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Biomedical subjects

J K Lynch

Publications and source records attributed to J K Lynch.

13 recordsLinked to original sources
PubMed2001

Epidemiology of perinatal stroke.

Perinatal stroke has become increasingly recognized, but the incidence is probably underestimated because of variation in the presentation, evaluation, and diagnosis. Based on estimates from population-based studies of infants with seizures, perinatal stroke occurs in approximately 1 in 4000 term births. Most perinatal strokes involve the middle cerebral artery and are caused by thromboembolism from an intracranial or extracranial vessel, the heart, or the placenta. Cardiac disorders, coagulation abnormalities, and infection are risk factors for stroke in the perinatal period. This article discusses the epidemiology of ischemic stroke occurring in the perinatal and neonatal period, including cerebrovascular events that are diagnosed during the perinatal period and those diagnosed retrospectively, when evidence of hemiparesis or postneonatal seizures leads to later evaluation and neuroimaging.

Blood Coagulation Disorders↗
PubMed2001

Cerebrovascular disorders in children with the factor V Leiden mutation.

Since 1995, at least 128 children with a cerebrovascular disorder, cerebral palsy, or both and the factor V Leiden mutation have been reported. The majority of these strokes were in the first year of life, many of them in the perinatal period. Two thirds had an additional exogenous risk factor for thrombosis, and 42% had another recognized endogenous prothrombotic risk factor in combination with the mutation. We review the association of the factor V Leiden mutation and a cerebrovascular disorder in children younger than 16 years of age and describe the clinical features of 8 children with cerebral palsy and the Leiden mutation. This mutation should be considered in the evaluation of children with a stroke or its sequelae, including infants with perinatal stroke.

Cerebral Infarction↗
PubMed1998

ABT-594 [(R)-5-(2-azetidinylmethoxy)-2-chloropyridine]: a novel, orally effective antinociceptive agent acting via neuronal nicotinic acetylcholine receptors: II. In vivo characterization.

The antinociceptive effects of ABT-594, a novel nicotinic acetylcholine receptor (nAChR) ligand, were examined in rats in models of acute thermal (hot box) and persistent chemical (formalin test) pain. Also, the effects of ABT-594 treatment on motor function and electroencephalogram (EEG) were determined. In the hot box and formalin test (i.e., phase 1 and 2), acute treatment with ABT-594 (0.03, 0.1 and 0.3 mumol/kg i.p.) produced significant dose-dependent antinociceptive effects. In the hot box, the efficacy of ABT-594 was maintained after a repeated dosing paradigm (5 days b.i.d.i.p.). ABT-594 was fully efficacious in the formalin test when administered before formalin, and also retained significant efficacy (0.3 mumol/kg i.p.) when administered after formalin injection. The antinociceptive effects of ABT-594 in the hot box and formalin tests were attenuated by pretreatment with the nAChR antagonist, mecamylamine, and in animals treated with the nAChR antagonist chlorisondamine, given centrally (10 micrograms/rat i.c.v. 5 days before), but not in animals pretreated with the opioid receptor antagonist, naltrexone. Acute treatment with ABT-594 produced an initial decrease in open-field locomotor activity, which was absent in animals dosed repeatedly (5 days b.i.d.) with ABT-594. Also, acute treatment with ABT-594 decreased body temperature and decreased the amount of time the animals could maintain balance in an edge-balance test. These effects were no longer present in animals dosed repeatedly with ABT-594. At antinociceptive doses, ABT-594 produced activation of free running EEG in contrast to the sedative-like effects of morphine. Full antinociceptive efficacy was maintained in both the hot box and formalin tests after oral administration, whereas the effects on motoric performance were attenuated. In conclusion, these data demonstrate that ABT-594 is a potent antinociceptive agent with full efficacy in models of acute and persistent pain and that these effects are mediated predominately by an action at central neuronal nAChRs. In addition, antinociceptive effects were maintained after repeated dosing, whereas effects of ABT-594 on motor and temperature measures were attenuated in animals treated repeatedly with ABT-594. Thus, compounds acting at nAChRs may represent a novel approach for the treatment of a variety of pain states.

Administration, Oral↗
PubMed1997

Rollback in posterior cruciate ligament-retaining total knee arthroplasty. A radiographic analysis.

