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Epidural Abscess and Meningitis After Epidural Corticosteroid Injection

2004; Elsevier BV; Volume: 79; Issue: 5 Linguagem: Inglês

10.4065/79.5.682

1942-5546

W. Michael Hooten, Michelle A. O. Kinney, Marc A. Huntoon,

Spine and Intervertebral Disc Pathology

Epidural abscess with and without associated meningitis after epidural corticosteroid injections for radicular back pain is a rarely reported complication. We report the occurrence of an epidural abscess and meningitis in a 70-year-old man after 2 epidural corticosteroid injections for treatment of acute radicular lumbar back pain. At the time of diagnosis, cerebrospinal fluid cultures grew Staphylococcus aureus, and the patient was treated with intravenous antibiotics. Possible predisposing factors for the development of an epidural abscess and meningitis in this patient include a 2-year history of neutropenia and an accidental dural puncture that occurred during performance of the first epidural injection. A literature search identified 11 reported cases of epidural abscess, 2 of epidural abscess and meningitis, and 1 of meningitis attributed to epidural corticosteroid injections. Eight of the 14 reported patients were immunocompromised, and 8 (67%) of the 12 in whom cultures of blood, cerebrospinal fluid, or epidural pus were performed had results positive for S aureus. Antibiotic prophylaxis for S aureus should be considered for immunocompromised patients undergoing epidural corticosteroid injections. Epidural abscess with and without associated meningitis after epidural corticosteroid injections for radicular back pain is a rarely reported complication. We report the occurrence of an epidural abscess and meningitis in a 70-year-old man after 2 epidural corticosteroid injections for treatment of acute radicular lumbar back pain. At the time of diagnosis, cerebrospinal fluid cultures grew Staphylococcus aureus, and the patient was treated with intravenous antibiotics. Possible predisposing factors for the development of an epidural abscess and meningitis in this patient include a 2-year history of neutropenia and an accidental dural puncture that occurred during performance of the first epidural injection. A literature search identified 11 reported cases of epidural abscess, 2 of epidural abscess and meningitis, and 1 of meningitis attributed to epidural corticosteroid injections. Eight of the 14 reported patients were immunocompromised, and 8 (67%) of the 12 in whom cultures of blood, cerebrospinal fluid, or epidural pus were performed had results positive for S aureus. Antibiotic prophylaxis for S aureus should be considered for immunocompromised patients undergoing epidural corticosteroid injections. The incidence of spontaneous epidural abscess in the general medical population ranges from 0.33 to 1.96 abscesses per 10,000 hospital admissions per year.1Hlavin ML Kaminski HJ Ross JS Ganz E Spinal epidural abscess: a ten-year perspective.Neurosurgery. 1990; 27: 177-184Crossref PubMed Scopus (420) Google Scholar After placement of an indwelling epidural catheter for operative anesthesia or postoperative analgesia, the odds of developing a perioperative epidural abscess vary from 0 to 1 in 1930 catheters.2Wang LP Hauerberg J Schmidt JF Incidence of spinal epidural abscess after epidural analgesia: a national 1-year survey.Anesthesiology. 1999; 91: 1928-1936Crossref PubMed Scopus (245) Google Scholar, 3Dahlgren N Tornebrandt K Neurological complications after anaesthesia: a follow-up of 18,000 spinal and epidural anaesthetics performed over three years.Acta Anaesthesiol Scand. 1995; 39: 872-880Crossref PubMed Scopus (297) Google Scholar Epidural abscess is a rarely reported complication of epidural corticosteroid injection for treatment of radicular back pain, and the incidence remains undetermined. In a series of 215 patients who received 790 cervical epidural corticosteroid injections over a 4-month period, no epidural abscesses were identified.4Waldman SD Complications of cervical epidural nerve blocks with steroids: a prospective study of 790 consecutive blocks.Reg Anesth. 1989; 14: 149-151PubMed Google Scholar A study of the Medicare population between 1993 and 1999 showed that the annual number of cervical, thoracic, and lumbar epidural corticosteroid injections peaked at more than 680,000 in 1998.5Carrino JA Morrison WB Parker L Schweitzer ME Levin DC Sunshine JH Spinal injection procedures: volume, provider distribution, and reimbursement in the U.S. Medicare population for 1993 to 1999.Radiology. 