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Biomedical subjects

P N Tyrrell

Publications and source records attributed to P N Tyrrell.

At least 19 recordsLinked to original sources
PubMed2007

Angiography of primary central nervous system angiitis of childhood: conventional angiography versus magnetic resonance angiography at presentation.

BACKGROUND AND PURPOSE: To systematically analyze conventional angiographic (CA) features of children with primary central nervous system angiitis (cPACNS), to compare and correlate CA and MR angiography (MRA) lesion characteristics, and to define the sensitivity and specificity of MRA with CA as a reference standard. METHODS: A retrospective, single-center cohort study of consecutive patients with cPACNS was performed. Patients with CA and MRA studies at diagnosis were included. Imaging studies were blindly reviewed by 2 neuroradiologists using a standard analysis protocol. CA and MRA studies were compared using nonparametric analysis. RESULTS: Of 45 patients with MRA at diagnosis, there were 25 for whom CA and MRA studies were performed within 1 month of each other. These comprised the study group. The CA distribution of lesions was multifocal (76%) and proximal (86%) (P < .05) with a trend toward unilaterality (P = .06) with anterior circulation involvement (P = .08). The sensitivity and specificity of MRA for CA abnormality was 70% and 98%, respectively. There was no significant difference between MRA and CA for lesion detection or characterization (P = .87), and the modalities showed a fair correlation (kappa = 0.4). CONCLUSION: Angiographic lesions are multifocal and occur proximally and unilaterally within the anterior circulation. There is no significant difference in the ability of MRA to detect and characterize lesions when compared with CA.

Adolescent↗
PubMed2006

Tumour necrosis factor alpha inhibitors in the treatment of childhood uveitis.

OBJECTIVE: To describe the efficacy of anti-TNF-alpha agents in the treatment of childhood uveitis. METHODS: We performed a retrospective chart review of all children with uveitis treated with TNF-alpha blockers at The Hospital for Sick Children, Toronto. RESULTS: Twenty-one children with uveitis were treated with the anti-TNF-alpha agents etanercept (11 patients) and infliximab (13 patients), resulting in 24 treatment courses. All patients had persistently active uveitis despite treatment with at least one standard immunosuppressive drug before the start of anti-TNF-alpha therapy. Six of 21 patients (29%) had idiopathic uveitis. In the other 15 patients, the underlying disease was juvenile idiopathic arthritis in 12 (57%), Behçet disease in two (9%) and sarcoidosis in one (5%). Response to etanercept treatment was good in 27%, moderate in 27% and poor in 45% of patients. Response to infliximab treatment was good in 38%, moderate in 54% and poor in 8% of patients. The difference in the percentage of patients with a moderate or good response was statistically significant (P = 0.0481). We also observed a lower rate of complications, such as new-onset or worsening glaucoma or cataract in the infliximab-treated group. CONCLUSION: Anti-TNF-alpha treatment was beneficial in a high percentage of patients with childhood uveitis refractory to standard immunosuppressive treatment. Infliximab resulted in better clinical responses with less ocular complications than etanercept.

Adolescent↗
PubMed2006

MR imaging and angiography of primary CNS vasculitis of childhood.

BACKGROUND AND PURPOSE: Primary angiitis of the central nervous system of childhood (cPACNS) is a rare and ill-defined disease. In the absence of a brain biopsy, the diagnosis is based on typical clinical and imaging abnormalities. The aim of this study was to analyze systematically the MR imaging and MR angiographic (MRA) abnormalities in a large cohort of children with cPACNS. METHODS: We analyzed the MR imaging features of a single pediatric center cohort of 45 cPACNS patients. MR imaging studies were performed for all patients, and both MR imaging and MRA were performed for 42 patients, who formed the cohort for review of the presence and correlation of lesions. Proportions were calculated by using the Fisher exact test, and agreement between MR imaging and MRA was calculated by using the McNemar test. The sensitivity of each diagnostic technique was established. RESULTS: The most-common pattern of parenchymal abnormality was multifocal, unilateral involvement, each in 42/45 patients (93%). The lateral lenticulostriate artery terrritory was affected in 56% of cases, with involvement of a supratentorial deep gray matter structure in 91%. No infratentorial lesion occurred in the absence of supratentorial abnormality. MRA was normal in 12/42 patients (28.6%). Among the abnormal studies, stenosis was detected on MRA in 83% and was "benign" in appearance in 73% of patients and "aggressive" in 16.7%. Involvement was proximal in 83% and distal in 27% of patients. Multiple ipsilateral lesions were seen in 63%. MR imaging was abnormal in every patient where MRA was abnormal. With the assumption of MR imaging as the gold standard, the sensitivity of MRA was 72%. The agreement between MR imaging and MRA for abnormality was significant (P = .04). CONCLUSION: We have illustrated the MR imaging and MRA appearances of cPACNS in the largest cohort to date. Both parenchymal and vascular lesions were predominantly proximal, unilateral, and multifocal within the anterior circulation. There was good agreement between MR imaging and MRA for lesion location. MR imaging findings were abnormal in all cases at diagnosis, and this remains the most sensitive technique to the detection of vasculitis.

