Brief Summary: Vitamin D has been shown to impact prognosis in a variety of retrospective and randomized clinical trials within an intensive care unit (ICU) environment. Despite these findings, there have been no studies examining the impact of hypovitaminosis D in specialized neurocritical care units (NCCU). Given the often significant differences in the management of patients in NCCU and more generalized intensive care units there is a need for further inquiries into the impact of low vitamin D levels in this specific environment. This study proposes a randomized, double-blinded, placebo-controlled, single center evaluation of vitamin D supplementation in the emergent NCCU patient population. The primary outcome will involve length-of-stay for emergent neurocritical care patients. Various secondary outcomes, including in-hospital mortality, ICU length-of-stay, Glasgow Outcome Score on discharge, complications and quality-of-life metrics. Patients will be followed for 6 months post-discharge.

Detailed Description: Vitamin D has been shown as an important marker of prognosis in a variety of clinical settings, including overall mortality, acute respiratory distress syndrome (ARDS), infection/sepsis, asthma, cardiovascular disease, diabetes, and pediatric/medical/surgical intensive care unit outcomes. Vitamin D not only plays a role in bone maintenance, but also a variety of extra-axial functions including immune-dysregulation and systemic inflammation. In addition, a number of randomized clinical trials support the supplementation of vitamin D as improving outcome in critical care patients. While the evaluation of vitamin D levels remains a standard-of-care at our institution, the widespread use of vitamin D monitoring and impact on neurocritical care patients remains limited. The investigators' recent prospective observational study of vitamin D levels in neurocritical patients showed that deficiency (\<20ng/dL) was highly associated with prolonged hospital stay and increased in-hospital mortality for emergent patients. Moreover, a number of limitations arise from this study due to its observational nature. This study proposes a randomized, double-blinded, placebo-controlled, single center evaluation of vitamin D supplementation in the neurocritical care patient population. Patients admitted to the neurocritical care unit for emergent cases and with vitamin D deficiency (\<20ng/dL) will undergo vitamin D serum draw on admission and be randomized to receive cholecalciferol/vitamin D3 supplementation (540,000 IU once orally) or placebo. The primary outcome measured will be hospital length-of-stay. Secondary outcomes will include length of ICU course, complications, medication adverse events, discharge Glasgow Outcome Score, in-hospital and 30-day mortality, as well as quality-of-life. Power analysis estimates 198 patients will be needed for each subgroup to determine a 2 day difference in length-of-stay, and the study plans to recruit 218 patients per treatment arm to account for dropout, which will take approximately 6-9 months to recruit. Interim analysis and safety monitoring will be performed. The investigators hypothesize that vitamin D supplementation may make a significant impact on reducing morbidity and mortality in the neurocritical care population. The possibility of reducing hospital length of stay and mortality from a simple, safe, and cost-effective intervention such as vitamin D supplementation may be a useful adjuvant treatment in the neurocritical care population.