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Biomedical subjects

D Pang

Publications and source records attributed to D Pang.

At least 73 records · Page 4Linked to original sources
PubMed1989

Spinal cord injury without radiographic abnormality in children--the SCIWORA syndrome.

Spinal cord injury in children frequently occurs without fracture or dislocation. The clinical profiles of 55 children with spinal cord injury without radiographic abnormalities (SCIWORA) are reported in detail to illustrate features of this syndrome. No patient had vertebral fracture or dislocation on plain films and tomographies. There were ten upper cervical (C1-C4), 33 lower cervical (C5-C8), and 12 thoracic cord injuries; of these, 22 were complete or severe lesions and 33 were mild lesions. The mechanism of the neural injury probably relates to the inherent elasticity of the juvenile spine, which permits self-reducing but significant intersegmental displacements when subjected to flexion, extension, and distraction forces. The spinal cord is therefore vulnerable to injury even though the vertebral column is spared from disruption, and this vulnerability is most evident in children younger than 8 years. All but one of the 22 children with profound neurologic injuries were younger than 8 years (p less than 0.000001), whereas 24 of 33 children with mild injuries were older. Younger children were also more likely to have severe upper cervical lesions (p less than 0.05); lower cervical lesions were distributed evenly through the ages of 6 months to 16 years. Thoracic injuries most commonly resulted from distraction or crushing. Distraction invariably involved violent forces, and crush injuries were usually caused by children being run over while lying prone, when the spinal column was acutely bowed towards the spongy abdominal and thoracic cavities. Fifteen children had delayed onset of neurologic deficits; nine of these had transient warning symptoms of paresthesia, subjective paralysis, and Lhermitte's phenomenon 30 minutes to 4 days before the onset of deterioration. Eight other children suffered a second SCIWORA 3 days to 10 weeks after the initial SCIWORA. The spines in these children were presumably rendered incipiently unstable by the initial injury and thus were susceptible to additional, often more severe, neurologic trauma. The long-term neurologic outcome in children with SCIWORA is solely determined by their admission neurologic status. Realistically, the outcome can thus only be improved by: 1) ruling out occult fractures and subluxation which will require surgical fusion; 2) identifying patients likely to have delayed deterioration; and 3) preventing recurrent SCIWORA. Our experience and recommendations in these regards are discussed.

Adolescent↗
PubMed1988

Spinal cord injury in I-cell disease.

I-cell disease (ICD), mucolipidosis II, is an autosomal recessive syndrome resulting from defective phosphorylation of acid hydrolases. The diagnosis is made in early childhood and in most cases death occurs by age 5 as a result of cardiorespiratory complications. Pathologic changes are limited to mesenchymal tissues. We treated two children with ICD who developed atlantoaxial dislocation and myelopathy following minor injuries. The first child developed cardiovascular instability with manipulation of the C1 ring at operation, necessitating removal of the arch of C1 and fusion from occiput to C2. The second child was quadriplegic following anatomic reduction of the C1-C2 dislocation at operation during which somatosensory evoked potentials (SSEPs) showed no deleterious change. The atlantoaxial joint is unstable in ICD due to an incompetent transverse ligament infiltrated by storage cells. A cartilaginous, rather than calcified, odontoid process may contribute to the instability. The intraoperative neural injury occurred during attempts to effect anatomical reduction of the chronically dislocated C1-C2 joints and could have resulted from inadvertent trauma to the vertebral arteries and subsequent infarction of the cord. The lack of change in the intraoperative SSEPs was probably due to relative sparing of the posterior columns during the cord injury. We recommend that children with ICD and atlantoaxial instability undergo closed reduction of any existing malalignment followed by posterior C1-C2 fusion as long as the operative risk is not prohibitive. If preoperative closed reduction is not readily feasible and the cord is severely compromised, the C1 arch should be removed and the occiput fused to C2. Forceful attempts at anatomical reduction of the chronically dislocated C1-C2 segments should be avoided.

Child↗
PubMed1988

Thoracic outlet syndrome.

Much controversy exists regarding the pathogenesis, diagnosis, and management of thoracic outlet syndrome. The authors review the embryology of several fibroosseous anomalies at the superior thoracic aperture and relate normal and morbid anatomy of this region and the putative roles of anthropomorphic, postural, and dynamic factors to the genesis of neurovascular symptoms. The salient clinical features of this syndrome are described, with emphasis on the peculiar pattern of motor weakness and the physiology of painful symptoms. Diagnostic methods are critiqued. The various surgical approaches for this syndrome are evaluated according to their facility for wide exposure, their potential morbidity, and their beneficial results.

