Can disorganisation of semantic memory account for the abnormalities of thought in schizophrenia-a controlled experimental study.

BACKGROUND: Disorganisation of semantic memory could provide a cognitive explanation for the disturbances of thinking and reasoning in schizophrenia. In this study, we directly test this explanation by identifying patients with disorganised semantic categories and then examine how they use their knowledge about these same categories in an inductive reasoning task. METHOD: Experiment 1 utilised a semantic category-sorting task to identify patients with disorganisation of semantic memory. In Experiment 2, the patients with disorganised categories carried out a category-based inductive reasoning task. Accurate performance on this task requires access to well-organised semantic knowledge about the objects and categories used in Experiment 1. RESULTS: Patients with disorganised semantic categories in Experiment 1 did not demonstrate any difficulties or unusual responses when reasoning about the same categories in Experiment 2. CONCLUSION: Disorganisation of semantic memory may not be the primary cause of disturbed reasoning or thought in schizophrenia. Patients with schizophrenia tend to generate ad hoc categories, which are unsuited to the current context. Impaired performance on semantic memory tasks can arise from a misunderstanding of social context.

Ketamine sedation for the reduction of children's fractures in the emergency department.

BACKGROUND: There recently has been a resurgence in the utilization of ketamine, a unique anesthetic, for emergency-department procedures requiring sedation. The purpose of the present study was to examine the safety and efficacy of ketamine for sedation in the treatment of children's fractures in the emergency department. METHODS: One hundred and fourteen children (average age, 5.3 years; range, twelve months to ten years and ten months) who underwent closed reduction of an isolated fracture or dislocation in the emergency department at a level-I trauma center were prospectively evaluated. Ketamine hydrochloride was administered intravenously (at a dose of two milligrams per kilogram of body weight) in ninety-nine of the patients and intramuscularly (at a dose of four milligrams per kilogram of body weight) in the other fifteen. A board-certified emergency physician skilled in airway management supervised administration of the anesthetic, and the patients were monitored by a registered nurse. Any pain during the reduction was rated by the orthopaedic surgeon treating the patient according to the Children's Hospital of Eastern Ontario Pain Scale (CHEOPS). RESULTS: The average time from intravenous administration of ketamine to manipulation of the fracture or dislocation was one minute and thirty-six seconds (range, twenty seconds to five minutes), and the average time from intramuscular administration to manipulation was four minutes and forty-two seconds (range, sixty seconds to fifteen minutes). The average score according to the Children's Hospital of Eastern Ontario Pain Scale was 6.4 points (range, 5 to 10 points), reflecting minimal or no pain during fracture reduction. Adequate fracture reduction was obtained in 111 of the children. Ninety-nine percent (sixty-eight) of the sixty-nine parents present during the reduction were pleased with the sedation and would allow it to be used again in a similar situation. Patency of the airway and independent respiration were maintained in all of the patients. Blood pressure and heart rate remained stable. Minor side effects included nausea (thirteen patients), emesis (eight of the thirteen patients with nausea), clumsiness (evident as ataxic movements in ten patients), and dysphoric reaction (one patient). No long-term sequelae were noted, and no patients had hallucinations or nightmares. CONCLUSIONS: Ketamine reliably, safely, and quickly provided adequate sedation to effectively facilitate the reduction of children's fractures in the emergency department at our institution. Ketamine should only be used in an environment such as the emergency department, where proper one-on-one monitoring is used and board-certified physicians skilled in airway management are directly involved in the care of the patient.

Leukocyte entry into sites of inflammation requires overlapping interactions between the L-selectin and ICAM-1 pathways.

Leukocyte interactions with vascular endothelium during inflammation depend on cascades of adhesion molecule engagement, particularly during selectin-mediated leukocyte rolling. Leukocyte rolling is also facilitated by members of the integrin and Ig families. Specifically, leukocyte rolling velocities during inflammation are significantly increased in ICAM-1-deficient mice, with ICAM-1 expression required for optimal P- and L-selectin-mediated rolling. Elimination of ICAM-1 expression in L-selectin-deficient mice significantly reduces leukocyte rolling. Whether disrupted leukocyte rolling in L-selectin and ICAM-1 double-deficient (L-selectin/ICAM-1-/-) mice affects leukocyte entry into sites of inflammation in vivo was assessed in the current study by using experimental models of inflammation; thioglycollate-induced peritonitis, chemokine-induced neutrophil migration to the skin, delayed-type hypersensitivity responses, rejection of allogeneic skin grafts, and septic shock. In many cases, the loss of both L-selectin and ICAM-1 expression dramatically reduced leukocyte migration into sites of inflammation beyond what was observed with loss of either receptor alone. In fact, the effects from loss of both L-selectin and ICAM-1 effectively eliminated multiple chronic inflammatory responses in L-selectin/ICAM-1-/- mice. By contrast, the combined loss of L-selectin and ICAM-1 expression had minimal effects on the generation of Ag-specific T cell responses or humoral immunity. Thus, members of the selectin and Ig families function synergistically to mediate optimal leukocyte rolling and entry into tissues, which is essential for the generation of effective inflammatory responses in vivo.

