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Biomedical subjects

J Oxbury

Publications and source records attributed to J Oxbury.

11 recordsLinked to original sources
PubMed2000

Temporal lobe epilepsy with and without psychosis: exploration of hippocampal pathology including that in subpopulations of neurons defined by their content of immunoreactive calcium-binding proteins.

We have investigated relationships between hippocampal/temporal lobe neuropathology and psychosis in subjects with temporal lobe epilepsy, paying particular attention to possible differences in density of hippocampal neurons immunoreactive for calcium-binding proteins. There was a trend for a greater prevalence of left handedness in the psychotic (n = 6) than the non-psychotic (n = 26) cases (P = 0.0504). Psychotic cases also differed from non-psychotic ones in having: (1) more focal lesions outside the hippocampus (P = 0.006); (2) less severe CAI neuron loss (P = 0.015); and (3) a trend, after Bonferroni correction, for a higher density of calbindin-immunoreactive neurons in the CA4 (P = 0.022). An additional finding was that dentate granule cell dispersion was significantly associated with the presence of a reduced density of calretinin-immunoreactive neurons in CA4 (P = 0.002) and with a more severe loss of CA4 neurons visible with Nissl stain (P = 0.003). Thus, cases of temporal lobe epilepsy with psychosis were distinguishable on the basis of a higher density of calbindin-reactive neurons in CA4 as well as on more general aspects of their pathology.

Adolescent↗
PubMed2000

Five cases of brain injury following amniocentesis in mid-term pregnancy.

This paper describes the neuroimaging and neuropathological findings in five cases of severe brain damage after traumatic mid-trimester amniocentesis, all performed between 1986 and 1994. Although fetal injury after amniocentesis has been reported, reports of brain injury are infrequent. Continuous ultrasound monitoring may reduce the risk of fetal injury but follow-up ultrasound scans can be falsely reassuring. Withdrawal of blood-stained fluid, particularly if it contains tissue fragments, should alert the operator to the possibility of fetal damage. Histological examination of such tissue fragments may confirm the nature of the fetal damage. The consequences of fetal brain injury are severe, all five of our cases showed evidence of disruption of brain development compatible with mid-term injury. Obstetricians and their patients should be aware of the small but significant risk of brain damage after mid-term amniocentesis.

Adult↗
PubMed1999

Somatosensory extinction for meaningful objects in a patient with right hemispheric stroke.

Implicit, high level processing of extinguished objects has often been described in the visual modality. In the tactile domain, however, research on this topic is meagre and it is still uncertain whether processing of tactually presented stimuli can be affected by the same attentional disorders as visual stimuli. In this paper we describe a patient, ENM, with visual neglect and light touch extinction who, in a naming task of objects presented in the tactile modality, simultaneously to both hands, showed extinction for left hand objects. He was, nevertheless, able to make above chance Same/Different judgements on the two stimuli. We also tested two neurologically intact subjects who performed the test wearing a ski-glove on the left hand to impair the recognition of left hand objects. In these subjects, Same/Different judgements were at chance level when recognition rate was as low as that found in patient ENM. This happened when either the objects, although sharing the same name were different in shape (conditions Same-Different) or when the two objects were different with respect to the category name but were actually physically similar (conditions Different-Similar). However, when the objects were either identical or completely different, i.e., in a condition where judgement could be based simply on the physical analysis of the object shape (condition Same Identical and Different Dissimilar), their Same/Different judgements were above chance, despite the tactual deficit. Our conclusion was that patient ENM showed implicit recognition of left hand objects, at least in the Same Different and in the Different-Similar conditions, whereas, in the same conditions, normal subjects with an artificial sensory impairment did not. Our results also show that Same/Different judgements may be, in some conditions, less demanding than naming tasks, as suggested by Farah et al. Furthermore, patient ENM performed the test both with uncrossed and crossed hands. We found that extinction always affected the hand contralateral to the brain damage, although there was a tendency for a decrement of the ipsilesional hand performance in the crossed condition. We discuss these findings with reference to the most recent theories on the existence of a body centered spatial frame of reference.

Aged↗
PubMed1997

Severe amnesia: an usual late complication after temporal lobectomy.

A patient developed the severe amnesic syndrome 8 years after temporal lobe surgery for epilepsy. He underwent left temporal lobectomy (6 cm, 43.5 g; hippocampal sclerosis) aged 19, and remained seizure free for 8 years until a convulsion followed a head injury. He became severely amnesic after a fourth convulsion 16 months later. He was right-handed, pre-operative IQ was average, verbal memory poor and non-verbal memory normal. Post-operatively, these were unchanged. After the first post-operative seizure he began professional training. After onset of amnesia IQ was unchanged, anterograde memory severely impaired and retrograde amnesia dense for at least 16 months. He died 2 years later. Magnetic resonance imaging before amnesia showed absence of anterior left temporal lobe, atrophy of left fornix and mamillary body, and normal right temporal lobe. Four months after onset of amnesia, right hippocampal volume had reduced by 36%. Autopsy showed: previous left temporal lobectomy with absence of left amygdala and hippocampus, atrophy of fornix and mamillary body; neuronal loss in the right hippocampus, severe in CA1 and CA4; intact right amygdala and parahippocampal gyrus; recent diffuse damage associated with cause of death. A convulsion can cause severe hippocampal damage in adult life. Hippocampal zones CA1 and/or CA4 are critical for maintaining memory and the amygdala and parahippocampal gyrus cortex alone cannot support acquisition of new memories.

