Literature ReviewObesity in Neurosurgery: A Narrative Review of the Literature
Introduction
Obesity places an increasing burden of disease on the Australian population. Australia has the third highest prevalence of obesity among the 35 OECD (Organisation for Economic Co-operation and Development) countries and the 25th highest in the world; 28.3% of Australian adults are obese, defined as a body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters) of 30 or higher.1 A total of $8.3 billion is spent annually on direct health care costs of obese patients, representing 9.5% of health expenditure, with a further $13.6 billion allocated to government subsidies.2 Furthermore, the prevalence of obesity is increasing steadily, with greater than two thirds of the population estimated to be overweight or obese by 2025.3 Obesity has been shown to increase morbidity and mortality in many aspects of medicine and surgery,4 but there is a relative paucity of data on its effects on neurosurgical procedures specifically.
Obesity may be defined in several ways, ranging from BMI, to skinfold size, to waist circumference. Although by no means a perfect measurement, because it does not distinguish lean muscle mass from adipose, BMI has become the worldwide surrogate measure of obesity because of convenience of calculation. The World Health Organization classifications of BMI are shown in Table 1. The cause of obesity is multifactorial, with both genetic and environmental components; however, the fundamental cause is an imbalance between energy intake and expenditure. Exogenous obesity is the most common cause and is believed to be at least partly to the result of an obesogenic environment consisting of an increasingly sedentary lifestyle and addictive, high-calorie processed food. However, multiple genetic factors are also believed to be at play, with more than 400 genes6 associated with weight regulation. In addition, there are multiple medical conditions that cause secondary obesity.7 Obesity is associated with greater all-cause mortality8; a BMI of 30–34.9 confers a relative risk (RR) for death of 1.44 (95% confidence interval [CI], 1.38–1.50), whereas a BMI greater than 40 confers an RR of 2.51 (95% CI, 2.30–2.73) compared with normal-weight controls. Table 2 shows that obesity has effects on multiple organ systems, including the nervous system, and has been linked with increased rates of intervertebral disk degeneration, lower back pain, sciatica, and spinal surgery.12 We have previously described our own anecdotal experience with the numerous challenges presented by morbid obesity in the setting of acute spinal trauma.13 These challenges include difficulties with surgical positioning, ventilation in the prone position, fluoroscopic imaging in theater, a need for instruments and retractors of sufficient length, weight and size limits of magnetic resonance imaging scanners, intravenous access and airway management, postoperative bracing, and perioperative nursing care. Here, we review the literature on the impact of obesity on outcomes and perioperative complication rates in neurosurgical patients undergoing cranial procedures and elective spine surgery. The role of obesity in idiopathic intracranial hypertension and spinal epidural lipomatosis was excluded from this review.
Section snippets
Methods
A broad search of the literature was performed on the Ovid Medline and PubMed databases using their respective search engines. The initial search string used was “Obesity AND (neurosurgery OR spine OR spinal OR craniotomy) AND (outcome OR complication*)” and MeSH terms were used wherever possible. Further searches were made in reference to specific procedures or complications, to maximize data collection. The Cochrane database was also consulted. References cited in the articles identified were
Discussion
The effect of obesity on cranial and elective spinal surgery is broadly similar. In both groups, there is a clear increase in complication rates but the impact on surgical outcomes is lower or controversial.
Other than some specific situations such as peritoneal catheter placement, and CSF leak in posterior fossa surgery, the effect of obesity on surgical outcomes after cranial procedures is minimal. The effect of obesity on outcomes after spine surgery is more complex. Most studies report
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.