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Biomedical subjects

G T Plant

Publications and source records attributed to G T Plant.

At least 37 records · Page 2Linked to original sources
PubMed2004

[Treatment of optic neuritis].

Optic neuritis manifests itself as a reversible loss of vision. It can be a clinically isolated incident or one of the (first) manifestations of multiple sclerosis (MS). Its differential diagnosis is extensive, and management of other disorders can differ radically. In a typical case, treatment with corticosteroids hastens recovery of vision but does not affect the eventual degree of recovery. There is a substantial risk of developing MS after isolated optic neuritis (approximately 50% within 20 years), especially if asymptomatic white matter lesions are found on MRI scanning of the brain. Intravenous treatment with methylprednisolone may delay the onset of MS somewhat, but after three years the benefit of this treatment is lost. Treatment with interferon beta-Ia in high-risk patients also slows down the progression to clinically definite MS, but the long-term benefits are uncertain. MR imaging of the brain has implications for prognosis but not for treatment.

Brain↗
PubMed2004

Functional magnetic resonance imaging of the cerebral response to visual stimulation in medically unexplained visual loss.

BACKGROUND: Medically unexplained visual loss occurs in 1 to 5% of patients attending ophthalmology clinics and for many it runs a chronic course. A psychogenic aetiology is presumed in such cases, but little is known about the underlying neural mechanisms. Recent studies have established the value of functional magnetic resonance imaging (fMRI) in understanding the mechanisms of unexplained motor and sensory symptoms. The purpose of this study was to use a similar strategy (fMRI) to evaluate the cerebral responses to visual stimulation in a group of patients with medically unexplained visual loss, in an attempt to determine the underlying neural mechanisms. METHOD: Brain activation induced by periodic (monocular) 8 Hz visual stimulation was detected by fMRI in five patients with unexplained visual loss who fulfilled DSM-IV criteria for conversion disorder, and seven normal volunteers. Between-group differences in mean power of activation were estimated by fitting a one-way analysis of variance (ANOVA) model at each intracerebral voxel in standard space. RESULTS: Compared with controls, patients showed reduced activation in visual cortices, but increased activation in left inferior frontal cortex, left insula-claustrum, bilateral striatum and thalami, left limbic structures, and left posterior cingulate cortex. CONCLUSIONS: This preliminary study has identified novel neural correlates in patients with unexplained visual loss. The abnormal pattern of activation may reflect inhibition of primary visual cortex or a shift towards non-conscious (implicit) processing.

Adolescent↗
PubMed2004

Neuro-ophthalmological disorders in HIV infected subjects with neurological manifestations.

AIMS: To determine the frequency and features of neuro-ophthalmological manifestations in neurologically symptomatic HIV infected patients and to assess whether or not the visual evoked potential (VEP) features in these patients differ from those of neurologically asymptomatic HIV infected patients. METHODS: Neuro-ophthalmological evaluation was performed in 166 neurologically symptomatic confirmed HIV positive patients, of whom 75 with normal ophthalmological examination were further studied by means of VEPs. The VEPs values were compared to those obtained from 53 other confirmed HIV positive subjects with neither ophthalmological nor neurological manifestations, who served as a comparison group and to the references values of our laboratory. RESULTS: An abnormal neuro-ophthalmological examination was noted in 99/166 patients (60%). Eye movement disorders were present in 99 patients (51%). Visual field defects were detected in 39% of the patients. Optic neuropathy was noted in 31%, papilloedema in 27% and ocular motor nerve palsies in 26% of the patients. Toxoplasmosis and cryptococcosis were the most frequent associated pathologies, though in some patients the HIV itself was the presumed cause. VEPs were abnormal in 57% and 42% of patients with and without neurological manifestations, respectively. Compared to asymptomatic patients, symptomatic patients had a significantly increased mean latency; however, both groups had significant increase in mean latency compared to reference values. CONCLUSION: Neuro-ophthalmological manifestations are common in neurologically symptomatic HIV infected patients. Subclinical dysfunction in the visual pathways is a common phenomenon in both HIV infected patients with and without neurological symptoms, but neurologically symptomatic patients seem to have more damage in their visual pathways.

Adult↗
PubMed2004

Raised intracranial pressure presenting with spontaneous periorbital bruising: two case reports.

