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.
Aim: To determine the safety and feasibility of an early (12 h) waking and extubation protocol for out-of-hospital cardiac arrest (OHCA) patients receiving targeted temperature management (TTM). Methods: This was a single-centre, prospective, non-randomised, observational, safety and feasibility pilot study which included successfully resuscitated OHCA patients, of presumed cardiac cause. Inclusion criteria were: OHCA patients aged over 18 years with a return of spontaneous circulation, who were going to receive TTM33 (TTM at 33 °C for 24 h and prevention of hyperthermia for 72 h) as part of their post cardiac arrest care. Clinical stability was measured against physiological and neurological parameters as well as clinical assessment. Results: 50 consecutive patients were included (median age 65.5 years, 82% male) in the study. Four (8%) patients died within the first twelve hours and were excluded from the final cohort (n = 46). Twenty-three patients (46%) were considered clinically stable and suitable for early waking based on the intention to treat analysis; 12 patients were extubated early based on a variety of clinical factors (21.4 ± 8.6 h) whilst continuing to receive TTM33 with a mean core temperature of 34.2 °C when extubated. Of these, five patients were discharged from the intensive care unit (ICU) <48 h after admission with a mean ICU length of stay 1.8 ± 0.4 days. Twenty-eight patients (56%) were discharged from the ICU with a modified Rankin Score of 0-2. The overall intra-hospital mortality was 50% (n = 25). Conclusions: It is safe and feasible to wake selected comatose OHCA patients at 12 h, allowing for earlier positive neuro-prognostication and reduced ICU stay.
Abstract: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.
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