Spondylodiscitis diagnosis [Neurosurgery Wiki]

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====== Spondylodiscitis diagnosis ======

Early diagnosis is crucial in the management of [[spondylodiscitis]] because delayed treatment can lead to increased morbidity and mortality.

Diagnosis is verified by MRI. Microbial aetiology is pursued by blood cultures or surgical biopsy, however, some cases remain culture-negative
((Bangstrup M, Brummerstedt M, Barfod TS. [Diagnostics and treatment of
spondylodiscitis]. Ugeskr Laeger. 2016 Sep 26;178(39). pii: V04160271. Danish.
PubMed PMID: 27697126.
)).
===== Clinical examination =====
The [[clinical examination]] includes [[inspection]] concentrating on local changes and taking a detailed neurological [[status]]. There is typically pain on heel strike, impaction, and percussion, but little local pain on pressure. The patient takes a relieving posture and avoids stressing the ventral sections of the spinal column. In particular, inclination and re-erection are described as being painful.

===== Laboratory features =====
The laboratory parameters to be determined are [[leukocyte]]s, [[C reactive protein]] (CRP), and [[erythrocyte sedimentation rate]] (ESR). In patients with acute disease, there is a massive increase in the inflammation parameters and in the ESR. In patients with chronic disease, these may be normal or exhibit threshold increases. There may be no [[leukocytosis]], but a marked increase in CRP is typical.

====Blood culture====
Blood culture is the easiest procedure to detect the pathogen. A positive culture can be expected in as many as 70% of patients not previously treated with antibiotics. Sobottke et al., recommend that at least two to three pairs of blood cultures should be taken. The pathogen is often successfully detected, not only in the acute phase of fever or with septic disease, but also in clinically bland cases and afebrile patients.

====Pathogen detection====

Specific antibiotic therapy is one of the keystones of spondylodiscitis treatment and this necessitates specific identification of the decisive pathogen and determination of its sensitivity to antibiotics. Overall, the pathogen can be detected in 49% to 83% of cases – more often in acute than in chronic cases. One of the main reasons for failure to identify the pathogen is prior systemic antibiotic therapy.

For this reason, it is particularly important only to start antibiotic therapy after the material for the microbiological diagnosis has already been isolated. If antibiotic treatment had already started, the authors have considered its discontinuation for some days up to the puncture of the focus of infection, coupled to close monitoring of the course of the disease.

===== Radiology =====

Irregularity of the adjacent vertebral [[endplate]]s, with sparing of the [[pedicle]]s (except for tuberculosis, which may involve the pedicles)
----

Conventional x-rays – If a patient suffers from diffuse pain in the spinal column, the first investigation is to take a conventional x-ray, although this procedure is unreliable in the early phase of spondylodiscitis, as there are usually no skeletal changes.

Even in the later stages, the radiological changes may only be slight and may be impossible or difficult to distinguish from degenerative diseases of the spinal column.

===== Magnetic resonance imaging (MRI) =====

[[Spondylodiscitis Magnetic resonance imaging]]

===== CT-guided biopsy in suspected spondylodiscitis =====

[[CT-guided biopsy in suspected spondylodiscitis]]


===== Computed tomography (CT) =====

Three basic changes on CT
((Kopecky KK, Gilmor RL, Scott JA, et al. Pitfalls of CT
in Diagnosis of Discitis. Neuroradiology. 1985; 27:
57–66))
(if all 3 are present, pathognomonic for discitis; if only the 1st 2 are present, then only 87% specific for discitis):

1. endplate fragmentation

2. paravertebral soft-tissue swelling with obliteration of fat planes

3. paravertebral abscess
----

Computed tomography is inferior to magnetic resonance imaging with respect to the specificity and sensitivity in the diagnosis of spondylitis.

On the other hand, computed tomography provides a much more detailed image of bone destruction.

Moreover, compute tomography can provide good images of paravertebral abscesses after administration of contrast medium.

Computed tomography is indicated when magnetic resonance imaging is not possible, perhaps because the patient wears a cardiac pacemaker.