The venous drainage of the orbit is known to be via the ophthalmic and vortex veins which communicate with the cavernous sinus. We describe two patients with raised intracranial pressure presenting with periorbital bruising. In one patient dural venous sinus thrombosis was demonstrated and it is suspected that the cause of the raised intracranial pressure may have been the same in the second. We suggest that the abrupt rise of pressure in the cerebral venous system was transmitted via the cavernous sinus to the orbital venous system.

Adult↗
PubMed2004

Axonal degeneration and inflammation in acute optic neuritis.

AIMS: To investigate whether plasma biomarkers for axonal injury and inflammation are related to loss and recovery of visual function in acute optic neuritis (ON). METHODS: Eighteen patients with ON and 14 controls were investigated in a longitudinal, prospective study. Plasma phosphorylated neurofilament heavy chain (NfHSMI35; a surrogate marker of axonal injury), nitric oxide metabolites (NOx), and citrulline (surrogate markers of inflammation) were measured. RESULTS: Patients with ON had higher median plasma NfHSMI35 values than controls (0.17 versus 0.005 ng/ml; p < 0.05) and higher NOx values (49 versus 35.5 microM; p < 0.001). Plasma NfHSMI35 values correlated inversely with visual acuity at presentation (R = -0.67; p = 0.01). NfHSMI35 was higher in patients with poor recovery of visual acuity than in those with good recovery (0.25 ng/ml versus 0.09 ng/ml; p < 0.05). Three of four patients with high NfHSMI35 and high NOx values experienced a poor recovery as opposed to only one of five with high NOx but normal NfH(SMI35) values. CONCLUSIONS: NfHSMI35, a surrogate marker for axonal damage, is a prognostic indicator and should be considered in the design of neuroprotective treatment strategies.

Acute Disease↗
PubMed2004

Optic chiasm enhancement associated with giant aneurysm and yttrium treated pituitary adenoma.

A patient with a history of pituitary tumour treated with yttrium 29 years before presented with an asymmetrical chiasmal neuropathy. Magnetic resonance imaging showed a partially thrombosed giant aneurysm of the right internal carotid artery, with enhancement of the chiasm and right optic tract adjacent to the aneurysm. It was thought that, in addition to the effects of compression, a peri-aneurysmal inflammatory reaction had developed, causing breakdown of the blood-brain barrier and consequent inflammatory changes in the optic chiasm. High dose steroid treatment led to significant improvement in vision within two weeks. Steroids may have a role in the acute preservation of vision in similar cases, as well as in cases of deterioration following coiling or embolisation of aneurysms where thrombosis within the aneurysm has been induced.

Adenoma↗
PubMed2003

Chronic relapsing inflammatory optic neuropathy (CRION).

We describe the clinical characteristics and early natural history of a form of inflammatory optic neuropathy which is frequently bilateral and often painful, and is characterized by relapses and remissions. MRI scans of the brain are normal and those of the optic nerves often, but not always, show high signal abnormalities which enhance. The symptoms and signs respond well to corticosteroid treatment, although long-term immuno suppression is often necessary. The syndrome behaves in a way which is typical of the condition known as granulomatous optic neuropathy, but during a median follow-up of 8 (2-26) years in no case has evidence for systemic sarcoidosis been identified. We suggest that the disorder be named chronic relapsing inflammatory optic neuropathy (CRION).

Adult↗
PubMed2003

"Bottom-up" and "top-down" effects on reading saccades: a case study.

OBJECTIVE: To investigate the role right foveal/parafoveal sparing plays in reading single words, word arrays, and eye movement patterns in a single case with an incongruous hemianopia. METHODS: The patient, a 48-year-old right handed male with a macular sparing hemianopia in his left eye and a macular splitting hemianopia in his right eye, performed various reading tasks. Single word reading speeds were monitored using a "voice-trigger" system. Eye movements were recorded while reading three passages of text, and PET data were gathered while the subject performed a variety of reading tasks in the camera. RESULTS: The patient was faster at reading single words and text with his left eye compared with his right. A small word length effect was present in his right eye but not his left. His eye movement patterns were more orderly when reading text with his left eye, making fewer saccades. The PET data provided evidence of "top-down" processes involved in reading. Binocular single word reading produced activity in the representation of foveal V1 bilaterally; however, text reading with the left eye only was associated with activation in left but not right parafoveal V1, despite there being visual stimuli in both visual fields. CONCLUSIONS: The presence of a word length effect (typically associated with pure alexia) can be caused by a macular splitting hemianopia. Right parafoveal vision is not critically involved in single word identification, but is when planning left to right reading saccades. The influence of top-down attentional processes during text reading can be visualised in parafoveal V1 using PET.

