Infectious disorders of the spinal cord

Author(s): Saloni Sharma, MD

Originally published:07/17/2013

Last updated:08/25/2016

1. DISEASE/DISORDER:

Definition

Infectious disorders that affect the spinal cord can be divided according to their anatomic location, including the following:

  1. Spinal column: pyogenic osteomyelitis, spondylodiscitis and discitis,1 Pott disease,2 and spinal fungal infections.
  2. Epidural space: epidural abscess.3
  3. Meninges: arachnoiditis.
  4. Spinal cord: intramedullary abscess, neurosyphilis, and viral infections of the spinal cord.

Etiology

Most common cause of spine and spinal cord infections are bacterial in origin. Causative organisms include the following:

  1. Staphylococcus species
  2. Streptococcus species
  3. Salmonella in patients with sickle cell anemia
  4. E.coli, Proteus mirabilis, and Enterococcus in patients who are immunocompromised
  5. Pseudomonas aeruginosa and Brucella in intravenous (IV) drug abusers
  6. Mycobacterium tuberculosis in patients with spinal tuberculosis (Pott disease)
  7. Treponema pallidum, which causes neurosyphilis

Immunocompromised patients are at high risk of developing viral infections that can affect the spinal cord. Causative agents include the following:

  1. Human immunodeficiency virus
  2. Herpes simplex virus I and II
  3. Cytomegalovirus
  4. Varicella zoster virus
  5. Human T-cell lymphotrophic virus

Fungal infections are extremely rare. However, these may also occur in immunosuppressed individuals. The most common organisms in fungal infection of the spine are Aspergillus and Candida. 4 Common fungal species include the following:

  1. Aspergillus
  2. Candida
  3. Cryptococcus
  4. Coccidioides
  5. Blastomyces

Epidemiology including risk factors and primary prevention

Risk factors that may contribute to developing infections within the spinal cord or surrounding structures include the following:

  1. Age (pediatric and geriatric populations)
  2. Poor nutritional status
  3. Immunosuppression
  4. IV drug use
  5. Spine surgery and/or instrumentation
  6. Hemodialysis

The incidence of pyogenic osteomyelitis, spondylodiscitis, and discitis has been reported to be between 0.2 and 2 cases per 100,000 per year. Approximately 95% of pyogenic spinal infections involve the vertebral body and/or the intervertebral disk, with only 5% involving the posterior elements of the spine.1

Men are more frequently diagnosed to have spinal infections.5 The annual incidence of osteomyelitis varies in different geographic populations. A 40-year population study reported the adjusted annual incidence of osteomyelitis to be as high as 21.8 cases per 100,000 in some populations.

Tuberculosis (TB) of the spine accounts for 1% to 5% of all TB cases and for about 50% of the cases of articulo-skeletal TB infections.2

Spinal fungal infections and viral infections of the spinal cord are extremely rare. Most occur in immunosuppressed patients.

Spinal epidural abscess has an estimated incidence rate of 0.2 to 2.8 cases per 10,000 per year.3

Arachnoiditis is caused by irritation or inflammation of the subarachnoid space, leading to scarring, and arachnoid thickening, opacification, and formation of adhesions.

Patho-anatomy/physiology

Most common modes of inoculation are the following:

  1. Hematogenous spread
  2. Contiguous involvement
  3. Direct inoculation after trauma, surgery, or therapeutic intervention

Hematogenous infections may spread from the oral cavity, skin, respiratory tract, genitourinary system, or the gastrointestinal tract, leading to bacteremia. Causative agents may then seed into the vertebral endplates via low flow arteriolar network. The infection then spreads by contiguous involvement when the infectious focus ruptures from the endplates into the disk or surrounding paravertebral tissue.

Specific secondary or associated conditions and complications

Systemic signs of infection including fever, and chills may or may not be present with localized or radicular pain.

Neurologic deficits that suggest spinal cord involvement include the following:

  1. Sensory changes
  2. Weakness
  3. Severe intractable regional and/or radicular pain
  4. Urine retention or incontinence
  5. Bowel impairments
  6. Saddle anesthesia

2. ESSENTIALS OF ASSESSMENT

History

It is imperative to obtain a full history in order to formulate a differential diagnosis and treatment plan.