A clinical and radiographic study of 49 posterior cruciate ligament-retaining total knee arthroplasties in 38 patients (11 bilateral, 27 unilateral), using prostheses of the same design, was undertaken to quantify the amount of in vivo rollback (ie, the anteroposterior translation of the tibia with respect to the femur during flexion). The mean difference in the distances between the contact points of the knees in full extension and in 90 degrees flexion (ie, the rollback distance) was a posterior translation of the contact point of -0.2 mm (-12.7 to +7l6 mm; SD, 4.7 mm) relative to the prosthetic tibial tray, corresponding to an average translation of 0% of the prosthetic tibial tray depth, and -0.2 mm (-12.5 to +9.1 mm; SD, 4.8 mm) relative to the tibia itself, corresponding to an average translation of 0% of the true tibial surface depth. The differences between the rollback values obtained from the 90 degrees and full-extension radiographs relative to the prosthetic tibial tray (P = .63) and the true tibia (P = .89) were not statistically significant. Intraobserver (P = .27-.50) and interobserver (P = .13-.72) reliability tests showed that the differences between radiographic measurements taken by the same observer at two different points in time and by two different observers were not statistically significant. No correlations were found between the degree of translation of the tibiofemoral contact point relative to the prosthetic tibial tray and the posterior tilt of the tibial tray (R2 = .12), the preoperative tibiofemoral angle (R2 = .34), and the postoperative tibiofemoral angle (R2 = .027). No correlations were found between the degree of translation of the tibiofemoral contact point relative to the true tibia and the posterior tilt of the tibial tray (R2 = .16), the preoperative tibiofemoral angle (R2 = .14), and the postoperative tibiofemoral angle (R2 = .034). In conclusion, this study indicated no demonstrable rollback occurring in the posterior cruciate ligament-retaining total knee arthroplasty used in this study.

Aged↗
PubMed1994

MR diagnosis of tears of anterior cruciate ligament of the knee: importance of ancillary findings.

OBJECTIVE: Detection of tears of the anterior cruciate ligament with MR is usually based on the appearance of the ligament. However, other MR findings may be useful to establish the diagnosis. We assessed the utility of these ancillary MR findings for detecting tears and for differentiating partial from complete tears of the anterior cruciate ligament. MATERIALS AND METHODS: MR images of 68 patients who had arthroscopic correlation were retrospectively reviewed by two radiologists who did not know the arthroscopic findings. The reviewers noted the presence and location of bone bruises (nonlinear low signal in the bone marrow on T1-weighted images), assessed posterior displacement of the posterior horn of the lateral meniscus, and measured the posterior cruciate ligament angle. At arthroscopy, 39 patients had tears of the anterior cruciate ligament (24 complete, 15 partial) and 29 had intact anterior cruciate ligaments. RESULTS: The presence of bone bruising in the posterolateral tibial plateau had sensitivities of 50% and 46%, with corresponding specificities of 97% and 97% for the two reviewers. Posterior displacement of the posterior horn of the lateral meniscus had a sensitivity of 56% for both reviewers, with 100% and 97% specificities. An angle of the posterior cruciate ligament less than 105 degrees had sensitivities of 72% and 74%, with corresponding specificities of 79% and 86%. The prevalence of these findings was similar in patients with partial tears and those with complete tears. CONCLUSION: Ancillary MR imaging findings may be helpful for diagnosing tears of the anterior cruciate ligament when diagnosis based on the MR appearance of the ligament is equivocal. Ancillary findings cannot be used to differentiate patients with partial tears from those with complete tears. The presence of bone bruising in the posterior aspect of the tibial plateau and posterior displacement of the posterior horn of the lateral meniscus are highly specific for a torn anterior cruciate ligament; therefore, the presence of either of these findings should be considered strong evidence of a tear of the anterior cruciate ligament.

Adult↗
PubMed1992

A methodological review of "method skeptic" reports.

The literature purporting to demonstrate that clinical neuropsychology is of limited validity in the forensic setting is reviewed critically and alternative interpretations are discussed. The methodological, procedural, conceptual, data analytical and survey/research design limitations are evaluated.

Female↗
PubMed1992

Can MR imaging effectively replace diagnostic arthroscopy?

A study was performed to determine whether magnetic resonance (MR) imaging is cost-effective and reduces the need for diagnostic arthroscopy of the knee. During a 9-month period, 103 consecutive patients with knee injury that justified diagnostic arthroscopy underwent MR imaging. The MR images were interpreted by means of consensus of three radiologists and reviewed with the referring sports medicine orthopedists. After the examination, 44 patients (42.7%) underwent immediate arthroscopy. The 59 other patients (57.3%) did not undergo arthroscopy; follow-up was performed in 55 of these 59 patients (93%) at a mean of 22 months. The outcome was successful in 49 of 55 patients (89%); 40 patients had normal function and no limitation in activity, six patients with chronic injury of the anterior cruciate ligament underwent reconstruction, and three patients underwent arthroscopy with negative findings. Without the use of MR imaging, all patients in this study would have undergone diagnostic arthroscopy. Because of the diagnoses based on MR images, 53 patients (51.4%) avoided a potentially unnecessary diagnostic arthroscopy, and, as a result, the net savings was $103,700 in the 103 patients.

