Biomedical subjects
Publications and source records attributed to C Kennard.
A subacute necrotizing myopathy developed in a patient treated with epsilon amino-caproic acid (EACA) for subarachnoid hemorrhage. The muscle biopsy showed features suggesting that the muscle fiber necrosis might have been due to capillary damage. An attempt to induce EACA myopathy in the rat was made, but no abnormality developed.
Damage to the striate cortex usually causes blindness in those regions of the visual field which map to the area of neural damage. Nonetheless, there are reports that some patients with such damage can localize and perform certain visual discriminations between light stimuli presented within the 'blind' area of the visual field. Experiments on animals with different brain areas ablated suggest that visual function is served by two principal projection pathways from the retina. That to the striate cortex is primarily responsible for fine discrimination between stimulus parameters such as colour and spatial pattern, whereas that to the superior colliculus in the midbrain is responsible for visual localization of stimuli. The residual visual functions in patients with cortical damage are usually attributed to the non-striate retinal projection to the superior colliculus. We now present measurements of spatial discrimination in two observers with large visual field defects (scotomata) caused by damage to the striate cortical region. Both exhibit a near normal ability to discriminate displacements of targets when two lights are flashed sequentially in their defective visual field, but they are unable to discriminate spatial pattern or size. We argue that these results are consistent with the 'two visual systems' interpretation of ablation studies on non-human species.
Eye-head movements to target steps of amplitude 3.75 degrees to 30 degrees were analyzed in 9 untreated patients with idiopathic Parkinson's disease. Testing was performed before and after the introduction of a dopamimetic drug (L-dopa or bromocriptine) and compared with 9 normal controls. The patients showed a significantly greater scatter of mean head latencies prior to treatment, although their mean latencies were not significantly prolonged. When compared to controls, the patients' head movements were of reduced peak velocity and gain. Treatment resulted in an improvement of gain but not velocity. Analysis of the frequency of gaze types showed no significant effect of treatment.
Fourteen patients in the latent phase of Menière's disease and 14 control subjects were tested on a moving platform apparatus as part of a protocol of investigations for Menière's disease. Subjects were tested under 3 different visual conditions (eyes open, eyes closed, sway feedback) and 2 proprioceptive conditions (fixed platform and ankle stabilization). There was a significant interaction between subject group and visual condition, Menière's patients had a larger RMS sway amplitude than controls with their eyes open and closed, but this difference was abolished by sway feedback. Loss of either visual or proprioceptive sensory information increased sway amplitude, indicating that both cues influence postural control, and in different ways, but patients were able to use these cues to maintain upright posture almost as effectively as controls. More patients than controls lost balance with ankles stabilized and eyes closed, but the difference was not statistically significant (P = 0.0516). There was no detectable relationship between clinical ratings of disease severity and sway scores. The dynamic platform tests described in this report are more suitable for tests involving comparisons between groups of subjects rather than for diagnostic testing of individuals.