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Biomedical subjects

D Pang

Publications and source records attributed to D Pang.

At least 19 recordsLinked to original sources
PubMed1996

Mortality study of nickel platers with special reference to cancers of the stomach and lung, 1945-93.

OBJECTIVES: To re-examine mortality patterns in a cohort of nickel platers with no history of chromium plating. METHODS: All 284 men first employed by the company in 1945-75 with a minimum employment of three months in the nickel plating department were identified. Workers who had worked in the chromium plating or nickel/chromium plating departments were excluded. Standardised mortality ratios (SMRs), P values, and 95% confidence intervals were calculated. Poisson regression was used to carry out statistical modelling of mortalities within the cohort (internal standard). Four variables were considered to have the potential to influence mortality within the cohort: attained age (age at follow up or age at death), year of starting nickel work, period of follow up (measured from the first period of work with nickel exposure), and duration of exposure to nickel. RESULTS: The only significant difference between observed and expected numbers, when investigated by site of cancer and by broad non-cancer groupings, was that for stomach cancer (observed eight, expected 2.49, SMR 322). CONCLUSIONS: The study provides only weak evidence that nickel plating is associated with an excess risk of stomach cancer. This cohort of nickel platers does not seem to have experienced any discernible risk of occupational lung cancer. Other studies of nickel platers rather than nickel/chromium platers would be useful.

Cohort Studies↗
PubMed1996

The role of somatosensory evoked potentials in the evaluation of spinal cord retethering.

Early detection of clinically significant spinal cord retethering is of paramount importance for the preservation of neurologic function in patients with repaired spinal dysraphic lesions. We retrospectively analyzed 90 children who were followed with serial peroneal somatosensory evoked potentials (SEPs) after a repair of their spinal dysraphic lesions with the objective of evaluating whether SEPs were a useful way of monitoring these children to facilitate early detection of clinically significant retethering. Three hundred and nine studies were performed on these children yielding a mean of 3.4 studies per patient. The median time between SEP studies was 13 months. A clinical examination was performed at the time each SEP was done. Sixty-one patients (68%) had a myelomeningocele; 25 (28%) had a lipomyelomeningocele while other types of dysraphic lesions were found in the remaining 4%. Nineteen patients (21%) had no change in serial SEPs; 7 of these 19 (37%) had a deterioration in clinical status while the SEPs were stable. Twenty-six patients (29%) showed improvement in serial SEPs, however, 3 of the 26 had clinical worsening at the time SEPs improved. SEPs deteriorated in 45 patients (50%); 13 of the 45 had an associated clinical deterioration, and the remaining 32 were stable clinically. Twenty-three patients (26%) had a clinical deterioration; of these only 13 had a corresponding deterioration in SEPs, 7 patients had stable SEPs while 3 had improvement in SEPs at the time of clinical deterioration. This results in a false-positive rate of 71% and a false-negative rate of 43%. We conclude that serial SEPs do not correlate well with clinical status and are not a useful modality for monitoring patients at risk for retethering.

Adolescent↗
PubMed1996

Comparison of simultaneous versus delayed ventriculoperitoneal shunt insertion in children undergoing myelomeningocele repair.

The timing of cerebrospinal fluid shunt insertion for those neonates with hydrocephalus in association with myelomeningocele remains controversial. To examine whether there was a difference in either the complication rate or mean hospital stay for neonates undergoing myelomeningocele repair and shunting under the same anesthetic (simultaneous group) versus those in whom shunt insertion was delayed for several days after myelomeningocele closure (sequential group), we reviewed the results obtained with these two approaches in a series of 69 consecutive patients who underwent both myelomeningocele closure and shunt insertion at our institution between 1987 and 1993. Twenty-one infants underwent simultaneous myelomeningocele repair and shunting, and 48 underwent sequential procedures. The decision to shunt concurrently with myelomeningocele repair rather than in a delayed fashion was based primarily on surgeon preference rather than initial head circumference, which did not differ significantly between the two groups. The frequency and type of hydrocephalus-related complications (e.g., wound leak, cerebrospinal fluid infection, or shunt malfunction) that occurred during the first 6 months after myelomeningocele closure were compared between the two groups. Neither the overall frequency of complications nor the frequency of cerebrospinal fluid infection, shunt malfunction, or symptomatic Chiari malformation differed significantly between the two groups. In contrast, there was a significantly higher rate of myelomeningocele wound leak in the sequential group versus the simultaneous group (eight versus zero; P = .05). Mean hospital stay for the sequential group was also significantly longer than the simultaneous group (22 days versus 13 days; P = .05). These results suggest that simultaneous myelomeningocele repair and ventriculoperitoneal shunt insertion reduces hospital stay and back wound morbidity in those patients with evidence of hydrocephalus at birth, without an inordinate increase in shunt-related complications.

