Title of article: Spondylodiscitis
Authors: Rand Al-Qaseer, Qusay Fadel
Scientific Editor :- Dr. Adam M. Abdallah

Keywords: vertebral osteomyelitis, spondylitis, Pyogenic infections, discitis, Spondylodiscitis 

 

Overview

Spondylodiscitis is an infectious inflammation of the vertebrae, discs, and surrounding structures. Bacteria or non-bacterial pathogens can cause it; in the former case, a wide range of pathogens are thought to cause spondylodiscitis. The largest spondylodiscitis cases are caused by Staphylococcus aureus, Escherichia coli, brucellosis, and mycobacterium tuberculosis. [43,13,4].

Spondylodiscitis affects seven out of every million people, with men three times more likely than women to be affected. Due to vascular architecture, the pure discitis described previously does not occur in children. Because the intervertebral disc has a network of vascular anastomoses, the infection begins in the disc and subsequently travels to the vertebral endplates.

Even though spondylodiscitis is a rare disease, the widespread use of immune-suppressing medicines and an aging population have increased infection cases [4,44]. However, the disease is most common in those in the sixth decade of life, it can affect anyone at any age. Diabetes mellitus, malnutrition, conditions that cause weight loss, steroid administration, rheumatic diseases, and spinal surgery are also risk factors in addition to age. Often, the actual source of infection is no longer detectable at diagnosis [45,46,47]. Also, secondary spinal infections and soft-tissue consequences should be considered in managing COVID-19 patients with neuromuscular symptoms, and a thorough neurological and neurosurgical evaluation is required to rule out spinal involvement [48]. Finally, the best therapeutic approach is not precisely defined—contrary to adult SD, for which treatment guidelines have been issued, no guidelines exist for pediatric patients. Optimal antimicrobial treatment is still under debate in terms of molecule and duration. Several data suggest that a long-term therapeutic course is usually required to control symptoms and normalize laboratory tests [50].

Etiology and pathogenesis:

Spondylodiscitis can be caused by various bacteria and fungi, which must be considered when diagnosing and treating patients.  The main causative organisms are staphylococci [4] [19] [21]. Also, as mycobacterium tuberculosis [19] [9]. Staphylococcus causes pyogenic spondylodiscitis, which has become more common in recent years due to the increased life expectancy of older individuals with chronic physical disabilities. This type of spondylodiscitis represents 2-5% of all cases of osteomyelitis and is more prevalent in patients older than 50 years [21]. Tuberculous spondylodiscitis is another common type of spondylodiscitis. In this situation, the causal bacteria is Mycobacterium tuberculosis. Patients between the ages of 30 and 40 are most likely to develop this type of spondylodiscitis [19].

The classic route of infection is hematogenous bacterial colonization [22]. Pathogen-associated spondylodiscitis usually starts in the vertebral endplates and extends to the adjacent intervertebral disc in adults. On the other hand, the infection frequently affects the intervertebral disc first in adolescents because of the blood flow. Irrespective of age, the infection can spread paravertebrally, subdurally, and epidurally [25]. Subdural abscesses and spread to the central nervous system, such as meningitis, myelitis, or encephalitis, are additional problems in addition to paravertebral or epidural abscesses.

Spondylodiscitis is primarily caused by bacterial pathogens, mostly in the context of urogenital, dermal, or respiratory infections. The most common pathogens are Staphylococcus aureus (up to 60%), followed by enterobacteria (up to 30%), and more rarely e.g., B. Staphylococcus epidermidis, Haemophilus influenza, or streptococci species [22]. Mycobacteria, fungi, and parasitoses play a much lower influence, with Mycobacterium tuberculosis being the most common. Candidiasis, aspergillosis, coccidioidomycosis, blastomycosis, cryptococcosis, and atrichosporosissis are all fungal infections [26].

Cervical signs are usually linked to intravenous drug misuse, whereas thoracic manifestations are more commonly linked to tuberculosis. Tuberculous spondylodiscitis or spondylitis often affects more than two segments and, like a fungal infection, can affect the dorsal parts of the vertebrae in particular, such as the posterior parts of the arch or vertebral processes [25].

