Neurosurg Focus 32 (6):E4, 2012 Is posttraumatic cerebrospinal fluid fistula a predictor of posttraumatic meningitis? A US Nationwide Inpatient Sample database study *ASHISH SONIG, M.D., M.S., M.CH., JAI DEEP THAKUR, M.D., PRASHANT CHIttIBOINA, M.D., M.P.H., Imad SAEED KHAN, M.D., AND ANIL NANda, M.D., M.P.H. Department of Neurosurgery, Louisiana State University Health Sciences Center in Shreveport, Louisiana Object. Various factors have been reported in literature to be associated with the development of posttraumatic meningitis. There is a paucity of data regarding skull fractures and facial fractures leading to CSF leaks and their as- sociation with the development of meningitis. The primary objective of this study was to analyze the US Nationwide Inpatient Sample (NIS) database to elucidate the factors associated with the development of posttraumatic meningitis. A secondary goal was to analyze the overall hospitalization cost related to posttraumatic meningitis and factors as- sociated with that cost. Methods. The NIS database was analyzed to identify patients admitted to hospitals with a diagnosis of head injury from 2005 through 2009. This data set was analyzed to assess the relationship of various clinical parameters that may affect the development of posttraumatic meningitis using binary logistic regression models. Additionally, the overall hospitalization cost for the head injury patients who did not undergo any neurosurgical intervention was further categorized into quartile groups, and a regression model was created to analyze various factors responsible for escalating the overall cost of the hospital stay. Results. A total of 382,267 inpatient admissions for head injury were analyzed for the 2005–2009 period. Men- ingitis was reported in 0.2% of these cases (708 cases). Closed skull base fractures, open skull base fractures, cranial vault fractures, and maxillofacial fractures were reported in 20,524 (5.4%), 1089 (0.3%), 5064 (1.3%), and 88,649 (23.2%) patients, respectively. Among these patients with fractures, meningitis was noted in 0.17%, 0.18%, 0.05%, and 0.10% admissions, respectively. Cerebrospinal fluid rhinorrhea was reported in 453 head injury patients (0.1%) and CSF otorrhea in 582 (0.2%). Of the patients reported to have CSF rhinorrhea, 35 (7.7%) developed meningitis, whereas in the cohort with CSF otorrhea, 15 patients (2.6%) developed meningitis. Cerebrospinal fluid rhinorrhea (p < 0.001, OR 22.8, 95% CI 15.6–33.3), CSF otorrhea (p < 0.001, OR 9.2, 95% CI 5.2–16.09), and major neurosurgical procedures (p < 0.001, OR 5.6, 95% CI 4.8–6.5) were independent predictors of meningitis. Further, CSF rhinorrhea (p < 0.001, OR 2.0, 95% CI 1.6–2.7), CSF otorrhea (p < 0.001, OR 2.3, 95% CI 1.9–2.7), and posttraumatic menin- gitis (p < 0.001, OR 3.1, 95% CI 2.5–3.8) were independent factors responsible for escalating the cost of head injury in cases not requiring any major neurosurgical intervention. Conclusions. Cerebrospinal fluid rhinorrhea and CSF otorrhea are independent predictors of posttraumatic men- ingitis. Furthermore, meningitis and CSF fistulas may independently lead to significantly increased cost of hospital- ization in head injury patients not undergoing any major neurosurgical intervention. (http://thejns.org/doi/abs/10.3171/2012.5.FOCUS1269) KEY WORDS • cerebrospinal fluid fistula • meningitis • head injury EAD injury accounts for significant mortality and ated with head injury. Additionally, the development of morbidity in the US, with approximately 1.5 mil- meningitis has shown to contribute substantially to in- lion persons per year being reported to have a head creased mortality and morbidity in such patients.1,2,23,32 Hinjury.26 Apart from the traumatic brain insult and associ- Various factors that are associated with the develop- ated hemodynamic alterations, various factors, including ment of posttraumatic meningitis include skull fractures, posttraumatic meningitis and CSF fistula, are recognized facial fractures (mainly involving the paranasal sinuses), as prognostic parameters in the clinical spectrum associ- otological injuries, development of CSF fistulas, and pneu- mocephalus.6,8,13,15,16,20,25,31 Typically, fractures of the skull or facial bones may lead to the formation of CSF fistu- Abbreviations used in this paper: CCS = Clinical Classification 25 Software; EVD = external ventricular drain; HCUP = Healthcare las, which in turn increase the likelihood of meningitis. Cost and Utilization Project; ICD-9-CM = International Classifi- There are limited data to support an independent associa- cation of Diseases, Ninth Revision, Clinical Modification; NIS = tion of meningitis with skull fractures, facial fractures, and Nationwide Inpatient Sample. subsequent CSF