Cerebral blood flow (CBF) is regulated by vasomotor, chemical, metabolic, and neurogenic mechanisms. Even though the innervation of cerebral arteries is quite extensively described and reviewed in the literature, its role in regulation of CBF in humans remains controversial. We believe that insufficient attention has so far been focused on the potential role of the innervation of the cerebral vasculature in cerebral autoregulation in humans. We have performed an extensive search and selection of available literature on electrical, chemical, and surgical manipulations of the sympathetic innervation of cerebral arteries, and the effects of circulation sympathetically active agents on CBF. Studies on (surgical) ganglion block show a role of sympathetic tone in preventing increases in CBF in humans, which are consistent with the view based on animal studies. Both direct innervation of the cerebral arteries from cervical ganglia and stimulation of adrenergic receptors by circulating sympathomimetics prevent sudden increases of CBF associated with hypertension and hypercapnia. We postulate that under normal physiological conditions neurogenic control has little influence on cerebral autoregulation as other methods of control (vasomotor, chemical, and metabolic) are dominant. In severely challenging circumstances, such as delayed cerebral ischaemia after subarachnoid haemorrhage, these methods might be overwhelmed, increasing the relative importance of neurogenic, sympathetic control of CBF. This insight might lead to future therapeutic possibilities.
CASE A 22-year-old man was brought to the ED complaining of abdominal pain after a rollover motor vehicle accident. He was the front seat passenger and was wearing a seat belt. Although he was trapped in the vehicle and it caught on fire, he did not suffer any cutaneous burns. History The patient's past medical history was significant for attention-deficit hyperactivity disorder. He admitted to using tobacco and alcohol socially, but denied illicit drug use. He denied any medication use or drug allergies. A review of systems was positive for complaints of abdominal pain and anxiety. Physical examination The patient's vital signs were: BP, 112/51 mm Hg; heart rate, 110 beats/minute; respirations, 23; SpO 2 , 95% on room air; and temperature, 37.4° C (99.3° F). On ED arrival, he was awake, alert, and oriented but appeared anxious and agitated. His pupils were equal, round, and reactive to light. His head was normocephalic with a 2-cm laceration on the left ear. The pati...
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