Hemianopsia↗
PubMed2003

Spinal cord MRI in clinically isolated optic neuritis.

BACKGROUND/METHODS: One hundred and fifteen patients with clinically isolated optic neuritis underwent magnetic resonance imaging (MRI) of the brain and spinal cord within 3 months of the onset of symptoms. RESULTS: Eighty one (70%) patients had brain lesions and 31 (27%) had cord lesions. Cord lesions were seen in 12% with a normal brain MRI, 21% with between one and eight brain lesions, and 45% with nine or more brain lesions. When the new diagnostic criteria for MS were applied, MRI cord imaging used for evidence of dissemination in time and space allowed a diagnosis of MS in only one additional asymptomatic patient at 1 year, two additional asymptomatic patients at 3 years. CONCLUSIONS: Using existing criteria, spinal cord imaging rarely contributes to the diagnosis in patients with clinically isolated optic neuritis.

Adolescent↗
PubMed2003

Giant cell arteritis mimicking idiopathic orbital inflammatory disease.

PURPOSE: To report an unusual presentation of giant cell arteritis, referred from primary care, mimicking orbital apex syndrome. CASE REPORT: A 72 year old woman was referred with a two week history of pyrexia, dull right eye ache, 2mm of right proptosis, mild conjunctival chemosis and restriction of right eye movements. RESULTS: An erythrocyte sedimentation rate (ESR) was 90 and fluorescein angiography showed almost complete choroidal non-perfusion suggestive of giant cell arteritis. Temporal artery biopsy confirmed the diagnosis. CONCLUSIONS: Giant cell arteritis (GCA) typically presents with anterior ischemic optic neuropathy (AION), choroidal ischemia, central retinal artery occlusion, infrequently manifesting as an ocular motility problem, but has rarely been known to mimick idiopathic orbital inflammatory disease. Prompt recognition and therapy can minimize the chance of ipsilateral ocular involvement and protect the fellow eye.

Aged↗
PubMed2002

Management of acute optic neuritis.

Optic neuritis is a common condition that causes reversible loss of vision. It can be clinically isolated or can arise as one of the manifestations of multiple sclerosis. Occasional cases are due to other causes, and in these instances management can differ radically. The treatment of optic neuritis has been investigated in several trials, the results of which have shown that corticosteroids speed up the recovery of vision without affecting the final visual outcome. Other aspects of management, however, are controversial, and there is uncertainty about when to investigate and when to treat the condition. Here we review the diagnostic features of optic neuritis, its differential diagnosis, and give practical guidance about management of patients. The condition's association with multiple sclerosis will be considered in the light of studies that define the risk for development of multiple sclerosis and with respect to results of trials of disease-modifying drugs in these individuals.

Adrenal Cortex Hormones↗
PubMed2002

Functional magnetic resonance imaging of the cortical response to photic stimulation in humans following optic neuritis recovery.

Recovery from optic neuritis has been shown to be associated with an abnormal functional MRI (fMRI) response following exposure of the eye to an epoch based (ON-OFF design) flickering photic stimulus. Visual cortex activation is reduced during photic stimulation, whilst extra-occipital areas are extensively activated with a peak blood oxygen level dependent response during the OFF phase of the stimulus paradigm. We performed a further fMRI experiment to determine whether the abnormal extra-occipital response is a phase-specific phenomenon or whether it results from a delayed haemodynamic response. A cohort of patients that recovered from optic neuritis was studied, this time using a longer photic stimulation epoch (40 s). The extra-occipital response again peaked during the baseline condition, indicating that the phenomenon is phase dependent. Our results also reinforce the important findings of extra-occipital activation following optic neuritis which may represent an adaptive reorganization of the cerebral response.

Adult↗
PubMed2002

Normal-appearing brain tissue MTR histograms in clinically isolated syndromes suggestive of MS.

Segmented normal-appearing brain tissue (NABT) was investigated in 40 patients with a recent onset and 13 patients with a remote onset of a clinically isolated syndrome (CIS) using magnetization transfer ratio (MTR) histograms. Abnormalities were present in patients with a high risk for MS (recent onset and T2-weighted lesions present) and in those with a low risk for relapse (recent onset without T2-weighted lesions). Similar mild NABT abnormality was present with CIS and no further disease activity 14 years later. NABT MTR abnormality in CIS may indicate susceptibility to demyelination but not to disease progression.

Adult↗