2002; 225: 723-729Crossref PubMed Scopus (105) Google Scholar As the annual number of epidural corticosteroid injections increases, pain medicine specialists and physicians caring for patients treated with epidural corticosteroids must become aware of the potential infectious complications of this procedure.5Carrino JA Morrison WB Parker L Schweitzer ME Levin DC Sunshine JH Spinal injection procedures: volume, provider distribution, and reimbursement in the U.S. Medicare population for 1993 to 1999.Radiology. 2002; 225: 723-729Crossref PubMed Scopus (105) Google Scholar We report the occurrence of an epidural abscess and meningitis after a patient received 2 epidural corticosteroid injections for treatment of acute radicular lumbar back pain. A 70-year-old man developed acute left hip and thigh pain after sustained heavy lifting. His medical history was remarkable for a 2-year history of leukopenia, with an absolute neutrophil count of less than 1.0 × 109/L while taking hydroxychloroquine for treatment of inflammatory polyarthritis. Three weeks after the onset of pain, an outpatient evaluation by his primary care physician identified tenderness overlying the left trochanteric bursa. Left trochanteric bursitis was diagnosed, and the bursa was injected with methylprednisolone (80 mg) and 0.25% bupivacaine (2 mL). The patient reported minimal pain relief, and magnetic resonance imaging (MRI) of the left hip 3 days later revealed no evidence of fracture or dislocation. Five days after the initial evaluation, the patient was admitted to the hospital for treatment of intractable left hip and back pain. The total leukocyte count on admission was 1.8 × 109/L (reference range, 3.5-10.5 × 109/L), and the absolute neutrophil count was 0.79 × 109/L (reference range, 1.7-7.0 × 109/L). Hydroxychloroquine therapy was discontinued. A pain medicine consultation was obtained, and subsequent lumbar spine MRI revealed L2-3 disk extrusion with neural foraminal encroachment. Opioid analgesia was initiated, and the patient was dismissed from the hospital and scheduled for an outpatient epidural corticosteroid injection. Three days after hospital dismissal, the patient was readmitted because of persistent left hip and back pain. Physical examination revealed reduced tactile sensation on the lateral aspect of the left thigh. Results of repeated lumbar spine MRI were unchanged, and electromyographic findings were consistent with an acute left L2 radiculopathy. The pain medicine service was reconsulted, and the diagnosis of an acute left L2 radiculopathy was established on the basis of the clinical presentation, distribution of pain, and physical examination, MRI, and electromyographic findings. After obtaining informed consent, an epidural corticosteroid injection was administered at bedside under aseptic precautions (povidone-iodine skin preparation that was allowed to air dry, application of a sterile skin drape, and use of sterile gloves and face masks by all personnel). With use of a midline approach, an 18-gauge Tuohy needle was inserted into the L2-3 interspace. The procedure was complicated by an accidental dural puncture. The stylette was reinserted and the needle removed. The epidural needle was placed successfully in the L3-4 interspace with use of an interlaminar approach, and triamcinolone (80 mg in 2 mL of preservative-free normal saline) was injected. The stylette was reinserted and the needle removed. The patient reported near-complete resolution of back pain at 1-day follow-up, and no symptoms of a persistent cerebrospinal fluid (CSF) leak were reported. Two days after the epidural corticosteroid injection, the patient was diagnosed as having an incarcerated left inguinal hernia, which was surgically repaired under general anesthesia without complication. Intravenous cefazolin (1 g) was administered preoperatively and again 6 hours postoperatively. The patient was subsequently dismissed from the hospital and scheduled for a repeated lumbar epidural corticosteroid injection in 2 weeks. On follow-up in the outpatient pain medicine clinic, the patient reported that the severity of left hip and back pain had improved 25% in comparison to his previous continual, intractable pain. Physical examination revealed mild tenderness over the lumbar spine and reduced tactile sensation on the lateral