Animals↗
PubMed1988

Recurrent spinal cord injury without radiographic abnormalities in children.

Spinal cord injury without radiographic abnormality is a well-known entity in the pediatric age group. Age-related elasticity of the vertebral ligaments as well as immaturity of the osseous structures in the pediatric spine allow momentary subluxation in response to deforming forces. The resultant neurological injuries range from transient dorsal column dysfunction to complete cord transection. Between 1960 and 1985, 42 such injuries were treated at the Children's Hospital of Pittsburgh. Management of these radiographically occult spinal cord injuries consisted of cervical immobilization for 2 months in a hard collar and restriction of contact sports. Recurrent cord injury occurred in eight cases during the 2-month immobilization period. A clearly defined traumatic episode was identified in seven of the eight patients, although in four children the recurrent trauma to the spine was trivial. Five of the children removed their collars briefly before the second injury, and two children incurred reinjury with the hard collar in place. The remaining child was too young for hard-collar immobilization, and recurrent neurological deterioration occurred during sleep. Serial flexion-extension films failed to detect frank instability in any of the eight cases. The children most susceptible to reinjury were those who sustained mild or transient neurological deficits from an initial cord injury and who rapidly resumed normal activities. Radiographically occult spinal instability resulting from the initial injury to the vertebral and paravertebral soft tissues presumably made these children vulnerable to recurrent spinal cord injury, often from otherwise insignificant trauma. During the last 21 months, 12 additional children have been managed with a more stringent protocol combining neck immobilization in a rigid cervical brace for 3 months and restriction of both contact and noncontact sports, together with a major emphasis on patient compliance. With this new protocol, no recurrent cord injuries have been documented.

Adolescent↗
PubMed1987

Cardiotonic agents. 1. Novel 8-aryl-substituted imidazo[1,2-a]- and -[1,5-a]pyridines and imidazo[1,5-a]pyridinones as potential positive inotropic agents.

Several 8-arylimidazo[1,2-a]pyridines, 8-arylimidazo[1,5-a]pyridines, and 8-arylimidazo[1,5-a]pyridinones were prepared and tested in vitro for potential cardiac inotropic and electrophysiological activity. Selected analogues were further tested in vivo in canine hemodynamic and cardiac electrophysiology models. Compounds having an imidazole substituent consistently showed activity. A pharmacophoric relationship between heterocycle-phenyl-imidazole and positive inotropic activity was noted. The significance of this relationship is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

Cardiotonic agents. 2. (Imidazolyl)aroylimidazolones, highly potent and selective positive inotropic agents.

A series of 4-alkyl-1,3-dihydro-5-[(1H-imidazolyl)benzoyl]-2H-imidazol-2-ones 9 was synthesized and evaluated in vitro for positive inotropic and cyclic AMP phosphodiesterase inhibitory activity. A wide range of inotropic and enzyme-inhibitory potencies was observed, substitution on the imidazolyl moiety being the major determinant of activity. The 4-ethyl-5-[4-(1H-imidazol-1-yl)benzoyl] congener 9g exhibited the highest potency in vitro. Incorporation of a methyl group at the imidazolyl 2-position gave 9h, which was less potent but remarkably selective in vivo for positive inotropic effects over heart rate and hypotensive effects.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

A new surgical approach to closure of large lumbosacral meningomyelocele defects.

A new method for the reconstruction of large thoracolumbar and lumbosacral meningomyelocele defects is described in which latissimus dorsi and gluteus maximus myocutaneous units are advanced medially and reapproximated in the midline, permitting primary closure of the defect in three layers. The flaps are based on the thoracodorsal and superior gluteal vessels and the intervening thoracolumbar fascia, providing tension-free, durable, and viable soft-tissue coverage over the dural repair. No lateral relaxing incisions, delays, or skin grafts are necessary. This technique has been used successfully in the repair of nine large meningomyelocele defects, and uncomplicated wound closure was achieved in all cases. The anatomic basis, technique, advantages, and functional implications of our approach are described. The flaps described do not alter the nerve supply of the muscles and merely redefine the muscle origins; therefore, no functional deficit from the reconstructive surgery is anticipated.

Follow-Up Studies↗
PubMed1987

Chronic granulomatous disease with cranial fungal osteomyelitis and epidural abscess. Case report.

A patient is described with osteomyelitis of the cranium and epidural abscess due to Aspergillus fumigatus as the presenting manifestations of chronic granulomatous disease. The diagnosis was suggested by the unusual nature of the organism isolated and confirmed by appropriate laboratory studies. The details of diagnostic assessment and therapeutic management are discussed, and the central nervous system manifestations of chronic granulomatous disease are reviewed.

