing brain to lead

Environmental lead exposure in young children who ingest household paint dust or other sources impairs their potential intelligence in a linear, dose-dependent fashion in contrast to its far more subtle effects on other neurologic functions. Basic investigations have identified three interrelated steps in synaptic neurotransmission at which low levels of lead can disrupt signal processing. Lead enhances background transmitter release, but impairs stimulated release, inhibits function at the N-methyl-D-aspartate-type glutamate receptor and stimulates background levels of the intracellular messenger protein kinase C. Taken together these effects have the effect of diminishing the synaptic signal to noise ratio. The ability of lead to enhance 'synaptic noise' during a critical early period of postnatal development may permanently disrupt the architecture of cortical processing units by depriving them of high resolution environmental signals needed to refine synaptic connections.

Experience with a vocabulary test for workers previously and still exposed to styrene

OBJECTIVES

This study examined the possible influence of styrene exposure on the results of vocabulary tests because verbal ability is assumed to be relatively resistant to the toxic effects of organic solvents and short vocabulary tests are used as "hold tests" in many neurobehavioral epidemiologic studies,

METHODS

To evaluate the chronic neurotoxic effects of styrene, a vocabulary test was administered to a group of still-exposed workers (N=27) and an earlier exposed group of workers (N=90). A self-administered questionnaire was filled out on life events, general health, educational level, and amount of education. The still-exposed group had a mean exposure duration of 4700 hours, and that for the formerly exposed group was 3610 hours.

RESULTS

The vocabulary score of the still-exposed group was significantly lower [12.5 (SD 2.9, range 6-18)] than that of their former colleagues [14.3 (SD 3.4, range 8-22)], even though they originally belonged to the same group and had done the same tasks. The exposure duration explained a significant part of the vocabulary results, resulting in decreasing vocabulary scores even when the influence of years of education and age was taken into account. Even after correction for the possible influence of having been laid off or staying at work, there remained a negative influence on the vocabulary score for the duration of styrene exposure.

CONCLUSIONS

The use of short vocabulary tests as hold tests in cross-sectional studies of solvent-exposed workers may be limited as they seem to lack the essential toxicity-independent property.

[Evaluation of the risk of neuropsychological damage from lead exposure in childhood]

Potential neurotoxicity of lead in children has been explored in many recent epidemiological studies carried out all over the world. Within a multicentric European study, an investigation was carried out also in Italy on children living in an industrial area and characterised by a non steady-state exposure condition with higher exposure at the early stages of life. This peculiar feature allowed to observe interesting associations between neurobehavioural functions and the levels of Pb measured in teeth, but not in blood. Indeed, Pb in teeth was associated with the results of psychometric tests which evaluate the discriminant ability and the attention. Other associations, like those found between the intelligence quotient (IQ) scores and Pb in teeth disappeared after correction for the socioeconomical status of parents. In general, in children exposed to environmental Pb, more consistent associations were found with visual-motor integration and attention than with IQ measurements. In agreement with literature data from other countries, we suggest that the relevance of neurotoxic effects of Pb is limited, at least at the current exposure levels, but also that a threshold Pb level associated with no effect cannot be identified.

Specificity of neurobehavioral outcomes associated with prenatal alcohol exposure

A current issue in alcohol research is whether a "neurobehavioral profile" can be identified for prenatal alcohol exposure, even when dysmorphic features are not present, or whether comparable neurobehavioral deficits are detected when damage is incurred by numerous neurotoxicants to which the fetus is exposed during a common developmental period. Failure to detect such differences may, in part, be an artifact of the global developmental tests used to assess outcome. Cognitive effects of prenatal exposure to three different teratogens [polychlorinated biphenyls (PCBs), alcohol, and cocaine] are examined to determine whether exposure to each substance results in a common or different pattern of impairment on the same set of newer, more narrow band infant tests. Comparison of findings from three independent cohorts indicate that PCB exposure was related to poorer recognition memory on the Fagan Test of Infant Intelligence (FTII) in Michigan infants exposed prenatally to PCB-contaminated fish, whereas prenatal alcohol exposure was unrelated to recognition memory but to slower processing speed on a new FTII measure and slower reaction time on Haith's Visual Expectancy Paradigm (VExP) in our Detroit alcohol-exposed infants. Preliminary findings from a new study of infants recently born to Taiwanese women accidentally contaminated with sizable amounts of PCBs indicate recognition memory deficits, confirming our Michigan findings, but no processing speed effects on the FTII. Recent findings from our Detroit cohort suggest that heavy prenatal cocaine exposure is related to poorer recognition memory on the FTII, but faster reaction times on the VExP, a pattern different from that seen for either PCBs or alcohol.