Adolescent↗
PubMed2005

The effectiveness of treating juvenile dermatomyositis with methotrexate and aggressively tapered corticosteroids.

OBJECTIVE: Childhood dermatomyositis (DM) is often a chronic disease, lasting many years. It has traditionally been treated with long-term corticosteroid therapy; side effects are often seen. For more than a decade, methotrexate (MTX) has been safely used for the treatment of juvenile arthritis. Here, we report use of MTX as first-line therapy for DM, along with aggressively tapered corticosteroids, in an attempt to reduce treatment-related side effects. METHODS: We studied an inception cohort of 31 children with DM who were rigorously followed up in our myositis clinic, and compared them with a control group of 22 patients with incident cases of juvenile DM who received treatment just before we instituted a policy of first-line therapy with MTX. The mean starting dosage of MTX in the study group was 15 mg/m(2)/week. RESULTS: Both groups had similar improvement in strength and physical function; however, the median time during which patients in the study group received corticosteroids was 10 months, compared with 27 months for controls (P < 0.0001). As a result, the cumulative prednisone dose in the study group was approximately half that in the control group (7,574 mg versus 15,152 mg; P = 0.0006). The study group had greater height velocity during the first year of treatment and a smaller increase in the body mass index over the first 2 years. In the control group, the relative risk of cataracts developing was 1.95 (95% confidence interval 1.05-4.17). Side effects of MTX were rarely observed. CONCLUSION: Use of MTX in conjunction with an aggressively tapered course of prednisone may be as effective as traditional long-term corticosteroid therapy for children with DM, while decreasing the cumulative dose of corticosteroids.

Dermatomyositis↗
PubMed2001

MRI detection of unsuspected vertebral injury in acute spinal trauma: incidence and significance.

OBJECTIVE: Multilevel spinal injury is well recognised. Previous studies reviewing the radiographs of spinal injury patients have shown an incidence of 15.2% of unsuspected spinal injury. It is recognised that magnetic resonance imaging (MRI) can identify injuries that are not demonstrated on radiographs. The objective of this study was to determine the incidence and significance of spinal injuries using MRI in comparison with radiographs. DESIGN AND PATIENTS: The radiographs and MR images of 110 acute spinal injury patients were reviewed independently of each other and the findings were then correlated to determine any unsuspected injury. RESULTS: MRI detected vertebral body bone bruises (microtrabecular bone injury) in 41.8% of spinal injury patients which were not seen on radiographs. These bone bruises were best appreciated on sagittal short tau inversion recovery MR sequences and seen at contiguous and non-contiguous levels in relation to the primary injury. CONCLUSION: This level of incidence of bone bruises has not previously been appreciated. We recommend that patients undergoing MRI for an injured segment of the spine are better assessed by MRI of the entire spine at the same time to exclude further injury.

Humans↗
PubMed2001

Magnetic resonance imaging assessment for unicompartmental knee replacement: a limited role.

The purpose of this study was to see if MRI has a role in pre-operative assessment of patients for unicompartmental knee replacement. Until now, surgeons have been unable to predict whether a patient is suitable until the operation itself when the anterior cruciate ligament is inspected. We found that 33% of patients with anteromedial osteoarthritis had a degenerate anterior cruciate ligament according to magnetic resonance imaging, compared to only 13% on surgical inspection. We conclude that MRI is too sensitive to changes of the anterior cruciate ligament to be of much practical value.

Anterior Cruciate Ligament↗
PubMed2000

Intra-articular ganglion cysts of the cruciate ligaments.

