Spinal infection Flashcards
A 39-year-old presents with 4 days of neck pain and unsteady gait. He had recently completed a course of antibiotics for cellulitis. ON examination he was myelopathic, with sensory impairment below C4 level. Reflexes were brisk globally with upgoing plantars. He is pyrexial with a temperature of 38.2 °C. Blood cultures grow Staph aureus. T1 contrast MRI is shown. Which one of the following is most likely?
a. Arachnoiditis
b. Epidural abscess
c. Epidural lipomatosis
d. Epidural metastasis
e. Subdural empyema
b. Epidural abscess
Epidural abscess can result from hematogenous
spread, local extension, or direct inoculation.
This condition is usually found in adults; risk factors include intravenous drug abuse, diabetes
mellitus, prior spine trauma, renal failure, and
pregnancy. The majority of cases are located in
the thoracic spine. Causative organisms are S.
aureus (70%), other staphylococcal species, aerobic streptococci, Enterobacteriaceae (mainly E. coli)
Pseudomonas species mixed bacterial infections
and fungi. The initial presentation includes localized pain and fever with elevation of the ESR,
CRP, and leukocyte count. Blood cultures are
positive in 60% of patients. MRI is able to visualize the degree of cord compression and extent of
abscess in all directions, and discitis/vertebral
osteomyelitis which commonly accompanies it.
Areas of infection have characteristically high signal intensity on T2-weighted image. Without
treatment, significant neurologic deficits occur
and eventually paralysis may develop. Significant
neurologic recovery is observed in patients with
mild neurologic deficits or paralysis of less than
36 h duration who undergo surgical intervention.
Complete paralysis of greater than 36-48 h duration has not shown recovery. The death rate associated with epidural abscess has been reported as 12%. The surgical approach is determined by the location of the epidural abscess. An abscess located posteriorly and extending over multiple levels is best treated by multiple-level laminotomies or laminectomy, taking care to preserve the facet joints. Alternatively, debridement of the spinal canal through fenestrations removing the ligamentum flavum and portions of adjacent lamina, and use of catheters can be considered.
An abscess located anteriorly and associated with
vertebral osteomyelitis is most directly treated
with an anterior surgical approach. If an abscess
involves both the anterior and posterior epidural
space, an anterior and posterior approach combined with spinal stabilization using posterior
instrumentation is considered. A symptomatic
epidural abscess is considered a medical and surgical emergency. The combination of surgical
and antibiotic treatment is required for a symptomatic epidural abscess. Nonoperative management is considered in patients who are extremely high-risk surgical candidates and in patients with an established complete neurologic deficit for greater than 72 h. In addition, neurologically intact patients without sepsis can be considered for a trial of culture-specific antibiotic therapy under close clinical supervision.
A 54-year-old renal transplant patient presents with back pain, fever, and a new thoracic kyphotic deformity. She is otherwise neurologicallyintact on examination. T2WMRIis shown.
Which one of the following is most likely?
a. Epidural abscess
b. Intramedullary abscess
c. Pyogenic vertebral osteomyelitis
d. Spinal subdural empyema
e. Tuberculosis spondylitis
c. Pyogenic vertebral osteomyelitis
Pyogenic vertebral osteomyelitis accounts for
2-7% of all osteomyelitis, and at-risk groups
include the elderly, diabetics, AIDS, IV drug
abusers, and the immunosuppressed. The most
common method for bacteria to spread to the
spine is by the hematogenous route. Common
sources of infection include infected catheters,
urinary tract infection, dental caries, IV drug
use, and skin infections. The next most common
route is local extension from an adjacent soft tissue infection or paravertebral abscess, followed
by direct inoculation via trauma, puncture, or following spine surgery. The nucleus pulposus is relatively avascular, providing little or no immune
response, and thus is rapidly destroyed by bacterial enzymes. The disc is nearly always involved in pyogenic vertebral infections, unlike in tuberculous spondylitis (granulomatous). The most consistent symptom is back or neck pain, fever,
neurologic deficits, radicular pain, weight loss,
and kyphosis. The spinal areas affected in descending order are lumbar, thoracic, and cervical.
