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Biomedical subjects

G T Plant

Publications and source records attributed to G T Plant.

At least 19 recordsLinked to original sources
PubMed2006

Structural anatomy of pure and hemianopic alexia.

BACKGROUND: The two most common types of acquired reading disorder resulting from damage to the territory of the dominant posterior cerebral artery are hemianopic and pure alexia. Patients with pronounced hemianopic alexia have a right homonymous hemianopia that encroaches into central or parafoveal vision; they read individual words well, but generate inefficient reading saccades when reading along a line of text. Patients with pure alexia also often have a hemianopia but are more disabled, making frequent errors on individual words; they have sustained damage to a brain region that supports efficient word identification. OBJECTIVE: To investigate the differences in lesion site between hemianopic alexia and pure alexia groups, as rehabilitative techniques differ between the two conditions. METHODS: High-resolution magnetic resonance images were obtained from seven patients with hemianopic alexia and from six patients with pure alexia caused by a left occipital stroke. The boundary of each lesion was defined and lesion volumes were then transformed into a standard stereotactic space so that regional comparisons could be made. RESULTS: The two patient groups did not differ in terms of damage to the medial left occipital lobe, but those with pure alexia had additional lateral damage to the posterior fusiform gyrus and adjacent tissue. CONCLUSIONS: Clinicians will be able to predict the type of reading disorder patients with left occipital lesions have from simple tests of reading speed and the distribution of damage to the left occipital lobe on brain imaging. This information will aid management decisions, including recommendations for reading rehabilitation.

Aged↗
PubMed2006

Is the frequency of abnormalities on magnetic resonance imaging in isolated optic neuritis related to the prevalence of multiple sclerosis? A global comparison.

The link between optic neuritis and multiple sclerosis is well established, as is the increased risk of conversion to multiple sclerosis, with lesions seen at presentation on the magnetic resonance imaging (MRI) scan of the brain. One or more asymptomatic lesions were present in 77% of the optic neuritis cohort from London, UK, a higher proportion than that reported in other large cohorts studied elsewhere, where generally lower prevalence rates for multiple sclerosis are also reported. These observations may support the hypothesis that optic neuritis is more likely to be associated with abnormalities on MRI and to be due to multiple sclerosis in geographical regions where multiple sclerosis is more common.

Adolescent↗
PubMed2006

Quantification of optic nerve head topography in optic neuritis: a pilot study.

AIMS: To investigate optic nerve head topography in patients with optic neuritis compared to controls using the Heidelberg retina tomograph-II (HRT-II) and to determine if detected changes are related to visual function and electrophysiology. METHODS: 25 patients with a previous single episode of unilateral optic neuritis and 15 controls were studied with HRT-II, visual evoked potentials, and pattern electroretinogram. Patients also had testing of visual acuity, visual field, and colour vision. RESULTS: In affected eyes compared to fellow eyes, there was reduction of both the mean retinal nerve fibre layer (RNFL) thickness at the disc edge (p = 0.009) and the neuroretinal rim volume (p = 0.04). In affected eyes compared to control eyes, the three dimensional optic cup shape measure was increased (p = 0.01), indicative of an abnormal cup shape. There were no other significant differences in HRT-II measures. Within patient interocular difference correlation was used to investigate the functional relevance of these changes and demonstrated associations between RNFL thickness change and changes in visual acuity, visual field, and colour vision. Colour vision change was also associated with change in neuroretinal rim volume. CONCLUSIONS: HRT detects functionally relevant changes in RNFL thickness and neuroretinal rim volume between eyes affected by optic neuritis and unaffected fellow eyes.

Adult↗
PubMed2006

Ventricular enlargement in MS: one-year change at various stages of disease.

OBJECTIVES: To investigate ventricular enlargement (VE) over 1 year at three different stages of multiple sclerosis (MS). METHODS: A semi-automated technique for measuring VE was applied to MRI scans in 26 patients with clinically isolated syndromes (CIS) suggestive of MS, 30 with early relapse-onset MS of 1 year duration, 41 with established relapsing remitting (RR) MS, and 23 with secondary progressive (SP) MS. RESULTS: VE at 1 year was seen in early MS (median increase 0.3 mL [p = 0.003]), RRMS (median increase 0.5 mL [p = 0.001]), and SPMS (median increase 1.1 mL [p = 0.001]). Allowing for age there was more VE in the SPMS group (p = 0.005). No VE was observed in the CIS only group (median decrease -0.001 mL [p = 0.829]). Significant increases in T2 and T1 hypointense lesion load volume were seen in all MS subgroups: there were no differences between the groups in T2 volume increase but there was a larger increase in T1 hypointense lesion volume in the SPMS group compared with early RRMS. CONCLUSIONS: Ventricular enlargement is a sensitive measure of progressive cerebral atrophy that is seen at all stages of multiple sclerosis (MS) and is more marked in secondary progressive than relapsing remitting MS.

