Gender Differences in Cerebral Blood Flow Velocity and Autoregulation between the Anterior and Posterior Circulations in Healthy Children

Abstract

There is little information on gender differences in cerebral autoregulation. The purpose of this study was to compare autoregulation of the anterior and posterior circulations using the tilt test method in healthy boys and girls who were 10 -16 y of age. Transcranial Doppler was used to measure middle cerebral artery and basilar artery flow velocities (Vmca and Vbas). Cerebral autoregulation (ARI) of the middle cerebral (ARImca) and basilar arteries (ARIbas) was examined using the tilt test method. An ARI Ͻ0.4 indicates impaired autoregulation. Among the 13 boys and 13 girls, Vmca and Vbas were higher in girls. All children demonstrated intact autoregulation, but boys had higher ARImca than girls, whereas girls had higher ARIbas than boys. Girls demonstrated greater autoregulation in the basilar artery, whereas boys demonstrated greater autoregulation in the middle cerebral artery. Girls had higher flow velocities in both vessels. This study provides normative data on cerebral autoregulation of the poste- Autoregulation of cerebral blood flow (CBF) is a physiologic and homeostatic process that maintains nearly constant CBF over a range of mean arterial pressures (MAPs). Disease states, including traumatic brain injury, can impair cerebral autoregulation, rendering the brain susceptible to inadequate (cerebral ischemia) or excessive (cerebral hyperemia) CBF (1). Despite its critical role in maintaining CBF, there is limited information on cerebral autoregulation in healthy children.Little has been published on pediatric cerebral autoregulation in children outside the clinical arena of neurogenic syncope (2-4). In one study that examined dynamic cerebral autoregulation in awake adolescent study participants, the time to return of middle cerebral artery flow velocity (Vmca) to normal after a transient hypotensive stimulus was reported to be more in healthy adolescents compared with their healthy adult counterparts (5). However, in a subsequent evaluation of cerebral autoregulation in children versus adults during general anesthesia using static autoregulation testing, the investigators reported no age-related differences in autoregulatory capacity and no difference in cerebral autoregulation compared with adults (6). Because both of these studies examined cerebral autoregulation of the anterior circulation only, differences in cerebral autoregulation between the anterior and posterior circulation in children could not be evaluated. In addition, to our knowledge, there is no information regarding cerebral autoregulation of the posterior circulation in children, no information on gender differences in cerebral autoregulation in children, and finally no normative data on cerebral autoregulation using the tilt test method. Therefore, the purpose of this study was to 1) provide normative data on cerebral autoregulation using the tilt test method, 2) describe cerebral autoregulation of the posterior cerebral circulation, and 3) examine gender-related differences in autoregulatory capacity in healthy, awake boys and girl...

Cerebral Blood Flow and Autoregulation After Pediatric Traumatic Brain Injury

“…For example, although anterior circulation flow velocities are higher in both boys and girls than posterior circulation flow velocities. Girls aged 4-16 years have higher V MCA and V BAS than age-matched boys [20,21]. Gender differences in blood viscosity because of hematocrit, or differences in hormones, vessel size, cerebral metabolism, and/or cerebrovascular resistance may partially explain these observed gender differences [21].…”

“…Beyond 10 years of age, CBFV decreases, approximating adult values (approximately 50 cm/sec) [15,16]. Table 1 shows referent mean CBFV estimates for middle cerebral artery (anterior circulation) (V MCA ) and basilar artery (posterior circulation) (V BAS ) by age and gender [14,19,20]. Although the specific age at which CBF peaked in one study using perfusion computed tomography (CT) scan in children with mild neurological diseases was lower (2-4 years), what is clear is that CBF is highest during early childhood [19].…”

“…This is important because tolerating lower blood pressure and therapeutic techniques such as deliberate hypotension in young children may not be appropriate and, in fact, result in cerebral ischemia. Additionally, like adult women who have higher CBF than men [65], there may be gender differences in pediatric cerebral autoregulation [16,20], but this has not been well studied. There may also be some quantitative differences in the latency of cerebral autoregulation between children and adults.…”

Transcranial Doppler in children

“…Velocities are slightly higher in pubertal girls than in boys [11]. Velocities in the vertebro-basilar system are lower than in the carotid system.…”

“…Disease states, including traumatic brain injury, can impair cerebral autoregulation, rendering the brain susceptible to inadequate (ischaemic) or excessive (hyperaemic) CBF. Autoregulation can be evaluated bedside with TCD by capturing changes in velocity in response to changes in arterial carbon dioxide tension (PaCO 2 ) and MAP [11].…”