aspect of the left thigh. Because the patient had partial improvement from the initial procedure, a repeated injection was recommended. After obtaining informed consent, a midline lumbar epidural corticosteroid injection was administered under aseptic precautions at the L2-3 interspace with fluoroscopic guidance. A 20-gauge Tuohy needle was placed successfully, and triamcinolone (80 mg in 3 mL of 1% lidocaine and 1 mL of preservativefree normal saline) was injected. The stylette was reinserted and the needle removed. On telephone follow-up 1 week later, the patient reported moderate improvement of left hip and back pain. Three weeks after the second epidural corticosteroid injection, the patient was admitted to the hospital because of frontotemporal headache, cervical neck pain, photophobia, and phonophobia. The symptoms had developed after discontinuation of all opioid analgesics. (Transcutaneous fentanyl, 25 µg/h, had been discontinued 8 days after the second lumbar epidural injection, and oxycodone, 15 mg orally as needed every 4 hours, had been discontinued 9 days after the second epidural injection. The opioid medications had been discontinued 15 to 16 days before hospital admission.) The patient was diagnosed as having opioid withdrawal and was dismissed from the hospital on a regimen of oxycodone tapering. Four days later, he was readmitted to the hospital with persistent headache, cervical neck pain, and photophobia and new-onset delirium. He was afebrile, the total leukocyte count was 2.7 × 109/L, and the absolute neutrophil count was 2.25 × 109/L. Lumbar spine MRI revealed a peripherally enhancing 3 × 2 × 3-cm collection of pus in the right posterior paraspinal musculature at the L2-3 level with ventral extension through the right L2-3 neural foramen (Figure 1). A 0.8 × 0.4-cm posterior epidural abscess was identified at the L2-3 level. With fluoroscopic guidance, a diagnostic lumbar puncture was performed at the left L2-3 interspace. The CSF obtained had a total protein level of 146 mg/dL (reference range, 14-45 mg/dL). The CSF glucose level was less than 20 mg/dL, and the concomitant serum glucose level was 113 mg/dL. Cerebrospinal fluid cultures grew oxacillinsensitive Staphylococcus aureus, but blood culture results were negative. Decompressive spinal surgery was not required, and a 3-month course of intravenous antibiotics was initiated. Throughout the hospital course, the patient experienced persistent low back pain and developed urinary retention. He was dismissed to a skilled nursing facility, where he resided for 2 weeks. At 5-month follow-up, the patient had regained complete bladder function, and the only residual symptom was mild back discomfort with prolonged periods of sitting. We reviewed the literature to identify predisposing epidemiological and clinical features of patients in whom epidural abscesses or meningitis developed after epidural corticosteroid injections. Our goal was to compare and contrast the findings in the reported cases with the clinical course of our patient. A MEDLINE and EMBASE literature search identified 11 reports of epidural abscess and 2 reports of epidural abscess and meningitis. Another report6Shealy CN Dangers of spinal injections without proper diagnosis.JAMA. 1966; 197: 1104-1106Crossref PubMed Scopus (60) Google Scholar described 2 patients with meningitis attributed to epidural corticosteroid injections, 1 of whom sustained a dural puncture. This patient subsequently developed a dural puncture headache that was treated with an epidural blood patch, and symptoms of meningitis occurred 7 days later. Because of the temporal relationship between the application of the blood patch and the onset of meningeal symptoms, this patient was excluded from further analysis (Table 1).Table 1Summary of Reported Cases of Epidural Abscess and Meningitis After Epidural Corticosteroid Injections*CSF = cerebrospinal fluid; EA = epidural abscess; ECI = epidural corticosteroid injection; LE = lower extremity; NS = not specified; UE = upper extremity.Clinical presentationReferencePatient age (y) and sexPatient historyECI (No. and site, agent)Time to symptom onset†From last injection.AbscessMeningitisSurgical treatment and culture resultsOutcomeShealy6Shealy CN Dangers of spinal injections without proper diagnosis.JAMA. 1966; 197: 1104-1106Crossref PubMed Scopus (60) Google Scholar58 MLow back pain, metastatic cancer4 lumbar, methylprednisolone4 moLE weakness and sensory loss; lumbar EAFever, delirium, neck rigidityLumbar laminectomy; blood, pus, and CSF cultures negativeLeft foot weakness, died of metastases at 6 moDougherty & Fraser7Dougherty Jr, JH Fraser RA Complications following intraspinal injections of steroids: report of two cases.J Neurosurg. 