Biomedical subjects

K S O'Neill

Publications and source records attributed to K S O'Neill.

5 recordsLinked to original sources

PubMed2002

Orbitofrontal cortex mediates inhibition of return.

Recent accounts have proposed that orbitofrontal cerebral cortex mediates the control of behavior based on emotional feedback and its somatic correlates. Here, we describe the performance of a patient with circumscribed damage to orbitofrontal cortex during a task that requires switching between sensory-motor mappings, contingent on the occurrence of positive and negative reward feedbacks. In this test, normal subjects and other patients with prefrontal damage show an increase in latencies for eye movements towards locations at which a negative feedback was presented on the preceding trial. In contrast, our patient does not show this reward-dependent inhibition of return effect on saccades. She was also found to make an increased rate of ocular refixations during visual search and used a disorganized search strategy in a token foraging task. These findings suggest that orbital regions of the prefrontal cortex mediate an inhibitory effect on actions directed towards locations that have been subject to negative reinforcement. Further, this mechanism seems to play a role in controlling natural search and foraging behavior.

Adult↗

PubMed2000

A retrospective study of surgical and conservative treatment for spinal extradural abscess.

The management of spinal extradural abscess (SEA), particularly the choice between surgical and conservative treatment, is controversial. We therefore undertook a retrospective study of patients admitted with this diagnosis: Details of presentation, treatment and outcome were obtained by review of inpatient notes and radiology. Twenty-five individuals with SEA aged 10-79 years were admitted between 1989 and 1995. Nine were treated non-operatively with antibiotics, of which three also underwent diagnostic CT-guided biopsy, and 16 underwent surgical drainage. There was no significant difference in the neurological features at presentation between the two groups. Two patients (8%) died; 11 (44%) patients remained the same and 12 (48%) improved following treatment. Four patients treated conservatively (44%) and seven treated surgically (43%) were capable of return to work or school, whilst a further seven patients (three treated conservatively and four treated surgically) were able to lead independent lives. No significant difference in outcome was demonstrated between patients treated non-operatively and those treated surgically. We conclude that certain carefully selected patients can be treated conservatively, but that surgery should remain the mainstay of management.

Abscess↗

PubMed1998

Cerebellitis presenting as acute hydrocephalus.

A 14-year-old boy presented acutely with occipital headache, nausea and vomiting. MRI showed obstructive hydrocephalus and marked bilateral cerebellar swelling with increased signal on T2-weighted imaging. Following treatment with oral corticosteroids, the clinical and radiological signs resolved. The clinical course and radiological appearances were consistent with cerebellitis associated with a significant mass effect and hydrocephalus.

Adolescent↗

PubMed1998

Cerebral blood flow and tissue oxygenation monitoring during aneurysm surgery.

Regional cerebral blood flow may be compromised during aneurysm surgery. This may occur during vessel occlusion by temporary clips or result from malposition of the definitive aneurysm clip. Post-operative cerebral vasospasm may also compromise cerebral blood flow and is an important cause of morbidity. This study addresses the need for a sensitive indicator of compromised cerebral function during aneurysm surgery by measuring brain tissue oxygenation and laser Doppler flow. Four patients were studied, all of whom had ruptured middle cerebral artery aneurysms. Brain tissue oxygenation measurements were made with a closed polarographic sensor placed in the ipsilateral cerebral hemisphere to the aneurysm. A laser Doppler flow probe and intracranial pressure monitor were similarly placed. The data were simultaneously processed using multimodality recording monitoring. The monitoring was continued during the post-operative period and totalled over 190 hours. Data were analysed as specific events and as trends. Initial tissue oxygen levels were low but improved in all cases as the intracranial pressure was reduced. This effect was independent of the cerebral perfusion pressure. Laser Doppler flow provided an indicator of compromised brain function and tissue oxygenation an indicator of established ischemia.

Aged↗

PubMed1992

Is peroperative smear cytology necessary for CT-guided stereotaxic biopsy?

Neuropathology is a relatively scarce resource with uneven geographical distribution, and some surgeons rely on macroscopic appearances of tissue and await later paraffin section histology for the final diagnosis. The effect of the introduction of a peroperative cytology service has been assessed in a 5-year series of CT-directed stereotaxic biopsies of intracranial mass lesions using a low cost adapted pre-CT stereotaxic frame. The technique has been mastered by 28 different surgeons with varying degrees of neurosurgical expertise and 259 procedures have been performed in 245 patients. Benign lesions were detected in 24 (9.8%) patients, confirming the importance of making a histological diagnosis prior to initiating treatment. Permanent morbidity was 6.5% and mortality 3.3% and morbidity was balanced by an improvement in 19.6% of the patients following the procedure. For the first 142 patients no peroperative histological diagnosis was available and a diagnostic rate of 86.6% was achieved. For the last 103 patients the availability of peroperative smears improved the diagnostic rate to 94.2% and reduced the number of second biopsies needed for diagnosis from seven to zero. Our series demonstrates the need for peroperative cytology in CT stereotaxic biopsies, and confirms that a complete neuropathology service is a prerequisite for neurosurgical patient care.

Adolescent↗