Role of glutamate receptor-mediated excitotoxicity in bilirubin-induced brain injury in the Gunn rat model

Severe hyperbilirubinemia in neonates with prematurity and/or systemic illnesses such as hemolytic disease, acidosis, and hypoxemia enhances their risk for developing cerebral palsy, paralysis of ocular upgaze, and deafness. This neurologic syndrome has been associated with selective neuronal vulnerability in the basal ganglia, certain brainstem nuclei, and Purkinje cells. However, the mechanism by which bilirubin damages neurons remains unclear. In these studies, we found that intracerebral injection of N-methyl-D-aspartate (NMDA), an excitotoxic analogue of glutamate, caused greater injury in jaundiced 7-day-old Gunn (jj) rat pups than in nonjaundiced heterozygous (Nj) littermate controls. NMDA injection caused even greater injury when protein-bound bilirubin was displaced with the sulfonamide drug sulfadimethoxine in jaundiced homozygous pups. In additional experiments, the acute signs of bilirubin-mediated neuronal injury, induced in homozygous (jj) Gunn rats by treatment with sulfonamide, were reduced by concurrent treatment with the NMDA-type glutamate channel antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohept-5,10-imine (MK-801, dizocilpine). The results suggest that bilirubin may cause encephalopathy and neuronal injury, at least in part, through an NMDA receptor-mediated excitotoxic mechanism. This conclusion is consistent with clinical observations that bilirubin encephalopathy is synergistically worsened by hypoxemia, which also shares an excitotoxic mechanism of neuronal injury.

Persistent structural modifications in nucleus accumbens and prefrontal cortex neurons produced by previous experience with amphetamine

Experience-dependent changes in behavior are thought to involve structural modifications in the nervous system, especially alterations in patterns of synaptic connectivity. Repeated experience with drugs of abuse can result in very long-lasting changes in behavior, including a persistent hypersensitivity (sensitization) to their psychomotor activating and rewarding effects. It was hypothesized, therefore, that repeated treatment with the psychomotor stimulant drug amphetamine, which produces robust sensitization, would produce structural adaptations in brain regions that mediate its psychomotor activating and rewarding effects. Consistent with this hypothesis, it was found that amphetamine treatment altered the morphology of neurons in the nucleus accumbens and prefrontal cortex. Exposure to amphetamine produced a long-lasting (>1 month) increase in the length of dendrites, in the density of dendritic spines, and in the number of branched spines on the major output cells of the nucleus accumbens, the medium spiny neurons, as indicated by analysis of Golgi-stained material. Amphetamine treatment produced similar effects on the apical (but not basilar) dendrites of layer III pyramidal neurons in the prefrontal cortex. The ability of amphetamine to alter patterns of synaptic connectivity in these structures may contribute to some of the long-term behavioral consequences of repeated amphetamine use, including amphetamine psychosis and addiction.

Low-dose vigabatrin (gamma-vinyl GABA)-induced damage in the immature rat brain

The antiepileptic drug, vigabatrin, inhibits GABA transaminase, thus elevating GABA levels in the brain. In adult animal experiments, high-dose (200 mg/kg/day) chronic vigabatrin administration is associated with potentially reversible myelin vacuolation, a phenomenon not documented in humans. We hypothesized that vigabatrin might adversely affect myelination in the developing brain. Rats were given vigabatrin in doses comparable to those used clinically (15-50 mg/kg/day), from age 12 to 16 days. The rats were killed at age 19-20 days. We observed decreased myelin staining in the external capsule, axonal degeneration in white matter, evidence of glial cell death in the white matter, and reactive astrogliosis in the frontal cortex. We did not detect myelin vacuolation. These findings indicate that vigabatrin can have adverse and potentially irreversible effects on the developing rat brain. The mechanism of damage could be direct toxicity of vigabatrin or an indirect effect mediated through elevated GABA levels. Vigabatrin has been recommended as a treatment for some forms of childhood epilepsy; therefore, further studies are needed to assess the risks in children.

Multifocal brain damage induced by phencyclidine is augmented by pilocarpine

Phencyclidine and other antagonists of the N-methyl-D-aspartate subtype of glutamate receptor cause psychosis in humans. In low doses these agents induce a reversible neurotoxic reaction in the rat brain that is limited to the retrosplenial granular cortex. Some investigators have reported that phencyclidine at higher doses or by more prolonged treatment causes a more disseminated pattern of damage. However, it has not been clearly demonstrated whether the disseminated damage is reversible or irreversible and whether it is consistently reproducible, nor is it known how many and which neurons are at risk. In the present study we addressed these questions using several histological approaches (plastic-embedded thin sections for light microscopy and ultrathin plastic sections for electron microscopy, paraffin-embedded haematoxylin and eosin sections, 72 kDa heat shock protein immunocytochemistry and de Olmos silver impregnation) to study the lesions induced in rat brain by phencyclidine (alone or when augmented with pilocarpine). We found that phencyclidine can kill a relatively large number of neurons distributed over many cerebrocortical and limbic brain regions, but the multifocal pattern of damage occurred in only a small percentage of treated rats. The addition of a low dose of pilocarpine to phencyclidine caused the widespread pattern of damage to manifest on a much more consistent basis. Available evidence suggests that disinhibition of multiple converging excitatory pathways is the mechanism by which phencyclidine triggers widespread neuronal degeneration; however, the specific combination of excitatory inputs that contributes to the pathological process may differ from region to region.

