Biomedical subjects
Publications and source records attributed to W A Stewart.
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OBJECTIVE: To determine the bone mineral density (BMD) status of our juvenile dermatomyositis (DM) population and to compare the frequency of osteopenia in patients with active disease requiring corticosteroids with that in patients with inactive disease who are not receiving corticosteroids. METHODS: Medical charts of all children diagnosed as having juvenile DM at our institution between 1989 and 1999 were reviewed for demographic and clinical data, including disease activity and duration of corticosteroid therapy. BMD measurements of the lumbar spine (L1-L4) were performed using dual x-ray absorptiometry (DXA). Z scores were calculated from the BMD data for comparison with published normative data. RESULTS: A total of 15 patients were assessed: 10 with active disease, and 5 with inactive disease who had not taken corticosteroids for an average of 6.0 years (range 3.4-8.1 years). Baseline BMD measurements demonstrated osteopenia or frank osteoporosis in the majority of patients, including 6 of the 10 patients with active disease and 4 of the 5 patients whose disease was in remission. Fourteen patients had serial BMD measurements. Persistent or worsening osteopenia was documented in all patients who had ongoing active disease, except for 3 patients who had been treated with bisphosphonates because of vertebral compression fractures. CONCLUSION: Osteopenia is common in patients with juvenile DM, and it usually worsens with ongoing disease. It can persist for many years after the disease enters remission. Bisphosphonates appeared to beneficially affect bone mineralization in our patients. Treatment to prevent the long-term complications of osteoporosis in patients with juvenile DM should be considered and requires further study.
Estimating the rate and scale of dispersal is essential for predicting the dynamics of fragmented populations, yet empirical estimates are typically imprecise and often negatively biased. We maximized detection of dispersal events between small, subdivided populations of water voles (Arvicola terrestris) using a novel method that combined direct capture-mark-recapture with microsatellite genotyping to identify parents and offspring in different populations and hence infer dispersal. We validated the method using individuals known from trapping data to have dispersed between populations. Local populations were linked by high rates of juvenile dispersal but much lower levels of adult dispersal. In the spring breeding population, 19% of females and 33% of males had left their natal population of the previous year. The average interpopulation dispersal distance was 1.8 km (range 0.3-5.2 km). Overall, patterns of dispersal fitted a negative exponential function. Information from genotyping increased the estimated rate and scale of dispersal by three- and twofold, respectively, and hence represents a powerful tool to provide more realistic estimates of dispersal parameters.
The incidence of respiratory depression following treatment of prolonged seizures with benzodiazepines is variable in the literature. We retrospectively reviewed the charts of children treated for prolonged seizure over a one year period. Of the 56 seizures treated, 30 received lorazepam, 19 diazepam, and seven both drugs. Twenty two episodes (39%) of prolonged seizure were treated with multiple doses of benzodiazepines. In eight events (14%), there was documented respiratory depression following the administration of one or more doses of benzodiazepine; in six of these, multiple doses were given. The doses used were often at the low end or less than the recommended dose for treatment of status epilepticus. These data support suggestions that multiple doses of benzodiazepines increase the risk of respiratory depression.
Krabbe's disease is characterized by normal neonatal development with subsequent regression and profound, medically intractable irritability. Two female infants presented at 5 months of age with increasing irritability, abnormal motor control, and developmental regression. Investigations confirmed the diagnosis of Krabbe's disease. Maximal treatment of gastroesophageal reflux and nitrazepam 0.1 mg/kg by mouth three times daily were unsuccessful in controlling irritability. Morphine was initiated and titrated to 0.06 mg/kg by mouth every 6 hours in Patient 1 and 0.1 mg/kg by mouth every 8 hours in Patient 2, resulting in remarkably successful control of irritability. The diagnosis of Krabbe's disease is devastating for families and is compounded by the marked irritability. Management is difficult, but in these two infants, irritability was successfully controlled with low-dose morphine.
The ketogenic diet has demonstrated good efficacy in children with pharmacologically resistant seizures. Relatively few serious complications have been reported in the more than 70 years in which the diet has been used. We report a child who developed acute pancreatitis and died. A 9-year-old girl had a seizure disorder with associated developmental delay owing to glucose transport protein deficiency. The ketogenic diet with medium chain triglyceride oil had been initiated shortly after diagnosis in infancy. She was not on anticonvulsants. She presented in coma with decreased respiratory effort and shock, requiring resuscitation. Investigations were consistent with pancreatitis. Despite fluid resuscitation and inotropic support, she had prolonged hypotension and acidosis. She subsequently had a cardiac arrest and died. A postmortem examination confirmed hemorrhagic pancreatitis. Hypertriglyceridemia is a risk factor for developing acute pancreatitis. The high fat content of the ketogenic diet often causes hyperlipidemia. The outcome for this patient raises concern regarding a potential consequence of the ketogenic diet.
