Prognostic value of 1H-MRS in neonatal encephalopathy

Optical Monitoring in Neonatal Seizures

BACKGROUND

Neonatal seizures remain a significant cause of morbidity and mortality worldwide. The past decade has resulted in substantial progress in seizure detection and understanding the impact seizures have on the developing brain. Optical monitoring such as cerebral near-infrared spectroscopy (NIRS) and broadband NIRS can provide non-invasive continuous real-time monitoring of the changes in brain metabolism and haemodynamics.

AIM

To perform a systematic review of optical biomarkers to identify changes in cerebral haemodynamics and metabolism during the pre-ictal, ictal, and post-ictal phases of neonatal seizures.

METHOD

A systematic search was performed in eight databases. The search combined the three broad categories: (neonates) AND (NIRS) AND (seizures) using the stepwise approach following PRISMA guidance.

RESULTS

Fifteen papers described the haemodynamic and/or metabolic changes observed with NIRS during neonatal seizures. No randomised controlled trials were identified during the search. Studies reported various changes occurring in the pre-ictal, ictal, and post-ictal phases of seizures.

CONCLUSION

Clear changes in cerebral haemodynamics and metabolism were noted during the pre-ictal, ictal, and post-ictal phases of seizures in neonates. Further studies are necessary to determine whether NIRS-based methods can be used at the cot-side to provide clear pathophysiological data in real-time during neonatal seizures.

Early proton magnetic resonance spectroscopy during and after therapeutic hypothermia in perinatal hypoxic-ischemic encephalopathy

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) remains a significant cause of mortality and neurodevelopmental impairment despite treatment with therapeutic hypothermia. Magnetic resonance H¹-spectroscopy measures concentrations of cerebral metabolites to detect derangements in aerobic metabolism.

OBJECTIVE

We assessed MR spectroscopy in neonates with HIE within 18-24 h of initiating therapeutic hypothermia and at 5-6 days post therapeutic hypothermia.

MATERIALS AND METHODS

Eleven neonates with HIE underwent MR spectroscopy of the basal ganglia and white matter. We compared metabolite concentrations during therapeutic hypothermia and post-therapeutic hypothermia and between moderate and severe HIE.

RESULTS

During therapeutic hypothermia, neonates with severe HIE had decreased basal ganglia N-acetylaspartate (NAA; 0.62±0.08 vs. 0.72±0.05; P=0.02), NAA + N-acetylaspartylglutamate (NAAG; 0.66±0.11 vs. 0.77±0.06; P=0.05), glycerophosphorylcholine + phosphatidylcholine (GPC+PCh; 0.28±0.05 vs. 0.38±0.06; P=0.02) and decreased white matter GPC+PCh (0.35±0.13 vs. 0.48±0.04; P=0.02) compared to neonates with moderate HIE. For all subjects, basal ganglia NAA decreased (-0.08±0.07; P=0.01), whereas white matter GPC+PCh increased (0.03±0.04; P=0.04) from therapeutic hypothermia MRI to post-therapeutic-hypothermia MRI. All metabolite values are expressed in mmol/L.

CONCLUSION

Decreased NAA and GPC+PCh were associated with greater HIE severity and could distinguish neonates who might benefit most from targeted additional neuroprotective therapies.

Clinical magnetic resonance spectroscopy of the central nervous system

Proton magnetic resonance spectroscopy (1H MRS) is a noninvasive imaging technique that can easily be added to the conventional magnetic resonance (MR) imaging sequences. Using MRS one can directly compare spectra from pathologic or abnormal tissue and normal tissue. Metabolic changes arising from pathology that can be visualized by MRS may not be apparent from anatomy that can be visualized by conventional MR imaging. In addition, metabolic changes may precede anatomic changes. Thus, MRS is used for diagnostics, to observe disease progression, monitor therapeutic treatments, and to understand the pathogenesis of diseases. MRS may have an important impact on patient management. The purpose of this chapter is to provide practical guidance in the clinical application of MRS of the brain. This chapter provides an overview of MRS-detectable metabolites and their significance. In addition some specific current clinical applications of MRS will be discussed, including brain tumors, inborn errors of metabolism, leukodystrophies, ischemia, epilepsy, and neurodegenerative diseases. The chapter concludes with technical considerations and challenges of clinical MRS.

Can We Predict Functional Outcome in Neonates with Hypoxic Ischemic Encephalopathy by the Combination of Neuroimaging and Electroencephalography?

BACKGROUND

Neonatal hypoxic ischemic encephalopathy (HIE) is a major cause of mortality, morbidity, and long-term neurological deficits. Despite the availability of neuroimaging and neurophysiological testing, tools for accurate early diagnosis and prediction of developmental outcome are still lacking. The goal of this study was to determine if combined use of magnetic resonance imaging (MRI) and electroencephalography (EEG) findings could support outcome prediction.

METHODS

We retrospectively reviewed records of 17 HIE neonates, classified brain MRI and EEG findings based on severity, and assessed clinical outcome up to 48 months. We determined the relation between MRI/EEG findings and clinical outcome.

