Metallic neurosurgical implants for cranial reconstruction and fixation: assessment of magnetic field interactions, heating and artefacts at 3.0 Tesla

The objective of this study was to evaluate the magnetic resonance imaging (MRI) compatibility of metallic neurosurgical implants commonly used for cranial reconstruction and fixation, in association with a 3.0 Tesla (T) MR system. Ten metallic neurosurgical implants used for cranioplasty operations were evaluated. The implants were tested ex vivo for magnetic field interactions (translational attraction and torque), heating (using saline and gel phantoms), and artefact production [using dual echo spin echo (DSE) and gradient echo (GRE) sequences] at 3.0 Tesla. None of the implants displayed translational attraction or torque, and heating was physiologically insignificant (maximal temperature elevation was 0.5 degrees C). MR artefacts were minimal with spin echo sequences; gradient echo sequences produced much larger artefacts. The neurosurgical implants evaluated in this study should not present a risk to patients undergoing MRI in the 3.0 T MR system. Although the implants do produce susceptibility artefacts, especially with gradient echo sequences, useful imaging should still be possible.

Imaging of cerebral blood flow and metabolism in brain injury in the ICU

The heterogeneity of the initial insult and subsequent pathophysiology has made both the study of human head injury and design of randomised controlled trials exceptionally difficult. The combination of multimodality bedside monitoring and functional brain imaging positron emission tomography (PET) and magnetic resonance (MR), incorporated within a Neurosciences Critical Care Unit, provides the resource required to study critically ill patients after brain injury from initial ictus through recovery from coma and rehabilitation to final outcome. Methods to define cerebral ischemia in the context of altered cerebral oxidative metabolism have been developed, traditional therapies for intracranial hypertension re-evaluated and bedside monitors cross-validated. New modelling and analytical approaches have been developed.

Physiological thresholds for irreversible tissue damage in contusional regions following traumatic brain injury

Cerebral ischaemia appears to be an important mechanism of secondary neuronal injury in traumatic brain injury (TBI) and is an important predictor of outcome. To date, the thresholds of cerebral blood flow (CBF) and cerebral oxygen utilization (CMRO(2)) for irreversible tissue damage used in TBI studies have been adopted from experimental and clinical ischaemic stroke studies. Identification of irreversibly damaged tissue in the acute phase following TBI could have considerable therapeutic and prognostic implications. However, it is questionable whether stroke thresholds are applicable to TBI. Therefore, the aim of this study was to determine physiological thresholds for the development of irreversible tissue damage in contusional and pericontusional regions in TBI, and to determine the ability of such thresholds to accurately differentiate irreversibly damaged tissue. This study involved 14 patients with structural abnormalities on late-stage MRI, all of whom had been studied with (15)O PET within 72 h of TBI. Lesion regions of interest (ROI) and non-lesion ROIs were constructed on late-stage MRIs and applied to co-registered PET maps of CBF, CMRO(2) and oxygen extraction fraction (OEF). From the entire population of voxels in non-lesion ROIs, we determined thresholds for the development of irreversible tissue damage as the lower limit of the 95% confidence interval for CBF, CMRO(2) and OEF. To test the ability of a physiological variable to differentiate lesion and non-lesion tissue, we constructed probability curves, demonstrating the ability of a physiological variable to predict lesion and non-lesion outcomes. The lower limits of the 95% confidence interval for CBF, CMRO(2) and OEF in non-lesion tissue were 15.0 ml/100 ml/min, 36.7 mumol/100 ml/min and 25.9% respectively. Voxels below these values were significantly more frequent in lesion tissue (all P < 0.005, Mann-Whitney U-test). However, a significant proportion of lesion voxels had values above these thresholds, so that definition of the full extent of irreversible tissue damage would not be possible based upon single physiological thresholds. We conclude that, in TBI, the threshold of CBF below which irreversible tissue damage consistently occurs differs from the classical CBF threshold for stroke (where similar methodology is used to define such thresholds). The CMRO(2) threshold is comparable to that reported in the stroke literature. At a voxel-based level, however (and in common with ischaemic stroke), the extent of irreversible tissue damage cannot be accurately predicted by early abnormalities of any single physiological variable.

Munchausen syndrome by proxy

Munchausen syndrome by proxy is the most difficult form of child abuse. It carries substantial morbidity and mortality. The diagnosis relies on appropriate suspicion and careful investigation. The psychological illness/need of the perpetrator is the main clinical feature. Early recognition and appropriate intervention prevent further abuse and criminal actions.

Morbidity in breast-fed and artificially fed infants. II

The advantages of breast-feeding in reducing morbidity was previously shown in a group of rural infants. Those observations are extended and refined. The protection afforded by breast-feeding is greatest during the early months, increases with the duration of breast-feeding, and appears to be more striking for serious illness. It operates independently of the effect of associated factors such as socioeducational status, family size, day-care exposure, and birth weight.

Morbidity in breast-fed and artificially fed infants

One-half of the healthy newborn infants at a rural medical center were initially breast fed; the proportion declined to 4% by one year of age. Breast-feeding was associated with significantly less illnes during the first year, especially if continued beyond 41/2 months of age. Breat-fedding was associated with a higher level of parental education and, by inference, higher socioeconomic status. The health advantage of breast-feeding was still evident after controlling for parental educational status. In better educated families the difference in significant illness between infants who were artifically fed and those who were breast fed for prolonged periods of time was two- to threefold.

Lymphomas and animal-protein consumption

Geographic comparison reveals a positive correlation between consumption of animal protein, particularly bovine protein, and lymphoma mortality. Allied observations suggest that excessive consumption of animal protein may, through antigen absorption and chronic persistent stimulation, impose considerable wear and tear on lymphoid tissue and thereby encourage malignant changes.

Childhood hypersensitivity pneumonitis due to dove antigens

A case of hypersensitivity pneumonitis due to doves is reported and compared with other cases due to dove or pigeon antigens reported in children. The diagnosis is substantiated by the presence of precipitating antibody to dove and pigeon serum, clinical improvement after contact with the doves was broken, and a positive response to inhalation challenge with pigeon serum. The insidious nature of this disease is emphasized as well as the importance of having detailed environmental information in children with unexplained respiratory disease.