 

Clinical presentation and complications:

Back pain is the most common presenting symptom (86%). Fever can be present in up to 60% of patients; in a systematic review of 14 studies, however, fever was often absent at presentation. The lack of fever in the setting of back pain can mask the possibility of infection, delaying the diagnosis from 11 to 59 days [26]. Manifestations of neurologic deficits at presentation, such as radiculopathy, limb weakness, or paralysis, can aid in the prompt and accurate diagnosis of spondylodiscitis but are present in only about 34% of cases [27]. The symptoms of spondylodiscitis are very non-specific. Back or neck pain is common but may be absent in up to 15% of cases. Also typical are constant pains that worsen at night and differential diagnosis of osteoid osteoma. Radicular radiating pain is not uncommon and can lead to misdiagnosis and unnecessary interventions. Fever occurs in only about half of patients. Neurological deficits are present in about one-third of the cases and are more likely to be associated with a delayed diagnosis, epidural abscesses, manifestations in the area of ​​the cervical spine, or tuberculous spondylodiscitis or spondylitis [28].

• Back or neck pain [4] [21].
• Constant pain, worse at night [13] [19] [21].
• Radicular pain radiating to the chest or abdomen.
• Fever (less common in patients with tuberculous spondylodiscitis, 1/2 of the cases). [4] [21] [21]
• Spinal deformities, predominantly kyphosis and gibbus formation (commoner in tuberculous spondylodiscitis). [29]
• Epidural abscess formation (cervical: severe cervical rigidity, dysphagia, or torticollis; thoracic: symptoms are localized at the legs; lumbar: spread through the ischiatic foramen and involve gluteus muscles; lumbosacral: cauda equine syndrome)
• Weight loss (when the delay in diagnosis is long) [21].
• Compared with adults, children are less likely to have comorbidities, and neurological deficits are uncommon [4].

The intensity of the infection does not necessarily fit the degree of the discomfort symptoms. According to N. Bettini et al., when digital pressure was given to the spinal area, the pain radiated to the homolateral periumbilical area, causing an increase in pain symptoms. Also, patients suffered radicular irradiation in the sciatica or crural fascia area. Untreated chronic infections can progress to sinus formation. Also, secondary instability can occur towards kyphosis deformity with paraplegia or tetraplegia. Cervical spondylodiscitis may manifest with dysphagia or torticollis [21]. Spontaneous pyogenic spondylodiscitis usually spreads hematogenously from infections of the skin, subcutaneous tissues, and urinary tract [30].

 

Diagnosis:

Infectious spondylodiscitis is one of the diseases that is hard to be diagnosed in its early phases because it has general symptoms like fever, weakness, and weight loss. [13] but the quick diagnosis and treatment enhance patient health status and management outcomes. [2] The diagnosis of discitis is based on a combination of clinical presentation, laboratory tests, and imaging. [17]

Laboratory and microbiological tests

Leukocytosis which is an elevation of white blood cell (WBC) count, can be one of the laboratory parameters but only exists in 36–61% of patients with Vertebral osteomyelitis. [14]

Erythrocyte Sedimentation Rate (ESR) is another parameter for this disease and it indicates that there is an inflammation in the body. High ESR is present in 76-80% of patients with spondylodiscitis. Also, is one of the most important diagnostic tests because ESR is mainly used while we are following the state of the patients after the administration of antibiotics and their response to the treatment. [14] The previous two parameters both commonly exist with epidural abscess formation which is one of the common side effects of this disease and usually these abscesses involve the thoracic region. [14] [5]

C-reactive protein (CRP) is seen to be elevated in 90%–98% of cases; this test is very beneficial because it reduces the time required for diagnosis. [2] CPR count has a sensitivity of 84% and a specificity of 71%. [13]

Moreover, it is important to know the causative agent of spondylodiscitis disease to use the proper antibiotic treatment. We can reach this essential information by using the culturing technique. [14] Firstly, we prepare at least two sets of blood cultures (aerobic/anaerobic) [13] then we analyze 3–5 tissue specimens, collected either during open surgery or by transpedicular biopsy with a 10-gauge Jamshidi needle. [15]

Spondylodiscitis tuberculosis is more commonly diagnosed by using the polymerase chain reaction (PCR) technique. [9]

Blood cultures are a significant step while treating the patients because spinal infection’s main route is through the bloodstream. [14] Thus, culture is considered one of the simplest, most affordable, and most effective methods for confirming the presence of a causative microorganism. Scientifically, we can detect the pathogens of infectious discitis in 40-70% of patients who still do not receive any antibiotic therapy. [2] [13] In addition, in patients who have epidural abscesses their blood cultures have a greater pathogen detectability which is up to 82% [13]

One of the most common pathogens because of spinal infection is Staphylococcus aureus, which can be detected using Species-specific PCR, which is the best technique to target this microorganism. [9]

Imaging: X-Ray, CT Scan, Radionuclide Imaging, MRI

X-Ray:- 

Radiographs are present in only one-third of patients [14]; it’s useful as the first imaging modality for patients with low back pain. [18] but X-rays have limited benefit in examining this disease because of the delay in appearance of characteristic findings. [14] when the characteristics appear it will look like a severe lesion, including two adjacent vertebrae with the collapse of the vertebral bodies and the intervening disc is highly suggestive of spondylodiscitis.