Cerebrospinal Fluid Shunts↗
PubMed1995

Surgical complications of open spinal dysraphism.

The embryogenesis, closure technique, and preoperative preparation of open myelomeningocele are described in this article. Both early and late complications of myelomeningocele closure are discussed with respect to predisposing factors, diagnosis, treatment, and prevention. These complications include worsened neurological level, wound dehiscence, wound infection, cerebrospinal fluid leak, postoperative ileus, symptomatic Chiari malformation, shunt infection, necrotizing enterocolitis, and problems related to kyphectomy.

Female↗
PubMed1995

Split cord malformations.

Previous classifications of split cord malformations (SCM's), including such terms as diastematomyelia and diplomyelia, have done little to foster a true understanding of these disorders. The authors instead propose a unifying classification in which all SCM's share a common embryogenesis. SCM's are divided into two types, based upon the composition of the dural coverings and intervening mesenchymal tissue. Type I malformations are composed of two dural sacs and a bony or fibrocartilaginous spur; Type II malformations are composed of a single dural sac and intradural fibrous bands. In either case, the intervening mesenchymal elements contribute to progressive neurologic, urologic, and orthopedic deterioration from spinal cord tethering. The natural history of these lesions supports an early and aggressive operative approach to untether the spinal cord before clinical deterioration begins.

Adolescent↗
PubMed1995

Supplementation with flaxseed oil versus sunflowerseed oil in healthy young men consuming a low fat diet: effects on platelet composition and function.

OBJECTIVE: To compare the effects of supplementing a low fat diet with an alpha-linolenic acid-rich (C18:3 n-3) oil with a linoleic acid-rich (C18:2 n-6) oil on platelet composition and function. DESIGN: Prospective study with random allocation to one of the two oils. SETTING: Free-living study. SUBJECTS: Eleven healthy young males recruited from within the University. INTERVENTIONS: Subjects were allocated to consume 40 g of either flaxseed oil (n = 5) or sunflowerseed oil (n = 6) daily for 23 days. Fasting blood samples were collected at commencement and completion of supplementation for analysis of platelet fatty acids and platelet aggregation. RESULTS: The platelet eicosapentaenoic acid (EPA) more than doubled in the group taking flaxseed oil (P < 0.05) but was unchanged in the sunflowerseed group. As a result the platelet EPA:arachidonic acid ratio, considered a marker for thromboxane production and platelet aggregation potential, increased in the flaxseed group (P < 0.05). The aggregation response induced by 0.75 and 2 micrograms of collagen was decreased in those taking flaxseed oil (P < 0.05). CONCLUSION: This study provides further evidence that consumption of alpha-linolenic acid-rich oils may offer protective effects against cardiovascular disease over linoleic acid-rich oils via their ability to decrease the tendency of platelets to aggregate.

Adult↗
PubMed1995

[National notification of incidence of chronic occupational poisoning during 1984-1993].

