Latent Brain Research Articles

Functional magnetic resonance imaging study of frontal lobe activation during word generation in obsessive–compulsive disorder

Background: Functional imaging studies have demonstrated abnormal patterns of brain activity in obsessive–compulsive disorder, which consistently suggest the alteration of frontal lobe functioning. We performed a brain activation study in obsessive–compulsive disorder using a cognitive task involving the frontal lobes. Methods: Twenty patients and 20 healthy control subjects were assessed with functional magnetic resonance imaging during a phonologically guided word generation task. The study analysis was based on the comparison of group average time-course functional changes occurring at the site of largest frontal cortex activation during alternating rest and task periods. Results: In terms of relative signal changes, patients showed a significantly greater activation during word generation and a defective suppression of this activation during the following rest period. Both abnormal imaging findings significantly correlated with the severity of the clinical process assessed by the Yale–Brown Obsessive–Compulsive Scale. Conclusions: The results indicate that functional magnetic resonance imaging during cognitive challenge may be useful to reveal distinctive features of latent brain dysfunction in obsessive–compulsive disorder.

Value of PCR for evaluating occurrence of parasitemia in immunocompromised patients with cerebral and extracerebral toxoplasmosis

PCR was used to evaluate the occurrence of Toxoplasma gondii parasitemia by detection of the B1 gene in blood samples in two groups of immunosuppressed patients (148 subjects) suspected of having cerebral or extracerebral infection, respectively. Group I consisted of 52 patients with AIDS with suspected cerebral toxoplasmosis. The diagnosis was clinically proven in 15 cases. Parasitemia was detected by PCR in only two of these patients (13.3%), both showing evidence of disseminated infection. Group II consisted of 96 immunocompromised patients, either with AIDS or receiving iatrogenic immunosuppressive therapy. Of these patients, 65 (34 with AIDS and 31 others) showed abnormalities only in chest radiography and were first screened for the presence of Toxoplasma DNA in bronchoalveolar lavage fluid. Blood was then analyzed when the parasite was detected in the bronchoalveolar lavage fluid. The remaining 31 subjects (22 with AIDS and 9 others) were suspected of having extracerebral, pulmonary, or disseminated toxoplasmosis, and blood was studied directly in these cases. Among the nine patients with clinically diagnosed extracerebral infection in group II, the parasite was detected by PCR in the blood of five patients (55.5%), all having pulmonary toxoplasmosis. If all patients with clinical manifestations of extracerebral toxoplasmosis (from both groups) who had not received antitoxoplasma therapy when the samples were collected are considered, PCR detected parasitemia in seven of the nine cases (77.8%). The present study indicates that examination of blood by PCR may be valuable in cases of extracerebral toxoplasmosis because of the disseminated nature of the disease. Since most cases of cerebral toxoplasmosis result from the local reactivation of latent brain cysts, detection of parasitemia by PCR is useful only in cases associated with severe cerebral infection or dissemination of this disease.

Target cells during early SIV encephalopathy

Early encephalopathy was studied in rhesus macaques in the first month following intravenous (i.v.) infection with SIV-mac-251. Histopathological analysis of brain tissues showed slight gliosis, associated with perivascular infiltrates and occasional glial nodules. Immunophenotyping of brain tissue showed microgliosis with expression of MHC class II molecule and macrophage infiltration associated with a few lymphocytes. At the early stage of infection, most infected cells were perivascular, suggesting that infiltrating cells are the main route of entry of the virus into the brain. Using combined immunochemistry and in situ hybridization, it was shown that these infected perivascular cells were mostly macrophages. Later, SIV infected a limited number of cells expressing the same CD68 monocyte/macrophage/microglia marker. Using different genome probes, hypotheses concerning SIV RNA expression during early brain infection were tested. It was shown that the latent brain infection was not due to a complete transcription block, but rather to productive replication of SIV at a low level in a small number of target cells in the brain. Injection of SIV by the intracerebral (i.c.) route induced the same slight encephalitis as observed in i.v. inoculated animals. The very small number of infected cells found around the site of i.c. inoculation suggests that resident microglia are poorly susceptible to infection by SIV.

