Intervertebral disk-space infection: CT changes. Work in progress

Clinical and MRI findings of brucellar spondylodiscitis

OBJECTIVE

The aim of this retrospective study was to report the clinical features and MR imaging findings of patients with brucellar spondylodiscitis.

MATERIALS AND METHODS

Twenty-two patients with spondylodiscitis, recruited among 152 patients with brucellosis referred from the Department of Infectious Diseases. Patients were diagnosed based on positive clinical findings, > or =1/160 titers of brucella agglutination tests and/or positive blood cultures. Magnetic resonance imaging (MRI) was performed to all of the patients with spondylodiscitis. Signal changes and enhancement of vertebral bodies, involvement of paravertebral soft tissues and epidural spaces, nerve root and cord compression and abscess formation were assessed.

RESULTS

All of the patients (n=22; 7 F, 15 M) had > or =1/160 titers of brucella agglutination test and blood culture was positive in 9. A great majority of the patients had involvement at only one vertebrae level (n=21, 95.5%), whereas one patient (4.5%) had multilevel involvement. In MRI, eight patients had soft tissue involvement and three had abscess formation. All cases had vertebral and discal enhancement. Additionally epidural extension was detected in four cases, posterior longitudinal ligament (PLL) elevation in five cases and root compression in two cases.

CONCLUSION

Brucella is still a public health problem in endemic areas. MRI is a highly sensitive and non-invasive imaging technique which should be first choice of imaging in the early diagnosis of spondylodiscitis.

Imaging in dialysis spondyloarthropathy

Destructive spondyloarthropathy has recently been described in patients who undergo maintenance hemodialysis for chronic renal disease. The condition most frequently involves the lower segment of the cervical spine, although the craniocervical junction also may be affected. Although the pathogenesis of destructive spondyloarthropathy remains unclear, the disorder is thought to relate to a hemodialysis-associated amyloidosis. It appears that the disease correlates with the duration of hemodialysis, although it has been reported in patients with chronic renal insufficiency not associated with hemodialysis. Radiographic features simulate those of an infectious process, encompassing a range of abnormalities from superficial erosions to large bony defects. Computed tomography (CT) images reveal osteolytic areas, with bone sclerosis of adjacent vertebral endplates, and minimal osteophytosis. The intervertebral spaces appear narrow or obliterated. On magnetic resonance imaging (MRI), the disorder may show the imaging characteristics of spondylodiskitis. The absence of high signal intensity on T2-weighted images generally helps to eliminate the diagnosis of an infection. With progression of the disease, collapse of a vertebral body and spinal instability may occur. Severe complications of destructive spondyloarthropathy in long-term dialysis patients may include spinal cord compromise, necessitating surgical decompression, with or without spinal stabilization.

Brucellar spondylodiscitis: MRI diagnosis

Early diagnosis of brucellar spondylodiscitis is often difficult because of the long latent period. Radiographs of the spine, bone scan, and computed tomography (CT) scan provide insufficient data. Among 25 patients with brucellar spondylodiscitis studied by magnetic resonance imaging (MRI), 9 were in the acute stage and 16 were in the chronic stage. MRI is the investigation method of choice in diagnosing brucellar spondylodiscitis.

Anatomy of the extradural compartments of the lumbar spinal canal. Peridural membrane and circumneural sheath