  1. Review of systems should include presence of fevers, chills, night sweats, back pain, radicular pain, weakness, sensory changes, and bladder or bowel changes. High level of suspicion for infection should also include persistent pain despite rest and anti-inflammatory medications.
  2. Significant medical and surgical history includes recent and previous infectious illnesses, recent and previous spinal surgeries, and procedures, diabetes, chronic steroid use, cancers, IV drug use, long-term access, such as peripheral or central lines, and/or indwelling bladder catheters.
  3. Additional historical elements that can direct diagnostic work up include vaccinations, transfusions, recent travel, drug abuse, and psychosocial history.

Clinical presentation of spinal epidural abscess includes fever, localized back pain, radicular pain, muscle weakness, paresthesias, sphincter dysfunction, and paralysis.3

Neurosyphillis involves the posterior columns of the spinal cord, and therefore patients with Tabes dorsalis develop impairment of vibration and position sense and progressive ataxia.

Physical examination

An initial comprehensive examination should be performed to identify neuromuscular deficits. This should include inspection and palpation of the spine as well as observation of gait including tandem gait, upper and lower limb manual muscle testing, sensory exam, and assessing reflexes including Hoffman’s and Babinski. Serial exams should also be performed to assess for disease progression or resolution.

If myelopathy is suspected, an American Spinal Injury Association Impairment Scale (AIS) exam should be performed for neurologic impairment classification.6

Pain on percussion of the spinous processes would suggest an infectious or fracture rather than musculoskeletal etiology.

Functional assessment

Assessment includes the following:

  1. Functional Independence Measure (FIM)
  2. Spinal Cord Independence Measure (SCIM)7

Laboratory studies

Laboratory studies should be aimed at determining the causative organism and infection location.

  1. Complete blood count.
  2. Erythrocyte sedimentation rate (ESR): ESR is a sensitive but nonspecific test that can assist in both infection screening and treatment response.
  3. C-reactive protein (CRP): CRP is an acute phase reactant that is nonspecific for infections. When used in conjunction with ESR, it can detect an active infection, monitor disease progression, and/or be used to determine treatment length and success.
  4. Specimen cultures: blood cultures for peripheral sites and intravenous access, urine cultures, and sputum cultures.

Imaging

Magnetic resonance imaging (MRI) of the spine is the modality of choice to assess for infections surrounding the spine and spinal cord. It allows for early detection of vertebral column and disk changes and better visualization of the surrounding soft tissue. T1-weighted sequences with IV gadolinium enhancement allow the differentiation of enhancing hyperemic inflammatory tissue from central pockets of non-enhancing pus. T2-weighted and short-tau inversion recovery images allow for better visualization of infected bone as high marrow signal intensity. Degree of confidence of MRI is high, with sensitivity between 88% and 100% and specificity of 75% to 100%.8

Additional imaging modalities that can aid in the diagnostic work up include the following:

  1. Plain films or x-rays are ordered initially to assess the involved area and rule out other causes of bone pain, such as fractures.
  2. Computer tomography scans to better characterize bony lesions.
  3. Bone scans with technetium-99 to evaluate the entire skeleton and detect additional involved sites.
  4. Bone scan or computer tomography are also recommended if MRI is contraindicated due to implanted cardiac devices or cochlear implants.9

Supplemental assessment tools

In some cases, for example if laboratory and imaging fail to provide a plausible explanation for neurologic impairments, clinicians should consider nerve conductions studies, electromyography, and somatosensory evoked potentials to assess for peripheral nerve injuries, myopathies, or psychogenic etiologies.

Early predictions of outcomes

Outcomes predictions are challenging, because it depends on the patient’s age, medical comorbidities, duration and severity of neurologic impairment, and time to initiation of treatment.

Koo et al10 performed a 5-year case control study on spinal epidural abscess neurologic outcomes in comparison with traumatic spinal cord injuries (TSCIs). Most of the spinal epidural abscesses were located at the thoracic and cervical spine. In addition, most individuals had a complete injury on AIS classification. The results showed that the spinal epidural abscess group started with lower motor scores on AIS evaluation and had an average older age. However, the spinal epidural abscess group had a higher average change in motor scores and a higher conversion rate from complete to incomplete status when compared with the TSCI cohort.