Other characteristics include endplate irregularity, defects of the subchondral portion of the end plate, and hypertrophic/sclerotic bone formation. [14]

CT Scan:- 

CT-scan is commonly used to guide biopsy taking and this feature gives the CT-scan little benefit over other imaging modalities. [14] [9] CT-scan and MRI are effective and sensitive in patients with chronic diseases. Although, they are less sensitive when the patients have an acute disease. [14] This type of imaging is well known for its role in detecting; soft tissue abnormalities and destruction of vertebral bodies. [14] [18] CT-scan, compared to MRI has very little sensitivity in detecting epidural abscess formation. [14]

case courtesy of Dr. Mostafa El-Feky ◉ rID: 56584

Radionuclide Imaging:- 

Bone scan is used when MRI cannot be addressed, especially in patients with artificial devices or pacemakers. [9] [14] In addition, radionuclide can be used when it’s difficult to distinguish the infection from the deterioration changes in the MRI images, in this scenario we can use fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET). [9]Many researchers confirm that the sensitivity of this scan is 90–95%.  unfortunately, it has poor specificity and cannot identify the abscesses. [14]

MRI:- 

This technique is considered one of the best imaging we are diagnosing due to its high sensitivity and specificity in detecting spondylodiscitis in its early phases. [18] T1 image features include; a lack of signal intensity and changes in the shape of vertebral bodies and intervertebral discs like a decrease in height. [14] Enhancement inT1 images are typical for an acute inflammatory process while in T2 images its main feature compared to T1 is the high signal intensity of the disk. In pyogenic and tuberculous spondylodiscitis was a low signal of the subcortical bone marrow on T1-weighted sagittal images, which had improved after Gd-DTPA administration and became intermediate or high on T2-weighted images. [14] [18] Recent studies approved that MRI is essential in showing the details of soft tissue and in revealing epidural abscesses. [14]

A comparative study was done on thirty-seven patients who were clinically suspected of having vertebral osteomyelitis had found that MRI with gadolinium enhancement is the optimal choice for image diagnosis of spondylodiscitis because of its high sensitivity and specificity, mainly because of its anatomical information. [9] [38]

Case courtesy of Dr. Mostafa El-Feky ◉ rID: 56584

 

http://img.medscapestatic.com/pi/meds/ckb/50/15350tn.jpg

Diskitis/osteomyelitis is seen on this T2-weighted MRI of the lumbar spine, demonstrating the destruction of the L3-4 disk space with the adjacent endplate and/or vertebral body. L3 and L4 vertebral bodies show increased T2 signals, indicating edema and/or infarction. Also shown is a retropulsion of debris, which compresses the thecal sac. The MRI will reveal air changes in the disc and possibly external involvement involving the bone or epidural regions.

Treatment and management:

Spondylodiscitis is a life-threatening condition and is considered an emergency, which varies in its severity according to patients’ health status and the pathogen that causes the disease[2]

The standard therapy for spondylodiscitis consists of antibiotics, fixing the affected intervertebral disc to protect and stabilize the spinal structure; spinal decompression surgery is performed to ensure that there is no pressure on the nerve to maintain the function and flexibility of the spine. [3] [4]

Antibiotics approach

In most cases, intravenous antibiotics are given only if we detect the causative agent using blood culture techniques, except for patients who come to the emergency room suffering from neutropenia and sepsis, they should be given antibiotics for the most common pathogens such as Staphylococcus aureus and Escherichia coli for at least two to four weeks via parenteral route. [2] [6]. [7]  If the patient’s condition improves and inflammation parameters start to return to normal values, we can start prescribing oral antibiotics with high bioavailability such as; fluoroquinolones, clindamycin, and linezolid. [4]

In high-risk patients like if the spondylodiscitis was due to tuberculous infection, we use antibiotic therapy for at least 18-24 months [8] It should be noted that for tuberculous infection cases, we use a six-month combination of isoniazid and rifampicin with pyrazinamide and ethambutol for the first two months. [9]

Until now, the efficiency and role of the combined antibiotics are still unclear. However, according to the latest studies, the best treatment approach after surgeries is using a combination of quinolones and rifampicin, which has shown good outcomes. [9]

Surgery approach

The surgical treatment whether it is by using an endoscope or open surgery; is applied when we want to:

1) Eliminate the infected tissue.

2) Relieve pressure on the root, spinal cord, or dura mater.

3) Recover the infected column segment and restore spinal alignment.

