Unravelling intricate interactions among atmospheric bromeliads with highly overlapping niches in seasonal systems.

Biotic and abiotic interactions are important factors that explain community assembly. For example, epiphytic communities are shaped by tree traits that can act as environmental filters, but also by positive and/or negative interactions among coexisting epiphytes on a tree. Here, we studied interactions among three widespread atmospheric bromeliads with overlapping niches (Tillandsia recurvata, T. tricholepis and T. pohliana), using experimental data about facilitation through seed capture, interspecific interaction during seed germination and competition among adult individuals. We aim to understand how species interactions are reflected in the natural coexisting patterns of epiphytes in communities at high and low tree densities. Tillandsia pohliana showed higher facilitation by capturing almost all wind-dispersing seeds, and had the largest reduction in seed germination in the presence of any adult individual, also presenting a relatively high rate of adult mortality in the presence of other individuals. Our results indicate higher colonisation ability for T. pohliana and distinct strategies of rapid exploitation of T. recurvata and T. tricholepis individuals. In natural communities, the coexistence among atmospheric bromeliads may be hampered by dispersal limitations in wind-dispersed epiphytes at high tree density conditions, but a negative effect of T. recurvata on T. pohliana is still reflected in their reduced coexistence. However, competitive patterns observed in the experimental data may be overshadowed by a possible mass effect driving large communities under such conditions. Our results show the joint effect of positive interactions and high dispersal levels on the community patterns of atmospheric bromeliads.

Cerebellar infarcts in the New England Medical Center Posterior Circulation Stroke Registry.

We report the clinical findings and stroke mechanisms of 63 patients with cerebellar infarcts. We divided the intracranial vertebrobasilar circulation into the proximal territory (P), fed by the intracranial vertebral arteries and their branches; the middle territory (M), fed by the proximal and middle basilar artery and its branches; and the distal territory (D), fed by the rostral basilar artery and its branches. Cerebellar infarcts were classified by vascular territories P, M, D, P&D, and middle-plus (P&M, M&D, and P&M&D). Patients with P infarcts (11 patients) frequently had vertigo, gait instability, limb ataxia, and headache, whereas patients with D infarcts (15 patients) most often had limb ataxia, gait instability, and dysarthria. Patients with P&D infarcts (17 patients) had signs and symptoms of both groups combined. Infarcts in which the middle territory was involved, either alone (three patients) or combined with other territories (17 patients) were dominated by brainstem signs and symptoms. The predominant stroke mechanisms in the P, D, and P&D groups were embolic due to intra-arterial or cardiac embolism. When the M territory was involved, either alone or with P, D, or P&D territories, stroke mechanisms were more varied, and there was often large-artery occlusion with hemodynamic ischemia.

Fatal meningoencephalitis caused by reactivation of Trypanosoma cruzi infection in a patient with AIDS.

We report a case of fatal chagasic meningoencephalitis in an AIDS patient. Acute exacerbation of chronic Chagas' disease with involvement of the CNS is uncommon and occurs only in immunocompromised patients. This is the third such reported reactivation and it underscores the importance of considering Chagas' disease in HIV-positive patients from endemic regions.

Cerebellar hemorrhagic infarction.

We investigated 17 patients with 26 cerebellar hemorrhagic infarcts for their vascular anatomy, stroke mechanisms, and clinical course. Sixteen infarcts involved the superior cerebellar artery, nine the posterior inferior cerebellar artery, and one the anterior inferior cerebellar artery territories. The infarcts involved the full territory of the supplying arteries in 19 of 26 infarcts (73%). Sixteen of 17 patients were stable or improving when the hemorrhagic infarction was detected. All but one patient had an imaging study at the time of presentation that was negative for blood; hemorrhagic infarction was detected on routine serial scans performed during the first 15 days. Nine of the 17 patients were on anticoagulants when the cerebellar hemorrhagic infarct was detected; anticoagulation was maintained in eight of them with no clinical worsening. The stroke mechanism in all patients was considered embolic from cardiac and intra-arterial sources. The causes, imaging findings, and consequences of hemorrhagic infarcts in the posterior circulation are similar to those in the anterior circulation.

Value of parasagittal magnetic resonance images in visualizing the vascular territories of the cerebellum.

The outcomes of infarctions of the cerebellar arteries may range from self-limited neuro-ophthalmic symptoms to sudden death. Identification of the affected territory may assist in clinical management because the vascular syndromes, as well as vascular mechanisms of cerebellar infarcts, are different according to the involved cerebellar arteries. However, it is usually difficult to tell the exact vascular territories using only transaxial imagings. Magnetic resonance imaging is a good tool for obtaining parasagittal and coronal images of the cerebellum, which are better for showing the vascular territories. To illustrate this point we report a 61-year-old woman and bilateral cerebellar infarcts (right posterior inferior cerebellar artery and left superior cerebellar artery who had vertigo, vomiting, headache, intermittent vertical diplopia, and difficulty walking. The clinical value of parasagittal imaging of the cerebellum in this case is discussed.

Heparin and oral anticoagulants in the treatment of brain ischemia.