McKinley et al11 performed a 10-year retrospective analysis on rehabilitation outcomes after infection-related spinal cord disease (IRSCD). When compared with TSCI patients, the authors found that patients with IRSCD were older, more often had incomplete injuries, and had lower FIM motor changes during rehabilitation. This lead to lower rates of home discharge despite similar rehabilitation length of stay.

Environmental

Environmental modifications depend on the level and severity of damage. To allow for greater independence, assistive devices and environmental modifications at home, work, and/or school (e.g., ramps and elevators, wide doorways, grab bars, environmental control units) may be needed.

Social role and social support system

Information regarding the patient’s family, friends, work and/or school, home, community, religion, and other support systems will help identify coping strategies that can provide emotional support throughout the individual’s medical and rehabilitation course. The family may need to assist with home IV antibiotic administration acutely.

3. REHABILITATION MANAGEMENT AND TREATMENTS

Available or current treatment guidelines

When initial labs and imaging reveal the focus of infection, tissue biopsy (bone, disk) or abscess drainage should be performed via surgical decompression or interventional radiology. This will allow for microorganism identification that will guide the antibiotic treatment course. Cultures should be taken prior to initiating antibiotics whenever feasible. After tissue cultures, empiric antibiotic treatment should be initiated and adjusted once culture results are available to prevent or avoid complications related to delayed antibiotic treatment (bacteremia, sepsis, infection-related mortality, etc).

After identifying the causative agent, a lengthy course of IV antibiotics is usually recommended. Depending on the isolated organism and response, initial recommendations can vary from 6 weeks to 3 months.9Consultation with an Infectious Disease specialist and possibly a spine surgeon is indicated. Patients may require surgical decompression and fusion if any of the following occur:

  1. Spinal instability
  2. Progressive neurologic deficits
  3. Intractable pain
  4. Sepsis
  5. Failure of medical management

The treatment plan incorporates rehabilitation management of specific consequences of spinal cord involvement, if present, including spasticity, neurogenic bladder, and gait impairment. If there is a spinal cord injury, then prevention and treatment of SCI related complications including deep vein thrombosis, spasticity, pressure ulcers and depending on the level of involvement autonomic dysreflexia should be addressed. Early mobilization, once medically stable, is recommended with evaluation of activities of daily living, transfers and mobility to improve neurological recovery.12

Coordination of care

Coordination of care with all disciplines ensures a safe and effective rehabilitation course aimed toward symptom minimization and/or resolution, functional improvement, and prevention of secondary complications.

Specific needs that should be addressed include the following:

  1. Equipment needs: manual versus power wheelchair, commode, and shower chairs.
  2. Home modifications: ramps, railings, grab bars, and widening doorway entries.
  3. Patient and family training on self-care skills including bladder/bowel management, spasticity management, transfers, pressure ulcer prevention techniques, mobility tasks, and medication administration, including IV antibiotics.

Patient & family education

It is important to provide education to patients, families, and caregivers regarding diagnosis, management, and possible complications. This will help them identify worsening signs and symptoms of infection and when to seek medical attention. In addition, better understanding of disease progression and prevention of secondary complications will support good physical and mental health. Some of the most common areas of training include the following:

  1. Bladder management: determination of the most appropriate method of bladder emptying (indwelling catheters or intermittent catheterization), frequency of device changes, medications to prevent urinary incontinence or leaking through device, and signs and symptoms that require clinical reassessment.
  2. Bowel management: the goal is to implement a bowel program that provides adequate bowel emptying, in a reasonable time (preferably 1h or less) without stool incontinence episodes. This may be achieved by a combination of oral and/or rectal stool softeners, stool stimulants, and prokinetic medications. The patient may also require digital stimulation for upper motor bowel injury or manual disimpaction for lower motor bowel injury.

4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE

Hyperbaric oxygen therapy has been demonstrated to be an effective adjuvant treatment in iatrogenic spinal infections.13

5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE

Gaps in the evidence-based knowledge

There are several areas of controversy in the current literature regarding the most appropriate treatment for infections of the spine and spinal cord that include the following:

  1. Lack of consensus regarding the role of tissue sampling in the pharmacologic management of infections.
  2. Pharmacologic treatment duration.
  3. Once an adequate tissue sample is obtained, can pharmacologic treatment alone eradicate an infection or is surgery necessary?
  4. Most appropriate timing for surgical intervention.
  5. Open versus minimally invasive surgical techniques for debridement.
  6. Surgical debridement only versus debridement plus spinal instrumentation.
  7. Can instrumentation be colonized with bacteria and cause recurrent infections?
  8. Recurrent rates of spine and spinal cord infections.

