Pediatric functional magnetic resonance imaging (fMRI): issues and applications

Functional magnetic resonance imaging (fMRI) represents a useful tool for studying brain functions and the neural basis of cognition in healthy children and in those in disease states. Functional magnetic resonance imaging is a relatively new use of existing magnetic resonance imaging technology that allows scientists and practitioners to observe the brain at work. It is based on the observation that local increases in blood flow are related to neural activity. This review considers principles of functional magnetic resonance imaging, issues relevant to imaging children, and research using functional magnetic resonance imaging to examine cognitive processing in pediatric populations. The focus is specifically on language studies to review strengths, limitations, and practical applications of this technology with children. Future directions for functional magnetic resonance imaging are presented.     

Ascorbate decreases Fabry cerebral hyperperfusion suggesting a reactive oxygen species abnormality: an arterial spin tagging study

PURPOSE: To test the hypothesis that reactive oxygen species contribute to the cerebral hyperperfusion in Fabry disease. MATERIAL AND METHODS: We examined the effect of intravenous injection of ascorbate on cerebral blood flow (CBF) using magnetic resonance arterial spin tagging. Nineteen patients with Fabry disease and 15 control subjects were studied as part of a randomized double-blind placebo-controlled trial of enzyme replacement therapy (ERT). RESULTS: Vertebro-basilar hyperperfusion was observed in patients with Fabry disease. A decrease in systemic ascorbate levels relative to healthy controls was found in the patients. CBF decreased after ascorbate infusion in both control subjects and patients treated with ERT. The placebo group had a significantly delayed decrease in the CBF response after ascorbate infusion. Myeloperoxidase levels were elevated in Fabry patients, consistent with ongoing inflammatory processes in these patients. CONCLUSION: Increased CBF in Fabry disease may be related to increased production of reactive oxygen species, while low plasma ascorbate levels suggests a global redox imbalance. These abnormalities were improved by ERT. These observations have implications regarding oxidative processes contributing to accelerated atherosclerosis in Fabry disease.     

Renal artery aneurysms: diagnosis and surveillance with 3D contrast-enhanced magnetic resonance angiography

The use of contrast-enhanced magnetic resonance angiography (CE-MRA) in screening for suspected renovascular disease may result in increased detection of renal artery aneurysms. We report the CE-MRA findings at diagnosis and follow-up in nine hypertensive patients with unsuspected renal artery aneurysms. A search of renal CE-MRAs of suspected renal artery stenosis at two tertiary referral institutions over 5 1/2 years was performed. All patients underwent CE-MRA using a fast spoiled gradient echo technique (TR/TE/flip 5.1–6 ms/1.6 ms/40°), scan matrix 512×196–224, 1 excitation, FOV 400–450 mm×266–360 mm, 32–50 mm×1.5–2 mm interpolated slices. Gadolinium-enhanced 3D images were obtained during breath holding. Images were evaluated and post-processed on a workstation by a single operator. Nine patients with renal artery aneurysms out of a total of 912 cases were found, all involving the main artery or divisions proximal to the renal hilum. Renal arteries distal to the hilum were not consistently visualized. The aneurysm was bilobed in one patient, multilocular in another and unilocular in all others. Severe stenosis of the renal artery proximal to the aneurysm was present in two. Four patients underwent follow-up showing no change in aneurysm size. CE-MRA reliably identifies aneurysms involving the main renal arteries and proximal branches. Once diagnosed, CE-MRA offers a safe, non-invasive modality for surveillance of aneurysm if active intervention is not planned.     

Development and psychometric evaluation of the patient knowledge of,and attitudes and behaviours towards pressure ulcer prevention instrument (KPUP)

The Patient Knowledge of, and Attitude and Behaviour towards Pressure Ulcer Prevention Instrument (KPUP) was developed and validated using a two‐stage prospective psychometric instrument validation study design. In Stage 1, the instrument was designed, and it is psychometrically evaluated in Stage 2. To establish content validity, two expert panels independently reviewed each item for appropriateness and relevance. Psychometric evaluation included construct validity and stability testing of the instrument. The questionnaire was administered to a convenience sample of 200 people aged more than 65 years, living independently in the community; reliability and stability were assessed by test/retest procedures, with a 1‐week interval. Mean knowledge scores at ‘test’ were 11.54/20 (95% CI = 11.10‐11.99, SD: 3.07), and ‘retest’ was 12.24 (95% CI = 11.81‐12.66, SD: 2.93). For knowledge, correlation between the test/retest score was positive (r=. 60), attitude section‐inter‐item correlations ranged from r = −.31 to r = .57 (mean intraclass correlation coefficient of r = .42), and internal consistency for the retest was the same as the test (α = .41 for the eight items). For health behaviours, individual inter‐item correlations for test items ranged from r = −.21 to r = .41 for the 13 standardised items. Psychometric testing of the KPUP in a sample of older persons in the community provided moderate internal consistency and general high test‐retest stability.     

Iliac artery rupture related to balloon insertion for placenta accreta causing maternal hemorrhage and neonatal compromise

Purpose

The use of internal iliac artery balloons for prevention of hemorrhage in cases of placenta accreta is increasing. Most described complications of this technique are maternal and thromboembolic in nature. Complications related to vascular rupture are rare, their presentation is not well described, and the resultant neonatal consequences are infrequently reported.