Anesthesia and analgesia for the ambulatory management of fractures in children.

The goal of anesthesia in the ambulatory management of fractures in children is to provide analgesia and relieve anxiety in order to facilitate successful closed treatment of the skeletal injury. Numerous techniques short of general anesthesia are available. These methods include blocks (local, regional, and intravenous), sedation (conscious and deep), and dissociative anesthesia (ketamine sedation). Important factors in choosing a particular technique include ease of administration, efficacy, safety, cost, and patient and parent acceptance. Local and regional techniques, such as hematoma, axillary, and intravenous regional blocks, are particularly effective for upper-extremity fractures. Sedation with inhalation agents, such as nitrous oxide, and parenterally administered narcotic-benzodiazepine combinations, are not region-specific and are suitable for patients over a wide range of ages. Ketamine sedation is an excellent choice for children less than 10 years old. With any technique, proper monitoring and adherence to safety guidelines are essential.

Bilateral peroneal nerve palsy secondary to a knee board: report of two cases.

We report on two patients who developed bilateral peroneal nerve palsy after using a knee board behind a water ski boat. This device causes the rider's knees to be in a hyperflexed position secured with a strap across the thighs. Treatment for this compressive neuropathy is conservative. Recreational users may wish to limit the duration and frequency of participation in this sport, thus decreasing the predisposition to prolonged nerve compression. In addition, manufacturers may consider making fundamental design changes such as padding the nylon straps or outrigger devices that contact the proximal lateral tibia.

Decline of bone and joint infections attributable to haemophilus influenzae type b.

Haemophilus influenzae has been a major cause of infectious diseases in children and has been attributed as a significant cause of septic arthritis and osteomyelitis in children. With the advent of widespread vaccination, the incidence of Haemophilus influenzae meningitis and other infections has been well documented. This is thought to be the first report that documents the effect of vaccination on bone and joint infections. One hundred sixty-five cases of acute hematogenous osteomyelitis or septic arthritis treated at the Department of Orthopaedics at Vanderbilt University in the years before and after the advent of the Haemophilus influenzae vaccine to assess whether vaccination affected the incidence of these diseases. The data indicate that the Haemophilus influenzae vaccine has reduced to near 0 the incidence of bone and joint infections because of Haemophilus influenzae. These findings suggest that coverage of Haemophilus influenzae as part of the empiric antibiotic coverage may be no longer needed in the management of acute hematogenous osteomyelitis and septic arthritis in children.

Paravertebral inflammation mistaken for neoplasm or abscess by MRI.

Magnetic resonance imaging (MRI) is a useful procedure for the evaluation of spinal pathology in children. The high sensitivity of soft tissue changes may lead to misinterpretation of paravertebral swelling caused by inflammation. We present a report of three patients with paravertebral soft tissue swelling caused by disk space infection or intervertebral disk space calcification. The findings shown by MRI were initially interpreted as neoplasm or abscess, which led to surgical procedures either planned or done. Surgeons need to exercise extreme care when interpreting soft tissue changes shown by MRI.

Video-assisted thoracoscopic diskectomy and fusion.

Thoracoscopic diskectomy has been described in adults as an alternative to thoracotomy for access to the anterior spine for correction of scoliosis, but its use in children for correction of spinal deformities has not been reported. Eight patients have undergone video-assisted thoracoscopic diskectomy with fusion before posterior instrumentation. In five patients, the posterior fusion and instrumentation followed the thoracoscopic procedure under the same anesthesia; in three patients it was staged and performed 1 week later. The mean time required for the thoracoscopic procedure was 174 minutes. Intraoperative bleeding requiring transfusion developed in one patient. No other complications occurred. The authors conclude that the minimally invasive approach for access to the thoracic cavity for anterior diskectomy and fusion will be the preferred approach because of the potential for significant reduction in postoperative discomfort and complications such as atelectasis and pneumonia. Postoperative hospitalization may not be decreased, however, because the patient must still recover from the open posterior instrumentation and fusion operation.

Osteochondritis dissecans as a cause of developmental dislocation of the radial head.

