Differentiation of multi-infarct and Alzheimer dementia by intracranial hemodynamic parameters.

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Abstract
The differentiation between the Alzheimer and multi-infarct types of dementia may still be equivocal considering clinical criteria, neuropsychological tests, and imaging techniques. Cerebral microangiopathic alterations underlying multi-infarct dementia should allow the characterization of dementia subgroups. Patients with a diagnosis of multi-infarct dementia (n = 17; mean age, 69.1 +/- 8.5 years) or Alzheimer dementia (n = 24, mean age, 65.8 +/- 9.0 years) according to standard testing criteria, clinical findings, and neuroimaging techniques (computed tomography and magnetic resonance imaging) were investigated prospectively by transcranial Doppler sonography and compared with a normal reference group (n = 64; mean age, 61.0 +/- 11.1 years). Transcranial Doppler sonography allows an indirect evaluation of peripheral flow resistance in the microcirculatory bed by quantifying pulsatility characteristics, as reflected in the effective pulsatility range (time-averaged mean blood flow velocity minus the peak-systolic to end-diastolic amplitude, in centimeters per second). A total of 204 vessels were investigated in 105 subjects. Mean and diastolic blood flow velocities as well as the effective pulsatility range were significantly lower in the multi-infarct dementia group compared with the Alzheimer and the normal reference groups (p < 0.001). By using receiver operating characteristic analysis, a cutoff point for effective pulsatility range values of -5 cm/sec gives a side-dependent sensitivity of 90.48-95.24% and a specificity of 64.71-70.59% in diagnosing Alzheimer-type dementia; the corresponding sensitivity and specificity for a value of -2 cm/sec are 82.35-88.24% and 80.95-90.48%, respectively. Pulsatility changes as reflected by the effective pulsatility range are a noninvasive additional criterion in the differential diagnosis of dementia.