Adolescent↗
PubMed1991

Magnetic resonance imaging of the surgically repaired meniscus: six-month follow-up.

The appearance and rate of healing of sutured meniscal repairs in 17 patients were evaluated using magnetic resonance scans. While prior studies in animals and humans (1-4) suggest that complete healing can occur as early as 6 wk postoperatively, we found that at 7 wk 15/15 patients demonstrated meniscal defects at the site of repair. At 6 mo, 11/11 patients showed persistent signal abnormalities. Two patients scanned at 11-12 mo also had defects at the site of repair. Therefore, complete meniscal healing appears not to occur as early as previously believed. This may affect decisions regarding the type of suture material used, the surgical treatment of associated injuries and the postoperative rehabilitation regimen. As defects may be present for relatively long periods of time following meniscal repair, caution must be exercised when attempting to diagnose new or recurrent tears in these patients.

Adolescent↗
PubMed1991

Follow-up of grade 2 meniscal abnormalities in the stable knee.

A prospective study of grade 2 meniscal abnormalities in patients with intact anterior cruciate ligaments was done to ascertain whether such lesions progress to complete tears. A follow-up magnetic resonance (MR) image was obtained in 22 patients in whom the initial MR image showed a grade 2 lesion in one or both menisci that had been proved at arthroscopy not to be torn. On the initial images, 27 menisci contained a grade 2 lesion. At follow-up, six of the 27 lesions appeared to have decreased in size (two had completely disappeared). Eighteen lesions appeared unchanged; only three had increased in size. The mean interval between the acquisition of initial and follow-up images was 27.3 months (range, 11-41 months). The two patients whose lesion disappeared were among the youngest patients evaluated. The three patients whose abnormality increased were slightly older and more active than average. The results suggest that in most patients grade 2 lesions are stable at up to 3 years follow-up.

Adolescent↗
PubMed1990

Osteochondritis dissecans of the knee: a historical review of etiology and treatment.

Osteochondritis dissecans (OCD) is a common entity in both the juvenile and adult populations, with an incidence of 3 to 6/10,000 in adults. Much of the early literature grouped juvenile and adult osteochondritis dissecans, osteochondral fracture, and accessory ossification into the same category. Conclusions were then drawn on the combined group. Nonetheless, this is a diverse group. This review discusses only OCD. There have been multiple etiological theories of OCD, ranging from trauma to ischemia to accessory centers of ossification and to genetics. It is evident that the true etiology is probably multifactorial. Bone scan, computed tomographic scan, and magnetic resonance imaging advances have enhanced the physician's ability to make the diagnosis of osteochondritis dissecans as well as to stage operative intervention. There is a vast difference between juvenile and adult OCD, as seen in the natural history, prognosis, and treatment options. In general, the juvenile patients have better results overall. The indications for operative intervention for these juvenile patients are a nonhealing attached fragment, fully or partially detached lesions of the articular surface, and loose bodies. Nonoperative treatment in the adult patient has been shown to accelerate degenerative arthritis, which involves all 3 compartments of the knee. Therefore, symptomatic lesions and loose bodies comprise the surgical indications for adult OCD. An understanding of this disease process will help the physician optimize the patient's results.

England↗
PubMed1989

Independent home versus supervised rehabilitation following arthroscopic knee surgery--a prospective randomized trial.

This prospective study compared 30 patients randomly assigned to either a home exercise program or supervised outpatient physical therapy following arthroscopic partial medial meniscectomy. Their knee functions were assessed at 2, 4, and 8 weeks postoperatively using isokinetic analysis and subjective questionnaires. At each evaluation, the home exercise group performed as well or better than the supervised physical therapy group. There were no statistically significant differences between the two groups. At 4 weeks postoperation, the mean percent deficit in torque (strength) between the affected and unaffected limbs was 22.1% in the supervised rehabilitation group and 22.0% in the home exercise. The percent deficit in terms of endurance was 7.7% in the supervised group and 3.6% in the home group. Similar results were noted with regard to the patients' subjective evaluations of their knee function and ability to resume work and recreational activities. We conclude that a well-planned, unsupervised home exercise knee rehabilitation program can produce equally good postoperative recovery as compared to a supervised outpatient physical therapy regimen in properly selected patients following arthroscopic partial meniscectomy of the knee.

Adult↗