Osteochondritis dissecans of the capitellum produces an area of focal necrosis that may result in a potentially unstable relationship between the capitellum and the radial head. Seven patients with developmental instability of the radial head secondary to osteochondritis dissecans of the capitellum treated between 1984 and 1995 were studied. All patients were male with an average age of 13 years. The most common symptom was pain with a decrease in range of motion. Patients lacked an average of 24.3 degrees extension. Initial plain radiographs were most helpful for evaluating the relationship of the radial head to the capitellum, and tomography or magnetic resonance imaging were helpful for the detection of loose bodies. The most common direction for instability was posterolateral. Treatment varied from conservative management with nonsteroidal antiinflammatory medication to open reduction and internal fixation of an osteochondral fragment. The average followup was 3.2 years. At latest followup, 11 patients were pain free; however, they lacked an average of 17 degrees extension. Only 2 patients progressed to complete dislocation of the radial head. Developmental instability of the radial head may occur secondary to osteochondritis dissecans of the capitellum. Plain radiographs are sufficient for initial detection and followup. Treatment is determined by the presence of loose bodies and the characteristics of the osteochondral defect. Initial symptoms will resolve; however, lack of extension may persist.

Acute slipped capital femoral epiphysis: the value and safety of urgent manipulative reduction.

A 40-year experience consisting of 91 cases of acute slipped capital femoral epiphysis (SCFE) was reviewed to assess the safety of manipulative reduction and to determine whether urgent reduction has an effect on the development of avascular necrosis (AVN) of the capital femoral epiphysis. All patients had a history of sudden onset of severe hip pain and were documented to have an unstable (acute) slipped epiphysis. Treatment modalities included manipulative reduction under general anesthesia followed by internal fixation (41 hips), epiphysiodesis and internal fixation (15 hips), epiphysiodesis and cast immobilization (31 hips), and cast immobilization alone (three hips). One case was treated with cast immobilization after reduction by skeletal traction. Patient follow-up averaged 44 months, and ranged from 12 to 216 months. Radiographic review identified 13 (14%) cases of AVN in the series of 91 hips. Of 42 hips reduced in <24 h from presentation, AVN developed in three (7%). Of 49 hips reduced in >24 h from presentation, AVN developed in 10 (20%). Manipulative reduction of the acute SCFE may be accomplished without increased risk of AVN. Time to reduction may be an important risk factor for development of AVN after acute SCFE.

Humoral immune responses in L-selectin-deficient mice.

L-selectin regulates lymphocyte migration by mediating lymphocyte attachment to high endothelial venules of peripheral lymph nodes (PLN). L-selectin-deficient mice display a 70 to 90% reduction in the number of lymphocytes within PLNs and a 30 to 55% increase in spleen cellularity. The altered distribution of lymphocyte subpopulations in L-selectin-deficient mice resulted in significantly elevated serum IgM and IgG1 levels and augmented humoral immune responses to T cell-independent and T cell-dependent Ags following i.p. immunization. By contrast, s.c. immunization of L-selectin-deficient mice with a T cell-dependent Ag resulted in serum IgM responses that were 40% lower when compared with wild-type littermates on day 7, while primary IgG responses were essentially absent. Most serum Ig responses were normal by day 14 and secondary responses were higher in L-selectin-deficient mice. Although lymphocytes from L-selectin-deficient mice were unable to enter Ag-stimulated lymph nodes through high endothelial venules, the cellularity of draining lymph nodes increased significantly following immunization. Germinal centers developed rapidly following immunization, although PLNs of L-selectin-deficient mice contained few follicles. Germinal centers within PLNs and the spleen were also consistently much larger and more well defined in L-selectin-deficient mice when compared with wild-type littermates. These results confirm that lymphocyte migration plays an important role in the initiation of humoral responses and demonstrate complementary and overlapping roles for the spleen and other peripheral lymphoid tissues in the generation of immune responses.

Stress fractures in skeletally immature patients.

Stress fractures are a common injury in an active population. As children become increasingly involved in organized sports, the recognition of stress fractures and differentiation from infections or neoplasms requires a knowledge of their most common sites, presentation, and clinical course. We retrospectively reviewed 34 stress fractures in 32 skeletally immature patients from June 1977 to May 1993. Age, fracture location, treatment, time to union or healing, associated conditions, complications, radiographs, and clinical outcome were recorded. Fifty percent of patients were involved in sports; the most common complaint was pain with activity. The most common site was the tibia (47%) followed by the fibula (21%) and femur (12%). All had resolution of symptoms and returned to normal activity. All but two healed with either activity modification or cast immobilization. The radiographic findings included early periosteal callus formation that rapidly consolidated to new bone on serial studies. A careful history, physical examination, and radiographs can help diagnose most common stress fractures in the skeletally immature individual and can differentiate stress fractures from infection or neoplasm with appropriate conservative treatment.

