eMedicine Specialties > Emergency Medicine > Neurology

Spinal Cord Infections

Author: Andrew K Chang, MD, Associate Professor, Department of Emergency Medicine, Albert Einstein College of Medicine, Montefiore Medical Center
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Updated: Sep 14, 2009

Introduction

Background

Infections involving the spinal canal include epidural abscesses (infection in the epidural space), meningitis (infection of the meninges), subdural abscesses (infections of the subdural space), and intramedullary abscesses (infections within the spinal cord). Because the first 3 infections are discussed elsewhere in this journal (see Epidural and Subdural Infections, Meningitis), this article addresses only intramedullary abscesses.

Intramedullary spinal cord abscesses are extremely rare lesions. Since the original description in 1830 by Hart, approximately 100 cases have been reported. Their rarity, compared with brain abscesses, has been attributed to the relatively lower volume of the spinal cord and its particular blood supply.

Pathophysiology

Mechanisms of infection include (1) hematogenous spread from an extraspinal focus of infection, (2) contiguous spread from an adjacent focus of infection, (3) direct inoculation (ie, penetrating trauma, postneurosurgery), and (4) cryptogenic mechanisms (ie, no documented extraspinal focus of infection). In a 1998 review of 25 cases, hematogenous spread accounted for 8%, contiguous spread accounted for 24%, direct inoculation accounted for 4%, and 64% were cryptogenic.¹ In children, the abscesses are associated with prior anatomic spinal canal defects, such as dermal sinus tracts, which result from the incomplete partition of epithelial ectoderm and neuroectoderm in early fetal life.

Bacteria, such as staphylococci and streptococci, are the most common organisms responsible for these infections. Infections may also be caused by viral, fungal, or parasitic organisms. A diverse list of pathogens include, but are not limited to, cysticercosis, Mycobacterium tuberculosis, Listeria monocytogenes, Toxoplasma gondii, Nocardia asteroides, Histoplasma capsulatum, brucellosis, and the tapeworm spargana.

Initially, the area of the bacterial nidus is infiltrated with polymorphonuclear cells, leading to a suppurative myelitis. This evolves into central necrosis and liquefaction, which can spread along the long spinal tracts. Although the average extent of the process before 1975 was 6 vertebral levels, the average current length appears to be 3 levels. This change may be due to earlier detection and more effective antibiotics. At the periphery of this infectious process, fibroblasts proliferate and the central purulent area eventually becomes encapsulated by fibrous granulation tissue. The most commonly affected area is the dorsal thoracic spinal cord.

Frequency

International

Various reviews of the literature describe different numbers, with a range of approximately 80-100 cases since the first description in 1830. In a 2003 review, only 38 pediatric cases were identified in the medical literature since 1830.²

Mortality/Morbidity

Although the first reported cases had high mortality rates, prognosis has improved significantly with the advent of antibiotics.

• The mortality rate without surgical intervention is practically 100%, and those patients who died despite surgery almost exclusively were affected in the preantibiotic era.
• The current mortality rate (cases reported in the last 2 y) is 8-12%, although 70% of survivors had persistent neurologic deficits.
• In a review of 38 pediatric cases, 20% died, 60% had residual neurologic deficits, and only 20% recovered without sequelae.²

Race

Ethnic preference does not appear to exist, although some geographic differences are present. All intramedullary paracoccidioidomycosis cases were reported in Brazil.

Sex

In one study in which sex was reported, spinal cord infections were 2.5 times more common in males than in females.

Age

• All ages are affected though children younger than 5 years are more likely affected.
• Female patients are affected mainly in the first 4 decades of life, whereas the incidence among male patients is distributed more evenly, with a peak in the third decade of life (see Media file 1).

Clinical

History

Menezes and VanGilder have classified patients by the duration of symptoms into acute, subacute, and chronic categories.³ In one study, the average time from the onset of symptoms to diagnosis was 46 days, with a range of 0-540 days.

• Patients in the acute category present with symptoms lasting less than 1 week.
  • Patients who present acutely have a clinical picture of transverse myelitis (with rapid onset of motor and sensory loss) and sphincter disturbances.
  • Pain is common, and fever with signs of concomitant infection typically is present.
• Patients in the subacute category present with symptoms that are 1-6 weeks old. The clinical picture resembles that of a chronic presentation.
• Those in the chronic category present with symptoms of greater than 6 weeks' duration.
  • Patients with chronic spinal cord abscesses present with signs and symptoms that are more consistent with an intramedullary tumor (ie, with a slowly progressive and stuttering neurologic deficit).
  • Patients may complain of a radicular-type pain and are frequently afebrile.
• Radiculopathic pain can present in the back, neck, extremities, or, occasionally, as abdominal or chest pain of undetermined origin. At least one reported case exists in which abdominal surgery was performed and later diagnosis proved intramedullary abscess of the spinal cord to be the origin of the problem.
• A review of 25 patients, published in 1998, revealed fever in 40%, back or radicular pain in 60%, and a triad of fever, pain, and neurologic deficits in 24%.¹

Physical

A thorough physical examination to determine the extent of the motor and sensory deficit and its levels is of primary importance to guide diagnostic modalities later. Examine the cervical, dorsal, and lumbar regions carefully looking for dermal sinuses, suggestive lesions, and signs of local infection.

First findings of intramedullary spinal cord abscess include fever (in acute forms), radiculopathic pain, and neurologic deficit.

• Root pain can present along a well-defined dermatome or, occasionally, as abdominal or chest pain of undetermined origin.
• Palpation of the spinous processes or straight-leg raising is unlikely to elicit pain on examination.
• Motor deficit usually progresses from slight paresis of one or more limbs to a flaccid paraplegia or tetraplegia with sensory loss below the level of the lesion and eventual sphincter disturbances (urinary retention or incontinence and/or loss of rectal tone).
• A review of 25 patients, published in 1998, revealed the following¹ :
  • Motor deficits only (24%)
  • Sensory deficits only (4%)
  • Motor and sensory deficits (68%)
  • Brainstem dysfunction (4%)
  • Urinary incontinence (56%)
  • Meningismus (12%)

Causes

• Presence of spinal dysraphism (congenital midline neuroectodermal defects) with persistent dermal sinus can lead to development of an intramedullary abscess by contiguity.
  • These abscesses usually are observed early in life. In a review of 25 patients, 36% had spinal dysraphisms.¹
  • Tethered cord syndrome can lend itself to iatrogenic spinal cord infection and damage via a lumbar puncture.
• The existence of chronic conditions (eg, alcoholism, diabetes, intravenous drug use) can predispose patients to the development of this rare pathology of intramedullary abscess.
• Immunosuppression (eg, AIDS) alters the bacteriology of spinal abscesses.
• Organisms also can cause spinal cord infections.

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