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Biomedical subjects

J R Heron

Publications and source records attributed to J R Heron.

At least 19 recordsLinked to original sources
PubMed1997

Early impairment of foveal magno- and parvocellular pathways in juxta chiasmal tumours.

Foveal pathway visual function was assessed in 11 patients having tumours extending into the suprasellar region but without evidence of visual impairment as assessed by visual acuity and Bjerrum screen campimetry. Psychophysical and routine visual evoked potential (VEP) measurements were obtained from the eye ipsilateral to the maximal suprasellar extension. The sensitivity of luminance and chromatic pathways was assessed psychophysically by measuring increment thresholds for white and red flashes of light presented on a white adapting field. Temporal sensitivity was assessed psychophysically by measuring threshold modulation sensitivity for sinusoidally modulating stimuli (de Lange attenuation characteristic). The patient group showed approximately equal significant psychophysical losses in chromatic, luminance and temporal sensitivities relative to normal controls. Midline VEP P100 latencies of the patient group did not significantly differ from those of the normal control group. It is concluded that tumours extending into the suprasellar region can cause foveal pathway dysfunction affecting both magno- and parvocellular pathways, even in the presence of normal visual acuity and fields suggesting a more widespread and insidious abnormality of the visual pathways in this condition than previously thought.

Adenoma↗
PubMed1995

Cerebral venous sinus thrombosis and antiphospholipid antibodies.

We report two cases of cerebral venous sinus thrombosis associated with an antibody to phospholipids, namely the lupus anticoagulant. Both patients later developed further immunologically mediated conditions. The importance of screening for the lupus anticoagulant in addition to anticardiolipin antibodies in this condition and the need for follow-up of such patients is discussed.

Adult↗
PubMed1994

Optic neuritis. Differential losses of luminance and chromatic function near a scotoma.

Visual sensitivity to achromatic and chromatic stimulus flashes was determined at sites just inside, on the boundary and just outside scotomata in 11 patients with recovered optic neuritis. The colour of the flashes and the size of the steady background on which they appeared were such that detection was more likely to be mediated by either the large-diameter, magnocellular fibres or the small-diameter, parvocellular fibres of the anterior visual pathway. The spacing of the test sites ranged from 0.5 degrees to 4 degrees visual angle, depending on the shape and location of the scotomata. The greatest differences in sensitivity were between sites just inside and just outside the scotoma and in response to achromatic stimuli more likely to involve the magnocellular fibres. This effect may be due to the size of magnocellular fibres or to their relatively smaller numbers.

Adult↗
PubMed1993

Abnormalities of visual function in hereditary motor and sensory neuropathy.

Visual function was studied in a group of 15 patients with hereditary motor and sensory neuropathy (HMSN). Psychophysical measures of luminance and chromatic threshold and temporal contrast sensitivity were undertaken, together with visual evoked potentials (VEPs), visual fields and clinical neuro-ophthalmological examination. A patchy loss of visual function was found in individual cases of HMSN. In the group analysis there was evidence of a selective loss of luminance threshold and temporal contrast sensitivity at low temporal frequencies; the VEP P100 latency was not significantly prolonged. The losses of visual function in HMSN were discussed and compared with visual losses in multiple sclerosis, which had been detected using identical experimental techniques.

Adolescent↗
PubMed1993

Recurrent confusion and hypopituitarism.

Three women in late middle age had recurrent episodes of confusion which could not be explained solely on the basis of an associated infection. All three patients had latent hypopituitarism diagnosed on final presentation. Each patient had a previous history of a severe postpartum haemorrhage followed by two further pregnancies. Experienced clinicians had not made a diagnosis of confusional episodes due to hypopituitary encephalopathy because the history was not immediately available in the confused patient, and the significance of deficient axillary and pubic hair was not given due emphasis.

Confusion↗
PubMed1990

Optic neuritis: variations in temporal modulation sensitivity with retinal eccentricity.

Temporal modulation sensitivity functions were measured centrally and at eccentricities of 2.5 degrees, 5 degrees and 10 degrees in the temporal visual field of 12 patients with recovered optic neuritis and in a group of matched normal controls. A circular, spatially uniform stimulus of 1 degree angular subtense was presented with sinusoidal modulation at 5, 8, 14 and 23 Hz. The general pattern of results in patients was a loss of sensitivity relative to normal controls at all temporal frequencies at 0 degree and 2.5 degrees eccentricity, with rather greater losses occurring at the medium-to-lower temporal frequencies. At 5 degrees eccentricity, the losses were confined to medium temporal frequencies only, and at 10 degrees eccentricity there was no significant loss at any temporal frequency. These findings may be explained by a greater vulnerability of optic nerve fibers of small diameters to the effects of demyelinating disease.

Adult↗
PubMed1990

Visual loss in multiple sclerosis and its relation to previous optic neuritis, disease duration and clinical classification.