Adolescent↗
PubMed2005

Magnetization transfer histograms in clinically isolated syndromes suggestive of multiple sclerosis.

In established multiple sclerosis, magnetization transfer ratio (MTR) histograms reveal abnormalities of normal-appearing white matter (NAWM) and grey matter (NAGM). The aim of this study was to investigate for such abnormalities in a large cohort of patients presenting with clinically isolated syndromes suggestive of multiple sclerosis. Magnetization transfer imaging was performed on 100 patients (67 women, 33 men, median age 32 years) a mean of 19 weeks (SD 3.8, range 12-33 weeks) after symptom onset with a clinically isolated syndrome and in 50 healthy controls (34 women, 16 men, median age 32.5 years). SPM99 software was used to generate segmented NAWM and NAGM MTR maps. The volumes of T2 lesions, white matter and grey matter were calculated. Eighty-one patients were followed up clinically and with conventional MRI after 3 years (n = 61) or until they developed multiple sclerosis if this occurred sooner (n = 20). Multiple regression analysis was used to investigate differences between patients and controls with age, gender and volume measures as covariates to control for potential confounding effects. The MTR histograms for both NAWM and NAGM showed a reduction in the mean (NAWM, 38.14 versus 38.33, P = 0.001; NAGM 32.29 versus 32.50, P = 0.009; units in pu) and peak location, with a left shift in the histogram. Mean NAWM and NAGM MTR were also reduced in the patients who developed clinically definite multiple sclerosis and multiple sclerosis according to the McDonald criteria but not in the 24 patients with normal T2-weighted brain magnetic resonance imaging (MRI). MTR abnormalities occur in the NAWM and NAGM at the earliest clinical stages of multiple sclerosis.

Adult↗
PubMed2005

Modification of MRI criteria for multiple sclerosis in patients with clinically isolated syndromes.

BACKGROUND: The McDonald criteria include MRI evidence for dissemination in space and dissemination in time for the diagnosis of multiple sclerosis in young adult patients who present with clinically isolated syndromes (CIS) typical of the disease. Although a major advance, the criteria have limited sensitivity for making an early diagnosis. OBJECTIVE: To compare the performance of McDonald criteria and modified McDonald criteria for dissemination in space and time for assessing the development of clinically definite multiple sclerosis. METHODS: McDonald criteria were modified using the combination of a less stringent definition for dissemination in space and allowing a new T2 lesion per se after three months as evidence for dissemination in time. Modified and McDonald criteria were applied in 90 CIS patients at baseline and at three month follow up scans. RESULTS: Both criteria were highly specific (>90%) but the modified criteria were more sensitive (77% v 46%) and more accurate (86% v 73%). CONCLUSIONS: These modified criteria should be evaluated in other CIS cohorts.

Cohort Studies↗
PubMed2005

Brain biopsy in dementia.

Brain biopsy has an uncertain role in the diagnosis of dementia. Here we report a retrospective analysis of 90 consecutive cerebral biopsies undertaken for the investigation of dementia in adults at a tertiary referral centre between 1989 and 2003. In most cases (90%), biopsy consisted of a right frontal full thickness resection of cortex, white matter and overlying leptomeninges. Fifty-seven per cent of biopsies were diagnostic: the most frequent diagnoses were Alzheimer's disease (18%), Creutzfeldt-Jakob disease (12%) and inflammatory disorders (9%). Other diagnoses in individual patients included Pick's disease, corticobasal degeneration and other tauopathies, Lewy body dementia, multiple sclerosis, Whipple's disease, progressive multifocal leucoencephalopathy, cerebral autosomal dominant arteriopathy with subcortical ischaemic leucoencephalopathy, vasculopathies and paraneoplastic encephalopathy. The most frequent biopsy finding in the non-diagnostic group and for the series as a whole (37%) was non-specific gliosis variably affecting both cortex and white matter. Complications (11%) included seizures, intracranial and wound infections, and intracranial haemorrhage; there were no deaths or lasting neurological sequelae attributable to the procedure. No trends in diagnostic yield or complication rate over the course of the series were identified. Information obtained at biopsy determined treatment in 11%. A raised cerebrospinal fluid cell count was the only robust predictor of a potentially treatable (inflammatory) process at biopsy. The constellation of behavioural change, raised CSF protein and matched oligoclonal bands in CSF and serum was associated with non-specific gliosis at biopsy. This series underlines the value of cerebral biopsy in the diagnosis of dementia, and suggests that certain clinical and laboratory features may be useful in guiding the decision to proceed to brain biopsy where a treatable disease cannot be excluded by other means.