Arthrogryposis multiplex congenita and bilateral mid-brain infarction following maternal overdose of co-proxamol

We report a case of arthrogryposis multiplex congenita secondary to fetal hypokinesia in a 41-week gestation infant following antenatal central nervous system injury. The mother's pregnancy was complicated by an episode of attempted self harm, with an overdose of co-proxamol at 22 weeks of gestational age, and by the use of cocaine in combination with excess alcohol intake. Magnetic resonance imaging showed bilateral mid-brain cysts and marked atrophy of the basal ganglia and thalami.

Cerebral complications of murine monoclonal CD3 antibody (OKT3): CT and MR findings

Treatment of acute renal allograft rejection with mouse monoclonal antibody (OKT3) is associated with systemic and neurologic side effects. We describe cerebral abnormalities in a 13-year-old boy with steroid-resistant renal allograft rejection. After treatment with OKT3, an acute neurologic syndrome developed, including seizures, lethargy, and decreased mental function. CT and MR imaging revealed confluent cerebral lesions at the corticomedullary junction. Contrast-enhanced MR images showed patchy enhancement, indicating blood-brain barrier dysfunction. The diagnosis of OKT3-induced encephalopathy with cerebral edema and capillary leak syndrome was made. Although CT and MR findings are nonspecific, neuroradiologists should be aware of this condition in transplant patients treated with OKT3.

Opioid neurotoxicity: fentanyl dose-response effects in rats

Opioids, when administered in large doses, produce brain damage, primarily in the limbic system and association areas in rats. This investigation examined the relationship between opioid dose and severity and frequency of brain damage in rats. Forty male Sprague-Dawley rats were anesthetized with halothane/N2O and underwent tracheal intubation, mechanical ventilation, arterial/venous cannulation, and insertion of a rectal temperature probe and biparietal electroencephalogram electrodes. After surgery, halothane was discontinued and O2/N2O 30%/70% was administered for 1 h. Rats were then randomly assigned to one of eight groups. The control group received a loading dose (LD) of 4 mL/kg of 0.9% normal saline solution (NSS) and a maintenance dose (MD) of 4 mL.kg-1.h-1 NSS. The other groups were given fentanyl lypophilized and reconstituted in NSS with the LD ranging from 50 to 3200 micrograms/kg and the MD from 2 to 128 micrograms.kg-1.min-1. After 2 h of fentanyl or NSS infusion; all rats received 100% O2 and, when alert, their tracheas were extubated; after 7 days the rats underwent cerebral perfusion fixation, followed by light microscopic evaluation. Histopathologic lesions (primarily eosinophilic neuron degeneration) were subjectively graded by a pathologist unaware of the experimental treatment; the grades were based on the percentage of dead neurons. There were no lesions observed in the brain areas in any of the control or 200-8 (LD, microgram/kg; MD, microgram.kg-1.min-1) groups. Eleven of 20 rats in the 400-16, 800-32, 1600-64, and 3200-18 groups showed evidence of brain damage primarily in limbic system structures and association areas (P < 0.05). Our data confirm that fentanyl produces limbic system brain damage in rats, and that the damage occurs over a broad range of doses.

A 3-year follow-up of the intellectual and academic functioning of children receiving central nervous system prophylactic chemotherapy for leukemia

This prospective study compared the intellectual and academic functioning of two groups of children treated for cancer over the 3 years after their diagnosis. One group consisted of children who received central nervous system (CNS) prophylactic chemotherapy, and the other group consisted of children with cancer who did not receive CNS chemotherapy. The results suggest that the children who received CNS chemotherapy experienced more adverse effects from their treatment in the area of academic functioning than the children who did not receive CNS chemotherapy. Although there were no differences in the academic functioning of the two groups of children immediately after their diagnosis, 3 years postdiagnosis, the CNS-treated children scored more poorly on academic tests of reading, spelling, and arithmetic than the non-CNS-treated children. The results suggest that CNS chemotherapy prophylaxis may impede academic achievement.