Brain Abscess↗
PubMed1986

Lysis of intraventricular blood clot with urokinase in a canine model: Part 1. Canine intraventricular blood cast model.

To test the safety and feasibility of using direct instillation of urokinase to induce rapid lysis of intraventricular clots, an animal model of intraventricular blood cast is required. Injections of 11 ml of fresh, unclotted autologous blood into the ventricles of adult mongrel dogs did not produce a solid blood cast in the ventricular system, suggesting that the adult dogs have an unusual ability to clear uncoagulated whole blood from the ventricles and subarachnoid space. Injection of 9 ml of preclotted blood resulted in a subtotal cast of the ventricles, leaving only portions of the occipital horns free of solid clots. This volume of injected clots incurred no mortality and minimal morbidity, whereas injection of 10 to 12 ml resulted in a mortality of 42% and formidable morbidity. The technique of producing this intraventricular blood cast model, as well as that of implanting an indwelling ventricular catheter-reservoir system useful in chronic urokinase administration, is described.

Animals↗
PubMed1986

Lysis of intraventricular blood clot with urokinase in a canine model: Part 2. In vivo safety study of intraventricular urokinase.

It was determined from in vitro experiments that the minimal dose of urokinase required to lyse 10 ml of clotted canine blood within a closed space must exceed 10,000 IU. We empirically doubled this minimum effective dose and tested the in vivo safety of injecting 20,000 IU of urokinase every 12 hours for 4 days into the ventricles of six adult mongrel dogs through an implanted catheter-reservoir system. The animals were monitored carefully for local and systemic bleeding by neurological and clinical examination, hematological tests reflecting systemic fibrinolytic status, serial computed tomography, and postmortem histological examinations of the brain, meninges, and peripheral organs. It was found that this intraventricular dose regimen of urokinase did not cause intracranial hemorrhage even though the dogs had recent brain wounds related to transcerebral ventricular catheterization. Mild activation of systemic fibrinolysis, implying passage of the enzyme from ventricle to blood, occurred 4 to 6 hours after each intraventricular injection, but no systemic hemorrhages were seen. This dose regimen also did not cause acute or chronic inflammatory changes in the brain or meninges and did not disturb cerebrospinal fluid circulation.

Animals↗
PubMed1986

Lysis of intraventricular blood clot with urokinase in a canine model: Part 3. Effects of intraventricular urokinase on clot lysis and posthemorrhagic hydrocephalus.

Nine millilitres of preclotted autologous blood was injected into the ventricles of 10 adult mongrel dogs (control dogs) to create subtotal ventricular casts with solid clots. The neurological status and systemic fibrinolytic profiles were closely monitored, and the changes in clot and ventricular volumes were measured by serial computed tomography (CT) for 3 months. The control animals showed severe neurological impairment for 7 to 9 days. No visible lysis of the intraventricular clots occurred for 5 to 7 days, after which slow clot lysis occurred at a constant rate. Complete lysis of the 10 clots took 38 to 65 days, indicating that canine cerebrospinal fluid normally possessed limited capacity for in situ fibrinolysis. Of the 10 control dogs, 8 developed progressive ventricular enlargement after a transient initial shrinkage parallel with initial clot lysis. Their final ventricular volume at 3 months was as much as 14 times the base line ventricular volume. Necropsy studies disclosed increased basal subarachnoid fibrosis and extensive ependymal and subependymal damage in the lateral ventricular walls of the hydrocephalic dogs. Ten other dogs (UK dogs) were given similar ventricular clot injections. Six hours later, each UK dog was begun on a regimen of 20,000 IU of intraventricular urokinase every 12 hours until solid clots were no longer seen in the ventricles on CT. In all 10 UK dogs, intraventricular urokinase induced complete lysis in 3 to 6 days without causing local or systemic hemorrhages. The neurological status of all 10 dogs also improved promptly. In 8 UK dogs, the ventricles that were initially distended by clots showed rapid shrinkage parallel with thrombolysis to a final volume at 3 months of less than four times the initial ventricular volume. Only 2 animals had persistently large or expanding ventricles. At necropsy, the ependymal and subarachnoid spaces of the UK dogs were remarkably free of damage and fibrosis. The possible mechanisms by which intraventricular urokinase may prevent posthemorrhagic hydrocephalus are discussed.

Animals↗
PubMed1984

Connatal brain tumors in patients with tuberous sclerosis.