Incidence and distribution of chronic occupational poisoning caused by toxic chemicals during 1984 to 1993 throughout the country were summarized and analyzed. Totally, 28,901 cases of chronic occupational poisoning were notified during this period. Lead, benzene and trinitrotoluene were three major toxic chemicals which caused poisoning, with chronic lead poisoning listed the first place, accounting for 47.5% of the total cases. Most of the cases distributed in Laioning, Hunan and Jiangsu Provinces, and 75.4% of the cases occurred in machinery, chemical, metallurgical, non-ferrous, light industries, etc. Incidence of poisoning presented a decreased trend during the past 10 years and the reason of it was described in the paper. The authors indicated that quality assurance in notification of occupational diseases depended on regular implementation of the work in prevention and treatment of occupational diseases.

Benzene↗
PubMed1994

Dissemination of low grade intracranial astrocytomas in children.

The authors report three cases of histologically benign intracranial astrocytomas that developed in children and disseminated within the neuraxis. Multicentric disease was evident at the time of diagnosis in two of these patients, one of whom subsequently developed peritoneal seeding of tumor after placement of a ventriculoperitoneal shunt. To our knowledge, this latter represents the first documented case of extraneural seeding of a benign astrocytoma. All three children are currently alive and well 17-117 months after the diagnosis of tumor dissemination. We review the literature regarding this uncommon problem and discuss the pathophysiology and treatment options. Our results indicate that the presence of disseminated disease may not preclude long term survival, provided the lesions are truly benign histologically and that adjuvant therapy is instituted promptly.

Astrocytoma↗
PubMed1994

Magnetic resonance imaging in the evaluation of spinal cord injury without radiographic abnormality in children.

Seven children aged birth to 17 years with spinal cord injury without radiographic abnormality (SCIWORA) were studied with magnetic resonance imaging (MRI) between 3 hours and 16 days after the injury. There were six cervical cord injuries and one thoracic cord injury. The MRI findings were divided into two groups: extraneural and neural. The extraneural findings included one case of anterior longitudinal ligament disruption and anterior C6-C7 disc herniation associated with hyperextension; one case of posterior longitudinal ligament disruption and C2-C3 disc herniation associated with lateral flexion; and one case of C6-C7 disc abnormality consistent with increased water content occurring with hyperflexion. These ligament and disc injuries did not correlate with late instability. The neural MRI findings included one case of cord transection with rostral cord stump hemorrhage and one case of hemorrhage involving the majority of the cord's transverse diameter, both associated with permanent complete cord injuries; one case of hemorrhage involving a minor portion of the cord and of the brain stem's transverse diameter associated with a severe partial cord injury but subsequent incomplete improvement; one case of edema without hemorrhage associated with Brown-Séquard syndrome and subsequent incomplete improvement; and three cases of normal cord signal and outline. Two of the latter patients had mild cord injuries that recovered completely. In the third, a child with complete T12 sensorimotor paralysis at presentation, the normal MRI findings predicted the subsequent complete recovery. No extraaxial compressive lesion was demonstrated in these seven children.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Low-pressure hydrocephalic state and viscoelastic alterations in the brain.

Most shunt-dependent hydrocephalic patients present with predictable symptoms of headache and mental status changes when their cerebrospinal fluid shunts malfunction. Their intracranial pressure (ICP) is usually high, and they usually respond to routine shunt revision. This report describes 12 shunted patients who were admitted with the full-blown hydrocephalic syndrome but with low to low-normal ICP. All 12 patients had been maintained previously on medium-pressure shunts. Their symptoms included headache, lethargy, obtundation, and cranial neuropathies. At peak symptoms, their ventricular sizes were large (ventricular/biparietal ratio of 0.35 to 0.45) in six and massive (ventricular/biparietal ratio > 0.45) in six and their ICPs ranged from 2.2 to 6.6 mm Hg, with a mean of 4.4 +/- 1.3 mm Hg (+/- standard deviation), i.e., below or well within the pressure range of their shunts. The pressure volume index of three patients at peak symptoms ranged from 39.2 to 48.5 ml, with a mean of 43.9 +/- 4.6 ml, which represents a 190% increase from the predicted normal value. Seven patients failed to improve with multiple shunt revisions, including the use of low-pressure valves. In 11 patients, symptoms and ventriculomegaly were not reversed except with prolonged external ventricular drainage at subzero pressures (mean external ventricular drainage nadir pressure of -5.7 +/- 3.6 mm Hg, for a mean period of 22.2 days). During external ventricular drainage treatment, symptoms correlated only with ventricular size and not with ICP. All 11 were subsequently treated successfully with a new medium- or low-pressure shunt. One patient was treated successfully with prolonged shunt pumping. We postulate that: 1) the development of this low-pressure hydrocephalic state is related to alteration of the viscoelastic modulus of the brain, secondary to expulsion of extracellular water from the brain parenchyma, and to structural changes in brain tissues due to prolonged overstretching; 2) certain patients are susceptible to developing low-pressure hydrocephalic state because of an innate low brain elasticity due to bioatrophic changes; 3) low-pressure hydrocephalic state symptoms are due not to pressure changes but to brain tissue distortion and cortical ischemia secondary to severe ventricular distortion and elevated radial compressive stresses within the brain; and 4) treatment must be directed toward allowing the entry of water into the brain parenchyma and the restoration of baseline brain viscoelasticity.