Adult↗
PubMed1997

Hemifield-specific visual recognition memory impairments in patients with unilateral temporal lobe removals.

Recent evidence on visual neglect suggests that each hemisphere maintains a retinotopically organized representation of the visual world contralateral to the current fixation point and that this representation is based not only on analysis of the current retinal input but, equally importantly, on information retrieved from memory. This idea predicts that unilateral damage to memory systems should produce a lateralized impairment of memory for the retinotopically contralateral visual world. To test this prediction we examined visual recognition memory performance in the left and right visual hemifields of patients who had undergone partial unilateral temporal lobe removals for the relief of epilepsy, either in the left hemisphere (n = 5) or the right (n = 5). The patients were given complex artificial scenes to remember, constructed of independent left and right halves, and were then tested for recognition of the left and the right halves separately. Stimuli were exposed tachistoscopically throughout and fixation was maintained on a central position. Patients made significantly more errors with half-scenes in the hemifield contralateral to their removal than in the ipsilateral hemifield, an increase of 50% in the error rate on average. The effect was seen equally in patients with left and right removals. This finding supports the idea that visual memory retrieval is retinotopically organized.

Adult↗
PubMed1995

Selective amygdalohippocampectomy for hippocampal sclerosis: postoperative MR appearance.

PURPOSE: To analyze the anatomic consequences of selective amygdalohippocampectomy (AH) in patients with hippocampal sclerosis and to correlate the clinical outcome with the MR appearance. METHODS: Seventeen patients were examined with clinical and neuropsychologic examination and cranial MR after AH (7 transcortical AH, 10 trans-Sylvian AH). The clinical and neuropsychologic outcomes after AH were compared with those of anterior lobectomy (ATL). RESULTS: There was no significant difference in seizure cure between transcortical or trans-Sylvian AH and ATL. However, patients with left AH fared significantly better in terms of verbal IQ and nonverbal memory when compared with those with left ATL. Verbal memory and cognition were not significantly different in the two AH groups. Variable amounts of hippocampal and amygdala remnants were found in both AH groups and did not correlate with seizure cure. White matter change consistent with gliosis probably secondary to wallerian degeneration was demonstrated in the anterior temporal lobe to a mean distance of 4.5 cm after transcortical AH and to a lesser degree as a consequence of trans-Sylvian AH. Nine patients (53%) (4 transcortical All, 5 trans-Sylvian AH) demonstrated wallerian degeneration in the optic radiations after surgery. All had incomplete contralateral quadrantanopia. CONCLUSIONS: There is more secondary damage to the temporal lobe after AH than was previously recognized. The extent of hippocampal and amygdala resection in AH do not seem to be directly related to seizure cure. Visual field defects are common in AH because of the anterior but variable course of the optic radiations

Adolescent↗
PubMed1992

Levels of processing for visual stimuli in an "extinguished" field.

Volpe et al. (Nature 282, 722, 1979 [19]) described an experimental study of four patients with parietal tumours who were able to judge whether two simultaneous stimuli were identical or different, even when they were unable to name the stimulus contralateral to their brain injury. We report the case of another patient, E.M., in whom we have investigated this phenomenon further. E.M. had undergone a right temporal lobectomy to prevent recurrent seizures. She could correctly name photographs of objects presented in isolation to either the left or right visual field, at 150 msec exposure (although she was impaired for single objects on the left at 10 msec exposures). She was able to judge correctly whether two simultaneous objects on the left and right had the same or different names, even though she was often unable to name the object on the left. These judgements remained above chance when same-name pairs of stimuli showed the same object but seen from two different viewpoints, or even when they showed visually dissimilar exemplars of the same name category. This implies that the patient based her same-different judgements on categorical information about the pair of objects, even though she was often unable to name the contralateral object.

Adult↗
PubMedDate not supplied

The role of light scatter in the residual visual sensitivity of patients with complete cerebral hemispherectomy.

Various residual visual capacities have been reported for the phenomenally blind field of hemispherectomized patients, providing evidence for the relative roles of cortical and subcortical pathways in vision. We attempted to characterize these functions by examining the ability of five patients to detect, localize, and discriminate high-contrast flashed, flickering and moving targets. Dependent measures were verbal, manual, and oculomotor responses. As a control for light scatter, intensity thresholds for monocular detection of targets in the hemianopic field were compared with thresholds obtained when using an additional half eyepatch to occlude the blind hemiretina of the tested eye. One unilaterally destriate patient was tested on the same tasks. In photopic conditions, none of the hemispherectomized patients could respond to visual cues in their impaired fields, whereas the destriate patient could detect, discriminate, and point to targets, and appreciate the apparent motion of stimuli across his midline. Under reduced lighting, the threshold luminance required by hemispherectomized patients to detect stimuli presented monocularly was similar to that required for their detection when all visual information was occluded in the blind field, and only available to the visual system indirectly via light scatter. In contrast, the destriate patient's monocular threshold in his blind field was substantially lower than that for stimuli directly occluded in the blind field. As we found no range of stimuli which the hemispherectomized patients could detect or discriminate that was not also associated with discriminable scattered light, we conclude that the subcortical pathways which survive hemispherectomy cannot mediate voluntary behavioural responses to visual information in the hemianopic field.

Adolescent↗