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Biomedical subjects

P D Griffiths

Publications and source records attributed to P D Griffiths.

At least 37 records · Page 2Linked to original sources
PubMed2005

Imaging findings and referral outcomes of rapid assessment stroke clinics.

AIM: A rapid assessment stroke clinic (RASC) was established to provide a rapid diagnostic service to individuals with suspected transient cerebral or ocular ischaemia or recovered non-hospitalized strokes. In this report we review imaging findings and clinical outcomes of patients proceeding to the carotid surgery programme. METHODS: Between October 2000 and December 2002, 1339 people attended the RASC. The findings of head CT and carotid Doppler ultrasound of the 1320 patients who underwent brain and carotid imaging were reviewed, and the number subsequently proceeding to carotid angiography and intervention was reported. RESULTS: CT head scans were normal in 57% of cases; 38% demonstrated ischaemia or infarction; and 3% yielded incidental or other significant findings not related to ischaemia. On screening with carotid Doppler ultrasound, 7.5% showed greater than 50% stenosis on the symptomatic side. A total of 83 patients (6.2%) proceeded to cerebral angiography and 65 (4.8%) underwent carotid endarterectomy or endovascular repair. CONCLUSION: Rapid-access neurovascular clinics are efficient in selecting patients for carotid intervention, but this is at a cost and the number of potential strokes prevented is small. Alternative management pathways based on immediate medical treatment need to be evaluated.

Adult↗
PubMed2005

MR imaging of patients with localisation-related seizures: initial experience at 3.0T and relevance to the NICE guidelines.

The purpose of this study is to describe our initial experience of imaging adults with localisation-related epilepsy using MR imaging at 3.0T. We discuss the findings in the context of the recently released NICE guidelines that provide detailed advice on imaging people with epilepsy in the UK. 120 consecutive people over the age of 16 years with localisation-related epilepsy were referred for clinical MR examinations from a regional neuroscience centre in England. None of the people had had MR examinations prior to the present study. High resolution MR imaging was performed taking advantage of the high field strength and high performance gradients of the system. Two experienced neuroradiologists reported on the examinations independently and the presence and type of pathology was recorded. There was complete agreement between the two reporters in all 120 cases. The overall frequency of abnormalities shown by MR was 31/120 (26%) and the commonest abnormality shown was mesial temporal sclerosis found in 10/120 (8%). Tumours were shown in 4/120, all of which appeared low grade as judged by imaging criteria. Epilepsy is the commonest neurological condition and demands a significant resource in order to provide good care for sufferers. Recent guidelines published in the UK have suggested that the majority of people with epilepsy should receive brain MR as part of their routine assessment. Our work shows that using the most sophisticated MR imaging in a highly selected population there is a modest pick-up rate of brain abnormalities. If a widespread epilepsy-imaging programme is started the detection rate is likely to be much lower. Although MR is acknowledged to be a reliable way of detecting pathology in people with epilepsy there is a dearth of information studying the health economics of imaging epilepsy in relation to patient management and outcomes.

Adult↗
PubMed2005

Cerebral haemodynamic disturbances in patients with moderate carotid artery stenosis.

OBJECTIVE: Dynamic MR perfusion imaging can detect cerebral perfusion deficits resulting from severe internal carotid artery (ICA) stenosis. It is unknown, however, whether moderate ICA stenosis (50-69%) also causes haemodynamic disturbance. We investigated whether cerebral perfusion deficits were detectable in patients with moderate ICA stenosis. METHODS: Eighteen patients underwent T2* weighted cerebral MR perfusion imaging with a gadolinium based contrast agent. Differences in mean time to peak (mTTP) and relative cerebral blood volume (rCBV) between cerebral hemispheres were calculated for middle cerebral artery territory regions by a reader blinded to the angiographic and clinical findings. RESULTS: There were significant differences in mTTP between cerebral hemispheres in 15 patients with a mean inter-hemispheric delay in mTTP of 0.49 s (95% confidence intervals, 0.25 and 0.72 s) which was statistically significant ( p <0.001). In 1 patient with bilateral moderate stenosis there was no difference in mTTP. CONCLUSIONS: Moderate ICA stenosis results in significant ipsilateral cerebral perfusion delays detectable by dynamic susceptibility MRI. Follow-up studies might reveal whether these delays improve following carotid endarterectomy.

Aged↗
PubMed2005

First-line investigation of acute intracerebral hemorrhage using dynamic magnetic resonance angiography.