Intra-articular ganglion cysts of the cruciate ligaments are associated with non-specific clinical signs and symptoms. Familiarity with the MR appearances in particular is important to make an accurate diagnosis, exclude associated abnormalities, and avoid misdiagnosis.

Anterior Cruciate Ligament↗
PubMed1999

Spinal infection.

Spinal infection is a significant cause of morbidity. Despite advances in antibiotic treatment regimens, the incidence is not decreasing due at least in part to an increase in 'at-risk' populations, namely the elderly and the immunocompromised. Prompt diagnosis is greatly facilitated by early and appropriate imaging techniques together with microbiological assessment following culture from blood, needle aspirate and biopsy material. This article gives an overview of imaging of spinal infection with an emphasis on MR imaging, which has greatly contributed to early diagnosis, thus allowing implementation of timely appropriate treatment.

Adult↗
PubMed1999

MRI appearances of the infrapatellar fat pad in occult traumatic patellar dislocation.

AIM: A study was undertaken to determine the status of Hoffa's infrapatellar fat pad in instances of acutely dislocated patellae. MATERIALS AND METHODS: The study consisted of MR examinations performed on 18 consecutive patients with acutely dislocated and relocated patellae with a mean interval between injury and MR examination date of 14.8 days (range 1-60 days). An analysis of the attachments and intrinsic signal characteristics of the fat pad was performed for each individual case. RESULTS: Hoffa's fat pad was abnormal in all cases. Shear injury from the inferior pole of the patella was present in 16 cases. Intrasubstance disruption with fluid filled clefts were noted in 12 cases. In 17 cases diffuse oedema of Hoffa's fat pad had occurred. In nine cases the damaged fat pad mimicked a loose body, while in five cases an intra-articular post-traumatic loose body was identified. CONCLUSION: Post-traumatic change in Hoffa's fat pad is a constant secondary MR feature not previously reported, that can be added to the spectrum of indirect findings in cases of occult patellar dislocation. In addition, the MRI distinction between post-traumatic changes in Hoffa's infrapatellar fat pad from loose osteo-chondral bodies can be difficult, requiring further correlative imaging.

Adipose Tissue↗
PubMed1998

Gadolinium-DTPA enhancement of symptomatic nerve roots in MRI of the lumbar spine.

Disc prolapse presenting with sciatica may be associated with enhancement of the symptomatic nerve root following magnetic resonance imaging (MRI) with intravenous gadolinium (Gd)-DTPA. Previous studies have shown, however, that this does not occur in all cases. The aim of this study was to assess the incidence of nerve root enhancement in patients with sciatica and disc prolapse and to try to identify any specific features that might be associated with the phenomenon. A total of 227 patients presenting with low back pain and/or sciatica underwent a MRI study of the lumbar spine with intravenous contrast enhancement. Nineteen of 81 (23.5 %) patients with disc prolapse demonstrated nerve root enhancement. Nerve root enhancement had a highly significant association with sequestrated disc lesions (13/19, 68 %; P < 0.0005), and was primarily seen in the symptomatic ipsilateral nerve root (16/19, 84 %). The sensitivity of nerve root enhancement associated with disc prolapse was 23.5 % with a specificity of 95.9 %, a positive predictive value of 76 % and a negative predictive value of 69.3 %. Nerve root enhancement may be indicative of the symptomatic level but its poor sensitivity negates the routine use of Gd-DTPA in MRI for sciatica.

Contrast Media↗
PubMed1998

Ossification of the posterior longitudinal ligament in Down's syndrome.

Cervical myelopathy in patients with Down's syndrome is not uncommonly the result of atlanto-axial instability, a condition that is caused by ligamentous laxity and which may be associated with congenital osseous anomalies at the occipito-atlanto-axial axis. Ossification of the posterior longitudinal ligament (OPLL) is well described, particularly in the Japanese population, and may be associated with diffuse idiopathic skeletal hyperostosis. This is the first case, to our knowledge, of OPLL occurring in a person with Down's syndrome presenting with myelopathy.

Down Syndrome↗
PubMed1995

Signal changes in the intervertebral discs on MRI of the thoracolumbar spine in ankylosing spondylitis.

