Hassan S. Sharif, MD, FRCR •¿ David C. Clark, MB, ChB, FRCR e Mohamed Y. Aabed, MD, DMRD . Osarugue A. Aideyan, MB, BS, FRCR •¿ Tor A. Mattsson, MD, PhD •¿ Maurice C. Haddad, MD, FRCR Sven 0. Ohman, MD, PhD •¿ Ravi K. Joshi, MD, FAMS(Derma) •¿ Husham A. Hasan, MB, ChB, FRCS e Abdul Haleem, MBBS, MPhih, FRC Path

Mycetoma:

Comparison M

YCETOMAis a chronic granulo matous infection that affects the skin and extends to involve deep emtissues (1). True fungi and aerobic

Magnetic resonance (MR) images obtained in 18 patients with patho logically confirmed mycetoma in the body (n = 4) or lower extremity (n = 14) were retrospectively re viewed and compared with comput ed tomographic (CT) scans in 15 pa tients and surgical findings in 10. Ti-weighted images showed an in filtrating mass (same signal intensi ty as muscle) involving skin, subcu taneous fat, muscles, tendons, and other tissues. On T2-weighted im ages, the mass and affected struc tures showed moderately increased signal intensity. Bone marrow in volvement was detected in seven patients and was best visualized on Ti-weighted images. CT showed moderate enhancement of the infil trative process in all patients. Bone changes, seen in nine, included coarse trabeculation, periosteal reac tion, endosteal proliferation, and patchy destruction. MR imaging and CT were comparable and corre hated well with surgery in showing the extent of soft-tissue involve ment. Early bone changes (impor tant for therapy planning for pedal mycetoma) were seen only at CT. The study showed that MR imaging is sensitive for assessing the extent of mycetoma in the soft tissues. CT should be the method of choice for staging pedal lesions because it can be used to detect early bone in volvement. Index terms:

of MR Imaging

actinornycetes

are the causative

agents, introduced into the body af ten direct inoculation by a sharp ob ject such as a thorn (2—4).The disease is characterized by abscesses, multi ple draining sinuses, and fistulas from which pus containing the pathogen is discharged (1-3). The foot is the most frequently affected site, but in endemic countries the hand, the back, and the retmopenito neurn can be involved (1,3,5-9). In pedal rnycetornas, antimicrobial therapy is sometimes curative, but when theme is bone involvement, nonsurgical cure may be unlikely and partial resection or amputation may be required (2,10). Early recogni tion of bone involvement is therefore

essential to the overall management of these lesions (10). Mycetomas are common in the equatorial trans-African belt (Sudan, Somalia, Nigeria), the southern part of Saudi Arabia, India, and Central and South America (2-5,10). Plain ma diogmaphic and computed tomo graphic (CT) appearances of myceto mas have been previously reported, but the value of magnetic

resonance

(MR) imaging in assessing these le sions has not been described

(3,4,10—

15). In this study the features of my cetoma seen at MR imaging were evaluated in 18 patients with patho logically proved disease, and MR findings were compared with those of CT in 15 and with surgical data

Bones, infection, 40.215 •¿ Ex

tremities, MR studies •¿ Soft tissues, infection, 40.215 •¿ Soft tissues, MR studies, 40.1214

in 10.

Radiology 1991; 178:865-870

with CT'

MATERIALS

AND

METHODS

MR imaging studies of 18 patients with proved

mycetoma

were

retrospectively

reviewed, and the findings were com pared with those of CT scanning in 15 and with

the surgical

patients underwent

findings

in 10. All

diagnosis and treat

ment at the Riyadh Armed Forces Hospi tal between January 1987 and April 1990.

