Biomedical subjects

R Pottinger

Publications and source records attributed to R Pottinger.

2 recordsLinked to original sources

PubMed2000

A SPECT study of the effect of vagal nerve stimulation on thalamic activity in patients with epilepsy.

The mechanism by which vagal nerve stimulation (VNS) exerts an anticonvulsant effect in humans is unknown. This study used (99m)Tc-HMPAO single photon emission tomography (SPECT) to examine the effects of VNS on regional cerebral activity in thalamic and insular regions. Seven subjects with epilepsy who had been receiving vagal nerve stimulation for at least 6 months underwent SPECT scanning with simultaneous scalp electroencephalographic (EEG) recording. Subjects were studied in two states; during VNS activity and during a comparison condition of VNS inactivity. A region of interest analysis demonstrated that rapid cycling stimulation (7 seconds on, 12 seconds off) was associated with relatively decreased activity in left and right medial thalamic regions. No systematic stimulation-related changes were observed on visual or spectral analysis of EEG data. The thalamus is involved in modulation of ongoing cortical EEG activity in animals. Our results support the hypothesis that VNS may exert an antiepileptic action by an effect on thalamic activity.

Adult↗

PubMed1994

Monitoring vigilance during single and serial visual evoked potentials.

Full- and half-field visual evoked potentials (VEPs) are used to evaluate functional effects of optic chiasm compression by pituitary tumours. Reduction in VEP amplitude, typically from the temporal fields of vision, can occur even without demonstrable clinical deficit. An inherent problem of prolonged or serial testing is that changing levels of vigilance may affect the VEP. Gradual decrease in vigilance during a test sequence or with serial testing may cause a reduction in amplitude of the response mimicking the abnormality sought. This has serious implications when monitoring the effect of medical treatment since it may give a false impression of tumour growth requiring urgent surgery to prevent blindness. This report illustrates the nature of the problem and describes techniques using electroencephalograms (EEG), which have been used in an attempt to monitor vigilance. The ultimate aim is to produce a system to automate such monitoring during VEP recording.

Constriction, Pathologic↗