The development of newer and more accurate methods of identifying the structures within the spinal canal has given a much better understanding of the soft tissue structures that lie between the dura and the surrounding bone of the vertebral canal. One anatomic structure of special importance, but seldom spoken of, is the peridural membrane. Although it was mentioned in the writings of Fick14 as early as 1904, it was Dommissee12,13 who first described it accurately and who named it the peridural membrane. It appears to be a homologue of the periosteum. There is no periosteum at any point on the bone where this membrane is located . Spine surgeons have frequently noticed that, after removing a nuclear fragment that has extruded and crept upward or downward and has come to lie over the vertebral body, one sees only rough periosteum-free bone where the fragment had been lying. Premembranous hematomas may develop because a small fragment of nuclear material has extruded out at the rim of the vertebra, anterior to the attachment of the PLL, and in tearing loose may have caused bleeding. This fragment of nuclear material may creep upward or downward over the vertebral body. There may be a pool of blood around it. Hematomas are usually on one side or the other but can lie midline, because the bony ridge down the center of the posterior surface of the vertebral body is not always complete. In other words, there are gaps in it , and it is through these gaps or by actually lifting the deep PLL-membrane complex that the nuclear material or blood can pass, giving a midline mass seen on MR imaging. The plexus of veins in the body of the peridural membrane and penetrating it posteriorly in many places is part of Batson's plexus. They were first described by Willis38 in 1663. In recent years Dommissee13 and Crock8 have made major contributions to our understanding of these vessels. It is interesting to note that if a degenerated disk is injected with a mixture of barium, dye, and gelatin and radiographs are taken, it is seen that, in most cases, Batson's veins have filled. If the disk is not degenerated and does not take more than a few milliliters of this mixture, then Baxton's veins do not fill. It is very likely that these veins fill whenever we do diskography on anything beyond a moderately degenerated disk but we do not see them on the fluoroscope because the contrast is not dense enough and by the time we get around to taking permanent radiographs, the contrast has long since disappeared into the venous circulation. In the cadaver, the blood is not flowing so the gelatin with barium has time to set in veins. Interestingly, if contrast is injected into vertebral body by simply driving a needle through the cortex of the vertebral body, Batson's veins fill with contrast in the same way. The sheath surrounding the spinal nerves out lateral to the foramina was not well known until Kikuchi19 described it in 1982. He gave a very accurate description of it and called it the epiradicular sheath. The problem with calling it by this name is that it surrounds a true mixed peripheral nerve and not a radicule (root). Because of this, we propose the name circumneural sheath. It should be noted that there already is an epineural sheath, which is the outermost covering of peripheral nerves. There is also a perineural sheath and an endoneurium. These names have been used for nearly 100 years. The segment of spinal nerve commencing at the dura and ending just beyond the ganglion is commonly called a nerve root. It actually consists of two nerve roots, a motor and sensory, inside a sleeve of dura. At a point just beyond the ganglion the two roots blend together and become a typical mixed peripheral nerve. At this same point the dural sleeve becomes adherent to the nerve and henceforth is called the epineurium. For this 1- to 2- cm segment of spinal nerve from the dura to just beyond the ganglion we propose the name dural root sleeve. After all, it is a sleeve, it is made of dura, and it covers two nerve roots.

Spondylodiscitis. Clinical and magnetic resonance diagnosis

STUDY DESIGN

This study reviews 65 patients with spondylodiscitis, both spontaneous and postoperative and of different etiology, studied by magnetic resonance imaging.

OBJECTIVES

To define the magnetic resonance imaging characteristics of infections of the spine in acute and chronic stages and to evaluate the role of magnetic resonance imaging in defining their etiology.

BACKGROUND DATA

Early diagnosis of spondylodiscitis is often difficult because of the long latent period. Radiographs of the spine, bone scan, and computed tomography scan provide insufficient data.

METHODS

Among 65 patients with spondylodiscitis studied by magnetic resonance imaging, 24 were examined in the acute stage (clinical evolution between 7 days and 20 days), and 41 were examined in the chronic stage (3-6 weeks). The etiologic agent was staphylococcus in eight cases, Brucella in 13, Mycobacterium tuberculosis in 29, Salmonella in four, and unknown in 11.

RESULTS

In cases observed in the acute stage, the disc and the vertebral bodies were hypointense in T1 and hyperintense in T2; this relatively constant finding was not correlated with the etiologic agent. In the chronic stage, cases caused by Brucella or of unknown etiology showed long T1 and T2 relaxation times, with precocious contrast enhancement of the disc; in cases of tubercular etiology there was slight shortening of T1, with inhomogeneous enhancement of the involved vertebral bodies and late disc enhancement.

CONCLUSIONS

Magnetic resonance imaging is the investigation method of choice in diagnosing spondylodiscitis, especially in very early stages of the disorder, when other investigations still yield negative results. In chronic stages, magnetic resonance imaging also allows tubercular spondylodiscitis to be distinguished from cases of different etiology.

Advantages of diagnosing bacterial spondylitis with magnetic resonance imaging

We report on 16 cases of suspected spondylitis in which we used magnetic resonance (MR) imaging to confirm or exclude the diagnosis. MR has several advantages, one of which is to permit diagnosis of this disease in the early stages without major risks. In addition, MR permits recognition of complications such as paravertebral or intraspinal abscess formation with a high security and accuracy. Moreover, it is possible to show spondylitic alterations in three different planes. To differentiate this disease from metastatic or tumorous lesions the technique with T1- and T2-weighted images is helpful. As a result, MR imaging can shorten the time between onset and diagnosis of spondylitis.