PURPOSE: To report the initial experience of magnetic resonance (MR) digital subtraction angiography (MR-DSA) in the dynamic assessment of the cerebral circulation in acute non-traumatic intracerebral hemorrhage (ICH). MATERIAL AND METHODS: Twelve patients with acute ICH were investigated within 6 days of the ictus using a dynamic contrast-enhanced 2-D MR angiogram that produces subtracted images with a temporal resolution of 1-2 frame/s. The MR-DSA examinations were assessed for evidence of an intracranial vascular abnormality and were compared with (i) the routine MR sequences, (ii) non-dynamic time-of-flight MR angiography, and (iii) catheter angiogram performed during the same admission. RESULTS: All 12 MR-DSA examinations were considered to be technically satisfactory. MR-DSA detected an intracranial vascular abnormality in 7 patients (3 arteriovenous malformations, 2 aneurysms, 1 dural arteriovenous fistula, and 1 venous thrombosis). All abnormalities were confirmed by catheter angiography with the exception of one patient with venous sinus thrombosis found on MR imaging that did not undergo catheter angiography. All four arteriovenous shunts were detected by MR-DSA by virtue of early venous filling. CONCLUSION: MR-DSA can be performed satisfactorily in the setting of acute ICH and provides an alternative method to catheter angiography for identifying shunting vascular abnormalities such as arteriovenous malformations and fistulae, as well as large aneurysms and venous occlusions. MR-DSA is a contrast-medium-based technique that does not suffer from the T1 shortening effects of acute hemorrhage that can obscure abnormalities on conventional flow-based non-dynamic techniques.

Adult↗
PubMed2005

Cerebellar abnormalities on proton MR spectroscopy in gluten ataxia.

Gluten sensitivity can manifest with ataxia. The metabolic status of the cerebellum was investigated in 15 patients with gluten ataxia and 10 controls using proton MR spectroscopy. Significant differences were present in mean N-acetyl aspartate levels at short echo time and N-acetyl aspartate/choline ratios at long echo time between the patient and control groups. These data support the hypothesis that cerebellar neuronal physiology differs between patients with gluten ataxia and healthy controls.

Adult↗
PubMed2004

Diffusion tensor imaging for the assessment of upper motor neuron integrity in ALS.

BACKGROUND: High angular resolution diffusion tensor imaging (HARD) is an MRI technique that exploits the mobility of water molecules to yield maps of structural order and directionality of white matter tracts with greater precision than six-direction diffusion tensor imaging (DTI) schemes. OBJECTIVE: To assess whether HARD is more sensitive than conventional MRI or neurologic assessment in detecting the upper motor neuron (UMN) pathology of patients with ALS. METHODS: Twenty-five patients with definite UMN clinical signs and 23 healthy volunteers underwent conventional MRI. HARD datasets were collected from a subset of these participants plus four patients with isolated lower motor neuron (LMN) signs. ALS symptom severity was assessed by a neurologist, the conventional MR images were reviewed by neuroradiologists, and the DTI maps were subject to quantitative region of interest analysis. RESULTS: Motor cortex hypointensity on T2-weighted images and corona radiata hyperintensity on proton density-weighted images distinguished patients with UMN involvement from volunteers with 100% specificity, but only 20% sensitivity. Fractional anisotropy (FA) was reduced in the posterior limb of the internal capsule in patients with UMN involvement compared to volunteers. A FA threshold value with a sensitivity of 95% to detect patients with ALS (including those with isolated LMN signs) had a specificity of 71%. CONCLUSIONS: High angular resolution diffusion tensor imaging may be more sensitive than conventional MRI or neurologic assessment to the upper motor neuron (UMN) pathology of ALS, but it lacks the specificity required of a diagnostic marker. Instead, it is potentially useful as a quantitative tool for monitoring the progression of UMN pathology.

Adult↗
PubMed2004

Kinetics of cytomegalovirus load decrease in solid-organ transplant recipients after preemptive therapy with valganciclovir.

The availability of valganciclovir (VGCV) has significantly simplified the treatment of human cytomegalovirus (HCMV) infection after solid-organ transplantation. We show that there was no difference in the kinetics of the decrease in HCMV load after preemptive therapy with VGCV in 22 solid-organ transplant recipients (T1/2=2.16 days), compared with that in 23 patients treated with intravenous ganciclovir (GCV) (T(1/2) = 1.73 days; P=.63). Preemptive therapy with VGCV provides control of HCMV replication that is comparable to that achieved with preemptive intravenous therapy with GCV.

