Acute haemorrhagic and hypoxic-ischaemic brain damage in the neonate

Autopsy approach to stroke

Stroke is a major cause of morbidity and mortality but the brain and other relevant tissues are often examined only cursorily when stroke patients come to autopsy. The pathological findings and clinical implications vary according to the type of stroke and its location and cause. Large ischaemic strokes are usually associated with atherosclerosis of extracranial or major intracranial arteries but can be caused by dissection. Most small cerebral infarcts are caused by arteriosclerosis or, in the elderly, cerebral amyloid angiopathy (CAA). However, vasculitides and coagulopathies can cause a range of different patterns of ischaemic (and, occasionally, haemorrhagic) stroke. Global brain ischaemia, caused by severe hypotension or raised intracranial pressure, produces damage that is accentuated in certain regions and neuronal populations and may be confused with hypoglycaemic injury. The main cause of subarachnoid haemorrhage is a ruptured berry aneurysm but CAA, arteriovenous malformations and infective aneurysms are occasionally responsible. These can also cause parenchymal brain haemorrhage, although this most often complicates hypertensive small vessel disease. Sometimes the haemorrhage arises from a neoplasm. Performing an adequate autopsy in stroke requires proper preparation, awareness of the likely pathological processes, familiarity with intracranial vascular anatomy, careful gross examination and dissection, and appropriate use of histology.

The timing of perinatal hypoxia/ischemia events in term neonates: a retrospective autopsy study. HSPs, ORP-150 and COX2 are reliable markers to classify acute, perinatal events

Background

The understanding of the cellular responses implicated in perinatal brain damages and the characterization of the various mechanisms involved might open new horizons for understanding the time of onset of a brain hypoxic-ischemic lesion and for effective therapeutic strategies.

Methods

We performed an immunohistochemical investigation on brain and brainstem sections of 47 peripartum deaths. The gradation and localization of the expression of antibodies such as TNFα, IL-1β, IL-6, HSPs, β APP, anti-TrypH, GAP43, GFAP, COX2, ORP-150, could be correlated with an hypoxic-ischemic damage to document a significant correlation between response and the time of onset acute (≤8 hs) or non-acute (≥8 hs ≤48 hs).

Results and Discussions

In non-acute cases HSP70 reaction was prominent in the neuron cytoplasm, while in acute cases a mild reaction was evident in sporadic fields. HSP90 exhibited a similar pattern of positivity as HSP70. In acute group, ORP150 expressed an intense reaction showing a granular pattern in the cytoplasm of the neurons in the cortex of the infarcted areas. In non-acute group the positive reaction was more intense in astrocytes and less extended in neurons. COX2 reaction exhibited the strongest positive reaction in the neuronal cell bodies of acute cases, while a immunolabeling was prominent in the glial cytoplasm in the non-acute cases.

Conclusions

Chaperones HSP70 and 90, ORP-150 reaction, and COX2 protein, have provided very interesting results. These results would suggest to the clinicians to extend the differential diagnosis of a too large perinatal hypoxic-ischemic insult category to delineate a more accurate chronological judgement.

Quantitative tissue echogenicity of the neonatal brain assessed by ultrasound imaging

The aim of this study was to propose a method for measuring the echogenicity of several neonatal brain structures for quantitative interpretation of ultrasound images. To do this, 40 preterm neonates (24-34 weeks' gestation) with adequate birth weight for gestational age were studied. On the third day after delivery, anterior fontanelle ultrasound imaging of the brain was performed in standard coronal and sagittal views. Four regions-of-interest (ROIs) were identified: periventricular, choroid plexus, cerebellar vermis and basal ganglia. Two consecutive images from each ROI were digitally stored. For off-line analysis, the ROI corresponding to each structure was delineated and the mean pixel brightness (PB) calculated. In addition, the brightness of bone tissue obtained at the same depth of the studied ROI was calculated. This value was considered as the maximum possible echogenicity for that individual image. The relative echogenicity (RE) was then calculated as: PB ROI/PB BONE( *)100. Differences in RE between the ROIs and RE variations according to gestational age and reliability reproducibility were determined. We found that among the studied structures, RE values (mean/SD) were significantly higher in the choroid plexus (mean [SD] 56.38 [6.0] and in the cerebellar vermis 51.20 [6.0] than in the basal ganglia 37.29 [5.7] and the periventricular area 37.04 [5.6]) (p<0.05). These values showed no variation in relation to gestational age at birth. Interobserver reproducibility was 0.91 in the choroid plexus, 0.89 in the cerebellar vermis, 0.82 in basal ganglia and 0.77 in the anterior periventricular area. In conclusion, semiquantitative estimation of RE offers a reproducible method for evaluating at-risk areas of the neonatal brain.

The pathogenesis of neonatal post-hemorrhagic hydrocephalus

Hydrocephalus after intraventricular hemorrhage (IVH) has emerged as a major complication of preterm birth and is especially problematic to treat. The hydrocephalus is usually ascribed to fibrosing arachnoiditis, meningeal fibrosis and subependymal gliosis, which impair flow and resorption of cerebrospinal fluid (CSF). Recent experimental studies have suggested that acute parenchymal compression and ischemic damage, and increased parenchymal and perivascular deposition of extracellular matrix proteins--probably due at least partly to upregulation of transforming growth factor-beta (TGF-beta)--are further important contributors to the development of the hydrocephalus. IVH is associated with damage to periventricular white matter and the damage is exacerbated by the development of hydrocephalus; combinations of pressure, distortion, ischaemia, inflammation, and free radical-mediated injury are probably responsible. The damage to white matter accounts for the high frequency of cerebral palsy in this group of infants. The identification of mechanisms and mediators of hydrocephalus and white matter damage is leading to the development of new treatments to prevent permanent hydrocephalus and its neurological complications, and to avoid shunt dependence.