- Volume 69 , Number 3
- Page: 219–24
MRI in clinically asymptomatic neuropathic leprosy feet: a baseline study
ABSTRACT
This study was undertaken to analyze the magnetic resonance imaging (MRI) findings in the clinically asymptomatic neuropathic feet of leprosy patients. Since in the literature no MRI data are available concerning the asymptomatic neuropathic foot in leprosy, the interpretation of MRI examinations in clinically suspected neuropathic feet in leprosy is difficult. We examined 10 adult leprosy patients with clinically asymptomatic neuropathic feet. Inclusion criteria were a normal or near normal neuropathic foot, without signs of inflammation. All patients underwent an MRI protocol with the inclusion of twopoint Dixon chemical shift imaging as fat suppression sequence. We found MR1 changes in almost all patients. The most striking were the changes located in the region of the first metacarpophalangeal (MTP) joint. These changes ranged f rom degradation and interruption of the subcutaneous fat to effusion/synovitis in the first MTPjoint. This study reveals significant MRI changes in clinically asymptomatic neuropathic feel in patients with leprosy. These changes may relate to the development of ulcerations. MRI may play an important role in detecting feet at risk and may influence clinical decision making.RÉSUMÉ
Cette élude a été enterprise pout analyser les données obtenues par résonnance magnétique nucléaire (RMN) sur les pieds neuropathiques mais cliniquement asymptômatiques tic patients hanséniens. Comme la littérature ne conlienl pas de données au sujet des pieds neuropathiques asymptômatiques de la lèpre, l'interprétation des examens RMN est difficile parmi les cas cliniquement suspects de pieds neuropalhique dans le cadre de la lèpre. Nous avons examinés 10 patients adultes hanséniens avec des pieds neuropathiques cliniquement asymptômatiques. Les critères d'inclusion dans l'étude étaient un pied neuropalhique normal ou presque normal, sans signe d'inflammation. Il a élé réalisé chez, tous les patients un protocole île RMN incluant une dérive chimique de Dixon en deux points comme séquence de suppression du tissu adipeux. Chez presque tous les patients, des modifications furent détectées par RMN. Les plus évidentes furent des modifications localisées à la région de la première jointure métotarsophalangienne (MTP). Ces modifications s'étendaient de dégradation et d'interruption du tissu adipeux sous cutané à des épenchements synoviaux/synovites de la première jointure MTP. Celle élude révèle des modifications RMN significatives chez les pieds neuropathiques asymptômatiques chez, les palienls lépreux. Ces modifications pourraient être liées au développement d'ulcérations. La RMN pourrait jouer un rôle important pour détecter les pieds à risque et pourrait influencer les prises de décisions cliniques.RESUMEN
Se hizo el estudio del pie eon neuropatía clínicamente asintomática en los pacientes con lepra utilizando la resonancia magnética de imagen (RMI). Puesto que no hay datos en la literatura sobre la aplicación de la RMI en este tipo de neuropatía, los resultados obtenidos con esta técnica resultan algo difícil de interpretar. Examinamos 10 pacientes adultos con lepra, con neuropatía del pie clínicamente asintomática. El criterio básico de inclusión lue que los pacientes tuvieran un pie neuropático clínicamente normal o casi normal, sin signos de inflamación, 'lodos los pacientes se sometieron al examen por RMI, el cual incluyó el cambio de imagen do los punios (Dixon) y una secuencia de supresión de grasa. Encontramos anormalidades en la RMI en casi lodos los pacientes. Los cambios más marcados estuvieron localizados en la región de la primera articulación melacarpol'alángica (MTP). Eslos cambios variaron desde la degradación e interrupción de la grasa subcutánea, hasta la efusión y sinovias en la primera articulación MTP. El estudio revela cambios significativos en la RMI en el pie neuropático. clínicamente asinlomático, délos pacientes con lepra. Como estos cambios pueden estar relacionados con el desarrollo de ulceraciones, la RMI podría ser de utilidad en la delección del pie en riesgo, y podría ayudar a decidir el manejo clínico de los pacientes y su tratamiento.Leprosy is an infectious disease caused by Mycobacterium leprae that affects 2K) million patients worldwide. It preferably invades skin and peripheral nerves.
In leprosy the neuropathic foot is one of the major contributors to morbidity due to peripheral nerve damage. Repeated injury subsequently may lead to considerable osseous and articular destruction secondary to sensory loss. The skeletal abnormalities may be severe and are evident in 20%70% of hospitalized patients (15). The (Charcot deformity) in leprosy is comparable to that in diabetes and may lead to tarsal disintegrationeuro-osteoarthropalhyn with osteolysis, fragmentation and progressive bone resorption. In extreme cases, dissolution of the midfoot results in separation of the forefoot and the hind foot, changing all biomechanics and weight bearing areas.
