Decreased brain metabolism, rather than an increased intracranial pressure, is the cause of decreased cerebral blood flow after superior cervical sympathetic ganglionectomy

"The reduced brain metabolism and consequently reduced cerebral perfusion in the late 

postsympathectomy period could account for reduction in CSF production (Bering3)."

"In support of the above statement we mention that on the late postsympathectomy (11 to 24 months) group of dogs besides the lowered CBF 

(31.36 ml/100 gm brain weight/minute) and MCP (79.3 mm NS) also a lowered MVP (46.5 mm NS) was found. These data indicate that cervicalsympathectomy has a profound and intricate effect on the dynamics of cerebrovascular fluids and probably, in the background of all observedphenomena, a decreased cerebral metabolism as a sympathectomy effect is the underlying cause. Correspondingly the cerebral metabolic rate ofoxygen (CMR O2) decreased to 2.94 and 2.43 ml of O2/IOO gm brain weight/ minute in the sympathectomized groups." 

"Decreased brain metabolism, rather than an increased intracranial pressure, is the cause of decreased cerebral blood flow after superior cervical sympathetic ganglionectomy."

http://archsurg.ama-assn.org/cgi/content/summary/90/3/418

After the sympathectomy, the high night time excretion was clearly abolished

The amount of 6-sulphatoxymelatonin, the chief metabolite of melatonin, in the urine was measured in nine patients, who were subjected to bilateral sympathectomy at the second thoracic ganglionic level for treatment of hyperhidrosis of the palms. All patients showed before surgery a normal 6-sulphatoxymelatonin excretion with a peak in the excretion 
during the night time. After the sympathectomy, the high night time excretion was clearly abolished in five patients but remained high in four patients...
http://www.ncbi.nlm.nih.gov/pubmed/16647807