thiopental and Alzheimer-Disease

Pathological brain regions generate proportionately less high-frequency (beta) activity than non-pathological regions, a phenomenon accentuated by barbiturate administration.. Previously, we reported a loss of high-frequency brain electrical response to thiopental in dementia of the Alzheimer's type (DAT). The current study examines whether this phenomenon may be detected in early stages of the illness.. Using quantitative electroencephalography, we examined power in the 20-28 Hz band in patients with early DAT (n=7, age 71.0+/-3.2 years, Folstein Mini Mental State Score, MMSE 26.2+/-0.8), normal controls (n=8, age 74.3+/-3.2 years, MMSE 29.0+/-0.3) and subjects with moderately severe DAT (n=6, age 76.6+/-3.0 years, MMSE=12.5+/-3.7) at baseline and following an intravenous bolus of thiopental (0.5 mg/kg).. No significant group differences in beta power were detectable at baseline. In response to thiopental, early DAT subjects compared to controls showed a significantly smaller beta power response in the frontal region at 1-3 min postinjection. Losses were smaller than those of subjects with moderately severe DAT and demonstrated a non-linear correlation with decreases in cognitive function as assessed by the MMSE score (r2=0.75).. In early stages of DAT, a barbiturate challenge may unmask abnormalities in brain electrical activity not seen at baseline. Such changes may reflect underlying cortical deafferentation.

Topics: Aged; Alzheimer Disease; Analysis of Variance; Electroencephalography; Humans; Hypnotics and Sedatives; Thiopental; Time Factors

Abnormal brain regions generate proportionately less high-frequency (beta) activity than nonpathological regions, a phenomenon accentuated by barbiturate administration. Using quantitative electroencephalography we examined power in the 20- to 28-Hz band in patients with dementia of the Alzheimer's type (DAT), vascular dementia (VaD), and normal elderly controls (CON) following an IV bolus of thiopental (0.5 mg/kg). Compared to both CON and VaD subjects, DAT subjects showed a marked loss of beta power elicited across the cortex, with largest differences noted in the frontal region. Losses were most significant for the peak response recorded at 30 to 90 s postinjection and persisted during the 5-minute follow-up period. We hypothesize that differences in this electrocerebral response reflect differences in the underlying neuropathology of DAT and VaD subjects. A thiopental challenge may be well suited for the in vivo assessment of brain function in dementias characterized by prominent cortical pathology.

Topics: Aged; Alzheimer Disease; Dementia, Vascular; Electroencephalography; Female; Humans; Hypnotics and Sedatives; Male; Thiopental