Spontaneous improvement in reduced vasodilatory capacity in major cerebralarterial occlusive disease

Reduced vasodilatory capacity resulting from occlusive lesions of the major cerebral arteries may return to normal without surgical revascularisation. We aimed to determine prospectively the frequency and predictors of recove ry of impaired haemodynamics as demonstrated by acetazolamide (ACZ) reactiv ity on single-photon emission computed tomography (SPECT). Vasoreactivity w as mea sured by I-123-IMP SPECT with an ACZ challenge, in 37 medically trea ted patients with unilateral occlusive disease of the internal carotid or m iddle cerebral artery at an interval of 1-2 years. Each ACZ challenge test was analysed semiquantitatively by calculating the degree of increase in ce rebral blood flow (CBF) asymmetry after ACZ administration (Delta AI). Vaso dilatory capacity was abnormal initially in 20 patients (65 %); eight of wh om (40 %) exhibited spontaneous normalisation on follow-up. Although the ba seline characteristics did not differ significantly between patients with o r without increase in reactivity, logistic regression analysis revealed tha t the initial Delta AI (P < 0.05) and the type of vascular lesion (stenosis or occlusion) (P < 0.05) correlated significantly with a return towards no rmal of reduced ACZ reactivity. Spontaneous improvement of impaired vasodil atory capacity may not be a rare phenomenon. We found that mild reduction i n the initial ACZ reactivity and a stenosis, but not complete occlusion, we re independent factors contributing to normalisation of impaired cerebral h aemodynamics.