Three patients had been included in pre vious studies (16,17). All patients underwent MR imaging means of a 0.5-T whole-body supercon

by

ductive imager (Gyroscan; Philips Medi cal Systems International, Best, The Neth erlands) adjusted nique. The spine

for the spin-echo tech and lower extremities

were evaluated with sagittal and coronal images, while the body regions were evaluated with coronal and axial images. Sections 5-7 mm thick with a gap of 1 mm in a 256 X 256 matrix were imaged. Six patients underwent reassessment after the intravenous administration of gado pentetate dimeglumine in a dose of 0.2 mmol

per kilogram

of body weight.

following imaging parameters

The

were used:

(a) Multisection, multiplane images were obtained by means of a pulse sequence with a repetition time (TR) of 500 msec and an echo time (TE) of 30 msec (TRITE = 500/30)

(the same

pulse

sequence

was

used after intravenous administration of gadopentetate dimeglumine), and (b) multisection, multiplane images were ob tamed by means of a TR/TE of 2,000 /50, 100. The following MR findings were con

sidered evidence of involvement by the infiltrative process: (a) patchy or diffuse loss of signal from subcutaneous fat and muscle planes with the short TR/TE se

quence; (b) anatomic distortion of skin, muscles, and other organs; (c) high signal intensity on images obtained with long

TR/TE, especially from areas that showed decreased signal intensity on the images obtained with short TR/TE; and (d) areas of increased signal intensity on postcon trast images.

I From

the

Departments

of

Radiology

(H.S.S.,

DCC.,

M.Y.A.,

O.A.A.,

TAM.,

M.C.H.),

Internal

Fifteen patients underwent CT. Four teen underwent scanning with a GE 9800

Medicine (5.0.0., R.K.J.), Orthopaedic Surgery (H.A.H.), and Histopathology (A.H.), Riyadh Armed Forces Hospital, P0 Box 7897, Riyadh 11159, Saudi Arabia. Received June 13, 1990; revision requested July 27; revision received October 1; accepted October 4. Address reprint requests to

Abbreviations:

H.S.S. C RSNA,

1991

TE = echo time, TR = repeti

tion time.

865

scanner

(GE Medical

Systems,

Milwau

kee) that imaged 3-mm-thick contiguous sections of the foot, knee, and spine and 10-mm-thick sections of the thoracic cavi ty, abdomen, and pelvis. One patient un derwent scanning with a Somatom 2 (Sie mens, Erlangen, Federal Republic of Ger many) that imaged a section thickness of 5 mm. Patients

with

body

lesions

(n

4)

and seven patients with lower extremity involvement were studied before and af ter intravenous injection of contrast mate rial (100 mL [300 mg of iodine per millihi ter] of iohexol [Omnipaque; Nyegaard, Oslo]). Bone and soft-tissue windows of sagittal and coronal images were assessed. Complete or partial amputation was performed in seven of the 14 patients with lower-extremity mycetoma, while partial resection of the inflammatory mass and affected structures was per formed in three of four patients with body lesions. Skin biopsies were per formed in the rest of the patients, and histologic identification of the type of

pathogen was achieved in all. Histologic material from 10 of those patients was

available for review. Seven of those were

d.

U.

classified as having actinomycotic myce toma and three as having eumycotic my

cetoma. Actinomycotic mycetoma includ ed five cases of infection with Streptomy ces somaliensis and two of infection with Streptomyces madurae. Eumycotic myceto ma included two cases of infection with

Madurella mycetomii and one case of un classified eumycotic mycetoma.

CT and MR studies were evaluated sep arately and independently ologists

(M.Y.A.,

O.A.A.,

by three radi M.C.H.)

blinded

to the final diagnosis. For each imaging technique and every patient, the follow ing points were assessed: location and ex tent of lesion, organ involvement, and type of pathologic

condition

(ie, inflam

matory vs neoplastic). Whenever there was disagreement, the majority opinion was accepted. In cases of partial or complete amputa tion of lower-extremity

mycetoma

(n

c.

7),

surgical and pathologic data obtained from patient records were compared with imaging findings with regard to the ex tent of soft-tissue involvement (subcuta neous fat, muscles, tendons) and the ex tent of bone

involvement.

In the three

patients with body mycetoma who under went partial resection of their lesions, comparison also included evaluation of involvement of the spine, spinal cord, dura, kidney, adrenal glands, sels, rectum, and prostate.

