Preterm outcomes research: a critical component of neonatal intensive care

While early preterm outcome studies described the lives of preterm survivors to justify the efforts required to save them, subsequent studies demonstrated their increased incidence of cerebral palsy, mental retardation, sensory impairments, minor neuromotor dysfunction, language delays, visual-perceptual disorders, learning disability and behavior problems compared to fullterm controls. Because infants born at the lower limit of viability require the most resources and have the highest incidence of neurodevelopmental disability, there is concern that resources have gone primarily to neonatal intensive care and are not available for meeting the followup, health, educational and emotional needs of these fragile infants and their families. Despite many methodological concerns, preterm outcome studies have provided insight into risk factors for and causes of CNS injury in preterm infants. Nevertheless, it remains difficult to predict neurodevelopmental outcome for individual preterm infants. Perinatal and neonatal risk factors are inadequate proxies for neurodevelopmental disability. Recent randomized controlled trials with one to five year neurodevelopmental followup have provided valuable information about perinatal and neonatal treatments. Recognizing adverse longterm neurodevelopmental effects of pharmacological doses of postnatal steroids is a sobering reminder of the need for longterm neurodevelopmental followup in all neonatal randomized controlled trials. Ongoing longterm preterm neurodevelopmental studies, analysis of changes in outcomes over time and among centers, and evaluation of the longterm safety, efficacy and effectiveness of many perinatal and neonatal management strategies and proposed neuroprotective agents are all necessary for further medical and technological advances in neonatal intensive care.

Neurodevelopmental care in the NICU

Neurodevelopmental care, which is any NICU intervention undertaken to improve neurodevelopmental outcome, includes NICU design, nursing routines, nursing care plans, management of pain, feeding methods and, most importantly, encouraging parental involvement with their NICU infant. Recognition that sensory stimulation can overwhelm preterm infants and increase physiologic signs of stress led to attempts to reduce sensory input. More recent approaches judiciously add back soothing sensory input (e.g., therapeutic touch, soft music). Circadian light/dark cycles and physical activity improve preterm growth. Attention to infant positioning and handling affects physiologic variables and joint mobility, if not functional motor abilities. A highly organized system of care for NICU infants is Als' NIDCAP (i.e., Neonatal Individualized Developmental Care and Assessment Program). Although NIDCAP may reduce need for respiratory support and hospital length of stay, it does not significantly influence neurodevelopmental outcome at 2-3 years. Pain management includes benign interventions (e.g., nonnutritive sucking, oral glucose), but the prolonged use of narcotics must be balanced against the consequences of sedation and dependency. The foremost challenge for NICUs remains parent disenfranchisement. Kangaroo care, which involves parent/infant skin-to-skin contact, improves preterm growth, decreases nosocomial infections and may shorten hospital length of stay. A great deal of work needs to be done to identify and demonstrate efficacy of specific interventions and changes that humanize the NICU, encourage parental involvement, support infant development and optimize preterm neurodevelopmental outcomes.

Enhancement of the somatosensory N140 component during attentional training after stroke

OBJECTIVE

To evaluate the training effect on the N140 component of the somatosensory event related potential in patients suffering from first ever stroke in the middle cerebral artery area and prove the influence, if any, on a component related to spatial attention.

METHODS

Forty patients were studied. Twenty were enrolled in a daily discrimination training task using an oddball paradigm with cutaneous electrical stimuli. The training period was 3 weeks. Twenty control patients were untrained. Electroencephalographic signals were recorded from scalp electrodes during each training session. In the controls, only two recordings were made, at baseline and after 3 weeks. Disability at the time of admission and discharge were evaluated using the functional independence measure (FIM). Twenty healthy control volunteers were also studied.

RESULTS

During training, event related potentials took the form of a large positive-negative complex over the period 106-160ms after the stimulus, followed by a smaller P300 component. The amplitude of the responses was smaller over the affected hemisphere (P<0.05). In the treatment group, N140 was present in 3 patients from the beginning and in 16 after training. Four of the untrained control patients showed a N140 at baseline, whereas it was seen in only 6 after 3 weeks (Chi-square 8.1; P<0.001).

CONCLUSIONS

In stroke patients, training improved the recovery of N140. That potential was prognostic of general outcome since its presence at baseline was correlated with a higher FIM score on discharge.