REFERENCES

  1. Cheung WY, Luk KD. Pyogenic spondylitis. Int Orthop. 2012;36:397-404.
  2. Trecarichi EM, Di Meco E, Mazotta V, Fantoni M. Tuberculous spondylodiscitis: epidemiology, clinical features, treatment, and outcome. Eur Rev Med Pharmacol Sci. 2012;16 Suppl 2:58-72.
  3. Rabih O, Darouiche MD. Spinal epidural abscess. N Engl J Med. 2006;355:2012-2020.
  4. Ganesh, Devin MD, Gottlieb, Jonathan MD, Chan, Sherilynn MS, Martinez, Octavio PhD, Eismont, Frank MD. Fungal infections of the spine. Spine. 2015;40(12):E712-728.
  5. Hilal Maradit Kremers, MD, MSc, Macaulay E. Nwojo, MD, Jeanine E. Ransom, BS, Christina M. Wood-Wentz, MS, L. Joseph Melton III, MD, Paul M. Huddleston III, MD. Trends in the Epidemiology of Osteomyelitis A Population-Based Study, 1969 to 2009. J Bone Joint Surg Am, 2015;97 (10): 837-845.
  6. 6.American Spinal Injury Association. International Standards of Neurologic Classification of Spinal Cord Injury. Atlanta, GA: American Spinal Injury Association; 2011.
  7. Itzkovich, M Gelernter I, Biering-Sorensen F, et al. The spinal cord independence measure (SCIM) version III: reliability and validity in a multicenter international study. Disabil Rehabil. 2007;29:1926-1933.
  8. Khan AN. Acute pyogenic osteomyelitis imaging. Available at: http://emedicine.medscape.com/article/393120-overview#a21. Accessed April 8, 2013.
  9. Koo DW, Townson AF, Dvorak MF, Fisher CG. Spinal epidural abscess: a 5-year case-controlled review of neurologic outcomes after rehabilitation. Arch Phys Med Rehabil. 2009;90:512-516.
  10. McKinley W, Merrell C, Meade M, Brooke K, DiNicola A. Rehabilitation outcomes after infection related spinal cord disease: a retropective analysis. Am J Phys Med Rehabil. 2008;87:275-280.
  11. 12. Kemal Nas, Mehmet Karakoç, Abdulkadir Aydın, Kadriye Öneş. Rehabilitation in spinal infection diseases. World J Orthop. 2015;6(1):1–7.
  12. 9. Berbari EF, Kanj SS, Kowalski TJ et al. Executive Summary: 2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adults. Clinical Infectious Disease. 2015; 61(6):859-63.
  13. Onen, Mehmet Resid MD, Yuvruk, Evren MD, Karagoz, Gul MD, Naderi, Sait MD. Efficiency of Hyperbaric Oxygen Therapy in Iatrogenic Spinal Infections. Spine. 2015;40(22):1743-8.

Bibliography

Cadotte DW, Stroman PW, Mikulis D, et al. A systematic review of spinal functional MRI research: outlining the elements of experimental design. J Neurosurg Spine. 2012;17(1 Suppl):102-118.

Vertisky T, Krasnokutsky MV, Augustine M, Bammer R. Cutting edge imaging of the spine. Neuroimaging Clin N Am. 2007:17:117-136.

Baleriaux DL, Neugroschl C. Spinal and spinal cord infection. Eur Radiol. 2004;14 Supp 3:E72-83.

Guerado E, Cervan AM. Surgical treatment of spondylodiscitis. An update. Int Orthop. 2012;36:413-420.

Kupershtein I, Vives M. Spinal and spinal cord infections. In: Kirshblum S, Campagnolo DI, eds. Spinal Cord Medicine. Philadelphia, PA: Lippincott Williams & Wilkins; 2011:588-599.

 

Original Version of topic

Saloni Sharma, MD. Infectious disorders of the spinal cord. 2013/07/17.

Author Disclosures

Saloni Sharma, MD
Nothing to Disclose

 

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