Adolescent↗
PubMed1994

The long-term outcome in children with late-onset aqueductal stenosis resulting from benign intrinsic tectal tumors.

Benign intrinsic tumors arising in the dorsal midbrain have long been recognized as a potential cause of late-onset aqueductal stenosis. Where histopathological studies of such lesions have been performed, the majority have been reported to be low-grade gliomas. Because these tumors often present with a paucity of neurological findings and a characteristic radiographic appearance and because there has been substantial uncertainty regarding their potential for long-term progression, the authors have routinely deferred biopsy and/or radiotherapy for these lesions until there has been clear-cut evidence of disease progression. Herein, the authors report their experience with 16 children manifesting this syndrome who were treated between 1979 and 1992. The patients ranged in age from 6 months to 14 years at presentation (median 9.75 years). In general, symptoms of increased intracranial pressure developed insidiously; three of the older children had exhibited profound macrocephaly since infancy, which predated the onset of other symptoms of hydrocephalus by several years. Only one of the 16 children showed evidence of brain-stem dysfunction at presentation, a partial Parinaud's syndrome that resolved following placement of a ventriculoperitoneal shunt. In 12 patients, the tumor was detected by magnetic resonance (MR) imaging at initial evaluation as a bulbous enlargement of the tectal plate. In four patients who presented before the advent of MR imaging, initial computerized tomography (CT) scans failed to delineate the tectal lesion convincingly; however, subsequent MR studies clearly demonstrated the presence of an intrinsic tectal mass. All 16 patients underwent cerebrospinal fluid diversion initially, with conservative management of the tectal lesion and close long-term follow-up monitoring. Four children ultimately demonstrated clinical signs of progressive tumor growth with the insidious onset of partial or complete Parinaud's syndrome, despite the presence of a functioning shunt. The median interval to symptom progression was 7.8 years from the time of shunt insertion and 11.5 years from the onset of initial symptoms and signs of hydrocephalus. Follow-up CT and MR studies demonstrated obvious tumor enlargement in three of the four patients who then underwent stereotactic or open biopsy. The histological diagnosis in these three was benign mixed glioma, anaplastic astrocytoma, and low-grade astrocytoma. All four patients with clinical evidence of disease progression were treated with conventional radiotherapy; the patient with an anaplastic astrocytoma also received focal stereotactic radiosurgery. These patients subsequently remained clinically stable, with three showing tumor regression and one showing stable disease on serial MR studies (median follow-up period from tumor progression, 4.25 years).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1994

Accurate placement of coronal ventricular catheter using stereotactic coordinate-guided free-hand passage. Technical note.

