Pott's Disease:Tuberculous Spondylitis

Medicine Morning ReportMarch 30, 2009Michael Craig

Introduction

HistoryEpidemiologyPathophysiologyClincal FindingsDifferential DiagnosisRadiologic and Diagnostic StudiesTreatment

History

Classic description first in 1779 by Percival Pott, an English surgeon. Other notable achievements:

First to link cancer to environmental carcinogens (scrotal cancer in chimney sweeps)Pott's fracture - bimalleolar ankle fracturePott's puffy tumor - subperiosteal abcess and osteomyelitis of the frontal bone, serous complication of sinusitis

One of oldest diseases of which we have evidence

4000 BC Egyptian mummies noted with typical featuresDNA from vertebral lesion in 12-year-old from 1000 AD identified M. tuberculosis

Epidemiology

20% of TB patients in the US have extrapulmonary TBPott's diseease occurs in 5% of those with extrapulmonary tuberculosis45% with spinal involvement have associated neurological deficits1-2% of overall tuberculosis cases

Much more common in the undeveloped world

Endemic areas - tends to occur about 1 year after primary infection and more common in children & young adultsDeveloped nations - more often late reactivation disease and occurs more in adults

PathophysiologyUsually occurs via hematongenous spread

Vertebral bodies vulnerable due to high blood flow

Lumbar and lower thoracic involvement more common, although can involve cervical vertebrae

Usually begins in anterior vertebral body

Neurological symptoms and cord compression from abcesses, dural involvement or scarring tissue

Kyphosis develops from collapse of anterior spine (mainly amongst thoracic vertebrae)

Clinical FindingsUsual presents as local pain

Can be indolent in onset with gradually worsening over weeks to monthsAs worsens usually severe muscle spasm and rigidity

Systemic symptoms (fever, weight loss, etc.) present <40% of patients

60-90% with no evidence of extraspinal tuberculosis

Many (~50% in endemic areas) present with neurologic symptoms

Kyphosis may be seen on presentation in advanced disease

Gibbious Deformity

Anterior wedging leads to focal kyphosisthis is the angular gibbious deformity, or "humpbacked" appearance

Differential DiagnosisInfection

Staph aureus vertebral osteomyelitisBrucellosisActinomycesCandidaHistoplasmosisBlastomycosisOther mycobacterium

Cancer

Metastatic lesionsSpinal tumors

Radiologic Studies - X-RayLikely normal in early diseaseFirst changes in anterior part of vertebral body with demineralization of endplateNext the opposite vertebral endplate will become involvedWith progression, anterior wedging develops50% cases spare the disk spaceMay also show evidence of abcess

Radiologic Studies - MRI

Show the anterior endplate involvement and relative sparing of the disk and posterior vertebral body in more detailCan better demonstrate abcess formationBest method for demonstrating nerve root and spinal cord compression

Diagnostic Studies

PPD - 90% will have positive PPD May be negative in some immunocompetent and many immunosuppressed patientNot helpful in endemic areas

Biopsy and culture (with AFB smear) essential to confirm diagnosis and rule-out other causes

If surgical stabilization done may be done interoperativelyOtherwise, CT-guided needle biopsy is most common

Treatment

AntibioticsFour-drug therapy (isoniazid, rifampin, pyrazinamide & ethambutol)May be more complicated if concerns of multi-drug resistant TB or if associated with septicemiaAt least six months of therapyUsually responds well (even in severe cases)

Surgery

May play role in spinal stabilization or abcess drainage/debridementMore role if advanced neurologic deficits, worsening deficits on medical therapy or severe kyphosisUsually two-procedure process - first anterior decompression and reconstruction then posterior fusion

Take-Home Points

Pott's disease can be a indolent cause of back pain without necessarily any systemic symptoms of tuberculosis

Progression can lead to major deformity or neurologic consequences

Tuberculosis should be considered in any case of vertebral osteomyelitis or diskitis

Most patients do well with prolonged 4-drug anti-TB therapy

References

http://www.surgical-tutor.org.uk/default-home.htm?surgeons/pott.htm~right McLain R and Isada C. Spinal tuberculosis deserves a place on the radar screen. Cleveland Clinic Journal of Medicine 2004; 71(7):537-549.http://www.ccjm.org/content/71/7/537.full.pdf Wikipedia.org Emedicine.com Uptodate.com