RESULTS

We demonstrated a significant relationship between MRI findings and clinical outcome (Fisher's exact test, p = 0.017). EEG provided no additional information about the outcome beyond that contained in the MRI score. The statistical model for outcome prediction based on random forests suggested that EEG readings at 24 hours and 72 hours could be important variables for outcome prediction, but this needs to be investigated further.

CONCLUSION

Caution should be used when discussing prognosis for neonates with mild-to-moderate HIE based on early MR imaging and EEG findings. A robust, quantitative marker of HIE severity that allows for accurate prediction of long-term outcome, particularly for mild-to-moderate cases, is still needed.

Early hyperglycemia is associated with poor gross motor outcome in asphyxiated term newborns

BACKGROUND

Hyperglycemia after ischemic stroke in adults and after near-drowning in children is associated with a poor neurological outcome. Anaerobic metabolism of glucose leads to buildup of lactic acid, free radical production, mitochondrial failure, and ultimately an increase in neurological injury. In asphyxiated infants, high lactate peaks are seen in the basal ganglia with magnetic resonance spectroscopy. Because motor disability in asphyxiated full-term newborns often relates to injury in the basal ganglia, we hypothesized that hyperglycemia and associated buildup of lactic acid may lead to worse gross motor outcome.

METHODS

Glucose, blood gas values, and demographic data were abstracted from the medical records of 41 term infants with asphyxia and without confounding diagnoses. Their Gross Motor Function Classification System scores were determined from the medical record or by structured telephone interviews.

RESULTS

The outcomes of 14 infants were considered poor on the basis of death within the first 6 months or moderate-to-severe cerebral palsy (Gross Motor Function Classification System score 1-5). The other 27 infants had no gross motor disability (Gross Motor Function Classification System score 0). The highest recorded blood glucose correlated with poor outcome (P = 0.046 by logistic regression). Infants with hyperglycemia (blood glucose > 150 mg/dL) were more likely to have poor outcome (P = 0.017; odds ratio: 5.9; 95% confidence interval: 1.4-24.7).

CONCLUSIONS

High blood glucose in the first 12 hours is associated with poor gross motor outcome in this cohort of asphyxiated term infants. Clinicians should avoid hyperglycemia in managing term infants with asphyxia.

The use of magnetic resonance spectroscopy in the evaluation of epilepsy

Magnetic resonance spectroscopy (MRS) is indicated in the imaging protocol of the patient with epilepsy to screen for metabolic derangements such as inborn errors of metabolism and to characterize masses that may be equivocal on conventional magnetic resonance imaging for dysplasia versus neoplasia. Single-voxel MRS with echo time of 35 milliseconds may be used for this purpose as a quick screening tool in the epilepsy imaging protocol. MRS is useful in the evaluation of both focal and generalized epilepsy.

Protective effect of hypoxic preconditioning on hypoxic-ischemic injured newborn rats

Brief episodes of cerebral hypoxia-ischemia cause transient ischemic tolerance to subsequent ischemic events that are otherwise lethal. This study was conducted to evaluate the protective effect of hypoxic preconditioning on hypoxic-ischemic injury in the neonatal rat and the persistence of a protective window after hypoxic preconditioning. The rats were preconditioned with hypoxia (8% oxygen, 92% nitrogen) for three hours, subjected to ischemia using ligation of the right common carotid artery, and then exposed to another three hours of hypoxia. Using proton magnetic resonance spectroscopy, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining, and morphologic scores, this study shows that hypoxic preconditioning 6-hr to 1-day before hypoxic-ischemic injury increases survival rates and has neuroprotective effects against subsequent hypoxic-ischemic injury. The mechanism of the protective effects of hypoxic preconditioning in the newborn rat brain may involve downregulation of apoptotic cell death.

A combined a-EEG and MR spectroscopy study in term newborns with hypoxic-ischemic encephalopathy

OBJECTIVES

Brain damage following a perinatal hypoxic-ischemic (HI) insult has been documented by different diagnostic techniques. The aim of the present study was to relate a-EEG time course during the first 24h of life to brain metabolic changes detected by proton MR spectroscopy ((1)H-MRS) at 7-10days of life and to evaluate their correlation with outcome.

METHODS

Thirty-two patients with any grade HI encephalopathy were studied. Thirty-one out of 32 patients survived and underwent (1)H-MRS examination at 7-10days of life; a-EEG was recorded during the first 24h of life in 27/32 newborns; 26 patients underwent both examinations. Griffiths test, evaluation of motor skills, visual and hearing function were performed at regular intervals until the age of 2years.

RESULTS

a-EEG at 6, 12 and 24h of life showed a significant correlation with outcome. N-acetyl-aspartate/creatine (Cr), Lactate/Cr and myo-inositol differed significantly between patients with normal or poor outcome. a-EEG time course during the first 24h of life showed improvement in newborns with normal (1)H-MRS and good outcome and a deterioration in those with abnormal (1)H-MRS and poor outcome.

CONCLUSIONS

a-EEG time course may be able to document the severity and the evolution of the cerebral damage following an HI event. a-EEG is related to the severity of cerebral injury as defined by (1)H-MRS and both examinations showed a good correlation with outcome. These data, obtained in non-cooled infants, may represent reference data for future investigations in cooled infants.