Intervertebral disk space infection following translumbar aortography

After 1,748 translumbar aortograms three cases of intervertebral disk space infection were observed over a five-year period, for an incidence of 0.15%. Cultures suggested that the intervertebral disk had been inoculated with digestive tract organisms by the needle used to puncture the aorta. Diagnosis of this complication can be made early by retrieval of the responsible organisms from the intervertebral disk under CT control. Treatment consists of prolonged immobilization associated with appropriate antibiotic therapy for at least three months.

Infection of the intervertebral space following conventional and microsurgical operation on the herniated lumbar intervertebral disc. A controlled clinical trial

Review of the literature reveals that considerable knowledge has accumulated on intervertebral space infection following lumbar disc surgery. This is based on more than 400 observations. There are, however, no unifying concepts regarding the pathogenesis of the condition. While the reported incidence has seemed to increase in the last three decades, we noticed a significant reduction in frequency of this important complication of lumbar disc surgery after introducing microsurgical techniques. The significance of this finding is discussed with respect to pathogenesis.

Computed tomography in spondylitis. CT versus other radiographic methods

Eighteen patients with spondylitis underwent 21 examinations by computed tomography (CT). Bone destruction was found in all, paravertebral inflammatory mass in 18, and epidural extension in 12 examinations. Conventional techniques revealed a paravertebral mass in only two cases. Plain radiographs showed destruction in fewer vertebrae in nine cases, in one of which the plain radiographs were definitely negative. Simultaneous conventional tomography gave sufficient clinical information of bone changes but was not better than plain radiographs in the evaluation of soft tissue structures. Abscesses could only be demonstrated by CT. The operative findings were in agreement with CT scans in almost all cases operated. CT was valuable when planning the surgical approach.

Diagnosis of vertebral osteomyelitis: clinical, radiological and scintigraphic features

Incidence of non-tuberculous vertebral osteomyelitis has been increasing significantly over the past 15 years. Its prompt diagnosis remains difficult. Presented here are five cases of vertebral osteomyelitis studied clinically, with laboratory studies, radiographically, and with Tc-99m bone and In-111 labeled white blood cells (In-111 WBC) scintigrams. Three of the cases are described in detail. The In-111 WBC studies were not found useful in detecting the infection in four out of the five patients. Reasons for these false negative results are discussed. Clinical, etiopathogenic and radiographic characteristics of vertebral osteomyelitis are also presented.

Anatomic basis for the pathogenesis and radiologic features of vertebral osteomyelitis and its differentiation from childhood discitis. A microarteriographic investigation

Microarteriography has demonstrated the anatomy which explains the pathogenesis and radiologic features of adult vertebral osteomyelitis and of childhood discitis. Infarction is caused in the metaphysis by a septic embolus. The intraosseous arteries in children are anastomotic and a small portion of bone is destroyed. In adults a larger portion of bone is destroyed because the intraosseous arteries are end-arteries and septic thrombosis spreads into peripheral intraosseous arteries. The disc is avascular at all ages and is attacked by infection equally. The trans-equatorial spread of osteomyelitis occurs via an artery which is first described here. It joins the metaphyseal anastomoses of the same vertebral body in the midline.

Pitfalls of computed tomography in diagnosis of discitis

Sixteen patients with discitis from January 1980 through December 1983 underwent 18 CT scans for initial evaluation. In six scans the study produced a false negative result (sensitivity 63%, 11/16). In three of these six the scan was performed at the wrong disc level, and in three the error was interpretive. During the same time period 6 patients had a CT diagnosis of discitis which proved incorrect (positive predictive value 63%), three of which had fractures, two had normal post discectomy changes, and one had a neuropathic arthropathy. These studies were reviewed in a blinded fashion along with 30 CT scans of post operative patients without clinical or laboratory evidence of discitis. The CT findings in the discitis patients were: (a) anterior paravertebral soft tissue swelling with obliteration of paravertebral fat planes, (b) fragmentation or erosions of vertebral end plates, and (c) paravertebral fluid collection (abscess). Both (a) and (b) were seen in 13/15 patients, (a) alone in 1/15, (b) alone in 1/15, and all three (a, b, c) in 2/15. The CT scan is diagnostic of discitis in those with all three findings. In those patients with only (a) or both (a) and (b), the CT can be suggestive of discitis in the proper clinical setting when correlated with plain film findings: however, these CT findings are also observed in other conditions. Involvement of the spinal canal by inflammatory mass was seen in 6/16 patients with discitis. Low attenuation (hypodensity) of the affected disc was not observed.