leaks.8,13,16,20 Further, it is unclear whether * Drs. Sonig and Thakur contributed equally to this work. particular subtypes of skull fractures (closed skull base Neurosurg Focus / Volume 32 / June 2012 1 Unauthenticated | Downloaded 09/26/21 07:41 AM UTC A. Sonig et al. fractures, open skull base, cranial vault fractures) are as- Patients Without Fracture. All the patients with head sociated with increased risk of meningitis.5,24 injury who did not have a fracture were included in this We analyzed the NIS database to study the factors category. associated with the development of meningitis during the hospital stay in patients admitted for head injury. Addi- Patients With Meningitis. This variable was con- tionally, cases in which patients were admitted for head structed on the basis of CCS code 76 (meningitis [except injuries and did not undergo any major neurosurgical pro- that caused by tuberculosis or sexually transmitted dis- cedure were studied to assess the escalation of total hos- ease]). pital cost due to posttraumatic meningitis, CSF otorrhea, Patients With CSF Otorrhea. This variable was con- or CSF rhinorrhea. structed on the basis of ICD-9-CM code 388.61 (cerebro- spinal fluid otorrhea). Methods Patients With CSF Rhinorrhea. ICD-9-CM code The NIS is part of HCUP, which is sponsored by the 349.81 (cerebrospinal fluid rhinorrhea) was used to form Agency for Healthcare Research and Quality, formerly this category variable. the Agency for Health Care Policy and Research. The Neurosurgical Procedure Group. The following NIS is the largest all-payer inpatient care database that ICD-9 codes were used to identify patients who under- is publicly available in the US. It contains data from 5–8 went major neurosurgical procedures: 0101 (cisternal million hospital stays in about 1000 hospitals, which ap- proximate a 20% stratified sample of US community hos- puncture), 0123 (reexploration of craniotomy site), 0124 pitals. The NIS is drawn from those states participating (other craniotomy), 0125 (other craniectomy), 0202 (ele- in HCUP. vate skull fracture fragments), 0203 (skull flap formation) Nationwide Inpatient Sample data from the 2005– 022 (ventriculostomy), and 0221 (insertion/replacement 2009 period were analyzed. Both CCS and ICD-9-CM of EVD). codes were used. The CCS coding system was developed Comorbidity Accumulation Index at the Agency for Healthcare Research and Quality as a tool for clustering patient diagnoses and procedures into Data from 382,267 cases were assessed on an indi- a manageable number of clinically meaningful catego- vidual basis, and a comorbidity accumulation index was ries. It collapses diagnosis and procedure codes from the calculated. The following comorbidities were studied: IDC-9-CM. We used single-level CCS codes 228 (skull acquired immune deficiency syndrome (AIDS), alcohol and face fractures) and 233 (intracranial injury) to extract abuse, deficiency anemias, rheumatoid arthritis/collagen data from 25,669 hospitals. vascular diseases, chronic blood loss anemia, congestive heart failure, chronic pulmonary disease, coagulopathy, Categorical Variables uncomplicated diabetes, diabetes with chronic compli- The following categorical variables were used in this cations, drug abuse, hypertension, hypothyroidism, liver study. disease, lymphoma, fluid and electrolyte disorders, meta- static cancer, other neurological disorders, obesity, paral- Patients With Only Skull Vault Fracture. This vari- ysis, peripheral vascular disorders, pulmonary circulation able was constructed on the basis of ICD-9-CM code disorders, renal failure, solid tumor without metastasis, 800 (fracture of vault of skull) and comprised the follow- peptic ulcer disease excluding bleeding, valvular disease, ing ICD-9 subcategories: 80000, 80001, 80002, 80003, and weight loss. 80004, 80005, 80006, 80009, 80050, 80051, 80052, The comorbidity accumulation indices of individual 80053, 80054, 80055, 80056, and 80059. These catego- patients ranged from 0 to a maximum of 12 (Table 1). ries included open and closed fractures of the skull vault. Quartiles were calculated, and patients with comorbidity Patients With Closed Skull Base Fractures. This indices above the 75th percentile (comorbidity index of variable was constructed on the basis of ICD-9-CM code 2 or more) were assigned to the high comorbidity index 801 (fracture of base of skull) and comprised the follow- group. ing ICD-9 subcategories: 80100, 80101, 80102, 80103, Hospital Cost 80104, 80105, 80106, and 80109. Hospital costs were determined by the coded vari- Patients With Open Skull Base Fractures. This vari- able “total charges” in the NIS data. Total hospital cost able was also constructed on the basis of ICD-9-CM code was analyzed in the cohort of patients who did