Clinical features

A 35-yr-old term parturient with suspected placenta accreta underwent prophylactic endovascular placement of iliac balloons prior to Cesarean delivery. The patient complained of contraction-like pain during balloon placement, and an arterial wall tear was discovered after abdominal incision. This produced significant maternal bleeding and the birth of a neonate with an umbilical venous pH of 6.95 and Apgar scores of 3 and 7.

Conclusion

In addition to the known maternal risks, fetal risks must be considered when planning the placement of endovascular iliac balloons during pregnancy. We recommend continuous monitoring of maternal and fetal status when performing the procedure. Contraction-like pain during placement should raise the suspicion of arterial disruption.     

Plexiform neurofibromatosis of the mediastinum: CT appearance

We studied the CT findings in four patients with pathologically proved thoracic plexiform neurofibromatosis. In all four patients, CT showed an infiltrative process and masses that involved the mediastinum along the distribution of the sympathetic chains, phrenic, and vagus nerves. The lesions had lower attenuation values than did chest-wall muscle. In one patient, CT revealed calcifications and peripheral enhancement of nodular components after IV infusion of contrast material. In the appropriate clinical setting, CT detection of lesions in the distribution of the mediastinal nerves strongly favors the diagnosis of plexiform neurofibromatosis.     

The relationship between pulmonary artery pressure and pulmonary artery diameter in pulmonary hypertension

The pulmonary arteries dilate in response to many factors, principally increased pressure and flow. In patients who have pulmonary arterial hypertension but no increase in flow, we have compared main pulmonary artery size at computed tomography with pulmonary haemodynamic data obtained during right heart catheterisation. In patients with primary pulmonary hypertension and chronic thromboembolic pulmonary hypertension, dilatation correlated with raised pulmonary vascular resistance and reduced cardiac output but not with mean arterial pressure. In patients with chronic lung disease no correlations were shown though a trend between raised pressure and size was observed. We speculate that pulmonary artery compliance is an important factor which determines the degree of dilatation in response to raised pressure. Estimations of pressure cannot be made from measurements of pulmonary artery size without knowledge of the underlying lung disease.     

Histologic Findings One Year After Positive Crossmatch or ABO Blood Group Incompatible Living Donor Kidney Transplantation

Recent protocols have allowed successful positive crossmatch (+XM) and ABO incompatible (ABOI) kidney transplantation, although their long-term outcome is not clear. To begin to assess this issue we compared protocol biopsies performed 12 months posttransplant in 37 +XM, 24 ABOI and 198 conventional allografts. Although the majority in all three groups had only minimal histologic changes, transplant glomerulopathy (TG) was significantly increased in +XM (22% vs. 13% ABOI vs. 8% conventional, p = 0.015), and correlated with prior humoral rejection (HR) by multivariate analysis (odds ratio 17.5, p < or = 0.0001). Patients with a prior history of HR also had a significant increase in interstitial fibrosis (No HR 54% vs. HR 86%, p = 0.045). In the absence of HR no difference in histologic changes was seen between groups, although all three groups had a demonstrable mild increase in interstitial fibrosis from biopsies performed at the time of transplant. Thus, although HR is associated with an increase in TG, in its absence allograft histology is similar in +XM, ABOI and conventional allografts 1 year posttransplant.     

Interval laparoscopic appendectomy in children

BACKGROUND: Conservative management of advanced complicated appendicitis in children is becoming more common. Formation of an appendiceal mass or abscess may mitigate against urgent appendectomy during the acute stage, and conservative treatment followed by interval appendectomy has been advocated. We present our experience of interval laparoscopic appendectomy in our institution. MATERIALS AND METHODS: All children who were offered interval laparoscopic appendectomy between January 2000 and December 2004 were included. Retrospective case note analysis was performed and data collected included demographics, duration of symptoms, method of diagnosis, days of antibiotics, length of interval, operative time, length of hospital stay (conservative treatment and interval laparoscopic appendectomy), analgesia requirements, complications, and histology. RESULTS: Thirty-six children, median age 8 years (range, 1-15 years) diagnosed with appendiceal mass or abscess were offered interval laparoscopic appendectomy by two surgeons in our institution: one patient declined interval laparoscopic appendectomy. Median antibiotic treatment was 10 days (range, 3-23 days). Median length of stay for conservative treatment was 6 days (range, 1-27 days). Five children required percutaneous drainage. For the 35 children who had interval laparoscopic appendectomy, the median interval was 93 days (range, 34-156 days) and median operative time was 55 minutes (range, 25-120 minutes). Median length of stay for interval laparoscopic appendectomy was 1 day (range, 1-3 days). There were no complications following interval laparoscopic appendectomy. CONCLUSION: Interval laparoscopic appendectomy can be safely performed in children, is associated with a short hospital stay and minimal morbidity, analgesia, and scarring following conservative management of appendiceal mass or abscess. Interval laparoscopic appendectomy eliminates the risk of recurrent appendicitis and serves to excise undiagnosed carcinoid tumors. In future it may be possible to perform interval laparoscopic appendectomy as a day-case procedure in selected patients.