DiagnosticandInterventionalImaging(2012)93,884—886
LETTER / Musculoskeletal imaging
The role of computed tomography in the exploration of Madura foot (pedal mycetoma)
M. Bouziane
∗, O. Amriss , R. Kadiri , A. Adil
ServiceCentraldeRadiologie,CentrehospitalieruniversitaireIbnRochd,rueEl-Faidouzi, 20100Casablanca,Morocco
KEYWORDS Mycetoma;
Foot;
Imaging;
Computed tomography
Madurafootorpedalmycetomaisafungaloractinomycoticinfectionlocatedonthefoot andisquiterareoutsideofthetropicalareaswhereitisendemic.Thiscasereportfrom theCentralRadiologyDepartmentoftheIbnRochdHospitalCenterinCasablancadescribes thedifferentwaysthatMadurafootappearsonimaging.
Case report
Thiscaseconcerneda39-year-oldman,amasonbytrade,whosoughtcareforinflamed swellingoftherightfootwithmultiplesinustracts,andthedischargeofpuswithbothblack andwhitegranules.Swellinghadbeendevelopingfor18months,afterdirecttraumatohis barefootonaconstructionsite.Themicrobiologicalstudyfoundactinomycoticbacterial mycetoma.
StandardAPandprofileradiographyshowedinfiltrationofthesofttissueofthefoot, associatedwithosteolysisofthecuneiformbones,thenavicularandfirsttwometatarsal bones,as well asan irregular periosteal reaction (Fig. 1).Computed tomography (CT) showed diffuse infiltration of the plantar and dorsal surfaces of the foot, with dense thickenedtissue,enhancedheterogeneouslyoninjectionofcontrastproduct,withsev- eralhyperdensenodules.Itwasassociatedwithdiffuseosteolysisofthecuneiformbones, thefirstfourmetatarsalsandtwosesamoidbones,withdiscretelamellarandspiculated periostealreaction.Italsoshowedgeodesof thenavicularandcuboidbonesandinter- tarsaljointnarrowing.Itconfirmedtheintegrityoftheotherbonesofthefootandankle andruledoutthepresenceofbonesequestrationoraccumulation(Fig.2).
∗Correspondingauthor.
E-mailaddress:bouzianemoun@yahoo.fr(M.Bouziane).
2211-5684/$—seefrontmatter©2012Éditionsfrançaisesderadiologie.PublishedbyElsevierMassonSAS.Allrightsreserved.
http://dx.doi.org/10.1016/j.diii.2012.05.003
ComputedtomographyintheexplorationofMadurafoot 885
Figure1. Radiographyoftherightfoot,frontal(a)andlateral(b).
Infiltrationofthesofttissue,osteolysisofthecuneiform,navicular andfirsttwometatarsalbonesandanirregularperiostealreaction.
Inviewoftheextentofbonedamage,thefootrequired amputation.Thehistologicexaminationconfirmedthediag- nosisofactinomycoticmycetoma.
Discussion
Madura foot is defined as mycetoma of the foot, that is a chronic granulomatous pseudotumor due to fungi (eumycetoma) or actinomycotic bacteria (actinomyce- toma), soil saprophytes that produce mycelial filaments.
Mycetomaisendemicindrytropicalandsubtropicalregions [1—7].
Ahistoryofsomeminortraumaofabarefoot,oftenfor- gotten or neglectedby the patient, maybe found [1—4].
The infectiondevelops over severalyears, beginningwith painlessswelling,unless asuperinfectionor bone damage develops; otherwise multiple skin sinus tracts or fistulae developandoftenleadtoconsultation,ashere.Thesetracts dischargeblack,white,red oryellow granules,depending onthemicroorganisminvolved.Bonedamageisnotcorre- latedtothedegree ofclinicaldamage;itisgenerallylate anddeterminesbothprognosisandmanagement[1—7].Our caseisremarkablefortheearlyonset—–barely18months
—–ofadvancedbonedamage.
Imagingguides thepositivediagnosis whenclinical and other investigationsarenotdeterminative.It isespecially importantforstagingthedisease.
