Craniospinal cerebrospinal fluid volume changes after extreme bilateral frontotemporoparietal craniectomy and cranioplasty: a volumetric magnetic resonance imaging case report.

We report on an 18-year-old woman who sustained severe traumatic brain injury in a traffic accident. The resulting refractory intracranial hypertension required emergency bilateral frontotemporoparietal decompressive craniectomies, which left a large bilateral skull defect. Postoperatively, she developed a bilateral sinking skin flap syndrome, consistent with atmospheric pressure-driven collapse of the cranial compartment. She underwent full neuraxis 3D craniospinal imaging before and three months after elective bilateral cranioplasty using custom implants. Pre-cranioplasty volumetric assessment showed cranial cerebrospinal fluid (CSF) volume of 100.8 mL and spinal CSF volume of 78.2 mL (179.0 mL total). After cranioplasty, cranial CSF volume increased to 152.7 mL and spinal CSF volume to 91.1 mL (243.7 mL total), with an overall CSF net gain of 64.7 mL without relevant change in brain parenchyma volume. Clinically, after neurosurgical and neurointensive rehabilitation, the patient remained neurologically stable, with no new focal deficits, able to continue everyday life, finish high school, and enter university. The volumetric findings suggested global redistribution and expansion of neurofluids within the craniospinal axis when cranial boundaries were restored. Such findings are difficult to explain with the traditional model of CSF production and unidirectional circulation, but align with the Bulat-Klarica-Orešković hypothesis, which views CSF, intravascular and interstitial fluid as a single, hydrostatic, and osmotic capillary-driven system. This case indicates that quantitative craniospinal volumetry after cranioplasty can provide in vivo support for contemporary concepts of CSF physiology and may help guide cranioplasty timing in decompressive craniectomy patients.