Administration, Oral↗
PubMed2004

Effectiveness of intermediate care in nursing-led in-patient units.

BACKGROUND: The Nursing led inpatient Unit (NLU) is one of a range of services that have been considered in order to manage more successfully the transition between hospital and home for patients with extended recovery times. OBJECTIVES: To determine whether nursing-led inpatient units are effective in preparing patients for discharge from hospital compared to usual inpatient care. SEARCH STRATEGY: We searched The Cochrane Library, the Specialized Register of the Cochrane Effective Practice and Organisation of Care (EPOC) group, MEDLINE, CINAHL, EMBASE, BNI and HMIC databases. Citation searches were undertaken on the science and social science citation indices. Authors were contacted to identify additional data. SELECTION CRITERIA: Controlled trials and interrupted time series designs that compared the NLU to usual inpatient care managed by doctors. Patients over 18 years of age following an acute hospital admission for a physical health condition. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed study quality. MAIN RESULTS: Ten random or quasi-random controlled trials reported on a total of 1896 patients. There was no statistically significant effect on inpatient mortality ( OR 1.10, 95% CI 0.56 to 2.16) or mortality to longest follow up (OR 0.92, 95% CI 0.65 to 1.29) but higher qaulity studies showed a larger non-significant increase in inpatient mortality (OR 1.52, 95% CI 0.86 to 2.68). Discharge to institutional care was reduced for the NLU (OR 0.44 95% CI 0.22 to 0.89) and functional status at discharge increased (SMD 0.37, 95% CI 0.20 to 0.54) but there was a near significant increase in inpatient stay (WMD 5.13 days 95% CI -0.5 days to 10.76 days). Early readmissions were reduced (OR 0.52 95% CI 0.34 to 0.80). One study compared a NLU for the chronically critically ill with ICU care. Mortality (OR 0.62 95% CI 0.35 to 1.10) and length of inpatient stay differ did not differ (WMD 2 days, 95% CI 10.96 to -6.96 days). Early readmissions were reduced (OR 0.33 95% CI 0.12 to 0.94). Costs of care on the NLU were higher for UK studies but lower for US based studies. REVIEWERS' CONCLUSIONS: There is some evidence that patients discharged from a NLU are better prepared for discharge but it is unclear if this is simply a product of an increased length of inpatient stay. No statistically significant adverse effects were noted but the possibility of increased early mortality cannot be discounted. More research is needed.

Health Care Costs↗
PubMed2004

MR imaging and spectroscopy in Lhermitte-Duclos disease.

Lhermitte-Duclos disease is a rare abnormality occurring in the cerebellum with only 130 cases reported in the literature. There is debate as to whether this abnormality is a hamartoma, a malformation or a tumour. In this case report we discuss the spectroscopy findings from two patients presenting with this disease. The patients, one 40-year-old Caucasian woman with a 6-year history of headaches, unsteady gait and falls, deterioration in vision and another 28-year-old Caucasian man with a 1-year history of headaches and a previous history of a transient stroke, were found to have this lesion in the cerebellum. Proton spectroscopic data were obtained using a single-voxel PRESS technique (TE=135 ms, TR=1600 ms), from the region of the abnormality. The results were expressed as ratios under the three prominent resonances representing choline (Cho), creatine (Cr), and N-acetyl (NA) moieties. The metabolite ratios were compared to normative data. The two cases demonstrated reduced ratios in NA/Cho and NA/Cr in relation to the controls. The ratios of Cho/Cr appeared closer to the normal mean ratio. There were peaks attributable to lactate in both cases. The low NA/Cr and NA/Cho ratios could be due to the apparent lack of neuronal architecture and the presence of embryonic neural tissue, which does not express NA, indicating more favourably towards a 'benign' hamartoma rather than a tumour.

Adult↗
PubMed2004

Frequency and natural history of subdural haemorrhages in babies and relation to obstetric factors.