At MR imaging,

the signal intensi areas was similar

in

all patients. The infiltrating mass had the same signal intensity as the skele tal muscles on the short TR/TE im ages and showed only a moderate in crease in signal intensity on the long TR/TE images (Figs 1-5). Postcon trast studies

provided

866 •¿ Radiology

ial CT image

causing

shows

marked

marked

soft-tissue

cortical thickening,

swelling

and

mass

small bone spicules

surrounding

representing

the calcaneus

interrupted

and

periosteal

reaction (arrowheads), and coarse trabecular pattern. (c) Coronal spin-echo (500/30) MR im age obtained at the level of the calcaneus shows the large soft-tissue mass arising from the soft tissues of the heel and replacing the fat laterally. There is also infiltration into the soft tissues on the lateral aspect of the calcaneus. Note the cortical thickening on the medial wall of the calcaneus (arrowheads) most likely representing endosteal reaction. The marrow of the calcaneus appears normal. (d) Skin biopsy specimen obtained from the affected heel shows a mycetoma granule (formalin-fixed, paraffin-embedded section). A typical Madurella mycetomii with a colony of broad septate hyphae and spores lying in a brown-stained ground substance is shown. (Hematoxylin-eosin; original magnification, X 50.)

large yes

RESULTS ty of the affected

d.

Figure 1. Pedal mycetoma in a 23-year-old man. (a) A large tumorous lesion involving the heel has multiple discharging sinuses (arrows) and dry crusted lesions (arrowheads). (b) Ax

no more infon

ed deeper to involve muscles, ten

mation than that obtained with Ti and T2-weighted sequences. Involve ment of the skin and subcutaneous fat was noted in all patients and asso ciated with increased vasculamity

dons, and other body structures (Figs 1-5). The muscles were thickened or partially destroyed, or both (Fig 4).

(Figs 1, 5). At CT, the infiltrating

ity (n = i4), the knee was affected in

mass showed moderate but diffuse enhancement (Figs 3—5).Subcutane ous tissue and skin were affected in all the 15 patients who underwent

two patients. One of the severely af fected knees showed marked in volvement of muscles, tendons, sub cutaneous fat, cortical bone, and

CT scanning,

bone marrow (Fig 2). The abnormal

and the lesions extend

In mycetoma

of the lower

extrem

March 1991

b.

a.

c. Figure 2. Mycetoma involving the knee and proximal aspect of the lower leg in a 52-

year-old man. (a) Tumorous lesion involy ing the right knee is shown, along with multiple

discharging

sinuses

(arrowheads)

and scarred areas on the anterior and poste nor aspects. Enlarged inguinal lymph nodes

and two discharging sinuses in the groin (arrows)

d.

e.

areas showed relatively decreased signal intensity on Ti-weighted irn ages and moderately increased signal intensity on T2-weighted images. Theme was also evidence of enlarged inguinal lymph nodes. The size and extent of the infiltrating mass and evidence of involvement of muscles, tendons,

and subcutaneous

fat were

seen to a better advantage on Ti weighted images (Fig 2). Obliteration of the normal high signal intensity from subcutaneous fat on Ti-weight ed images was the best indicator of infiltration. On T2-weighted images, only moderately increased tensity could be obtained,

signal in making

differentiation between normal and abnormal tissues difficult (Figs 2, 3, 5). Pedal mycetomas showed changes comparable to those of the knee le sions (Fig i). MR and CT findings were compa rabie with regard to showing the ex tent of the lesions in the soft tissues of all 11 patients with lowem-extrern ity rnycetomas

who underwent

both

MR imaging and CT. Among the five patients who underwent partial or complete amputation of their affect ed feet, bone involvement was de tected at MR imaging in four and at CT in all five. The bone changes not ed at CT were more conspicuous and correlated well with pathologic find ings. They included peniosteal meac tion, cortical hypemostosis, cortical erosions, coarse trabeculation, and frank bone destruction (Fig 1). Of the four patients with body my cetoma, the most severe lesion affect Volume 178 •¿ Number 3

are seen.

