Safety of care
Spinal epidural abscess: a rare, insidious and potentially catastrophic infection
Originally published March 2008
This article summarizes information from the Association's database to help members reduce their exposure to risk.
Spinal epidural abscess is a rare suppurating infection of the epidural space surrounding the spinal cord. Cord damage develops as a result of direct compression, inflammatory injury or vascular compromise.
The early clinical features of spinal epidural abscess are variable, most often non-specific, and may be attributed to more common clinical reasons for back pain. Eventually, symptoms and signs progress to include some combination of fever, back/neck pain and neurologic abnormalities. The presence of neurologic dysfunction indicates advanced disease, and signals the need for urgent surgical intervention to lessen the risk of further spinal cord injury.
A case study from CMPA files
A 40-year-old insulin dependent diabetic female presented to her family physician with new complaints of mid-thoracic back pain, which had onset gradually following participation in a new exercise program. The patient was referred for physiotherapy and prescribed a muscle relaxant, but the pain intensified over the next week. Her family physician then prescribed narcotic analgesia and referred her to a family physician colleague with a special interest in back disorders who diagnosed T5-6 radiculitis. Local injection of trigger points and gentle spinal manipulation were carried out with temporary symptomatic relief.
Ten days after the onset of symptoms (see Figure 1 for timeline), the patient presented to the emergency department with unrelenting mid-thoracic pain, sweats and constipation. No neurologic symptoms were reported. The temperature was recorded at 37.4 C; the white blood cell count was 11.6 with 86 per cent neutrophils, and the ESR 54. Plain X-rays of the thoracic spine were unremarkable. The emergency physician admitted the patient to hospital for further investigation and management of a possible "infectious disc."
The patient's family physician reassessed her later on the morning of admission and consulted an internist who then referred her to an orthopaedic surgeon. The internist and orthopaedic surgeon suspected muscle strain and the orthopaedic surgeon further concluded an infectious process was unlikely.
A bone scan was ordered which was later confirmed as normal.
During the second day in hospital the patient remained fully ambulatory. However, on the evening of the third day, she fell three times. She reported being unable to stand for more than brief periods.
On the morning of the fourth hospital day, the patient reported weakness of her arms and legs and numbness of the soles of her feet. She experienced a loss of bladder control. She was again assessed by her family physician, who confirmed objective weakness of the left upper extremity. At approximately 10:30, her family physician ordered a consultation with a neurologist and re-consultation with the internist. However, her family physician made no personal contact with either consultant to convey the seriousness and urgency of the situation.
The patient was eventually assessed by the neurologist at approximately 17:00.Additional information available at that time included a white blood cell count of 22.4 X 109/L recorded at 12:30 that day. The patient's temperature was 37.3 C. The neurologist noted definite weakness and loss of tendon reflexes in the left upper extremity, but no definite weakness or sensory abnormalities in the lower extremities. The possibility of a spinal cord lesion was considered, but investigation was limited to ordering plain
At 02:00 on the fifth hospital day, the neurologist contacted a neurosurgeon who immediately suspected a spinal epidural abscess. The patient was transferred to a tertiary centre where an MRI scan revealed aposterior epidural mass extending from C1-2 to C7 causing moderately severe compression and anterior displacement of the cervical cord. At surgery, an extremely large epidural pus collection was identified.
Post-operatively, the patient was left paraplegic with complete motor paralysis of the lower extremities and associated bowel and bladder dysfunction. The left upper extremity weakness eventually resolved completely.
A legal action was commenced naming all the physicians involved in her care as defendants. Peer experts were unsupportive of the family physician and the neurologist. A settlement was paid by the CMPA on behalf of these two member physicians.
What the experts said
- There was no criticism of the medical management prior to the fourth hospital day. The slight increase in white blood cell count and elevation of the ESR on presentation were considered non-specific. Appropriate referrals were made in a timely fashion.
- Experts maintained that the family physician should have communicated personally with the neurologist on the morning of day four to convey the seriousness of the patient's clinical circumstances.
- Experts also felt that the neurologist should have recognized that the history of repeated falls beginning in the evening of day three and the associated neurologic abnormalities, including bladder dysfunction, suggested a cord lesion that required urgent attention.
A review of the Association's closed files from 1996 to 2006 related to spinal epidural abscess revealed a total of 33 cases. There were 30 civil legal actions (29 actual and one threatened) and three regulatory authority (College) cases.
Sixteen of the 30 legal cases resulted in the patient receiving a financial settlement paid by the CMPA on behalf of members (i.e., in favour of the plaintiff) and 13 were dismissed. In the single case that went to trial, the judgment was in favour of the physician.
In eight of the 16 cases that were concluded in favour of the plaintiff there was a documented misdiagnosis (e.g., sprain/strain of back/neck, neuralgia, drug withdrawal syndrome) that contributed to delay in identifying the correct diagnosis and treatment. In 10 of these 16 cases, there was a delay in performing appropriate diagnostic tests (e.g., general physical exam, neurological exam, blood work, CT or MRI scan).
The most common location for the cases concluded in favour of the plaintiff was the emergency department (eight of the 16 cases).
Review of our cases and opinions obtained from clinical experts have identified the following conditions as predisposing to spinal epidural abscess:
- Immunodeficiency (e.g., diabetes mellitus, AIDS, malignancy, alcoholism, intravenous drug abuse)
- Spinal procedures or surgery
- Spinal trauma
Of the 33 cases in this CMPA review, 11 developed in association with a spinal procedure. Seven of those 11 involved epidural or spinal anaesthesia. Six cases were associated with some form of recent trauma involving back neck or shoulders. Intravenous drug abuse was identified in five cases, diabetes mellitus in two and alcohol addiction in one.
Patient physical disability
Death occurred in three of the 33 cases. Quadriplegia was documented in five cases and paraplegia in four. Three other cases involved lesser degrees of neurologic deficit involving the legs, bladder and bowel.
Identify your risks
Based on a review of expert opinions obtained in the course of legal actions involving spinal epidural abscess, the CMPA has identified the following risk management considerations:
- Have you considered the diagnosis of spinal epidural abscess in patients presenting with back pain and unexplained fever?
- Are you familiar with conditions associated with spinal epidural abscess? Medical experts have identified IV drug users attending in the emergency department as a particularly high risk patient group.
- When the diagnosis of spinal epidural abscess is suspected, have you acted in a timely fashion to confirm or rule out the diagnosis with appropriate consultation and/or imaging studies (e.g., MRI or CT scanning)?
- When spinal epidural abscess is confirmed, have you arranged urgent neurosurgical or orthopaedic consultation?
Epidural abscess in perspective
The symptoms of back pain, and back pain with fever, are common reasons for patients to seek medical care. The early symptoms of epidural abscess often mimic less serious conditions and there is a varied rate of progression of the disease. Epidural abscess is rare. Many physicians will never see a patient with this condition. This article is provided to heighten awareness of epidural abscess, recognizing its early identification may challenge the skills of even the best clinicians. It is not meant to suggest most patients with back pain require investigation for epidural abscess.