1978; 48: 1023-1025Crossref PubMed Scopus (99) Google Scholar34 FLow back pain, 2 laminectomies3 lumbar, hydrocortisone2 dNoneFever, headache, neck rigidity, cellulitis at ECI siteNo surgery; grampositive cocci on CSF stain, no culturesFull recoveryChan & Leung8Chan ST Leung S Spinal epidural abscess following steroid injection for sciatica: case report.Spine. 1989; 14: 106-108Crossref PubMed Scopus (69) Google Scholar56 MDiabetes1 lumbar, triamcinolone10 dLow back pain, paraplegia; cervical, thoracic, and lumbar EANoneMultilevel laminectomy; blood culture, Staphylococcus aureusLE weakness at 3 mo, ambulates with walkerGoucke & Graziotti9Goucke CR Graziotti P Extradural abscess following local anaesthetic and steroid injection for chronic low back pain.Br J Anaesth. 1990; 65: 427-429Crossref PubMed Scopus (61) Google Scholar65 FDiabetes, previous S aureus sepsis3 lumbar, methylprednisolone21 dLow back pain, urinary retention; lumbar EAFeverLumbar laminectomy; blood and CSF culture, S aureusMarked LE weakness, bladder dysfunction, died of renal failure at 9 wkWaldman10Waldman SD Cervical epidural abscess after cervical epidural nerve block with steroids [letter].Anesth Analg. 1991; 72: 717-718Crossref PubMed Google Scholar55 MCervical neck pain3 cervical, NS3 dChills, neck rigidity; cervical EANoneCervical laminectomy; EA pus culture, S aureusPartial use of UEs at 6 moBromage11Bromage PR Spinal extradural abscess: pursuit of vigilance.Br J Anaesth. 1993; 70: 471-473Crossref PubMed Scopus (61) Google Scholar61 FPostherpetic pain8 thoracic, methylprednisolone10 dArm pain, quadriplegia; cervical EANoneCervical laminectomy; no culturesQuadriplegia, follow-up period NSMamourian et al12Mamourian AC Dickman CA Drayer BP Sonntag VK Spinal epidural abscess: three cases following spinal epidural injection demonstrated with magnetic resonance imaging.Anesthesiology. 1993; 78: 204-207Crossref PubMed Scopus (66) Google Scholar84 FLow back pain, metastatic cancer1 lumbar, NS14 dLE weakness, back pain, delirium, incontinence; lumbar EANoneLumbosacral laminectomy, EA pus culture, S aureusDied of postoperative ventricular tachycardiaKnight et al13Knight JW Cordingley JJ Palazzo MG Epidural abscess following epidural steroid and local anaesthetic injection.Anaesthesia. 1997; 52: 576-578Crossref PubMed Scopus (63) Google Scholar53 MRight radicular leg pain, diabetes2 caudal, triamcinolone3 dLE pain, headache, chills, nuchal rigidity; lumbar and cervical EANoneMultilevel laminectomy; blood and pus culture, S aureusParaplegia and memory impairment at 6 moGoris et al14Goris H Wilms G Hermans B Schillebeeckx J Spinal epidural abscess complicating epidural infiltration: CT and MR findings [letter].Eur Radiol. 1998; 8: 1058Crossref PubMed Scopus (13) Google Scholar44 MCervical neck pain1 cervical, NS2 dNeck pain and tenderness, UE paresis; cervical EANoneCervical laminectomy; EA pus culture, multidrug-resistant S aureusNSKluba & Martini15Kluba T Martini F Spinal epidural abscess following steroid injection for sciatica.Aktuelle Rheumatol. 1998; 23: 182-183Crossref Scopus (5) Google Scholar21 MLow back pain1 lumbar, NS3 dBack pain, lumbar spinal tenderness; lumbar EANoneLumbar laminectomy; EA pus culture, methicillin-resistant S aureusFull recoveryYamaguchi et al16Yamaguchi M Kawakubo A Ide R Hara K Sumikawa K Epidural abscess associated with epidural block in a patient with immunosuppressive disease [in Japanese].Masui. 1999; 48: 506-508PubMed Google Scholar71 MMyeloproliferative disorder, diabetes2 lumbar, dexamethasone2 dFever, leg pain, back pain; lumbosacral EANonePercutaneous drainage; EA pus culture, β-hemolytic streptococciLeft foot dysesthesia at 3 moSabel et al17Sabel M Felsberg J Neuen-Jacob E Lichota A Schnitzler A Herdmann J Enlargement of a chronic aseptic lumbar epidural abscess by intraspinal injections—a rare cause of progressive paraparesis.Zentralbl Neurochir. 2000; 61: 111-114Crossref PubMed Scopus (20) Google Scholar54 FDiabetes, splenectomy3 lumbar, NS7 dLE weakness and sensory loss; lumbar EANoneLumbar laminectomy; EA culture, negativeMild hypesthesia at right L5 dermatome at 6 dKaul et al18Kaul S Meena AK Sundaram C Reddy JM Naik RT Murthy JM Spinal extradural abscess following local steroid injection.Neurol India. 