Open reduction and internal fixation of pediatric forearm fractures.

Twenty-six skeletally immature patients with 27 displaced, diaphyseal forearm fractures treated by open reduction and internal fixation were reviewed. The mean age of the patients at the time of injury was 11.5 years (range, 4-15). Indications for surgery included open fractures (10), unacceptable closed reduction (14), and loss of reduction (three). Anatomic or near anatomic fixation was achieved with either compression plates or intramedullary wires. The average time to union was 3.5 months. The average length of follow-up was 39 months (range, 9-98). All but three patients regained full range of motion equal to that of the uninjured extremity. Three complications occurred, including one deep infection resulting in delayed union, one nonunion with failure of hardware, and one proximal radioulnar cross-union. We conclude that open reduction and internal fixation is indicated and can be safely performed in children with open or unstable or both-bone forearm fractures when closed treatment methods have failed. Fixation is reliably achieved with compression plating or intramedullary nailing.

Lyphocyte migration in L-selectin-deficient mice. Altered subset migration and aging of the immune system.

Lymphocyte trafficking across high endothelial venules (HEV) of peripheral lymph nodes (PLN) is dependent upon lymphocyte expression of L-selectin. Mice that lack this adhesion molecule provide an opportunity to determine the long-term role of L-selectin-mediated migration in the maintenance of leukocyte subpopulations. HEV in L-selectin-deficient mice were phenotypically, morphologically, and functionally comparable with wild-type mice, although there was a 70 to 90% reduction in the number of lymphocytes within PLN. These lymphocytes most likely entered PLN through the afferent lymphatics, since they did not migrate into PLN of normal mice during short-term homing experiments. The impaired trafficking of lymphocytes across PLN-HEV resulted in the accumulation of memory (CD18highCD44high) lymphocytes within PLN, and also altered the distribution of lymphocyte subpopulations within other tissues. Specifically, a 30 to 55% increase in splenic cellularity occurred due to increases in both naive and memory lymphocytes. Circulating lymphocyte numbers or subpopulations were not altered in young L-selectin-deficient mice, but circulating monocyte numbers were increased nearly threefold. In contrast, older L-selectin-deficient mice had disproportionate increases of both naive and memory CD4+ T cells present within spleen and blood. These results and the finding that memory lymphocytes in wild-type mice expressed L-selectin demonstrate a requirement for L-selectin in the regulation of memory lymphocyte migration. Therefore, L-selectin-dependent pathways of lymphocyte migration are important for the normal migration of both naive and memory lymphocytes.

Fusobacterium osteomyelitis and pyarthrosis: a classic case of Lemierre's syndrome.

Lemierre's syndrome, a systemic anaerobic infection caused by Fusobacterium necrophorum, is characterized by an acute oropharyngeal infection, septic thrombophlebitis of the internal jugular vein, sepsis, and multiple metastatic infections. It commonly leads to septic arthritis and occasionally to osteomyelitis. In the preantibiotic era, this infection was nearly universally fatal. Today it still poses a potentially grave threat to the young patients affected. Prompt recognition with appropriate debridement and antibiotic treatment results in complete recovery in most cases. We report a case of anaerobic septic arthritis and multifocal acute hematogenous osteomyelitis as part of a classic presentation of Lemierre's syndrome.

Nicardipine for controlled hypotension during spinal surgery.

Nicardipine is the first intravenously administered dihydropyridine calcium channel blocker. Its primary physiologic actions include vasodilatation with limited effects on the inotropic and dromotropic function of the myocardium. Several reports have documented its use in adult patients for pharmacologic control of blood pressure. We present our experience with nicardipine as an agent for controlled hypotension during spinal surgery in 24 children. After the induction of general anesthesia, nicardipine was started at 5 (22 patients) or 10 micrograms/kg/min (two patients). The target mean arterial pressure (MAP) of 55-65 mm Hg was reached in 5.1 +/- 2.1 min (range, 2-10). Intraoperative infusion requirements to maintain the target MAP varied from 0.5 to 7 micrograms/kg/min (mean, 2.5 +/- 1.1). No adverse effects related to nicardipine were noted. Nicardipine appears to be an effective agent for controlled hypotension in children. Future studies are required to determine its advantages/disadvantages compared with more commonly used agents such as sodium nitroprusside or adrenergic antagonists.