(b) Plain

radiograph

shows a large mass involving the soft tissues around the knee joint and extending from the distal third of the femur down to the proximal third of the tibia and fibula. Gen eralized osteopenia is seen in the bones, and there are areas of bone destruction as well as

ed a 34-year-old patient who had an external injury to his back 12 years before admission (Fig 4). The disease involved the entire thoracoabdorni nal wall and extended from the level of T-4 down to the upper thigh mus des. Almost all the erector spinae muscles and the psoas, quadmatus lumbomurn, glutei, and upper thigh muscles were symmetrically de stroyed and replaced by fat or in flammatory tissue, or both (Fig 4).

areas of slight bone sclerosis in the proximal tibia. Minimal periosteal reaction is seen in the posterior aspect of the femoral and tibial

cortices. (c) Midsagittal spin-echo (500/30)

MR image of the knee joint shows large lob ulated masses of the same intensity as mus des extending from the lower third of the femur down to the proximal third of the tib ia. Areas of decreased signal intensity in the marrow of the femur and tibia indicate in

volvement (arrowheads). The gastrocnemius muscles as well as the muscles

of the quadri

ceps are involved by this process, and there is extensive

The process extended into the epidu ral space, the posterior mediastinurn, the netnocrunal area, and the lumbar pamaspinal region. All the abdominal organs were displaced anteriorly, and the spleen was markedly en larged. MR and CT findings were cornpa mable in this patient with regard to the extent of the lesion in the soft tis

involvement

of the subcutane

ous fat (arrows). (d) Midsagittal spin-echo (2,000/100) MR image shows heterogeneous increased signal intensity of the involved muscles seen in b. Note the rounded area of low signal intensity in the proximal tibia (arrow) most likely representing a seques trum.

(e) Skin

biopsy

specimen

obtained

from the affected knee shows a typical St rep tomyces somaliensis granule (formalin-fixed,

paraffin-embedded

section) with pale pink

colony and a rim of filamentous material the subcortical area. (Hematoxylin-eosin;

in

original magnification, X50.)

sues. Bone changes, however, were mostly detected on the CT study and

were seen in the lower nibs and the thoracolumbar vertebrae. Several nibs appeared sclerotic and thickened, and their marrow cavities were oblit emated. Bone spicules (most probably representing periosteal reaction) (Fig 4) and slender osteophytes were seen in all affected vertebrae. Vertebral body and disk morphology appeared preserved

at CT and MR imaging

de

spite extensive panaspinal and intra spinal infiltration of the circumfer ential mass (Fig 4). In the patient with the cervical spi nal lesion, the extent of the infiltrat ing process in the soft tissues was comparable at MR imaging and at CT

and correlated well with the surgical findings (Fig 3). However, both mo dalities failed to allow detection of the presence of microscopic infil tnation

of the pemiosteum

of the me

moved larninae of C-i to C-4. Verte bnal bodies and disks appeared mom phologically intact at both modalities, although at MR imaging, abnormal signal intensity was detected from C-i to C-4, raising the possibility of involvement (Fig 3). No verification of a pathologic

condition

in any yen

tebmal body was possible during the operation. In the patient with the abdominal Radiology e 867

Figure 3. Mycetoma of the cervical spine in a 61-year-old

man.

(a) Axial

CT (window

level 45, window width 512) obtained at the level of C-2 shows loss of definition of the muscles of the cervical spine on the left side (splenius capitis and semispinalis). A soft tissue mass (*) is clearly visualized on the

lateral aspect of the facet joint. There is also evidence of extension into the spinal canal displacing the thecal sac (arrowheads) poste riorly and to the right side. (b) Midsagittal spin-echo (500/30) MR image shows a mass of the same signal intensity as muscles aris ing from the soft tissues of the neck posteri orly and invading the epidural space be

tween the posterior arch of C-i and the spi nous process

of C-2 (arrowheads).

a.

b.

The cord

is moderately compressed. Moderate signal loss is seen in the bodies of C-i to C-4. Note infiltration of the subcutaneous fat (arrow).