Adolescent↗
PubMed2005

Paroxysmal raised intracranial pressure associated with spinal meningeal cysts.

Raised intracranial pressure in association with spinal meningeal cysts has rarely been reported. We describe four patients in whom evidence of paroxysmal raised intracranial pressure was found in association with spinal meningeal cysts. Cerebrospinal fluid diversion procedures have previously been shown to relieve local symptoms due to spinal cysts. In our patients symptoms of paroxysmal headache were alleviated by this method, suggesting a causal relationship with the raised pressure. This association may be an under diagnosed cause of paroxysmal headaches. We review the medical literature on the classification of spinal meningeal cysts, evaluate the theories of their origin and offer suggestions on the pathogenesis of the abnormal CSF dynamics that may allow an interplay between raised intracranial pressure and spinal meningeal cysts to produce paroxysmal symptoms.

Adolescent↗
PubMed2005

The optic nerve sheath on MRI in acute optic neuritis.

Optic nerve sheath dilatation or gadolinium-enhancement on magnetic resonance imaging in acute optic neuritis have been previously reported but have been thought to be rare occurrences. This study recruited 33 patients with acute unilateral optic neuritis. All had their optic nerves imaged with fat-saturated fast spin-echo (FSE) imaging, and 28 had imaging before and after triple-dose gadolinium-enhanced fat-saturated T(1)-weighted imaging. Follow-up imaging was performed on 20 patients (15 following gadolinium). A dilated subarachnoid space at the anterior end of the symptomatic optic nerve on FSE imaging was seen in 15/33 cases. In three of these cases, dilatation was visible on short-term follow-up. Optic nerve sheath enhancement was seen in 21/28 cases acutely: seven at the anterior end of the lesion only, five at the posterior end only and nine at both ends. Optic sheath enhancement was seen in 13 patients on follow-up. This study suggests that optic nerve sheath dilatation on FSE images and optic nerve sheath enhancement on triple-dose gadolinium-enhanced images are common findings in acute optic neuritis. Optic nerve sheath dilatation may be due to inflammation of the optic nerve, with its associated swelling, interrupting the communication between the subarachnoid space of the diseased optic nerve and the chiasmal cistern. Optic nerve sheath enhancement suggests that meningeal inflammation occurs in optic neuritis, in agreement with pathological studies of both optic neuritis and multiple sclerosis.

Acute Disease↗
PubMed2005

Optic disc duplication or coloboma?

AIM: To describe lesions resembling optic disc duplication and highlight their unusual visual fields. The authors also report the first case of pseudo-duplication of the optic disc with overlying retinal nerve fibre layer. METHODS: Retrospective, non-comparative review of case notes. Humphrey visual fields and OCT-3 imaging were performed. RESULTS: All 11 cases represented peripapillary chorioretinal coloboma, some of which lie superior to the optic disc. A double blind spot or superior hemifield defects can be demonstrated by automated visual field testing. CONCLUSION: Clinical examination and identification of bridging retinal vessels from the true optic disc to the second pseudo disc can usually avoid unnecessary invasive and non-invasive investigations.

Adolescent↗
PubMed2005

ALK positive inflammatory myofibroblastic tumour of the pineal region.

Inflammatory myofibroblastic tumours (IMTs) are an uncommon spindle cell neoplasm with a dense inflammatory infiltrate, usually encountered in children. IMTs of the central nervous system are extremely rare. This report describes the case of an IMT in a 61 year old man, in the pineal region. The tumour was completely excised, and immunohistochemistry demonstrated anaplastic lymphoma kinase 1 expression. There was no tumour recurrence during 18 months of follow-up. Our case extends both the age range and sites of occurrence of this rare tumour.

Anaplastic Lymphoma Kinase↗
PubMed2005

Optic flow induced nystagmus.