The use of heparin, heparin analogues, and oral anticoagulation in the treatment of brain ischemia remains controversial. We review the mechanism of action of the heparins and warfarin as well as the data regarding their efficacy and complications in patients with ischemic stroke and venous sinus thrombosis. None of these drugs have proven effective for all forms of cerebral ischemia. Further studies examining the efficacy of anticoagulants in different stroke subgroups will be necessary in order to clarify optimal clinical practice.

Chronic spinal subdural hematoma.

A 55-year-old woman with chronic spinal subdural hematoma, diagnosed by magnetic resonance (MR) is presented. There was no coagulation defect, anticoagulant therapy, or trauma.

[Parkinson disease associated to a brain tumor: a case report]. / Parkinsonismo associado a tumor cerebral. Relato de caso.

We are presenting an uncommon case of cerebral tumor whose major manifestation was parkinsonism. The patient was a 50-year-old woman presented with a 5-month history of tremor of the right hand, particularly at rest, and headache. On neurological examination of March, 1987 there were: slight right-sided hemiparesis with symmetrical hyperreflexia; discrete bradykinesia in combination with cogwheel rigidity also on the right-side; resting tremor of the right hand; and bilateral papilledema. The neuropsychological examination disclosed: nominative aphasia, impaired recent memory and right-left disorientation. The computed tomography showed a large, left frontotemporal tumor. Angiograms of the left internal and external carotid arteries revealed a tumor blush in the left frontotemporal region supplied by a enlarged middle meningeal artery. An electromyogram revealed a 4-6 HZ tremor on right hand. A course of treatment with dexamethasone 16 mg/day and levodopa plus benzerazine (500 mg/day) was unsuccessful. A left fronto-temporo-parietal craniotomy was performed and an attached sphenoid wing tumor was macroscopically completely removed. Microscopy indicated that the tumor was a meningioma. Postoperatively, the patient made an uneventful recovery. After two weeks, her right-sided palsy and parkinsonism had disappeared, and neuropsychological deficits improved. Two months later there was no abnormalities on neurological and neuropsychological examination. It was concluded that the parkinsonism was caused by mechanical pressure on the basal ganglia.

HTLV-I associated myelopathy in Brazil: a preliminary report.

In this preliminary report the authors present the finding of a high prevalence (37.5%) of seropositivity of antibodies to HTLV-I tested by Western blotting in a sample of 16 Brazilian patients with chronic myelopathies of undetermined origin.

Reversible posterior leukoencephalopathy in a patient with autonomic dysreflexia: a case report.

STUDY DESIGN: Case report. OBJECTIVES: To report a case of reversible posterior leukoencephalopathy (RPL) in a patient with traumatic cervical spinal cord injury. SETTING: Neurologic inpatient Unit, Lahey Clinic, Burlington, MA, USA. METHODS: A 55-year-old woman with a residual spastic quadriparesis from a traumatic C5-C6 fracture developed, during an assisted cough maneuver, sudden severe headache followed by cortical blindness in the setting of high blood pressure. Magnetic resonance imaging (MRI) showed T2 hyperintensities in the subcortical white matter of both medial occipital lobes and left post-central gyrus. RESULTS: Elevation of the head of the bed during subsequent cough maneuvers with occasional use of sublingual nifedipine prevented further episodes of acute arterial hypertension and development of new symptoms. Repeat MRI of the head done one month later was normal. CONCLUSION: RPL can occur in the setting of autonomic dysreflexia in patients with traumatic cervical cord injury. The prompt recognition of this syndrome is of importance to prevent further morbidity and mortality in patients with spinal cord injury.

Diffusion- and perfusion-weighted MRI patterns in borderzone infarcts.

BACKGROUND AND PURPOSE: The pathophysiology of borderzone infarcts is not well understood. We investigated whether combined diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) could identify pathophysiologically meaningful categories of borderzone infarcts. METHODS: Seventeen patients with borderzone infarcts were identified from the Beth Israel Deaconess Medical Center Stroke Database. All patients had DWI and PWI, the majority of them within the first 24 hours of symptom onset. RESULTS: Three patterns of perfusion abnormalities were associated with the diffusion lesions: 1, normal perfusion (5 patients); 2, localized perfusion deficits matching the area of restricted diffusion (5 patients); and 3, extensive perfusion deficits involving 1 or more vascular territories (7 patients). All but 1 patient with pattern 1 had transient peri-infarct hypotension as the presumed stroke mechanism. Two patients with pattern 2 had cardiac or aortic embolic sources; none had large-artery disease or arterial hypotension. Reperfusion was detected in all patients with this pattern who submitted to a follow-up study. All patients with pattern 3 had severe stenosis or occlusion of a large artery: the internal carotid, anterior cerebral, or middle cerebral. CONCLUSIONS: We postulate that the perfusion abnormality varies according to the mechanism of the borderzone infarction. Transient perfusion deficits occurring with hypotension in the absence of significant large-artery disease may not be revealed by PWI. Embolism may cause some cases of small borderzone perfusion deficits. Critical large-artery disease may cause large territorial perfusion deficits and predispose to borderzone infarction.