Influence of cranioplasty on postural blood flow regulation, cerebrovascular reserve capacity, and cerebral glucose metabolism

Object. The indications for cranioplasty after decompressive craniectomy ar e cosmetic repair and, mainly, restoration of cerebral protection. Although neurological improvement after cranioplasty is repeatedly noted, the reaso ns for this remain unclear. Few observations concerning the impact of cereb rospinal fluid hydrodynamic and/or atmospheric pressure have been published during the last decades. Relevant data concerning the cerebrovascular rese rve (CVR) capacity and cerebral glucose metabolism before and after craniop lasty have been lacking until now. To gain further insight, this study was undertaken to investigate the impact of cranioplasty on indices of cerebral blood flow regulation and metabolism. Methods. Thirteen patients in whom extensive craniectomies had been perform ed underwent a meticulous study of blood flow velocities in the middle cere bral artery (MCA) and extracranial internal carotid artery (ICA), as assess ed by transcranial Doppler ultrasonography during postural maneuvers (supin e and sitting positions) and during stimulation with 1 g of acetazolamide f or the interpretation of CVR capacity. Twelve patients underwent 18-fluorod eoxyglucose positron emission tomography. These measurements were obtained before and 7 days after cranioplasty. Cranioplasty improved preoperative differences in MCA blood flow velocities when comparing those in the injured with those in the uninjured hemisphere . Similarly, cranioplasty resolved decreases in extracranial ICA blood flow in the injured hemisphere that were induced by postural changes, which was a constant finding prior to this procedure. More strikingly, however, the CVR capacity, which was severely impaired in both hemispheres, increased si gnificantly after the procedure. Metabolic deficits, which were observed in the injured hemisphere, were found to improve after reimplantation of the skull bone flap. Conclusions. Cranioplasty appears to affect postural blood flow regulation, CVR capacity, and cerebral glucose metabolism markedly. Thus, early cranio plasty is warranted to facilitate rehabilitation in patients after decompre ssive craniectomy.