Radiographyshowsinfiltrationofsofttissue,associated more or less with bone resorption. In 2003, Abd El Bagi [5] devised a 7-stage classification based on the extent of bonedamage ontheradiographs, rangingfromstage 0 (nobone damage)tostageVI(multidirectionalbonedam- age). Nonetheless, this damage is often underestimated by radiography, as in our patient, for whom it failed to identify the damageto the cuboid bone and the 3rd and 4th metatarsals. Ultrasound is especially interesting in
countries where the disease is endemic. It shows multi- ple cavities, with thickened walls and without posterior reinforcement,withmultiplehyper-reflectiveechoescorre- spondingtothemycetomagrains.Theexaminationismore preciseinthecaseoflesionswithoutsinustracts,because fibrosis of these tracts can make interpretation difficult [1].
MultisliceCTishighlyusefulforassessingosteoarticular damage.Itshowsamassisodensetomuscle,heterogeneous, whichcancontaindenserroundednodulesthatinfiltratethe skinandthesubcutaneousfattissues.Theaffectedmuscles arethickened or partiallydestroyed. Enhancement ishet- erogeneousandmoderate.CTismoresensitivethanMRIfor detectingosteoperiostealdamageandforearlyvisualization ofsmallcorticallesions,whichcanbesoughtmoreeasilyby visualizingthe hyperdensegranules indirect contactwith thebone[1,2,6].
The CT signs of bone damage essentially matchthose describedin conventional radiology [1,2].In ourcase, CT madeitpossibletodetect thedamagetothecuboidbone andthe3rdand4thmetatarsalsandtoconfirmtheintegrity oftheotherbones.
MRI is the most helpful examination for a positive diagnosis and for staging mycetoma, which appears, in comparison to muscle, as a discrete hyperintense signal with T2 weighting and as a hypo- or iso-intense sig- nal with T1 weighting. Contrast uptake after gadolinium injectionis moderateand heterogeneous; the signal from the mycelial granules remains clearly hypointense. The characteristic appearance is that of an infiltrating mass madeup ofsmall cavities,hyperintense onT2 weighting, and circumscribed by hypointense fine partitions con- taining central dots, hypointense on all sequences and creating a nearly pathognomonic sign, called the ‘‘dot- in-circle’’,especiallyuseful whenclinical,microbiological and histologicalfindings arenot determinative. This dot- in-circlesign iscorrelated withthe histology:the primary hypointensepointcorrespondstothemycelialgranule,the surroundinghyperintensesignaltotheinflammatorygranu- loma,andthehypointensepartitionstothefibrousmatrix [1,2,7].
At the initial stage, MRI is relatively insensitive, compared with CT, for demonstrating limited corti- cal erosion. Spongiosis is visualized on T1-weighted sequences where the hyperintense marrow fat signal is replaced by the hypointense mycetoma and especially onthe fat-suppressed T2 weighted sequences, where the hyperintense signal is clear. It is difficult to differen- tiate between the healthy muscle structures and the mycetomatous process, and the replacement of the T1- weighted hyperintense signal of the soft tissue fat by a hypointensesignal isoneofthe bestsignsofthisinvasion [1,2,6].
The diagnosis, evident when multiple sinuses in swollen tissue discharge mycelial granules, can be difficult at earlier stages, especially the initial pre- sinus tract phase. MRI seeking the dot-in-circle sign allows a differential diagnosis, ruling out an invasive soft-tissue or bone tumor, chronic osteomyelitis (no bone sequestration), tuberculous osteomyelitis, and neu- roarthropathy (no background of neurological disorders) [1,2,4,7].
886 M.Bouzianeetal.
Figure2. Volumecomputedtomography(CT)ofthefootafterinjectionofcontrastproduct.aandb:softtissuewindow:frontal(a)and sagittal(b)slices:diffuseinfiltrationofthedorso-plantarsofttissue,enhancedheterogeneouslywithhyperdensemicronodules;c,dande:
bonewindow:frontalandsagittalslices:diffuseosteolysisofthecuneiform,metatarsalandsesamoidboneswithgeodesofthenavicular andcuboidbonesandanirregularperiostealreaction.
Treatmentcombinesinvariouswayslong-termantibiotic orantifungalagentsandsurgery, whichcanincludeampu- tationinadvancedstagesofboneextension[1—4].
Conclusion
Madura foot or pedal mycetoma is a mycelial soft-tissue infection with the potentially severe complication of osteoarticularextensionthatcanresultinamputationofthe affectedbonesegment.Imaging,inparticularCTandMRI, allowaspecificassessmentoftheosteoarticulardamageand canthusguidetherapeuticmanagement.
Disclosure of interest
Theauthorsdeclarethattheyhavenoconflictsofinterest concerningthisarticle.
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