Diagnostic problems begin when a patient develops a neuropathic foot with clinical signs of inflammation, for example, ulceration, cellulitis, osteomyelitis and neuro-osteoarthropalhy (Charcot foot). Clinical signs often are not conclusive in discriminating between infection (cellulitis or osteomyelitis) and neuroosteoarthropathy (6). Early detection of feet at risk is preferable to help prevent these complications.
Diagnosing osteomyelitis is a well known challenge in diagnostic radiology (9-10). Magnetic resonance imaging (MRI) has been described as an important modality to assess the neuropathic feet of diabetic patients (2, 5, 18). For the detection of subtle bone marrow pathology it is mandatory to use fat-suppression sequences in stateoftheart musculoskeletal MRI (15). A homogeneous fat-suppression in the entire field of view, both before and after intravenous contrast material [Gadolinium-chelate (Gd)] is necessary to avoid confusion (14). This can adequately be achieved by the use of twopoint Dixon chemical shift imaging (TPD-CSI) (8).
The question was raised whether changes prior to the appearance of clinical signs are present and detected by early MRI. Since it is likely that early changes may occur, this lack of information may hamper the adequate reading of the MRI studies of symptomatic patients. All data available in the literature address clinically complicated neuropathic feet. To our knowledge, no papers concerning MRI in asymptomatic neuropathic feet exist.
In this study our goal was to answer the following questions: a) What is the MRI appearance of the asymptomatic neuropathic foot in leprosy patients? Are there MRI changes present in these patients? b) When changes are present, is there a role for MRI in relation to clinical management in the early assessment of the asymptomatic neuropathic foot in leprosy patients?
MATERIALS AND METHODS
Patients
From the database of the outpatient clinic of the Department of Dermatology, Academic Medical Center. Amsterdam, The Netherlands, 10 adult patients [5 male, 5 female; mean age 54 years (31-70 years)] with leprosy were selected. Inclusion criteria for entering this study were neuropathic feet with a normal or nearly normal foot, i.e., no Charcot deformity, no ulcer, and no signs of inflammation at the time of the study. The dermatologist in charge of the leprosy clinic (WRF) screened patients for inclusion. None of the feet had a history of osteomyelitis. The skin temperature was measured by palpation (7). No active ulcers and/or signs of inflammation were found. All patients entering the study signed an informed consent. The Medical Ethics Committee of our hospital approved the study.
A neuropathic foot was defined as a foot in which one or more of the neuronal functions, i.e., sensory, motor function or autonomic functions, were disturbed (consensus of the Dutch Neuropathic Foot Society). Sensory loss was tested using the SemmesWeinstein monofilament test (1). Patients were included when the sensory loss was a 10-gram force.
MRI procedure
An MRI examination was performed using a 1.5 Tesla Vision (Siemens, Erlangen, Germany). The foot of interest was placed inside the circularly polarized head coil. This coil was used because it provided the best signal to noise ratio.
The MRI protocol consisted of: Sagittal TurboSTIR (short tau inversion recovery) (3 mm), Tlweighted Dixon sequence (8), sagittal and coronal dual echo T2weighted FSE (fast spin echo) (3 mm); after the administration of Gd intravenously Tlweighted Dixon sequence and coronal fat suppression Tlweighted. The MRIexaminations were evaluated by a musculoskeletal radiologist blinded to the clinical findings (MM).
RESULTS
Clinical findings (Table 1)
The right foot was examined in eight patients and the left foot in two patients. The shape of the foot was completely normal in six patients. Claw toes were present in two patients, and two patients showed minor deformities due to earlier disease. No ulcers were present. Callus was present in three patients, twice located beneath the first metatarsophalangeal (MTP) joint and once beneath the fifth MTP joint. Sensory function was impaired in all patients. Motor function was normal in seven patients. Three patients showed a paresis. The autonomic function, as demonstrated by dry skin and fissures, was impaired in five patients.
MRI findings (Table 2)
Bone marrow. In 9 of the 10 patients there was a normal MR signal in the bone marrow: no bone marrow edema was found. There was no bone marrow enhancement seen after administration of contrast material. No bone destruction was found.
Joints. Joint effusion was seen in seven patients, and in all of these patients located in the first MTP joint. Local contrast enhancement in the first MTP joint was present in three patients.
Soft tissue. Infiltration of the subcutaneous fat was depicted in six patients, and in all of these patients was located plantar to the first MTP joint. The skin was intact on the surface of the foot in 9 of the 10 patients. An unexpected fistula was found in one patient, located at the first MTP joint.
