Musculoskeletal
Question 54 of 180
A 35 year old known intravenous drug user (IVDU), presents to the Emergency Department complaining of feeling generally unwell with low back pain which is worse at night and which has been progressively worsening over the last couple of weeks. On examination he has midline tenderness to gentle spinal percussion over vertebrae L4/L5. His observations are recorded as:
- Heart rate: 105 beats per minute
- Blood pressure: 123/98 mmHg
- Respiratory rate: 25 breaths per minute
- Temperature: 39.1°C
What is the most likely diagnosis?
Answer:
Most cases of epidural abscess arise from haematogenous seeding of the epidural space from a distant source of infection. A few cases are the result of direct extension of infection from the spine or paraspinal tissues. A spinal epidural abscess threatens the spinal cord or cauda equina by compression and also by vascular compromise. If untreated, an expanding suppurative infection in the spinal epidural space impinges on the spinal cord, producing sensory symptoms and signs, motor dysfunction, and, ultimately, paralysis and death.Spinal Infections
Musculoskeletal
Last Updated: 12th February 2021
Types
- Vertebral osteomyelitis
- Can develop from direct open spinal trauma, from infections in adjacent structures, from haematogenous spread of bacteria to a vertebra, or postoperatively. Left untreated, vertebral osteomyelitis can lead to permanent neurologic deficits, significant spinal deformity, or death. It can result in severe compression of the neural structures due to formation of an epidural abscess or due to a pathologic fracture resulting from bone softening.
- Discitis
- Discitis is an inflammation of the vertebral disc space often related to infection. Infection of the disc space must be considered with vertebral osteomyelitis; these conditions are almost always present together, and they share much of the same pathophysiology, symptoms, and treatment.
- Epidural abscess
- Most cases arise from haematogenous seeding of the epidural space from a distant source of infection. A few cases are the result of direct extension of infection from the spine or paraspinal tissues. A spinal epidural abscess threatens the spinal cord or cauda equina by compression and also by vascular compromise. If untreated, an expanding suppurative infection in the spinal epidural space impinges on the spinal cord, producing sensory symptoms and signs, motor dysfunction, and, ultimately, paralysis and death.
The most common source of spinal infections is staphylococcus aureus, followed by escherichia coli.
Risk factors
Risk factors for developing spinal infection include conditions that compromise the immune system, such as:
- Advanced age
- Intravenous drug use
- Human immunodeficiency virus (HIV) infection
- Long-term systemic usage of corticosteroids
- Immunosuppressants
- Diabetes mellitus
- Organ transplantation
- Malnutrition
- Malignancy
- Recent spinal surgery
Clinical features
- Vertebral osteomyelitis
- Progressively severe back pain
- Fever
- Rigors
- Weight loss
- Muscle spasms
- Painful or difficult urination
- Neurological deficits: weakness and/or numbness of arms or legs, incontinence of bowels and/or bladder
- Discitis
- Patients may initially have few symptoms, but eventually develop severe back pain.
- Generally, younger, preverbal children do not have a fever nor seem to be in pain, but they will refuse to flex their spines. Children age three to nine typically present with back pain as the predominant symptom.
- Epidural abscess
- Severe back pain with fever and local tenderness in the spinal column
- Radicular pain and paraesthesia
- Weakness of voluntary muscles, sensory loss and bowel/bladder dysfunction
- Paralysis
Investigation
- Bloods - FBC, CRP/ESR
- Blood cultures
- Urinalysis and culture
- Imaging
- Spinal x-ray
- Radiographic findings are usually normal in the first 2-4 weeks. If the disc space is involved, the disc space may narrow, and destruction of the endplates around the disc may be seen on the radiograph. Later, plain radiographs usually reveal rarefaction, loss of bony trabeculation close to the cartilaginous plate, and an irregular narrowing of the vertebral disk space. Vertebral body collapse may also be seen. Simultaneously, evidence of rapid bone regeneration may be evident, with the development of bone spurs and dense new bone. Plain films have little role to play in investigating a patient with suspected spinal epidural abscess, as no direct visualisation of the collection is possible.
- CT spine
- CT depicts osteomyelitis earlier than plain films do. CT findings include hypodensity at the site of infected disks, lytic fragmentation of the involved bone, gas within an involved vertebra, and decreased density of adjacent vertebrae and nearby soft tissues. Epidural and paraspinal extension of infection may also be seen, although CT even with contrast can struggle to demonstrate smaller collections.
- MRI spine
- Contrast enhanced MRI is the gold standard for identifying spinal infection and assessing the neural elements.
- Spinal x-ray
- CT-guided percutaneous biopsy of the vertebra or disc space
- This is a minimally invasive test used to obtain histologic confirmation of the disease and tissue samples for culture.
Management
- Non-surgical treatment
- Spinal infections often require long-term intravenous antibiotic or antifungal therapy and can equate to extended hospitalisation time for the patient. Patients generally undergo antimicrobial therapy for a minimum of six to eight weeks.
- Broad-spectrum antibiotics covering both gram-positive and gram-negative organisms, aerobes and anaerobes, including methicillin-resistant S aureus (MRSA), are administered initially until the organism is isolated.
- Immobilisation may be recommended when there is significant pain or the potential for spine instability.
- Surgical treatment
- Nonsurgical treatment should be considered first when patients have minimal or no neurological deficits and the morbidity and mortality rate of surgical intervention is high. However, surgery may be indicated when any of the following situations are present:
- Significant bone destruction causing spinal instability
- Neurological deficits
- Sepsis with clinical toxicity caused by an abscess unresponsive to antibiotics
- Failure of needle biopsy to obtain needed cultures
- Failure of intravenous antibiotics alone to eradicate the infection
- The primary goals of surgery are to:
- Debride the infected tissue
- Enable the infected tissue to receive adequate blood flow to help promote healing
- Restore spinal stability with the use of instrumentation to fuse the unstable spine
- Restore function or limit the degree of neurological impairment
- Nonsurgical treatment should be considered first when patients have minimal or no neurological deficits and the morbidity and mortality rate of surgical intervention is high. However, surgery may be indicated when any of the following situations are present:
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