Delayed sciatic neuropathy due to pelvic reconstruction plate loosening following complex acetabular reconstruction in total hip arthroplasty seems not be have been previously reported. We identified a 79-year-old woman who developed progressive neurologic signs of entrapment 6 months following reconstruction of a pelvic discontinuity due to fracture nonunion caused by radiation necrosis. Magnetic resonance imaging of the lumbar spine was unrevealing and electromyography demonstrated a peripheral neurogenic process involving the sciatic nerve. Sciatic nerve exploration was done at 12 months after surgery finding a loose screw in the pelvic plate impinging the nerve. Substantial improvement in clinical symptoms resulted from removal and nerve release.
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One hundred thirty-seven polytetrafluoroethylene infrainguinal bypass grafts were performed over 2 years. The results were analyzed using univariate and multivariate analyses. Our operative mortality was 3.2% and the post-operative amputation rate was 5.8%. Forty-eight reconstructions were done for claudication, with a 5-year secondary patency rate of 64%, no early amputations, and a 2.9% (one limb) late amputation rate. Sixty-six reconstructions were done for rest pain with a 5-year secondary patency rate of 58% and a 3-year limb salvage rate of 77%. The 5-year secondary patency rate for 23 patients with trophic changes was 30%, and the 3-year limb salvage rate was 71%. Multivariate analysis identified the ankle-brachial index as the most important independent factor predicting both primary and secondary graft patency. The cumulative primary and secondary patency rates for patients with an ankle-brachial index of less than 0.5 at 78 months was 37% and 46%, respectively; and 57% and 68%, respectively for patients with an ankle-brachial index of 0.5 or more.
Interest has developed in using magnetic resonance (MR) imaging to monitor the volume of tissue destroyed by interstitial laser photocoagulation (ILP). In these experiments, ILP was induced in the normal brains of 9 anesthetized cats by delivering 1.5 W of continuous-wave Nd:YAG laser energy (1,064 nm) from a single 400-microns core optical fiber for 1,000 s. The irradiations were monitored using proton spin-echo MR imaging during and immediately after ILP and at postirradiation survival times of 2, 5, and 14 days. At 2 days postirradiation, the necrotic thermal lesion consisted of a central cavity surrounded by 2 concentric zones of coagulative necrosis, one dense and the other dispersed. The lesion shrank and the zonal appearance became less obvious over the 14 day survival period. An enhancing halo on contrast-enhanced T1-weighted images acquired immediately postirradiation best approximated the total lesion diameter at 2 days. These images also indicated that the volume of tissue destroyed during ILP corresponded better to the necrotic volume determined at 2 days than at 5 days and 14 days postirradiation. T2-weighted images acquired during and immediately after ILP consistently underestimated the total lesion diameter at 2 days.
We have used the CPMG pulse sequence to measure proton T2 values and water content in spinal cord and brain samples from Hartley guinea pigs inoculated to produce experimental allergic encephalomyelitis (EAE). Relaxation data were fitted using minuit, a non-linear curve fitting routine. Three exponentials provided the best fit to spinal cord data (10 ms (13%), 76 ms (57%), 215 ms (30%)) and two exponentials for brain tissue (10 ms (4%), 92 ms (96%)). Least squares algorithms were also used to analyse the spinal cord data in terms of discrete and smooth distributions of relaxation times. The discrete least squares solutions consisted of three to five isolated spikes between 0.010 and 0.300 s. This type of solution was difficult to interpret in terms of water reservoirs. Smooth solutions consisted of two broad peaks, a small peak with a T2 near 0.010 s and a larger peak near 0.100 s. The integral ratio of the larger to the smaller peak was 7.092 +/- 1.782 for normal tissue, and increased to a maximum of 16 with increasing parenchymal cellular infiltration and demyelination. The short T2 peak has been assigned to water in the hydration layers of the myelin sheath. The width of the longer T2 peak was sensitive to tissue heterogeneity. The least squares and smooth distribution analysis models could be used to distinguish samples with extensive parenchymal infiltration from normal tissue, even though only a maximum of 60% of the tissue was affected.(ABSTRACT TRUNCATED AT 250 WORDS)
Porcine stress syndrome (PSS) which is an example of malignant hyperthermia (MH) in swine has previously been attributed to oxidative stress primarily due to an inherited antioxidant abnormality in MH susceptible (MHS) animals. C-phenyl-N-tert-butyl nitrone (PBN), a free radical spin trap, was selected to investigate whether free radicals are involved in MH. If free radicals cause the MH stress attack, then PBN should alter the time required for the onset of the stress attack, or perhaps protect the animal from experiencing the stress attack. In vivo phosphorus-31 (31P) magnetic resonance spectroscopy (MRS) was used to monitor metabolism in three to four week old normal and MHS piglets administered halothane as the stress challenge. Malignant hyperthermia was not reproducibly induced by halothane anesthesia. For those animals which did develop MH a dramatic fall in the level of PCr and a rise in the level of Pi was detected by 31P MRS. Intravenous administration of PBN prior to halothane exposure had no effect on the number of animals experiencing the stress attack. PBN does not appear to prevent, delay or reverse the onset of halothane-induced MH in three to four week old MHS piglets. The primary events leading to the MH syndrome do not appear to be influenced by the intervention of the type of free radicals normally trapped by PBN.