Otogenic brain abscess in childhood

Brain abscesses are quite rare complications of middle ear infections. Although temporal lobe abscesses are more common than cerebellar ascesses, the converse was found to be true in our series of 10 cases. Eight cases of cerebellar abscess and 2 cases of temporal lobe abscess in the paediatric age group were reported including 4 cases of latent brain abscesses which manifested themselves after mastoidectomy for middle ear infection. Brain abscess is by far the most serious of Otogenic complications.

Herpes simplex virus encephalitis of the human adult: reactivation of latent brain infection.

Herpes simplex virus encephalitis of the human adult: reactivation of latent brain infection.

CSF immune complexes in multiple sclerosis.

Immune complexes from the CSF of 12 individuals (6 with exacerbations of MS and 6 with other neurologic or psychiatric disease) were isolated and characterized. Three MS patients had complexed herpes simplex type I viral antigen and antibody; three patients had complexed myelin basic protein. Two MS patients and one with hypoxic encephalopathy had complexed antibody directed against brain glycolipids. CSF complexes were distinct from serum complexes, suggesting intrathecal origin. Reactivation of latent brain virus may play a role in exacerbations of MS.

Hyperventilation, Brain Damage and Flicker

SUMMARY Critical frequencies were measured and Berg's hexobarbitone test was applied in six normal young adult male volunteers, following 2 hours passive hyperventilation and again after 2 hours rest. Measured by reduction of the critical frequency, there was no significant difference in the response to hexobarbitone in the hyperventilated and control situations. At the present time there is a controversy as to whether hyperventilation, as applied in modern anaesthetic practice, is harmful to the central nervous system. The subject has been reviewed by several authors, e.g. Robinson and Gray (1961) and Allen and Morris (1962). Some investigators believe that the neurological effects of hyperventilat ion are due directly to changes in arterial carbon dioxide tension (PacO3) and hydrogen ion concentration and that the changes are completely reversible. Others consider that the neurological effects are the result of cerebral ischaemia due to the reduction in cerebral blood flow which occurs when the Paco, is lowered (Kety and Schmidt, 1946), and therefore hyperventilation is a potential cause of permanent damage to the brain. Berg (1949) developed a technique based on critical (c.f.f.) which, when combined with the administration of a small amount of hexobarbitone , made it possible for him to detect latent brain damage. Berg's test is based on the fact that while a subhypnotic intravenous dose of hexobarbitone may cause a slight transient fall in c.f.f., in normal subjects, the same dose administered to individuals who have suffered damage to the brain will cause a much greater and sustained decrease in c.f.f. Having determined the degree and duration of the reduction of c.f.f. in response to a given dose of hexobarbitone in a large number of normal indi* Present address: Department of Anaesthetics, The General Infirmary at Leeds, Great Georee Street, Leeds, 1. viduals, any subject showing a change in these parameters in excess of the mean plus four times the standard deviation obtained in the normal group, is regarded as having an abnormal result indicative of brain dysfunction. The critical frequency may be determined by using an intermittent source of light of constant intensity and increasing the number of exposures to the light per second until, to the subject, the light source appears uninterrupted or continuous. The results are then expressed in flashes per second and the point at which an intermittent light source appears continuous is called the critical frequency. The end point may be determined as the mean of values obtained proceeding from flicker to fusion and returning from fusion to flicker, the latter point giving a slightly lower value than the former. This was the procedure adopted in the present study. Alternatively the number of flashes per second may be kept constant and the intensity of the light source varied using a system, when again a point will be reached at which an intermittent light source appears continuous; this is the method described by Berg (1949) and using such a system the results are expressed in terms of filter units (F.U.). Berg (1949) has provided data relating results obtained using the two systems. Allen and Morris (1962) used Berg's test in patients who were subjected to passive pulmonary hyperventilation during anaesthesia for routine surgical procedures; these patients were managed in surgical wards in the usual way.

LATENT BRAIN ABSCESSES WHICH MANIFEST THEMSELVES AFTER MASTOIDECTOMY IN CHRONIC SUPPURATIVE OTITIS MEDIA.

LATENT BRAIN ABSCESSES WHICH MANIFEST THEMSELVES AFTER MASTOIDECTOMY IN CHRONIC SUPPURATIVE OTITIS MEDIA.

Latent Brain Abscess Becoming Evident with Symptoms of Atropine Poisoning

Latent Brain Abscess Becoming Evident with Symptoms of Atropine Poisoning