Staphylococcus aureus is the most common organism and has been identified in over 50% of cases. However, gram-negative organisms (Escherichia coli, Pseudomonas spp., Proteus spp.) are associated with spinal infections following genitourinary infections or procedures. Intravenous drug abusers have a high incidence of Pseudomonas infections. Anaerobic infections are common in diabetics and following penetrating trauma. Investigations should include FBC, CRP, ESR, and blood cultures. Vertebral body and adjacent discs appear hypointense on T1-weighted and hyperintense on T2 weighted MRI, and both
enhance on T1 + contrast imaging. Positive radiographic findings are not evident for at least
4 weeks after the onset of symptoms: the earliest
detectable finding is disc space narrowing, followed by localized osteopenia and finally destruction of the vertebral endplates. Technetium-99m bone scanning is valuable in the early diagnosis of pyogenic vertebral osteomyelitis because it demonstrates positive findings before X-ray changes.
CT is best at defining extent of bony destruction
and localization of lesions for biopsies. In the
absence of positive blood cultures, biopsy of the site of presumed vertebral osteomyelitis or discitis
is essential to provide a definitive diagnosis, identify the causative organism, and guide treatment.
The biopsy ideally should be performed before
initiation of antibiotics. If antibiotics have
been given, they should be discontinued for 3 days
before the biopsy. Computed tomography (CT)-
guided, closed Craig needle biopsy is safe and
effective and yields the etiologic organism in
70% of cases. If a closed biopsy is negative after
two attempts, an open biopsy can be considered.
Tissue samples should be sent for Gram stain,
acid-fast stain, aerobic and anaerobic cultures,
and fungal and tuberculosis (TB) cultures. Bacterial cultures should be observed for at least 10 days
to detect low-virulence organisms. TB cultures
may take weeks to grow. Histology studies should
also be performed to detect neoplastic processes
and to differentiate acute versus chronic infection. The goals in treating vertebral osteomyelitis
include early definitive diagnosis, eradication of
infection, relief of axial pain, prevention or reversal of neurologic deficits, preservation of spinal
stability, and correction of spinal deformity
Which one of the following statements about surgical management of vertebral osteomyelitis is LEAST accurate?
a. Simple laminectomy is the primary procedure for emergency management of neural element compression in vertebral osteomyelitis
b. Anterior or combined anterior-posterior approaches are required in the majority of cases
c. Posterior approach alone can be considered if there is disc space infection below the conus without anterior column instability
d. Refractory back pain after a period of nonoperative management is an indication for surgery
e. Correction of progressive spinal deformity is an indication for surgery
a. Simple laminectomy is the primary procedure for emergency management of neural element compression in vertebral osteomyelitis
Indications for operative treatment of pyogenic
vertebral osteomyelitis include: (1) need for open
biopsy; (2) failure of nonsurgical management
(high ESR/CRP, refractory back pain); (3) need
for open drainage of abscess; (4) neural decompression; (5) spinal stabilization; and (6) correction of progressive spinal deformity. As such, the location of the infection, presence/absence of
abscess, extent of bone destruction, and need for
stabilization are key. Spinal discitis/osteomyelitis
primarily affects the anterior spinal column, hence
anterior only or combined anterior and posterior
approaches are indicated in the majority of spinal
infections. Posterior approaches may be considered in special circumstances such as posterior epidural abscesses, disc space infections below the conus with satisfactory anterior column support, and in the absence of significant paravertebral abscess. Laminectomy alone is associated with deformity progression, instability, and neurologic deterioration, hence it is not recommended.
Surgery should achieve complete debridement
of nonviable and infected tissue, decompression
of neural elements, and long-term stability
through fusion (use of autogenous graft material
is gold standard). The surgical approach generally
should include anterior debridement and grafting
followed by a staged or simultaneous posterior
spinal stabilization procedure. While placing implants in infected environments would normally
be avoided, bone infections are better controlled
with antibiotics and bone stabilization than with
antibiotics alonein an unstable bony environment.
Use of titanium alloys is preferable to stainless
steel due to increased bacterial adherence to stainless steel implants. In this setting, advantages of posterior spinal instrumentation include:
1. preservation of spinal alignment and restoration of spinal stability following radical
debridement
2. increased fusion rates
3. ability to correct kyphotic deformities
4. avoidance of graft collapse or dislodgement
5. rapid patient mobilization and early rehabilitation without the need for an external
orthosis.