(c) Midsagittal spin-echo (2,000/100)MR im age shows patchy increased signal intensity of the mass seen in b and increased signal intensity of the bodies of C-i to C-4. (d) Cor onal spin-echo (2,000/50) MR image shows scoliosis deformity of the spine and extrinsic compression of the cord by the mass, which is of the same signal intensity as the sur rounding soft tissues. At operation, debulk ing of the inflammatory mass was per formed together with a long laminectomy, and granulation tissue was removed from the spinal canal. The removed posterior ele ments of C-2 to C-S were histologically af fected. Verification of involvement of the

vertebral bodies was not possible because of the posterior

surgical

approach.

d.

c.

rnycetorna, the right kidney was de stroyed

and replaced

by three

abscesshike collections rim enhancement

small

that showed

at CT and in

creased signal intensity on T2weighted images (Fig 5). Findings of both modalities were comparable and correlated well with those of surgery. Similar

changes

were noted

patient with mycetoma pelvic wall.

in the

of the might

DISCUSSION The term mycetoma refers to a slow ly progressive

infection

that onigi

abscesses (1,2,10). The fistulization of these abscesses, the presence of mi croonganisms in the discharged pus, and the associated turnefaction are the hallmarks of mycetorna (2,8,10) (Figs 1, 2). Histologically, a typical rnycetoma consists of a large granulo rnatous

area with a purulent

surrounded

center

by a thick, fibrous cap

on only slight

pain follows

the initial injury (2—4,10).The infec tion proliferates

beneath

the skin, in

vades muscles, and forms small, deep 868 •¿ Radiology

in this study

provided

limited

help

in detecting early changes of bone involvement. This is because, in my cetoma, bone is affected as a result of

sule (1,2,13) (Figs 1, 2). In pedal my

contiguous

cetornas, tendons and nerve sheaths are generally more resistant to the in

changes are mostly cortical, includ ing peniosteal elevation, cortical hy

fection,

pemostosis, cortical erosions, and end osteal proliferation (cortical changes are poorly detected at MR imaging

while

bone is frequently

in

vaded and destroyed (1,2). The treatment of mycetoma is de pendent on the causative agent, the location of the lesion, and the degree of invasion of the affected segment

nates in the skin after implantation of pathogens by a sharp object. Two (2,3). While 90% of cases of actinomy main groups of mycetoma are recog cotic mycetorna can be treated suc nized (i8). Actinomycotic mycetorna cessfuhly with antimicrobial agents, is caused by aerobic atinornycetes eurnycotic mycetorna is more diffi (Nocardia brasiliensis, Streptomyces so cult to manage conservatively and a maliensis, Steptomyces madurae), and combination of surgical and medical eurnycotic or maduromycotic myceto treatment is required (3). Body myce ma is caused by true fungi (Madurella mycetomii, Pyrenochaeta romeroi) (i —¿3). tornas (especially in the head and neck region) usually have a worse A long period of incubation during prognosis than those in the foot and which there may be no clinical rnani festations

involvement is therefore extremely important for planning treatment of extremity mycetomas (10). Contrary to its value in detecting bacterial osteomyehitis, MR imaging

the hand, and whenever bone is af fected, the nonsurgical cure of ex trernity lesions becomes extremely

unlikely

(iO,19). Recognition

of bone

spread

and the early

because of the absence of signal due to the lack of mobile protons) (Fig 1). Coarse trabeculam pattern, frank bone

destruction, sequestra

marrow infiltration, that are readily

and

detected

at

MR imaging are late manifestations of mycetoma (10,20-23) (Fig 2). CT of the lower-extremity mycetomas in this study proved more useful in aid ing decisions about further manage rnent (ie, surgical vs medical treat ment and complete

vs partial

ampu

tation). Furthermore,

the CT findings

of bone involvement

correlated

well

in the amputated

spec

with findings imens

(Fig

1).

In all our cases the signal

intensity

March 1991

a.

b.

C.

d.

e.