BACKGROUND: Subdural haematomas are thought to be uncommon in babies born at term. This view is mainly based on findings in symptomatic neonates and babies in whom subdural haemorrhages are detected fortuitously. We aimed to establish the frequency of subdural haemorrhages in asymptomatic term neonates; to study the natural history of such subdural haematomas; and to ascertain which obstetric factors, if any, are associated with presence of subdural haematoma. METHODS: We did a prospective study in babies who were born in the Jessop wing of the Central Sheffield University Hospitals between March, 2001, and November, 2002. We scanned neonates with a 0.2 T magnetic resonance machine. FINDINGS: 111 babies underwent MRI in this study. 49 were born by normal vertex delivery without instrumentation, 25 by caesarean section, four with forceps, 13 ventouse, 18 failed ventouse leading to forceps, one failed ventouse leading to caesarean section, and one failed forceps leading to caesarean section. Nine babies had subdural haemorrhages: three were normal vaginal deliveries (risk 6.1%), five were delivered by forceps after an attempted ventouse delivery (27.8%), and one had a traumatic ventouse delivery (7.7%). All babies with subdural haemorrhage were assessed clinically but no intervention was needed. All were rescanned at 4 weeks and haematomas had completely resolved. INTERPRETATION: Presence of unilateral and bilateral subdural haemorrhage is not necessarily indicative of excessive birth trauma.

Apgar Score↗
PubMed2004

Introduction: Is viral shedding a surrogate marker for transmission of genital herpes?

Genital herpes, caused by either herpes simplex virus type 1 or 2 (HSV-1 and HSV-2), is a significant public health problem worldwide. It increases the risk of infection with HIV, upregulates HIV after infection and can be associated with serious morbidity and mortality. It is now known that clinical and subclinical viral reactivation with resultant shedding from anogenital mucosa occurs frequently, resulting in transmission during sexual contact. Sexual transmission of HSV infection is common, even between monogamous individuals. Antiviral therapy reduces the frequency and degree of viral shedding and lowers the transmission rate in discordant monogamous couples, although transmission can still occur in people prescribed antiviral therapy. These encouraging data raise important questions for the management of genital HSV infection, particularly with regard to the prevention of transmission. Although the quantity of virus present is clearly important in transmission of some viruses, it is not clear whether this is the case for HSV transmission. Ideally, a surrogate marker needs to be able to identify individuals with detectable amounts of virus, and differentiate them from individuals with detectable amounts of virus that are transmissible. The aim of this supplement is to explore the issues surrounding the validation of surrogate markers of transmission of HSV, using examples from other human viral diseases, and to review the available evidence. In the future, exploration of these issues may shed light on management and prevention strategies. In particular, the results may clarify what evidence is required to warrant prescribing a drug for reducing HSV transmission, and for which patient populations this strategy is appropriate.

Biomarkers↗
PubMed2004

Lessons from HIV and hepatitis viruses.

Surrogate markers are an important component in the process of investigating management and prevention strategies, and for increasing understanding of viral diseases. The importance of surrogate markers and applied statistical models is particularly true for HIV. For HIV infection, the development of such methods provides new approaches for evaluation of HIV therapies and vaccines, and for the study of HIV transmission and its pathogenesis. The complex natural history of hepatitis B infection demonstrates that viral load is not the only predictor of transmission of this virus; for hepatitis C infection, viral load per se is not a prognostic factor for disease progression, but cumulative viral load may affect the outcome, and therapy is aimed at eliminating active viral replication.

Biomarkers↗
PubMed2004

HSV shedding.

Viral shedding of HSV occurs frequently in infected individuals. HSV is shed asymptomatically from multiple anatomical sites and shedding, like exposure, is a significant risk for transmission. However, the relationship between shedding frequency, viral titer and transmission is unknown. HSV-2 shedding is affected by the site and time since acquisition of infection. The advent of sensitive PCR techniques has shown that the magnitude and frequency of viral shedding is higher than shown previously with viral culture techniques. It has also clearly demonstrated that suppressive (daily) antiviral therapy reduces clinical and subclinical reactivation rates, and has been successfully used in the prevention of recurrent oral and genital HSV infections. A recent study has demonstrated that daily antiviral therapy with valaciclovir can significantly reduce transmission of HSV-2 between discordant heterosexual couples in monogamous relationships.

Acyclovir↗
PubMed2004

HSV-2 transmission.

