Keywords
Spinal TB - retropharyngeal abscess - Xpert MTB/RIF - rifampicin resistance
Introduction
Mycobacterium tuberculosis (MTB) can affect any part of the body, including bones. Skeletal tuberculosis (TB)
constitutes less than 2% of all TB cases.[1] The spine being the most common site of osseous involvement, accounts for approximately
50% of skeletal TB cases.[2] Tubercular spondylitis of cervical spine may rarely present with retropharyngeal
abscess.[3]
In patients with suspected TB, the use of NAATs, specifically Xpert MTB/rifampicin
(RIF) cartridge-based nucleic acid amplification testing (CBNAAT), has revolutionized
the diagnosis with its ability to detect MTB while simultaneously assessing rifampicin
resistance within 2 hours. Here, we report the case of an immunocompetent adolescent
male who was found to have multifocal involvement of spine and retropharyngeal abscess,
and emphasize the importance of Xpert MTB/RIF for early detection of rifampicin resistance.
Case Report
A previously healthy 12-year-old Indian male was admitted in our hospital with disabling
back pain, numbness in bilateral lower limbs for 6 months, and difficulty in swallowing
for 3 months. History of low grade, intermittent fever for 6 months with significant
weight loss were also present. There was no associated history of cough, chest pain,
hemoptysis, dyspnea, or stridor. Bladder and bowel habits were normal. The patient
had recent exposure to two pulmonary tuberculosis cases in his neighborhood.
On general examination, the boy was febrile, emaciated with severe pallor, and bilateral
enlargement of cervical lymph nodes which were mobile, discrete, and nontender. Axillary
and inguinal lymph nodes were also enlarged. There were gibbus on the midspine and
multiple papulonecrotic swellings over hands and legs (
[Fig. 1]
). Examination of the nervous system revealed decreased power in bilateral lower limbs
with muscle wasting, hypotonia, reduced deep tendon reflexes, and equivocal plantar
response. There was no sensory impairment. Examination of other systems was unremarkable.
However, oropharyngeal examination revealed a small fluctuant swelling located centrally
on the posterior pharyngeal wall.
Fig. 1 (A) Gibbus deformity on the spine, (B) papulonecrotic swelling on the dorsum of right hand, (C) papulonecrotic swelling on the medial aspect of right ankle.
Chest X-ray showed no obvious abnormality except few patchy changes. Ultrasonography
of abdomen revealed thickened mesentery with multiple enlarged mesenteric lymph nodes.
Also, MRI of spine revealed caries spine involving D8-D9 vertebra with multiple abscesses
along D-4, D-7, and D-9 (
[Fig. 2]
). The retropharyngeal abscess was drained under local anesthesia and pus was sent
for microbiological examination. Xpert MTB/RIF assay (CBNAAT) on pus detected presence
of MTB with rifampicin resistance. MTB was isolated from the same specimen on Lowenstein–Jensen
(LJ) medium after 5th week of culture, but smear microscopy following ZN staining
was negative. The second line–line probe assay (SL-LPA) conducted on the culture isolate
detected no additional resistance to fluoroquinolones or second-line injectable drugs.
Blood culture report was sterile after 7 days of incubation. The patient was HIV negative
and microbiological examinations on induced sputum were negative for MTB.
Fig. 2 MRI showing abscess in the body of vertebrae.
The patient underwent 6 months of intensive phase treatment with levofloxacin, kanamycin,
ethionamide, cycloserine, pyrazinamide, and ethambutol, followed by 18 months of continued
phase treatment with levofloxacin, ethionamide, cycloserine, and ethambutol, and was
declared clinically recovered after periodic follow-up visits. All the constitutional
symptoms disappeared and skin tuberculids were healed. However, the spinal deformity
called for orthopedic intervention.
Discussion
Although TB is primarily a disease of the lungs, extrapulmonary TB is an equally important
entity in modern clinical practice. Clinical expertise is of paramount importance
for making provisional diagnosis of extrapulmonary TB as well as choosing adequate
diagnostic tests. Because of the paucibacillary nature of the lesions, microbiological
diagnosis is often delayed in such cases. Despite the absence of any obvious abnormality
in chest X-ray in our case, a careful assessment of history, including the history
of exposure and general examination revealing lesions on the skin raised the suspicion
of TB, which was more evidenced after the MRI report strongly suggested spinal TB.
In spinal tuberculosis, infection sets in the subchondral region of vertebral bodies,
progressing to result in the collapse of vertebral bodies, which may be manifested
as wedging, kyphosis, sharp angulation, or gibbus deformity.[4] An abscess is usually formed inside the vertebral bodies with collection of exudates.
When the vertebral bodies cannot support the weight transmitted, they collapse and
squeeze out the internal contents of the abscess, which then track into the surrounding
tissues to form paravertebral abscess.[5] The exudative material from the cold abscess of the cervical spine may sometimes
traverse into the retropharyngeal space through the ruptured anterior and posterior
longitudinal ligaments, thus forming retropharyngeal abscess, which is a very rare
presentation.[4]
[6]
Early stages of spinal TB may present with constitutional symptoms such as low-grade
fever, weight loss, and back pain. In addition, dysphagia and torticollis may be manifested
in patients with retropharyngeal abscess. Our patient presented with all these symptoms
except torticollis. Paraplegia or paraparesis is often the first clinical manifestation
of the spinal TB. The neurological deficit in such cases is the result of external
compression of the spinal cord by extradural abscess, subluxation or collapse of vertebral
bodies, granuloma, and stretching of the spinal cord over bony ridges.[7] Early neurological deficit was also evident in our patient in terms of bilateral
progressive numbness in lower limbs.
The gold standard for diagnosis of any form of TB is culture of MTB which was positive
in our case, but it took time. On other hand, application of Xpert MTB/RIF improved
the diagnostic accuracy in terms of rapidity, exclusion of nontuberculous mycobacteria,
and detection of rifampicin resistance. While ultrasonography depicted intra-abdominal
involvement, MRI was helpful in differentiating between abscess and granulation tissue
and localizing the multiple lesions along the spine.
This case illustrates the importance of high index of suspicion of tuberculosis when
evaluating a patient with back pain and dysphagia even with no pulmonary symptom or
sign. Early imaging and appropriate microbiological testing using Xpert MTB/RIF (especially
for early detection of rifampicin resistance) can avoid diagnostic delay and facilitate
early effective treatment.
Conclusion
A high index of suspicion should be kept for tuberculosis in cases of retropharyngeal
abscess associated with spinal involvement to avoid diagnostic delays, which may lead
to irreversible damage. The microbiological workup using Xpert MTB/RIF, as a rapid
tool for detection of MTB as well as rifampicin resistance, showed the utility of
the test for analyzing nonrespiratory specimen and also facilitated early and lifesaving
treatment in this case.