Long-term patency of the ventricular catheter of a cerebrospinal fluid shunt depends on the positioning of the hole-bearing segment of the catheter. Placement of this segment near the choroid plexus or injured ependyma increases the probability of obstruction. Proper positioning for a coronal shunt in turn depends on the ventricular catheter length and target coordinates. The authors describe a method of calculating the catheter length based on bone landmarks on skull radiographs, and a technique for accurate ventricular catheter placement using free-hand passage guided by simple stereotactic coordinates based on visible and palpable surface anatomy. The insertion trajectory is aligned with the coronal obliquity of the lateral ventricle so that, even with slit ventricles, the entire hole-bearing segment of the catheter can be reliably situated within the anterior horn. The predetermined catheter length also fixes the tip at the foramen of Monro, away from the choroid plexus and injured ependyma. Of 160 children undergoing ventriculoperitoneal shunt insertion using this technique, only three required catheter revision during a mean follow-up period of 39 months. Radiographic grading of the ventricular catheter position in 112 children showed a satisfactory placement rate of 93.2%; all three children with occlusion showed poor catheter positioning. Thus, this method results in accurate ventricular catheter placement with a 1.9% obstruction rate, which compares favorably to the 16% to 18% incidence of proximal obstruction reported in the literature. This technique is applicable to patients of all ages but is particularly suitable for children because of the greater variability in head size.

Adolescent↗
PubMed1994

Intracranial infantile myofibromatosis.

Infantile myofibromatosis is a proliferative disorder of infancy and early childhood characterized by nodular or diffuse growth of lesions that are comprised of a mixture of mesenchymal elements within the skin, subcutaneous tissues, skeletal muscle, bone, and/or visceral organs. Although these pseudotumors are considered to be the most common fibrous "neoplasm" of infancy, central nervous system involvement is reportedly rare. During the last 7 years, the authors have treated three children with intracranial myofibromas who presented at 6 weeks, 7 months, and 3 3/4 years of age, respectively. Each child had a large calvarial mass that produced significant brain compression despite a paucity of neurological signs. On computerized tomography, these tumors were isodense to brain tissue, enhanced strongly with intravenous contrast material, and showed smoothly marginated bone erosion without surrounding sclerosis. On magnetic resonance imaging, the tumors were hypointense on T1-weighted images, with dense enhancement following the administration of intravenous contrast medium, and hyperintense on T2-weighted images. At operation, the tumors were highly vascular and appeared to arise from within the leaves of the dura, eroding through the overlying bone, but not violating the galeal or arachnoidal layers. Two of the lesions were adherent to major dural venous sinuses. Both of these lesions were completely resected in continuity with the involved dura, and have not recurred 6 years and 1 year, respectively, postoperatively. However, in one patient in whom the involved dura was not resected at the initial procedure, the tumor recurred rapidly. A complete excision of the tumor and involved dura was then performed and the patient is now recurrence-free, 5 1/2 years after the second surgical resection. All patients tolerated resection well, but two have required cranioplasty for persistent calvarial defects. The surgical experience with these lesions is reviewed and the distinctive features of their clinical presentation, radiographic appearance, operative management, and outcome are discussed.

Brain Neoplasms↗
PubMed1994

The influence of fixed rotational deformities of the femur on the patellofemoral contact pressures in human cadaver knees.

Patellofemoral contact pressures resulting from fixed rotational deformities of the femur were studied in human cadaver knees. The increase in the degree of fixed rotational deformities of the femur results in a nonlinear increase in patellofemoral contact pressures on the contralateral facets of the patella (i.e., external rotational deformity resulted in a contact pressure increase on the medial facet, and internal rotational deformity resulted in a contact pressure increase on the lateral facet of the patella). With the initial isometric tension of 200 N in the quadriceps tendon for 30 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion, the peak contact pressure showed no significant differences between the medial and lateral facets of the patella in its anatomic position. At 20 degrees of rotational deformity of the femur, only a slight increase was noted for the tension in the quadriceps tendon and the patellofemoral contact pressures on the contralateral facets of the patella. However, at 30 degrees rotational deformity of the femur, both the external and internal rotational deformity of the femur showed a significant increase in the tension of the quadriceps tendon and the patellofemoral contact pressures on contralateral facets of the patella. The greatest increase in patellofemoral contact pressures was observed at 30 degrees and 60 degrees knee flexion for both the external and internal rotational deformity of the femur. The external rotational deformity of the femur for all knee flexion angles showed significantly higher peak patellofemoral contact pressure increases on the medial facet of the patella as compared with the lateral patellofemoral contact pressure increase resulting from internal rotational deformity of the femur.

