Spinal Epidural Abscess - Spine

Introduction
Defined as a collection of pus or inflammatory granulation tissue between the dura mater and surrounding adipose tissue Epidemiology demographics usually seen in adults > 60 years of age location usually dorsal in thoracolumbar spine risk factors IV drug abuse immunodeficiency malignancy HIV immunosuppressive medications recent spinal procedure Pathophysiology origin hematogenous spread ~50% spread from diskitis ~ 33% pathogens staph aureus is most common (50-65%) gram negative infections such as E coli (18%) pseudomonas seen in patients with IV drug use Neurologic deficits 33% of patients with an epidural abscess will have neurologic symptoms 4-22% incidence of permanent paralysis can be caused from direct compression or infarction of spinal cord blood flow. Associated conditions often associated with vertebral osteomyelitis and discitis (spondylodiscitis) present in ~18% of patients with spondylodiscitis Prognosis preoperative degree of neurologic deficits is most important indicator of clinical outcome mortality ~ 5% early diagnosis is most essential factor in preventing devastating outcomes
Presentation
Symptoms systemic illness more profound than patients with vertebral osteomyelitis fever present in ~50% pain pain is often severe and insidious in onset an occurs in 87% Physical exam neurologic deficits present in ~33% may present as a radiculopathy or a myelopathy
Labs
WBC mean leukocytosis 22,000 cells/mm3 elevated in ~42% ESR elevated in > 90% of cases (mean 86.3) CRP elevated in 90% of cases
Imaging
Radiographs usually normal CT poor sensitivity for epidural abscess CT myelogram 90% sensitivity but invasive MRI with gadolinium the imaging modality of choice for diagnosis of spinal epidural abscess shows extent of abscess, presence of vertebral osteomyelitis, and allows evaluation of neurologic compression gadolinium allows differentiation of pus from CSF a ring enhancing lesion is pathognomonic for abscess entire spine MRI should be performed to rule out skip epidural abscesses concomitant infection outside of the spine delayed presentation (>7 days of symptoms) ESR > 95 mm/hr
Treatment
Nonoperative bracing and IV antibiotics indications small abscess with minimal compression on neural elements and no neurologic deficits and a patient capable of close clinical followup those who are not candidates for surgery due to medical comorbidities outcomes historically presence of epidural abscess has been considered a surgical emergency there has been a recent trend towards nonoperative management as new studies shows nonoperative treatment effective in patients without neurologic deficit medical treatment failure associated with: neurologic deficits (strongest predictor of medical treatment failure) diabetes CRP >115 mg/L WBC >12 k/mL positive blood cultures age >65 years MRSA Operative surgical decompression +/- spinal stabilization indications neurologic deficits present evidence of spinal cord compression on imaging studies persistent infection despite antibiotic therapy progressive deformity or gross spinal instability postoperative antibiotics indicated for 2-4 weeks if no bony involvement of infection indicated for 6 weeks if bony involvement
Techniques
Decompressive laminectomy most common form of operative treatment indications indicated when abscess is posterior and there is no contiguous spondylodiscitis avoid wide decompression and facetectomy as it will result in spinal instability Anterior debridement and strut grafting indications abscess is located anteriorly anterior vertebral body and discs are involved (presence of spondylodiscitis)