2000; 48: 181-183PubMed Google Scholar26 MLow back pain1 lumbar, hydrocortisone7 dHeadache, low back pain, emesis; lumbar EANoneLumbar laminectomy; CSF culture, negativeFull recoveryKoka & Potti19Koka VK Potti A Spinal epidural abscess after corticosteroid injections.South Med J. 2002; 95: 772-774PubMed Google Scholar69 FLupus, oral prednisone for 2 y2 lumbar, NS4 dLE weakness and sensory loss, fever, back pain; lumbar EANoneNo surgery; blood culture, S aureusFull recovery* CSF = cerebrospinal fluid; EA = epidural abscess; ECI = epidural corticosteroid injection; LE = lower extremity; NS = not specified; UE = upper extremity.† From last injection. Open table in a new tab The mean age of the 14 reported patients (8 men and 6 women) was 54 years (range, 21-84 years). Five patients had diabetes mellitus, 2 had metastatic cancer, 1 had a myeloproliferative disorder, and 1 had systemic lupus erythematosus treated with oral corticosteroids. Ten patients received lumbar epidural corticosteroid injections, 2 received cervical injections, and 1 each received thoracic and caudal injections. The mean number of epidural corticosteroid injections administered was 2.5. The time to symptom onset ranged from 2 days to 4 months. Excluding the patient who developed symptoms after 4 months, the mean time to symptom onset was 7 days. Cultures of blood, epidural pus, or CSF specimens were obtained from 12 patients; 8 (67%) were positive for S aureus and 1 for β-hemolytic streptococci. In the case reported by Shealy,6Shealy CN Dangers of spinal injections without proper diagnosis.JAMA. 1966; 197: 1104-1106Crossref PubMed Scopus (60) Google Scholar negative culture results were attributed to antibiotics the patient received before the CSF and epidural pus specimens were obtained for culture. Neuropathologic examination of epidural tissue in the case reported by Sabel et al17Sabel M Felsberg J Neuen-Jacob E Lichota A Schnitzler A Herdmann J Enlargement of a chronic aseptic lumbar epidural abscess by intraspinal injections—a rare cause of progressive paraparesis.Zentralbl Neurochir. 2000; 61: 111-114Crossref PubMed Scopus (20) Google Scholar yielded results consistent with an aseptic epidural abscess. Kaul et al18Kaul S Meena AK Sundaram C Reddy JM Naik RT Murthy JM Spinal extradural abscess following local steroid injection.Neurol India. 2000; 48: 181-183PubMed Google Scholar provided no explanation for the negative culture results in their patient. Clinical outcome was documented in 13 of the 14 reported cases. Four patients experienced a full recovery, 2 of whom did not undergo surgery. Two patients died of perioperative complications, 1 patient became quadriplegic, and 1 became paraplegic. The remaining patients had memory impairment or focal neurologic deficits involving the extremities or bladder. The clinical features and course of our patient reinforce some important similarities and trends evident in the cases reported in the medical literature. Our patient, who received lumbar injections, was immunocompromised as evidenced by a low absolute neutrophil count. In the case report group, 8 patients had underlying medical illnesses that adversely affect immune function, including 5 with diabetes mellitus. In addition, a meta-analysis of 915 patients with epidural abscess identified diabetes mellitus as the single most common risk factor.20Reihsaus E Waldbaur H Seeling W Spinal epidural abscess: a meta-analysis of 915 patients.Neurosurg Rev. 2000; 23: 175-204Crossref PubMed Scopus (603) Google Scholar The immunocompromised patients described in the literature all received lumbar epidural injections, except 1 who was treated with caudal injections. The immune status of our patient, as well as that of the patients in the case report group, could have been compromised further by the systemic effects of the depot corticosteroids.21Jacobs S Pullan PT Potter JM Shenfield GM Adrenal suppression following extradural steroids.Anaesthesia. 