Aged↗
PubMed1993

Sacral agenesis and caudal spinal cord malformations.

Thirty-three children and one adult with sacral agenesis (SA) were studied by computed tomographic myelography and/or magnetic resonance imaging and were monitored for a mean period of 4.7 years. Four children had the OEIS (concurrent omphalocele, cloacal exstrophy, imperforate anus, and spinal deformities) complex, and three others had VATER (vertebral abnormality, anal imperforation, tracheoesophageal fistula, and renal-radial anomalies) syndrome. All patients shared some of the characteristic features of SA, namely, a short, intergluteal cleft, flattened buttocks, narrow hips, distal leg atrophy, and talipes deformities. Neurologically, lumbosacral sensation was much better preserved than the motor functions, and urinary and bowel symptoms were universal. The level of the vertebral aplasia was correlated with the motor but not with the sensory level. The important neuroimaging findings of SA were as follows: 1) 12 patients (35%) had nonstenotic, tapered narrowing of the caudal bony canal, and 2 patients had hyperostosis indenting the caudal thecal sac; 2) 16 patients (47%) had nonstenotic, tapered narrowing and shortening of the dural sac, but 3 patients (9%) had true, symptomatic dural stenosis, in which the cauda equina was severely constricted by a pencil-sized caudal dural sac; 3) the coni could be divided into those ending above the L1 vertebral body (Group 1, 14 patients) and those ending below L1 (Group 2, 20 patients). Thirteen of 14 Group 1 coni were club or wedge-shaped, terminating abruptly at T11 or T12, as if the normal tip was missing. All 20 Group 2 coni were tethered: 13 were tethered by a thick filum; 2 were extremely elongated and had a terminal hydromyelia; 3 were terminal myelocystoceles; and 2 were tethered by a transitional lipoma. High blunt coni were highly correlated with high (severe) sacral malformations (sacrum ending at S1), but low-lying tethered coni were highly correlated with low sacral malformations (S2 or lower pieces present).(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormalities, Multiple↗
PubMed1993

Cervical myelomeningoceles.

Cervical myelomeningoceles are rare dysraphic lesions. Nine cases of cervical myelomeningoceles are reported. The external features of all nine myelomeningoceles were strikingly similar: They were sturdy, tubular protuberances from the back of the infants' necks, covered at the base by full-thickness skin and covered on the dome by thick squamous epithelium. Internally, these were tethered cord lesions in which fibroneural bands or sagittal midline fibrous septa were tightly tethering the cervical spinal cord to the adjacent dural or intrasaccular soft tissues. Six of our early cases (Group 1) were initially treated with simple subcutaneous resection of the sac and ligation of the dural fistula without release of the internal tethering structures. Five of these children subsequently deteriorated 13 months to 8 years later, all with worsening hand function and spastic legs. All five were reexplored, and the tethering bands and septa were excised; all showed improvement. The other three neonates (Group 2) treated in the last 4 years underwent initial intradural exploration of the lesions; in one case, the tethering fibrous elements were only partially eliminated and the patient deteriorated 4 years later, but improved after a second operation for resection of a missed ventral fibrous septum. The other two Group 2 infants had a thorough release of the fibroneural stalks initially, and both were neurologically stable 3 years later. We recommend that cervical myelomeningoceles should be studied preoperatively with magnetic resonance imaging and computed tomographic myelography to identify the internal structures. The minimum initial surgical treatment should be a two-level laminectomy, intradural exploration, and excision of all tethering bands and septa, in addition to resection of the sac. If a split cord is revealed by imaging studies, both the ventral and dorsal surfaces of the hemicords must be carefully inspected to locate the median septum.

Cervical Vertebrae↗