A 32-year-old recent immigrant from Southeast Asia presents with back pain and a new kyphotic deformity after tripping upin his flat. T1 and T2 W MRI are shown.Which one of the following is most likely diagnosis?
a. Ankylosing spondylitis
b. Discitis
c. Multiple myeloma
d. Pyogenic vertebral osteomyelitis
e. Spinal tuberculosis
e. Spinal tuberculosis
Tuberculosis is the most common granulomatous
infection of the spine. The three patterns of spinal
involvement are peridiscal (commonest), central,
and anterior. Peridiscal occurs adjacent to the vertebral endplate and spreads around a single intervertebral disc as the abscess material tracks
beneath the anterior longitudinal ligament (the
disc is usually spared unlike in pyogenic infections). Central involvement occurs in the middle
of the vertebral body and eventually leads to vertebral collapse and kyphotic deformity. This pattern of involvement can be mistaken for a
tumor. Anterior infections begin beneath the anterior longitudinal ligament, causing scalloping of the anterior vertebral bodies, and extend over multiple levels. The presentation is highly variable.
Mild back pain is the most common symptom.
Patients with tuberculous infections may present
with malaise, fevers, night sweats, and weight loss.
In addition, chronic infections may result in cutaneous sinuses, neurologic deficits (in up to 40% of patients), and kyphotic deformities. Certain factors define the high-risk population and should raise suspicion. Patients from countries with a high incidence of tuberculosis, such as Southeast Asia,
South America, and Russia are considered high
risk. Patients who live in confinement with others,
such as homeless centers and prisons, are also at
risk. Elderly adults, chronic alcoholics, patients
with AIDS, and patients with a family member
or a household contact with tuberculosis are additional high-risk groups. The leukocyte count may be normal or mildly elevated. The ESR is mildly
elevated (typically <50), but may be normal in
up to 25% of cases. Although the purified protein
derivative (PPD) skin test may detect active infection or past exposure, this test is unreliable because false-negative results may occur in malnourished and immunocompromised patients. Anergy panel testing should be included for this reason. Urine cultures, sputum specimens, and gastric washings may be helpful for diagnosis if the primary source is unknown. The most reliable test for diagnosis is CT-guided biopsy. The characteristic finding on histology is a granuloma, which is described as a multinucleated giant-cell reaction surrounding a central region of caseating necrosis. Molecular detection of mycobacterium DNA or RNA is useful for rapid diagnosis and for determining drug resistance. Radiographs: A clue to diagnosis is the presence of extensive vertebral destruction out of proportion to the amount of pain. Typically, the intervertebral discs are preserved in the early stages of this disease. Chest radiographs can be useful in demonstrating pulmonary MRI: The imaging modality of choice for diagnosis of spinal TBCT: Plays a role in defining the extent of bony destruction and localization for biopsies. Chemotherapy (four-drug regimen, for a minimum of 6-month duration, includes isoniazid, rifampin, pyrazinamide, and ethambutol) and brace immobilization are the initial treatment except in patients presenting with neurologic deficit or progressive deformity. The indications for surgery and the principles of surgical reconstruction are similar to those advised for pyogenic spinal infections.
Which one of the following statements regarding spinal subdural empyema is most accurate?
a. Two thirds are associated with discitis/
osteomyelitis
b. Are commoner than cranial subdural
empyemas
c. Lumbar puncture should be attempted
before proceeding to open surgery
d. MRI is definitive in distinguishing subdural
empyema from epidural abscesses
e. Commonly occur in adolescents
e. Commonly occur in adolescents
Spinal subdural empyemas are uncommon and
tend to occur in thoracolumbar spine, in those
in 5th-7th decades. Suggestions for why they
are less common than cranial subdural empyema
and spinal epidural abscesses include the lack of
air sinuses in the spine, the fact that the epidural
space in the spine is an actual rather than potential space, and blood is directed centripetally
in the spine, whereas it is directed centrifugally
in the brain. The pathogenesis of these infections can be categorized into one of four major
categories: hematogenous spread of primary
infection, iatrogenic (lumbar puncture, spinal
injections), direct extension into the subdural
space (dysraphism, penetrating trauma, spinal
infection), and cryptogenic. The most common
organism is Staphylococcus aureus, other Staphylococcus species, Streptococcus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Peptococcus magnus. The classical presentation of an SSE includes fever, neck/back pain, followed by symptoms of spinal cord/cauda equina compression. Presence of spinal tenderness may favor epidural abscess rather than subdural empyema. Routine tests include FBC, ESR, CRP; lumbar puncture is not performed due to risks of contaminating deeper meningeal layers. Contrast MRI is imaging of choice as allows better visualization of the spinal cord, vertebrae, disc spaces, extent of lesion, and extent of compression. The major limitation of MRI,
however, remains its inability to distinguish whether the lesion is intradural or extradural; the
presence of discitis/osteomyelitis accompanies
two thirds of SEAs. The mainstay of treatment
for these infections is surgical decompression
(laminectomy) with irrigation and drainage of
the subdural space followed by appropriate antibiotic therapy. The exposure should encompass the extent of the abscess. After copious irrigation, most authors advocate the primary closure of the dura. The arachnoid should be preserved if possible. A significant indication for surgery is obtaining a definitive organism to treat; therefore cultures should be obtained before using
antibiotic irrigation. The use of postoperative
antibiotics should be based on the given organism found during surgery. Empiric antibiotic
coverage for these infections must cover grampositive cocci. Some advocate the additional
use of corticosteroids (dexamethasone) during
the perioperative period as a prophylaxis against
the development of thrombophlebitis. Among
the surgically treated group, 82.1% made a complete recovery or improved, whereas 17.9%
died. In the conservatively treated group, 80%
died (4 of 5 patients) and only 20% (1 of 5
patients) improved. On the basis of these numbers, the current recommendations are for
aggressive surgical treatment followed by antibiotic therapy.