Contrary to standard teaching in magnetic resonance imaging (MRI), recent reports have documented calcification appearing as areas of increased signal intensity (SI) on T1-weighted images. Intervertebral disc calcification is a frequent finding on radiographs in chronic ankylosing spondylitis (AS). This study was performed to investigate the appearance of variable degrees of disc calcification in MRI. Thirty-six patients with AS of variable duration underwent an MRI scan of the thoraco-lumbar spine and the MR appearances, particularly of the discs, were compared with plain radiographs. Increased SI of the discs on T1-weighted images were found in 17 of 36 patients, occurring over a range of disc levels, and correlating with disc calcification on the radiographs in 78% of cases. This group tended to be older and have a longer duration of disease than those with normal appearing discs. Four different patterns of increased signal within the discs termed Type A (marginal), Type B (annular), Type C (central) and Type D (solid) were identified. In those with less than six discs involved Type A was the most common pattern. In those with more than six discs involved Type D was the most common pattern, suggesting a progression of disc involvement with more advanced disease. Although these findings will not affect the management of the disease, they do highlight the recently described phenomenon of calcification appearing as increased SI on T1-weighted images, likely to be related to the surface area of the calcium crystal. This should lead to the consideration of calcium in the differential diagnosis of increased SI on T1-weighted images. End-plate marrow changes were a relatively frequent finding in this study but did not correlate with the signal changes seen within the discs; in a number of cases they related to variable degrees of bony bridging.

Adult↗
PubMed1995

Short communication: a lateral will do?

Efforts to reduce the dose of diagnostic medical irradiation by applying selective criteria for radiographic examinations have been addressed by the Royal College of Radiologists in their Guidelines. Reduction of the number of views of an area has also been suggested by some authors. Deviating from one of the fundamentals of skeletal radiology which requires at least two views of any part of the skeleton may lead to misdiagnosis. This concept is considered in relation to the lumbar spine. Continued routine acquisition of at least two views for the radiographic examination of the lumbar spine is stressed.

Humans↗
PubMed1994

Multicystic dysplastic kidney: another application of 99mTc MAG3.

The value of 99mTechnetium-mercapto acetyl triglycine (99mTcMAG3) in the investigation of 10 children with suspected multicystic dysplastic kidney (MCDK) has been assessed. The condition has to be distinguished from hydronephrosis, usually caused by pelviureteric junction obstruction. Based on our findings, we propose that 99mTc MAG3 replace 99mTc DMSA because it allows a better assessment of the contralateral kidney and permits a full assessment where the diagnosis is hydronephrosis rather than MCDK.

Adolescent↗
PubMed1994

Pathogenesis of gall stones in Crohn's disease: an alternative explanation.

The increased prevalence of gall stones in Crohn's disease is thought to be related to depletion of the bile salt pool due either to terminal ileal disease or after ileal resection. This study was designed to examine whether this hypothesis is correct and explore alternative explanations. Two hundred and fifty one randomly selected patients (156 females, 95 males, mean age 45 years) were interviewed and screened by ultrasonography to determine the prevalence of gall stones in a large population of patients with Crohn's disease. Sixty nine (28%) patients had gall stones proved by ultrasonography (n = 42), or had had cholecystectomy for gall stone disease (n = 27). The risk factors for the development of gall stones including sex, age, site, and duration of disease, and previous intestinal resection were examined by multivariate analysis. Age and duration of disease were positive risk factors for gall stones and were covariables. The site of disease and of previous intestinal resection did not predispose to gall stones. Previous surgery was an independent risk factor for the development of gall stones, the risk increasing with number of laparotomies. It is suggested that mechanisms other than ileal dysfunction may predispose to gall stones. Postoperative gall bladder hypomotility with biliary sludge formation may be precursors of gall stone formation in patients with Crohn's disease.

Adolescent↗
PubMed1994

Magnetic resonance imaging appearances of fatigue fractures of the long bones of the lower limb.

Fatigue fractures may be confused with malignant bone lesions on radiography and hence are periodically referred for further imaging assessment with computed tomography (CT) and magnetic resonance imaging (MRI). The appearances on MRI are characteristic although not pathognomonic. Typical findings include: intramedullary bands of low signal intensity, continuous at some point with the cortex, indicative of a fracture line; intramedullary areas of high signal on both T2-weighted and short-tau inversion recovery (STIR) images representing marrow oedema or haemorrhage, together with evidence of periosteal oedema. We present seven cases of fatigue fractures of the long bones of the lower limb and discuss the MRI findings and compare CT and MRI in imaging these lesions.

Adolescent↗