Two neonates with tuberous sclerosis and giant cell astrocytomas diagnosed soon after birth are described. During attempted surgical resection of their tumors, both infants developed refractory intraoperative cardiac arrhythmias and died. At autopsy, both patients had multiple cardiac rhabdomyomas. Subependymal giant cell astrocytomas rarely present in the neonate, but genetic implications and associated cardiac hamartomas warrant special consideration of these connatal tumors. Surgical considerations suggest that an operative approach to these tumors should be delayed beyond the neonatal period.

Astrocytoma↗
PubMed1983

Craniocerebral injuries from dog bites.

Dog bites are a common cause of injury in infants and children, with the face and head frequently involved. While scalp injuries may be extensive and severe, only five cases of compound depressed skull fractures caused by dog bites have been reported, to our knowledge. Four cases are presented to point out the potential risks of cranial penetration and underlying brain injury when infants and children suffer dog bites to the head. The principles for management of these injuries are outlined.

Age Factors↗
PubMed1983

Characterization of phospholipase A2 activity in rat aorta smooth muscle cells.

Phospholipase A activity was measured in homogenates and acid extracts of smooth muscle cells from rat aorta and mesenteric artery using [1-14 C]oleate-labeled autoclaved Escherichia coli and 1-[1-14C]stearyl-2-acyl-3-sn-glycerophosphorylethanolamine as substrates. The results demonstrate the presence of neutral-active phospholipase(s) A that exclusively catalyze the release of fatty acid from the 2-position of phospholipids. Optimal activity was at pH 7.5, and there was an absolute requirement for low concentrations of Ca2+. Mg2+ did not substitute for Ca2+, and EGTA inhibited the activity. Phospholipase A2 activity was predominantly membrane-associated and was solubilized by homogenization in 0.18 N H2SO4. Sulfuric acid extracts of rat aortic smooth muscle cells were four times more active than extracts of mesenteric artery (710 vs. 170 nmol/h per mg protein). By comparison, acid extracts of rat lung, heart, and liver were less active (60-75 nmol/h per mg). Indomethacin, sodium meclofenamate, mepacrine and chlorpromazine, but not dexamethasone or aspirin, inhibited acid-solubilized phospholipase(s) A2 between 10(-6) and 10(-3) M in a dose-dependent manner. Preincubation with p-bromophenacyl bromide or diethylpyrocarbonate inhibited phospholipase(s) A2, suggesting the presence of a histidine residue at the active site. An extract from the leaves of feverfew plant (Tanacetum parthenium) was also a potent inhibitor of aortic smooth muscle phospholipase(s) A2.

Animals↗
PubMed1983

Use of an anal sphincter pressure monitor during operations on the sacral spinal cord and nerve roots.

The distinction of sacral roots and conus medullaris from lipoma, fibrous adhesions, and an abnormally thickened filum terminale can be difficult during operations on certain complicated dysraphic lesions. We describe a simple, noninvasive method of monitoring external anal sphincter "squeeze pressure" by means of an elongated, fluid-filled, polyethylene anal balloon connected to a pressure transducer. Cutaneous electrocardiographic (ECG) leads on both hips register the stimulus artifact from a monopolar nerve stimulator. The simultaneous display on the oscilloscope screen of the stimulus artifact and the resultant pressure response form an electromechanical coupling that allows the operator to identify a faulty stimulator probe and to distinguish true stimulus-induced external anal sphincter activity from spontaneous rhythmic contractions of the internal anal sphincter. Unilateral stimulation of the S-2, S-3, and S-4 roots generates tall pressure spikes between 40 and 75 torr in peak amplitudes, whereas S-1 and L-5 stimulation produces a stimulus artifact on the ECG but either no pressure response or a mere "ripple wave" of less than 7 torr. During operations on 11 patients with various dysraphic lesions, the S-2, S-3, and S-4 roots were identified easily and preserved, and the caudal extent of functioning neurons was localized within coni grossly distorted by intramedullary lipoma or chronic tethering. We prefer the anal sphincter pressure monitor to anal sphincter electromyography because of its simplicity, the inexpensive equipment, and its noise-free display that is virtually unaffected by other electronic systems in the operating room.

Adolescent↗
PubMed1983

Syndrome of the incidental herniated lumbar disc.

Lumbar myelographic defects consistent with herniated disc were found in 108 asymptomatic patients undergoing myelography for other reasons. Within 3 years, 64% of these patients developed symptoms of lumbosacral radiculopathy. The clinical features of these patients comprise a syndrome significantly different from that typically associated with classical lumbar disc herniation: the syndrome described here carries a much higher incidence of silent root compression with minimal pain. Incidental lumbar myelographic defects are not necessarily benign findings, and patients in whom they are encountered deserve close clinical follow-up review and appropriate treatment if the defects become symptomatic.

Adult↗