Spontaneous limbic seizures after intrahippocampal infusion of brain-derived neurotrophic factor

The results of several studies have contributed to the hypothesis that BDNF promotes seizure activity, particularly in adult hippocampus. To test this hypothesis, BDNF, vehicle (phosphate-buffered saline, PBS), or albumin was infused directly into the hippocampus for 2 weeks using osmotic minipumps. Rats were examined behaviorally, electrophysiologically, and anatomically. An additional group was tested for sensitivity to the convulsant pilocarpine. Spontaneous behavioral seizures were observed in BDNF-infused rats (8/32; 25%) but not in controls (0/20; 0%). In a subset of six animals (three BDNF, three albumin), blind electrophysiological analysis of scalp recordings contralateral to the infused hippocampus demonstrated abnormalities in all BDNF rats; but not controls. Neuronal loss in BDNF-treated rats was not detected relative to PBS- or albumin-treated animals, but immunocytochemical markers showed a pattern of expression in BDNF-treated rats that was similar to rats with experimentally induced seizures. Thus, BDNF-infused rats had increased expression of NPY in hilar neurons of the dentate gyrus relative to control rats. NPY and BDNF expression was increased in the mossy fiber axons of dentate gyrus granule cells relative to controls. The increase in NPY and BDNF expression in BDNF-treated rats was bilateral and occurred throughout the septotemporal axis of the hippocampus. Mossy fiber sprouting occurred in five BDNF-treated rats but no controls. In another group of infused rats that was tested for seizure sensitivity to the convulsant pilocarpine, BDNF-infused rats had a shorter latency to status epilepticus than PBS-infused rats. In addition, the progression from normal behavior to severe seizures was faster in BDNF-treated rats. These data support the hypothesis that intrahippocampal BDNF infusion can facilitate, and potentially initiate, seizure activity in adult hippocampus.

Topical application of brain derived neurotrophic factor influences upregulation of constitutive isoform of heme oxygenase in the spinal cord following trauma an experimental study using immunohistochemistry in the rat

Influence of brain derived neurotrophic factor (BDNF) on carbon monoxide (CO) production following spinal cord injury was examined using expression of the constitutive isoform of the enzyme hemeoxygenase-2 (HO-2) in a rat model. A longitudinal incision of the right dorsal horn on the T10-11 segment markedly increased the HO-2 immunostaining in the cord at 5 h. At this time period, breakdown of the blood-spinal cord barrier (BSCB) and edema formation were quite prominent. Repeated topical application of BDNF (20 microliters of a 1 microgram/ml solution) over the exposed surface of the cord significantly attenuated the edematous expansion of the cord and the disturbances in the BSCB permeability. In BDNF-treated rats, expression of HO-2 immunoreactivity was considerably reduced. These results strongly suggest that BDNF is neuroprotective in spinal trauma and this growth factor has the capacity to attenuate CO production by downregulating HO-2 expression.

Modelling cognitive dysfunctions with bilateral injections of ibotenic acid into the rat entorhinal cortex

Neurodegenerative diseases, traumatic brain injury and stroke are likely to result in cognitive dysfunctioning. Animal models are needed in which these deficits and recovery of the affected functions can be investigated. In the present study, the entorhinal area was chosen as the target for lesioning and for assessing the lesion-induced deficits in the Morris water maze. The entorhinal cortex is regarded as an interface between the hippocampus and neocortex. Deafferentiating the hippocampus through entorhinal lesions impairs spatial learning. The effects of lesions, induced by either electrocoagulation (experiment 1) or ibotenate excitotoxicity (experiment 2), on spatial orientation behaviour were investigated. Water maze performance after unilateral or bilateral ibotenate injections into the entorhinal cortex was studied in the third experiment. In an additional study, the replicability of the spatial learning deficit after lesions induced by bilateral injections of ibotenic acid into the entorhinal cortex was assessed by comparing the results of nine experiments. We found that spatial learning was impaired after bilateral lesions aimed at the entorhinal cortex. The electrolytic lesion technique produced a relatively large sham effect, whereas the excitotoxic lesioning method did not. Unilateral injections of ibotenic acid into the entorhinal cortex did not affect spatial navigation. The ibotenate-induced lesions replicably produced deficits in the Morris tasks. The degree of the induced spatial learning impairments and the effects on the rate of acquisition during training, however, differed between experiments. This result suggests that the fundamental biological diversity between shipments of rats can account for variation in the effects of parahippocampal damage on spatial learning even in highly standardized experimental set-ups. Rats lesioned by bilateral injections of ibotenic acid into the entorhinal cortex provide an interesting and reliable model for investigating cognitive dysfunctions in neurodegenerative diseases, stroke or traumatic brain injury.