===== Nuclear medicine =====

Very sensitive for discitis and vertebral osteomyelitis (85% sensitivity), but may be negative in up to 85% of patients with Pott’s disease. Uses either technetium-99 (abnormal as early as 7 days following onset of clinical symptoms) or gallium-67 (abnormal within 14 days). A positive scan shows focal increased uptake in adjacent endplates, and may be differentiated from osteomyelitis which will involve only one endplate. A positive scan is not specific for infection, and may also occur with neoplasms, fractures, and degenerative changes.

====Multiple phase scintigraphy====
With skeletal scintigraphy, it is not possible to distinguish between infections of the bone and activated osteochondroses. This is therefore not the diagnostic method of first choice. On the other hand, a normal skeletal scintigram provides very reliable evidence for the absence of osseous inflammation.

====Inflammation scintigraphy with labeled leukocytes or Tc-99m-labeled antibodies====
Leukocyte scintigraphy is a supplement to multiphase scintigraphy, in which radioactively labeled native blood cells or (now preferably) Tc-99m-labeled anti-granulocyte antibodies are used to detect inflammatory changes in bone tissue. However, anti-granulocyte antibodies also label hematopoeisis in the bone marrow, so that the spinal column is subject to physiological enrichment. In-flammation scintigraphy is therefore more suitable for the extremities.

====Positron emission tomography with fluorine-18 fluorodeoxyglucose (F-18 FDG PET)====
F-18 FDG PET is of increasing importance in the diagnosis of spondylodiscitis. There is hardly any physiological enrichment of F-18 FDG in the bone marrow or the spinal column, so that inflammatory processes are imaged as "hot spots." The degree of uptake of F-18 FDG is linked to the enhancement of glucose metabolism in the inflammatory cells. The advantages of F-18 FDG PET include the rapid imaging and the relatively low exposure to radiation (3.7 to 7.4 mSv).

In contrast to MRI, it is perfectly possible to distinguish between initial spondylodiscitis and degenerative changes in the vertebral body endplates. On the other hand, specific differentiation from malignant processes may present a problem
((Sobottke R, Seifert H, Fätkenheuer G, Schmidt M, Gossmann A, Eysel P. Current diagnosis and treatment of spondylodiscitis. Dtsch Arztebl Int. 2008 Mar;105(10):181-7. doi: 10.3238/arztebl.2008.0181. Epub 2008 Mar 7. PubMed PMID: 
19629222; PubMed Central PMCID: PMC2696793.)).

Owing to the high specificity of this method, a negative PET result in the setting of a diagnostically unclear case diminishes the need for surgical intervention. 18F-FDG-PET is therefore an important tool in inflammation imaging and can be used in the diagnostic cascade of difficult cases with suspected spondylodiscitis. In contrast, a positive PET result does not always clearly establish the cause of increased 18F-FDG uptake
((Hungenbach S, Delank KS, Dietlein M, Eysel P, Drzezga A, Schmidt MC.
18F-fluorodeoxyglucose uptake pattern in patients with suspected
spondylodiscitis. Nucl Med Commun. 2013 Nov;34(11):1068-74. doi:
10.1097/MNM.0b013e328365abec. PubMed PMID: 24025917.
))

====18F-FDG-PET/CT====
FDG-PET/CT demonstrated limited areas of abnormality allowing accurate delineation, and is thus useful to narrow the surgical fields. Since overall diagnostic accuracy of FDG-PET/CT was superior to that of MRI, FDG-PET/CT is a useful technique to narrow the surgical field for successful less invasive surgery
((Nakahara M, Ito M, Hattori N, Magota K, Takahata M, Nagahama K, Sudo H,
Kamishima T, Tamaki N, Iwasaki N. 18F-FDG-PET/CT better localizes active spinal
infection than MRI for successful minimally invasive surgery. Acta Radiol. 2015
Jul;56(7):829-36. doi: 10.1177/0284185114541983. Epub 2014 Jul 30. PubMed PMID:
25080515.
)).