A new form of nystagmus is described in this paper: optic flow induced nystagmus (OFN). Optic field flow, for example when driving or viewing films on a large screen, triggered non-fatiguable upbeat nystagmus. This type of nystagmus could not be induced by vestibular stimuli, positioning, or self motion. The aetiology and anatomical correlate of OFN remains unknown. Treatment with gabapentin suppressed OFN.

Adult↗
PubMed2004

Elevated white matter myo-inositol in clinically isolated syndromes suggestive of multiple sclerosis.

Normal-appearing white matter (NAWM) in established multiple sclerosis has been shown to be abnormal using a variety of magnetic resonance (MR) techniques, including proton MR spectroscopy ((1)H-MRS), although the stage at which these changes first appear is less clear. Using a 1.5 T scanner and single-voxel (1)H-MRS [TR 3000 ms, TE 30 ms, point-resolved spectroscopy (PRESS) localization], we determined NAWM metabolite concentrations in 96 patients a mean of 19 weeks (range 12-28 weeks) after onset of a clinically isolated syndrome (CIS) suggestive of multiple sclerosis and in 44 healthy control subjects. Absolute concentrations of N-acetyl-aspartate, total creatine and phosphocreatine (Cr), choline-containing compounds, glutamate plus glutamine, and myo-inositol (Ins) were estimated automatically using the LCModel. Compared with control subjects, the concentration of Ins was elevated in CIS NAWM (mean 3.31 mM, SD 0.86 versus mean 3.82 mM, SD 1.06; P = 0.001). The increase in Ins was also seen in the patient subgroup with abnormal T2-weighted MRI (mean 3.88 mM, SD 1.10; P = 0.001) and in those who satisfied the McDonald criteria for multiple sclerosis (mean 4.04 mM, SD 1.31; P = 0.001). An increase in Cr was also observed in CIS NAWM (P = 0.023), but other metabolites did not significantly differ between the whole CIS group and control subjects. There was no significant correlation between NAWM Ins and T2 lesion load. The early increase in Ins may reflect a process of pathogenic importance in multiple sclerosis NAWM. Follow-up studies will investigate whether the increase in NAWM Ins is of prognostic importance for future relapses and disability.

Adolescent↗
PubMed2004

Serial magnetization transfer imaging in acute optic neuritis.

In serial studies of multiple sclerosis lesions, reductions in magnetization transfer ratio (MTR) are thought to be due to demyelination and axonal loss, with later rises due to remyelination. This study followed serial changes in MTR in acute optic neuritis in combination with clinical and electrophysiological measurements to determine if the MTR changes over time mirror the picture in multiple sclerosis lesions, further validating MTR as a marker of tissue integrity. Twenty-nine patients were recruited who had acute optic neuritis for a median of 13 days (range 7-24 days) since the onset of visual symptoms. A clinical examination and measurement of visual evoked potentials (VEP) was performed on each patient. Their optic nerves were imaged with a fat-saturated fast spin echo (FSE) sequence and a magnetization transfer sequence. Twenty-one had multiple subsequent examinations over the course of 1 year. In addition, 27 control subjects had their optic nerves imaged up to three times over 1 year. A blinded observer segmented the optic nerves from the MTR maps. Lesions were defined on the acute FSE images and, from the coordinates, the ratio of mean lesion MTR : healthy nerve MTR (lesion ratio) was calculated for each dataset. The time-averaged mean MTR in control optic nerves was 47.7 per cent units (pu). In diseased optic nerves, baseline mean MTR was 47.3 pu, with a mean lesion ratio of 0.98. The diseased optic nerve MTR and lesion ratio declined over time with a nadir at about 240 days at a mean MTR value of 44.2 pu and mean lesion ratio of 0.91. Subsequently, diseased optic nerve MTR appeared to rise; after 1 year the diseased optic nerve mean MTR was 45.1 pu (mean lesion ratio 0.93), although the difference was not significant compared with the nadir value. For each 0.01 increase in time-averaged lesion ratio logMAR visual acuity recovery improved by 0.03 (95% CI, 0.002, 0.08, P = 0.02). Time-averaged VEP central field latency was shorter by 6.1 ms (95% CI 1.5, 10.7, P = 0.012) per 1 pu rise in time-averaged diseased optic nerve MTR. The early fall in diseased optic nerve MTR is consistent with demyelination and Wallerian degeneration of transected axons. The late nadir compared with studies of multiple sclerosis lesions may have been due to slow clearance of myelin debris. Remyelination may have influenced subsequent MTR changes. The observations support using MTR to monitor symptomatic demyelinating lesions.

Acute Disease↗