Magnetic resonance (MR) imaging can be used to monitor the development of thermal lesions induced in tissue using interstitial laser photocoagulation (ILP). A potential application for ILP is the treatment of surgically inaccessible brain tumors. For the successful clinical application of MR-monitored ILP, it is necessary to relate MR images of ILP lesions to the actual induced lesions. In this preliminary study we performed ILP in the normal brains of anesthetized cats by delivering interstitially 1.0, 1.5, and 2.0 W of continuous-wave Nd:YAG laser energy (1,064 nm) for 1,000 s via a plane-cut 400 microns core optical fiber. At 48 h post-irradiation the lesions consisted of four sharply demarcated concentric zones of thermal damage. Lesion diameter increased linearly with delivered power. T2-weighted proton spin-echo images acquired during ILP showed a region of complete or near signal loss that underestimated the actual lesion at 48 h. Gadolinium-enhanced T1-weighted spin-echo images acquired immediately post-irradiation showed the actual lesion precisely.
Anterior tarsal tunnel syndrome is a rarely reported entrapment neuropathy of the deep peroneal nerve under the extensor retinaculum at the ankle. The roof of the tunnel is the inferior extensor retinaculum. The floor is the fascia overlying the talus and navicular. Within the tunnel are four tendons, an artery, a vein, and the deep peroneal nerve. Two patients with foot pain and dysesthesias had prolonged peroneal distal latencies with reduced amplitudes from the extensor digitorum brevis (EDB). Electromyographic (EMG) abnormalities were confined to the EDB. Both patients underwent surgical decompression of the anterior tarsal tunnel with reduction of their pain and dysesthesias. If present, an accessory peroneal nerve, which does not go through the tunnel, can mask EMG findings in the EDB. Diagnosing anterior tarsal tunnel syndrome can also be difficult if there is a tendency to assume that fibrillation potentials in the EDB are due to shoe wear and prolonged peroneal latencies to cool extremities.
The potential use of quantitative MRI to characterize early, as well as late, immune-mediated lesions of multiple sclerosis (MS) has been investigated. Experimental allergic encephalomyelitis (EAE) was induced in 4 male Macaca fascicularis monkeys, and the development of the disease followed using quantitative MRI at 0.15 Tesla. Serial scans were recorded daily, beginning at day 9 after inoculation. Lesions were detected before the onset of clinical signs, due to an elevation in the spin-lattice (T1) and spin-spin (T2) relaxation times. The T1 and T2 values from the lesions were shown to increase over time, indicative of progressive change at a molecular level. The appearance of any new lesions and any changes in existing ones were noted; this allowed dating of the lesions postmortem. Pathological correlation showed the long T1 and T2 values to be associated with the presence of inflammation, demyelination and haemorrhagic necrosis. Microscopically similar lesions had the same MRI characteristics. In addition, these studies showed the oldest lesions to be the most haemorrhagic; this is contrary to the belief that haemorrhage is a secondary event in EAE. The results show that quantitative MRI is sensitive to variable pathology, and has the potential for use in characterizing the pathological progression in MS.
The case is presented of a 15-year-old boy with a mixed nongerminomatous germ-cell tumor of the pineal region associated with elevated cerebrospinal fluid and serum levels of the beta subunit of human chorionic gonadotropin. Treatment consisted of initial subtotal resection followed by radiotherapy and systemic chemotherapy with cisplatin, vinblastine, and bleomycin. The patient is alive without evidence of tumor 37 months after his initial diagnosis. A literature review of intracranial embryonal carcinoma and choriocarcinoma provided the rationale for a combined-modality approach to this otherwise lethal neoplasm.
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