Visual function was investigated in a group of 58 clinically classified cases of multiple sclerosis (MS). Psychophysical measures of luminance and chromatic threshold sensitivity and temporal contrast sensitivity were undertaken, together with visual evoked potentials and Bjerrum screen perimetry. The patient group was divided on the basis of optic neuritis (ON), clinical disease duration and clinical classification. A comparison of the results of all visual measures suggested a nonuniform loss of function in the patient group without ON and a more consistent loss of function in the group with ON. The various measures were equally efficient in detecting abnormal function, albeit from different areas of the central visual field. Clinical disease duration was not a significant independent factor in predicting visual dysfunction. In contrast, a comparison of clinical classification categories revealed significantly fewer abnormalities of visual function in the suspected MS category (31%) than in the ON, early probably and clinically definite categories (75-100%), a result which indicated the importance of clinical classification as a predictor of visual dysfunction.

Adult↗
PubMed1987

Paradoxical effects of temperature in multiple sclerosis.

Six cases of multiple sclerosis are reported in which cold produced a temporary exacerbation of symptoms and signs of the disease. Also, in one case investigated in detail by psychophysical methods, heating produced a paradoxical deterioration in vision and simultaneous improvement in sensory and motor function. The effect of temperature in multiple sclerosis is discussed and a physiological explanation for the paradoxical response to heating is suggested.

Adult↗
PubMed1986

The response to isoniazid of action tremor in multiple sclerosis and its assessment using polarised light goniometry.

Isonicotinic acid hydrazide (isoniazid) was evaluated in five patients as a treatment for the control of severe cerebellar action tremor occurring in multiple sclerosis. Oral doses of isoniazid BPC were increased every 2 weeks from 300 mg to 1200 mg daily over an 8 week period. Four patients reported considerable symptomatic benefit at doses ranging from 600 mg to 900 mg daily. Polarised light goniometry demonstrated a two to three-fold reduction of tremor in these patients when standard methods of clinical assessment showed only marginal improvement.

Adult↗
PubMed1985

Multiple sclerosis: abnormalities in luminance, chromatic, and temporal function at multiple retinal sites.

Visual function was assessed in a group of patients with multiple sclerosis (MS) and in a group of matched normal controls. In these patients the disease was relatively mild. For each subject, measures of a range of psychophysical visual functions were carried out at multiple sites in each eye. Previous reports have only included some of these functions. Here, luminance threshold, two-flash resolution, perceptual latency, luminance critical flicker frequency (CFF), and chromatic CFF were all measured. Variabilities of these functions and correlation between chromatic and luminance CFFs were also evaluated. For both the MS group and the normal control group, the correlations between pairs of visual parameters were not overall significantly greater than chance level. The MS group did give a significantly reduced value relative to the normal group for luminance CFF and for the gradient of the plot of chromatic CFF against luminance CFF. This group was then subdivided according to history of visual involvement. The subgroup with previous visual symptoms had significant impairment for luminance threshold, variability of luminance threshold, luminance CFF, variability of two-flash resolution, and for the gradient of the plot of chromatic CFF against luminance CFF. The subgroup without previous visual symptoms showed no significant impairment for any individual parameter, although the gradient of the plot of chromatic CFF against luminance CFF was lower than normal.

Adult↗
PubMed1985

Nonselective losses in foveal chromatic and luminance sensitivity in multiple sclerosis.

A psychophysical technique involving simple increment threshold measurements was used to determine foveal chromatic and luminance sensitivity in patients with multiple sclerosis (MS) and in matched normal controls. The patient group showed substantial and nonselective losses in chromatic and luminance sensitivity relative to the normal control group, and these losses were significantly correlated with each other over individual patients. It is suggested that impairment of foveal visual function due to demyelination is not more specific to fibers carrying chromatic information than to fibers carrying luminance information.

Adult↗
PubMed1984

Ambulatory electrocardiographic monitoring in patients with transient focal cerebral ischaemia.

Sixty-four patients with transient ischaemic attacks were investigated for the presence of an associated cardiac arrhythmia. 24-hour ambulatory monitoring showed arrhythmia in 41% of patients where the standard ECG had shown arrhythmia in only 25%. Significant arrhythmias were found in 21% of patients with focal transient ischaemic attacks on prolonged monitoring as compared to 7% in a control group. Where arrhythmias were specifically treated there was abolition or improvement of neurological symptoms.

Aged↗
PubMed1982

Rod- and cone-mediated visual function in multiple sclerosis.

Visual thresholds and perceptual latencies were determined in patients with multiple sclerosis (MS) and in normal control subjects. Measurements were made under light- and dark-adapted conditions, with stimuli chosen to stimulate rod and cone receptors selectively. More abnormalities in perceptual latency and luminance threshold were recorded in the light-adapted condition than in the dark-adapted condition, but this result was not specific to the rod or cone systems. Possible underlying pathophysiological processes are discussed, and it is suggested that reduced conduction velocity in the demyelinated visual pathway is the most likely explanation of the observed perceptual delays and that there is no evident retinal contribution.

Adult↗