A 19-year-old male presents with neck pain, fever, and numbness in his legs and trunk up to his arm pits. His neurological examination is consistent with an upper motor neuron lesion, and you note a small midline sinus on the back of his neck. Blood cultures grow
Streptococcus epidermis, T1 MRI with contrast is shown. Which one of the following is the next appropriate step?
a. MRI head with contrast
b. CSF analysis
c. Cardiac echo
d. Dental examination
e. Start IV antibiotics immediately
a. MRI head with contrast
Intramedullary spinal cord abscesses (ISCAs) are
rare, and patients are young. ISCAs occur
throughout the spine, but they are most frequently found in the thoracic region. The pathogenesis of ISCA can be divided into two broad
categories: hematogenous spread and direct
implantation. The more complex of the two is
hematogenous spread via arterial supply (septic
emboli), venous drainage (increased intrathoracic/abdominal pressure causing backflow in low pressure spinal venous system), or lymphatics (draining mediastinum, abdomen connect with Virchow Robins paces in spinal cord
via channels in spinal nerves). The most common primary infection is pulmonary, endocarditis, urinary tract infections, peritonitis, and
peripheral skin infections. The other major
route for the pathogenesis of ISCA is direct
implantation via a congenital midline neuroectodermal defect (e.g. dermal sinus tract), postoperative, after penetrating trauma. Most
commonly no cause is found (cryptogenic).
Causative organisms are Staphylococcus and Streptococci, with other significant organisms Actinomyces, Proteus mirabilis, Pneumococcus, Listeria monocytogenes, Hemophilus, and Escherichia coli. Cases of contiguous spread via a dermal sinus tract are most commonly due to Staphylococcus epidermidis, S. aureus, Enterobacteriaceae, anaerobes, and Proteus mirabilis. Postsurgical (contiguous) cases are most often due to S. epidermidis,
S. aureus, Enterobacteriaceae, and Pseudomonas
aeruginosa. The cases that arise from hematogenous spread reflect the site of primary infection.
The presenting signs and symptoms in patients
with ISCAs almost always involve motor deficits,
sensory impairment, loss of sphincteric control,
pain, and fever. Acute infections (<2 weeks) partial transverse myelitis commonly associated
with fever and leucocytosis, while subacute
(2-6 weeks) and chronic (>6 weeks) present like
intramedullary tumors. Investigations include
WCC, CRP, ESR, CSF analysis (usually
negative unless meningitis). Imaging of choice
is contrast MRI which may differentiate between
early and late myelitis. CT myelography may
show widening of the cord at a focal segment
with obstruction to CSF flow. X-rays are usually
normal at presentation. Other features are osteomyelitis, spinal deformity, spinal stenosis, and spinal dysraphism, current recommendations
are for immediate surgical treatment. The surgery should include laminectomies at the
involved levels, intradural exploration, midline
myelotomy, and irrigation and drainage of the
abscess cavity. Aggressive treatment with antibiotics requires empirical therapy until an
organism has been isolated. The choice of antibiotics for empirical therapy should be based on the suspected source of infection and then
adjusted on the basis of the operative culture
results. The current recommendation is a minimum of 4-6 weeks of parenteral therapy.
Patients presenting with acute symptoms have
a worse prognosis in terms of neurologic recovery. Overall, the death of a patient diagnosed
with an ISCA is most frequently due to the presence of multiple CNS abscesses and, specifically, to brain or brainstem abscesses.
