Introduction

Evidence from Egyptian mummies suggests that infections of the spine predate the era of written history. In his textbook On the Articulations, Hippocrates (400 bc) included reports of vertebral deformity that likely resulted from what was later described by Pott as tuberculous spondylitis. Today, infections of the spine are relatively rare clinicopathologic entities. When they do occur, however, these infections still pose both diagnostic and therapeutic challenges to clinicians.

Spine infections predominate in the lumbar region, followed by the thoracic and then the cervical regions. Nonetheless, cervical infections are particularly problematic because of their propensity to cause more rapid and severe neurological deficits. The discussion that follows will examine the most surgically relevant cervical spine infections: pyogenic vertebral osteomyelitis, spinal epidural abscess, discitis, subdural empyema, and intramedullary abscess.

Basic Science

Cervical infections may be viewed from the perspective of the infectious organism: bacterial, viral, fungal, or parasitic. Alternatively, they may be approached based on the response of the host to the inciting organism: pyogenic (“pus-forming”), or granulomatous. The classic example of a granulomatous infection is tuberculous spondylitis (Pott disease), in which the histology shows caseating central necrosis surrounded by Langhans giant cells. Granulomatous infections may also be caused by fungi, such as aspergillosis, coccidiomycosis, blastomycosis, and cryptococcosis. Parasitic infections of the cervical spine, including cysticercosis, schistosomiasis, and echinococcosis, are extremely rare, and data on their management are limited to case reports.

Overall, the most common causative agent for spinal infections in the United States is Staphylococcus aureus, which is present in more than 50% of cases. When the spine infection is associated with a genitourinary or gastrointestinal infection, Escherichia coli, Proteus, and other gram-negative bacteria are frequently responsible. Patients who have a recent history of intravenous drug abuse are more likely to be infected with Pseudomonas aeruginosaStreptococcus is a significant cause of intramedullary cervical abscesses, as it can spread through the lymphatic system from the retropharyngeal space.

There are several potential routes for the dissemination of infections to the cervical spine, including direct extension from contiguous structures, open spinal trauma or surgery, hematogenous, or lymphatic. Both venous and arterial mechanisms have been implicated in hematogenous spread. The Batson venous plexus was proposed as a valveless conduit through which infections of the pelvis, such as urinary tract infections, may spread to the spine. This venous mechanism has been largely refuted, and an alternative arterial route postulated.¹ In the case of vertebral pyogenic osteomyelitis, infection is thought to seed the metaphyseal (subchondral) bone near to the anterior longitudinal ligament via a rich arterial network. The posterior spinal arteries that branch off the dorsal artery entering the intervertebral foramen are probably responsible for cervical epidural abscesses. Infections of the retropharyngeal space can enter the lymphatics and spread along the spinal nerves to communicate with the spinal subarachnoid space and Virchow-Robin space, thus leading to cervical subdural empyemas or cervical intramedullary abscesses.

Interestingly, discitis is seen in two distinct patient populations: pediatric and adult. While discitis in the pediatric population is usually caused by a hematogenous source, adult discitis occurs in patients who have undergone prior surgery involving the disc space. The reason for this clear distinction is that, as the spine ages, there are changes that take place in its vascularity. Histologic studies have shown that an end-arteriolar supply of the disc is present during infancy and childhood, and these end arteries are obliterated by the third decade of life.²

Clinical Practice Guidelines

The guidelines that govern the diagnosis and treatment of cervical spine infections may vary on a case-by-case basis. However, there are certain common themes which ought to be emphasized.