[Hypoxic brain damage after carbon monoxide poisoning. Visual agnosia, reduced initiative and memory and delayed sequelae]

Four patients with hypoxic brain damage caused by carbon monoxide poisoning are described. Three of these had attempted suicide with car exhaust fumes. Two patients had visual agnosia due to lesions in the parieto-occipital cortex. Three patients had temporary Parkinsonian symptoms. In two of these patients CT and MRI showed lesions in the globus pallidus. They also showed reduced initiative, and in one patient this was combined with minor tics and obsessive symptoms. One patient had impaired memory as the only symptom. The patient with the longest lasting exposure developed delayed sequelae; three weeks after the poisoning he became apathetic and confused, with failing memory, Parkinsonian symptoms, and urinary and faecal incontinence. MRI showed demyelination in the periventricular white matter. His condition started to improve two months after the accident.

[Delayed symptoms of hypoxic brain damage after temporary improvement]

A shipyard worker was doing welding work inside a pipe with argon as cover gas. After taking a break he fainted while controlling the weld, also inside the pipe. He was rescued after 15-20 minutes and regained consciousness after a few hours. Two days later he was discharged from hospital in apparently good health. After a week he returned to the hospital suffering from confusion, failing memory, aphasia, apraxia and urinary incontinence. MR showed elevated signal intensity bilaterally in the caudate nucleus. He improved gradually and six months later was given less demanding work. The course of his illness is consistent with delayed neuropsychiatric sequelae after hypoxia, probably due to displacement of oxygen by argon. Delayed symptoms are caused by demyelination in the subcortical white matter.

Long-term consequences of subtle stimuli during the first twenty-four hours of seizure-induced brain injury

Chronically epileptic (induced by a single systemic injection of lithium and pilocarpine about 30 days before the experiment began) male rats were trained within a radial maze while they were administered either GABA-pentin (Neurontin), or prednisolone or given no treatment. There was no significant improvement in learning or memory between the groups. Numbers of trials per day were positively correlated with the time required to display the overt stereotyped forelimb clonus after the single pilocarpine injection. The numbers of correct trials completed during the first few days of acquisition were significantly greater for the rats that had receive weak (1 microT) complex, pulsed magnetic fields over the right hemisphere during the first 24 hr. after seizure induction than for those who received the same field over the left hemisphere or that had been exposed to reference conditions. Implications of the enhanced sensitivity of limbic neurons to subtle electromagnetic interaction during electrical lability are discussed.

The effects of methylenedioxymethamphetamine (MDMA, "Ecstasy") on monoaminergic neurotransmission in the central nervous system

Methylenedioxymethamphetamine (MDMA, Ecstasy) is a popular recreationally used drug among young people in Europe and North America. The recent surge in use of MDMA and increasing concerns about possible toxic effects of the drug have inspired a great deal of research into the mechanisms by which the drug may affect the central nervous system. This paper reviews studies on the neurochemical, behavioral and neurophysiological effects of MDMA, with emphasis on MDMA effects in regions of the brain that have been implicated in reward. Experiments in awake, behaving laboratory animals have demonstrated that single injections of MDMA increase extracellular levels of the neurotransmitters dopamine (DA) and serotonin (5HT) in the nucleus accumbens and in several other brain regions that are important for reward. Most of the behavioral and electrophysiological changes that have been reported to date for single doses of MDMA appear to be mediated by this MDMA-induced increase in extracellular DA and 5HT. As an example, MDMA-induced hyperthermia and locomotor hyperactivity in laboratory animals can be blocked by administering drugs that prevent MDMA-induced 5HT release and can be attenuated by administering 5HT receptor antagonists, whereas effects of MDMA on delayed reinforcement tasks appear to be mediated by MDMA-induced increases in extracellular DA. Similarly, the effects of MDMA on neuronal excitability in the nucleus accumbens and in several other brain regions can be prevented by administering drugs that block MDMA-induced 5HT release and can be attenuated by depleting brain DA levels or by administering either DA D1 receptor antagonists or 5HT receptor antagonists. In addition to the acute effects of MDMA, it is now well established that repeated or high-dose administration of MDMA is neurotoxic to a subpopulation of 5HT-containing axons that project to the forebrain in laboratory animals. Recent studies have shown that this neurotoxic effect of MDMA is associated with long-duration changes in both DA and 5HT neurotransmission in the nucleus accumbens. Whether these long-duration changes in neurotransmission might be related to reports of depression and other psychopathologies by some frequent users of MDMA remains to be determined. Methylene-dioxymethamphetamine has been found to increase extracellular levels of norepinephrine and to alter brain levels of several neuropeptides as well as altering levels of DA and 5HT. Much additional research is required to understand the multiple ways in which this complex drug may alter neurotransmission in the brain, both acutely and in the long term.