A number of important risk factors for the acquisition of HSV-2 have been established including female gender, black or Hispanic ethnic origin, HIV infection, age, and increased number of sexual partners. Transmission is influenced by a number of biological factors such as sexual behavior, use of condoms, duration of relationships, and knowledge of a partner's serologic status. Vertical transmission (transmission of HSV from mother to neonate) is potentially life-threatening; neonatal HSV infection is associated with significant morbidity and mortality. The valaciclovir transmission study provides evidence that an antiviral agent can interrupt the transmission of a viral sexually transmitted disease between serologically discordant sexual partners. This review explores the importance of the cofactors that affect transmission, and makes recommendations on considerations for the prophylactic use of antiviral agents for the prevention of transmission in other patient populations.

Acyclovir↗
PubMed2004

Corroboration of in utero MRI using post-mortem MRI and autopsy in foetuses with CNS abnormalities.

AIMS: To corroborate the findings of in utero magnetic resonance imaging (MRI) with autopsy and post-mortem MRI in cases of known or suspected central nervous system (CNS) abnormalities on ultrasound and to compare the diagnostic accuracy of ante-natal ultrasound and in utero MRI. METHODS: Twelve pregnant women, whose foetuses had suspected central nervous system abnormalities underwent in utero MRI. The foetuses were imaged using MRi before autopsy. The data were used to evaluate the diagnostic accuracy of in utero MRI when compared with a reference standard of autopsy and post-mortem MRI in 10 cases and post-mortem MRI alone in two cases. RESULTS: The diagnostic accuracy of antenatal ultrasound and in utero MRI in correctly characterizing brain and spine abnormalities were 42 and 100%, respectively. CONCLUSION: In utero MRI provides a useful adjuvant to antenatal ultrasound when assessing CNS abnormalities by providing more accurate anatomical information. Post-mortem MRI assists the diagnosis of macroscopic structural abnormalities.

Adult↗
PubMed2004

Differential growth rates of the cerebellum and posterior fossa assessed by post mortem magnetic resonance imaging of the fetus: implications for the pathogenesis of the chiari 2 deformity.

PURPOSE: To evaluate post mortem magnetic resonance imaging of the fetus to provide data on the rate of growth of the cerebellum, bony posterior fossa, supratentorial bony compartment and cerebrum. MATERIAL AND METHODS: Twenty fetuses subsequently shown to have normal brain and spines on autopsy were studied using MRI post mortem. MRI from 20 normal pediatric brain examinations in children aged 6 years or younger were studied for comparison. Post mortem MRI was performed using a high-resolution fast spin echo technique providing T2 weighted images. The area of the cerebellar vermis, posterior fossa, supratentorial skull cavity and cerebral hemispheres was measured in the sagittal plane in all cases. These measurements were compared over the age ranges studied. RESULTS: We have shown that there are differences in the rate of growth and the apparent commencement of growth between the structures under study. The cerebellum appeared to start its significant growth at 16.5 weeks with a rate of 16 mm2/week throughout pregnancy, while the cerebral hemisphere appeared to commence significant growth at 13 weeks at a rate of 184 mm2/week throughout pregnancy. This is in contrast to the bony posterior fossa, whose growth paralleled the supratentorial bony compartment at all ages studied. CONCLUSION: We interpret our findings as showing relatively late commencement of cerebellar growth compared to the cerebral hemispheres, whereas the growth of the bony posterior fossa appears to be in advance and independent of cerebellar growth. Our results support the hypothesis that posterior fossa development depends on raised hydrostatic pressure in the CSF containing structures of the posterior fossa. When this mechanism fails, as in some cases of myelomeningocoele, a small posterior fossa is formed which characterizes the Chiari 2 malformation.

Arnold-Chiari Malformation↗
PubMed2004

A method of generalized projections (MGP) ghost correction algorithm for interleaved EPI.

Investigations into the method of generalized projections (MGP) as a ghost correction method for interleaved EPI are described. The technique is image-based and does not require additional reference scans. The algorithm was found to be more effective if a priori knowledge was incorporated to reduce the degrees of freedom, by modeling the ghosting as arising from a small number of phase offsets. In simulations with phase variation between consecutive shots for n-interleaved echo planar imaging (EPI), ghost reduction was achieved for n = 2 only. With no phase variation between shots, ghost reduction was obtained with n up to 16. Incorporating a relaxation parameter was found to improve convergence. Dependence of convergence on the region of support was also investigated. A fully automatic version of the method was developed, using results from the simulations. When tested on in vivo 2-, 16-, and 32-interleaved spin-echo EPI data, the method achieved deghosting and image restoration close to that obtained by both reference scan and odd/even filter correction, although some residual artifacts remained.

Algorithms↗