Figure4. Extensivemycetomainvolving the posteriorthoracoabdominalwall in a 34-year old man. (a) Axial postcontrast CT scan obtained at the level of T-9 shows a large posterior mediastinal mass displacing the aorta anteriorly (*). The mass extends posteriorly to involve symmetrically all the muscles of the back. Epidural extension is seen (arrowhead). Patient underwent scanning in the prone position, as he was unable to lie supine. (b) Axial CT im age obtained at the level of L-1 shows the mass seen in a extending into the abdominal cavi ty around

the vertebral

body. Note involvement

of the erector

spinae muscles.

(c) Axial CT

image obtained at the level of L-2 shows considerable destruction of both psoas muscles and the erector spinae muscles. The muscles are replaced by fatty tissue and an irregular infil trating mass. Spicules (arrowheads) arising from the body of the vertebra most likely repre sent an irregular

periosteal

reaction.

There is epidural

extension.

The spleen

is enlarged.

Re

formatted images confirm circumferential epidural compression. (d) Coronal spin-echo (500/30)

MR image shows severe patchy destruction

of both glutei and erector

muscles

and

replacement by fatty tissue (arrowhead) and an infiltrating process (*). (e) Retroperitoneal coronal spin-echo (500/30) MR image shows splenomegaly and severe destruction of both psoas muscles with replacement by fatty tissue.

the lower ribs. These were detected only on the CT study. Morphologi caily, the vertebral bodies and disks appeared normal at both MR imaging and CT (Fig 4). The extent of disease in the soft tissues was comparable at both MR imaging and CT. In the other three cases of body mycetorna, the findings at MR imag ing and CT were also fairly compara ble with regard to the soft-tissue ex tent and organ involvement. MR im aging displayed the abnormalities in the cervical spinal lesion to better ad vantage because of the direct sagittal plane (Fig 3). In conclusion, this study has shown that, while MR imaging and CT are equally adequate for evaluat ing body rnycetomas, CT should be the method of first choice for pre therapy

assessment

of pedal

in allowing

detection

of early bone

involvement. Because of its direct multiplanam capability, MR imaging can be used in the initial

of the affected soft tissues (low on Ti-weighted and moderately in creased on T2-weighted images) was comparable, irrespective of the loca tion of the lesion (Figs 1—5).This probably reflects the underlying histopathologic picture in which the infection has induced the formation of thick fibrous matrix and granula tion tissue. In pyogenic osteornyeli tis, the markedly

abnormal

signal

in

tensity (low on Ti-weighted and high on T2-weighted images) ob tamed also reflects the underlying inflammatory response that classical iy includes extensive edema (extra cellular water), pus formation, and rapid marrow infiltration (19-24). In this study, Ti-weighted images were generally found to be more helpful than T2-weighted on postcontmast irn ages because they clearly displayed obliteration of the high signal inten sity from the subcutaneous

fat (Figs

1-5). T2-weighted images showed lit tle difference in signal intensity be tween affected and unaffected tissue, Volume 178 •¿ Number 3

presumably because of the minimal extnacehlular fluid produced by this rnycotic infection. Although mycetorna most fre quently affects the lower extremities (65%—70%of cases), it has been me

ported in other body locations such as the hand, back, perineum, thorax, skull, mandible,

paranasal

sinuses,

and testes (3,5,10—15).Because the in fection characteristically spreads by

and follow-up ma. I

their patients, and

the Department

Illustration

muscles,

flammatomy

tissue (Fig 4). Despite

phytes,

cortical

thickening,

emation of the rneduilary

Mariat

the

and obhit

cavities of

F, Destombes

P. Segretain

G.

The

mycetomas: clinical features, pathology, etiology, and epidemiology. Contrib Mi crobiol Immunol 1977; 4:1—39. Magana

M.

Mycetoma.

Int J Dermatol

1984;23:221—236. 3.

McGinnis

MR. Fader

contemporary North

extensive posterior rnediastinal mass with panaspinal and intraspinal spread, the only bone changes de picted were slender vertebral osteo

and

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2.

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1.

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