 4) Improving the spinal instability due to bone destruction. [8][9]

5) spinal canal abscesses

 6) paravertebral abscess >2.5 cm [16]

Endoscopy is very popular now in treating spondylodiscitis and in taking a biopsy because it is more suitable due to its ability to discectomy and drainage, and its outcome for bacterial recovery is greater than CT-guided spinal biopsy.

The biopsies should be studied in different cultures like aerobic, anaerobic, fungal, brucellosis, and mycobacterial cultures. [9]

Generally, the surgical approach is usually chosen when the conventional treatment fails to treat the symptoms and relieve the pain. Despite this, the majority of Vertebral osteomyelitis patients don’t undergo surgery. Only 50% of cases have an operation. [16]

One of the strange things in the neurosurgery world is that when spondylodiscitis is due to tuberculosis and the abscess and sequestered bone or disk is so extensive the surgeon feels more comfortable and works confidently in both surgery approaches and chemotherapy. The weird thing is that patients with active infection of tuberculosis show better outcomes after surgery than patients who were already healed. [9]

Prevention:

Prevention for spondylodiscitis aims to eliminate infection, preserve or restore the spinal structure, stability, and neurological impairments, as well as provide pain relief. Conservative treatment constitutes the standard of care, and most patients are successfully treated with non-operative means [37]. Most cases, antibiotics combined with non-pharmacological treatments like immobilization and physical therapy are effective. Immobilization with bed rest or bracing decreases pain stabilizes the spine and prevents deformity [37].

Zarghooni, Kourosh, et al. “Treatment of spondylodiscitis.” International Orthopaedics 36 (2011): 405-411.

Risk factors:

The infection of the vertebral bodies and the intervertebral disk space is relatively rare with an incidence between 1:100,000 and 1: 250,000 per year. [5] [10] Its rapidly increasing each year due to using intravenous drugs, spinal devices, and surgeries that all may lead to vertebral body infection as a side effect. [17]

Discitis can be divided into two categories; the first one is granulomatous (tuberculosis and other mycobacterial pathogens) and the second one is pyogenic (most commonly Staphylococcus aureus). [17]

Even though the injuries that are induced by spondylodiscitis are very harmful, specifically when the motor segment is injured, leading to instability and increasing the pressure on the neural elements. [5]

According to recent studies, spondylodiscitis incidence is higher with age and is diagnosed more often in males. [11] One of the retrospective studies identifies some risk factors that cause an elevation of the mortality rate due to spondylodiscitis, like cirrhosis, diabetes mellitus, hemodialysis use, malignancy, and concomitant infective endocarditis. [11]

One of the studies that were published on 13, Dec 2008, reported that this infectious disease should be in physicians’ minds when they are dealing with any patient complaining about localized pain at any level of the spine, particularly patients who suffer from uncontrolled diabetes mellitus and they had fever and indicators of acute phase response. [12]

Septic discitis can be associated with intravenous drug abuse, catheter-associated infections, surgical procedures, heavy drinkers, and immunosuppressed patients. [12]

Prognosis:

Spondylodiscitis had a poor prognosis before antibiotics became available. Even still, it also has the potential to be fatal. Current studies report that the meantime in hospital is from 30 to 57 days and that hospital mortality is from 2% to 17% [31, 32-34,35,36]. After spondylodiscitis treatment, either conservative or surgical, persistent symptoms are common.

 

Recent update:

The incidence of spinal infection has increased over the years. Although the improvement in imaging techniques, spondylodiscitis is still challenging due to the insidious onset and misleading clinical aspects. [5]

A recent retrospective observational study found that endoscopic surgery is an effective and safe treatment for discitis in the thoracic and lumbar regions, as well as for cases with epidural or paraspinal abscesses. Open surgery is recommended as a secondary approach if endoscopic surgery is unsuccessful for a certain reason. [40]

A study that was done in 2020, explains the relationship between obesity and spondylodiscitis. It was found that obese people were more susceptible to postoperative side effects like liver failure and sepsis. Moreover, they had a severe course of this disease and show a special bacterial spectrum compared to normal-weight patients. Despite this, the length of hospital stay and mortality rate were similar between both groups (overweight people and normal weight). [41]

Another study published in 2021 showed that neonatal spondylodiscitis could lead to vertebral body deterioration with resulting angular kyphosis and the surgery must be done in early phases to avoid surgical risks and severe deformities. [42]

Furthermore, it has been found that spinal epidural abscesses (SEA) cases have increased during the covid-19 outbreak and they hypothesized that it may be related to asymptomatic bacterial colonization and associated with the injury in the vascular endothelium prompted by COVID-19. [49]

References...