1983; 38: 953-956Crossref PubMed Scopus (93) Google Scholar The total number of corticosteroid injections that our patient received was similar to the mean number of injections received by the patients in the case report group. In our patient and in all but one of the patients with positive results in the case report group, cultures grew S aureus. In the meta-analysis of epidural abscesses by Reihsaus et al,20Reihsaus E Waldbaur H Seeling W Spinal epidural abscess: a meta-analysis of 915 patients.Neurosurg Rev. 2000; 23: 175-204Crossref PubMed Scopus (603) Google Scholar S aureus was the principal etiologic organism in 551 (73%) of 753 patients in whom a bacterial infection was identified. Assuming that the patient's skin was prepared adequately and an aseptic technique was maintained throughout the procedure, a potential source of infection could have been inoculation of the epidural space with residual cutaneous flora.22Sato S Sakuragi T Dan K Human skin flora as a potential source of epidural abscess.Anesthesiology. 1996; 85: 1276-1282Crossref PubMed Scopus (132) Google Scholar This assertion is supported by a recent study in which, despite skin preparation with 10% povidone-iodine, 18 (35%) of 52 epidural needles were found to be contaminated with Staphylococcus epidermidis (n=14) and S aureus (n=4) after insertion of an epidural catheter.23Yentur EA Luleci N Topcu I Degerli K Surucuoglu S Is skin disinfection with 10% povidone iodine sufficient to prevent epidural needle and catheter contamination?.Reg Anesth Pain Med. 2003; 28: 389-393PubMed Google Scholar Cutaneous antisepsis with chlorhexidine before intravascular24Maki DG Ringer M Alvarado CJ Prospective randomised trial of povidone-iodine, alcohol, and chlorhexidine for prevention of infection associated with central venous and arterial catheters.Lancet. 1991; 338: 339-343Abstract PubMed Scopus (706) Google Scholar, 25Mimoz O Pieroni L Lawrence C et al.Prospective, randomized trial of two antiseptic solutions for prevention of central venous or arterial catheter colonization and infection in intensive care unit patients.Crit Care Med. 1996; 24: 1818-1823Crossref PubMed Scopus (205) Google Scholar or epidural26Kinirons B Mimoz O Lafendi L Naas T Meunier J Nordmann P Chlorhexidine versus povidone iodine in preventing colonization of continuous epidural catheters in children: a randomized, controlled trial.Anesthesiology. 2001; 94: 239-244Crossref PubMed Scopus (132) Google Scholar catheter insertion has been shown to be superior to povidone-iodine and should be considered when an epidural corticosteroid injection is to be administered. Interestingly, our patient underwent repair of an incarcerated inguinal hernia 2 days after the first epidural injection. The perioperative antibiotics the patient received could have temporarily suppressed microbial growth in the epidural space and paraspinal tissues. The time to symptom onset for 1 of the 2 patients with an epidural abscess and meningitis described in the literature was similar to the temporal course in our patient, who developed meningeal symptoms 21 days after the last epidural injection. A possible predisposing factor for development of meningitis in our patient was the accidental dural puncture, which occurred during performance of the first epidural injection. Although the patient did not develop symptoms of a persistent CSF leak, the integrity of the dura was compromised, and the puncture site could have served as a site for entry of bacteria into the thecal sac. In the case report group, 12 of the 13 patients with an epidural abscess required decompressive spinal surgery. Conversely, our patient did not require surgery. The bulk of the abscess was located in the paraspinal musculature, which may have attenuated compression of the thecal sac and limited the degree of neurologic damage. In patients who have received epidural corticosteroid injections, the potential complications of this invasive procedure should remain paramount in the differential diagnosis of recalcitrant back pain or the onset of new neurologic symptoms. Specifically, our patient should have been evaluated fully for meningitis before he was diagnosed as having opioid withdrawal. Immunocompromised patients should be identified before treatment, and the procedure should be performed under aseptic precautions. In this subgroup of patients, the small but potentially devastating risk of an infectious complication should be weighed carefully against the potential benefits of the procedure. The epidemiological and clinical data abstracted from the small group of disparate patients identified in the literature should be interpreted with caution. However, antibiotic prophylaxis for S aureus should be considered when immunocompromised patients are treated with epidural corticosteroid injections.