[Impairment of vasoreactivity in brainstem and hemispheral small vessel disease: comparative study]

Cerebrovascular small vessel disease may lead to an impairment of vasoreactivity (VR). Vasoregulatory impairment in internal carotid artery distribution area has been established. In this study the authors sought the answer to the question if VR of vertebrobasilar (VB) territory was impaired in brainstem small vessel diseases and if vasoregulatory impairment differed between the two distribution territories.

VR of carotid and VB territory was compared applying different functional tests (ventilation, tilting, acetazolamide) in 25 patients with brainstem lacunar infarcts, 20 patients with periventricular leukoaraiosis and in 35 control subjects. Cerebral blood flow velocity (CBFV) of basilar artery (BA) and middle cerebral artery (MCA) was monitored with transcranial Doppler (TCD), systemic blood pressure and CO2 partial pressure of expired air were also registered.

In the BA territory the VR was significantly smaller in the patient than in the control group (3.1 +/- 4.6 cm/sec/kPa vs. 8.2 +/- 6.2 cm/sec/kPa, p = 0.01) during hypercapnia. In a subgroup of patients with mean baseline CBFV < 25 cm/sec, the VR was significantly smaller and Pl non-significantly higher than in patients with baseline CBFV > 25 cm/s (VRCO2 1.5 +/- 2.0 cm/sec/kPa vs. 6.5 +/- 6.5 cm/sec/kPa, p = 0.007; Pl 1.11 +/- 0.30 vs. 1.0 +/- 0.26, p = 0.4) indicating higher vascular resistance in the former group. Results of tilting tests showed similar but nonsignificant changes while acetazolamide tests revealed no differences between the two groups. In the MCA territory the VR was significantly lower in patients than in the controls during hypercapnia (4.7 +/- 3.7 cm/sec/kPa vs. 18.4 +/- 6.8 cm/sec/kPa, p < 0.001) and showed a nonsignificant tendency to be lower in patients than in controls during hypocapnia (14.6 +/- 13.8 cm/sec/kPa vs. 24.7 +/- 21.2 cm/sec/kPa, p = 0.1). Although CBFV measurements during acetazolamide test tended to support these findings, they showed no significant differences between patients and controls. During head-up tilt the CBFV did not differ significantly between the two groups. The VRCO2 is significantly higher in the MCA than in the BA territory (18.4 CI95 2.98 vs. 10.1 CI95 3.01; p < 0.001). The impairment of VRCO2 was more severe in the MCA territory (VR decreased to 26% of baseline in the MCA and to 34% in the BA territory).

The capacity of carotid territory VR exceeds that of VB territory. The impairment of VR is present in both the carotid and VB territories and is more severe in the former region. The most feasible test to reveal this impairment is the hypercapnic test. There is a strong correlation between the extent of vasoregulatory impairment and baseline CBFV in brainstem small vessel diseases.