Midfoot. In two patients, early osteoarthritic changes were found in the midfoot. No disintegration of the tarsus was found.
DISCUSSION
MRI is the most valuable imaging technique in the evaluation of complications of the diabetic neuropathic foot (9, 12, 17). The use of homogenous fat suppression in combination with contrast administration is found to be a very sensitive tool in evaluating neuropathic feet (9,11). All data are from diabetic patients, being by far the most common cause of neuropathic feet in the Western world.
This study is new because it includes leprosy patients who represent another important cause of neuropathic foot pathology. We investigated clinically asymptomatic feet in order to acquire a baseline MRI for leprosy patients. Since it can be expected that in the future MRI will be part of the imaging protocols for leprosy patients with complications of a neuropathic foot, it is to be expected that MRI results will gain influence on clinical decisionmaking. This necessitates a study in clinical asymptomatic patients in order to acquire a baseline database of MRI findings. This may be the only way to adequately detect the changes that represent osteomyelitis in the complicated patient group.
The results that we found are remarkable. All of our patients had no clinical symptoms at the time of the MRI, yet MRI abnormalities were found in almost all patients. The most striking findings were the changes located in the region of the first MTP joint in the majority of patients (90%). These abnormalities ranged from degradation and interruption of the subcutaneous fat, plantar fascia, and a small fistula to effusion/synovitis in the first MTP joint.
The soft tissue damage in the foot, plantar to the first metatarsal bone, has been described in diabetic feet with a significant difference between neuropathic and nonneuropathic feet (3). It was hypothesized that the subcutaneous lesions may consist of fibrosis (3) or hemorrhage (4). Moreover, it was suggested that the presence of this fatpad degradation might precede plantar ulceration. The same suggestion can be made in the leprosy population. Stress analysis studies in three-dimensional foot models of leprosy patients show that the musculoskeletal stresses during walking are higher in leprosy patients than in healthy controls, being 24%65% higher in early stage leprosy patients (13). Patil, et al. (13) conclude that the highest soft tissue stresses and shear stresses occur in the push off phase in scar tissue. The difference in shear stresses between the sole of the foot and the adjacent soft tissue layer in the scar tissue is about three times the normal value (13). Since the pushoff phase of the walking cycle takes place under the metatarsals, this may be related to the changes we found in our group of patients. Our findings support the conclusion that this may precede the development of plantar ulcers in these patients.
Fig. 1. Sagittal T1 out of phase Dixon image of the foot of patient 1. Note the normal plantar subcutaneous fat (with a bright signal). The interruption of the subcutaneous fat plantar to the metatarsophalangeal joint is illustrated with an arrow.
Our study reveals significant MRI findings in asymptomatic neuropathic feet in patients with leprosy. The changes we found with fatsuppressed contrastenhanced MRI are possibly related to the future development of ulcerations. It is conceivable that these changes can be detected when a more thorough physical examination is performed. A consequence of this study could be that more attention is paid to the clinical examination of asymptomatic neuropathic feet.
Fig. 2. Detailed Sagittal Dixon fat sat water image of the first metatarsophalangeal joint of patient 7. Note the enhancement of the head of the first metatarsal hone (one arrow) and the joint effusion/synovitis (two arrows).
Further research is necessary to investigate the potential role of MRI in the early detection of complications and its role in the clinical management of leprosy patients with neuropathic feet. Also, because of the recent introduction of less-expensive, dedicated extremity MRI, the implementation of MRI in the workup of leprosy patients may soon be possible outside the Western world.
Acknowledgment. The Q. M. Gastmann-Wichers Foundation financially supported this study. The authors wish to thank Dr. Gemila Hassan Bouber and Mrs. M. Evers-van Bavel for their support in the preparation of this manuscript. Prof. Dr. A. Huson is acknowledged for his critical review of the manuscript.
REFERENCES
1. Anderson, A. M. and Croit. R. P. Reliability of Semmes Weinslein monofilament and ballpoint sensory testing, and voluntary muscle testing in Bangladesh. Lepr. Rev. 70(1990)305-313.
2. Beltran, J.. Campanini, D. S.. Knight, C. and McCalla. M. The diabetic foot: magnetic resonance evaluation. Skeletal Radiol. 19(1990)37-41.
3. Brash. P. IX. Fostkr. J. E.. Anthony. P. and Tooki;, J. E. Magnetic resonance imaging techniques demonstrate soft tissue damage in the diabetic foot. Diabet. Med. 16(1999)55-61.
4. Brash. P. D.. Foster, J. E.. Vennart, W.. Daw, J. and Tooke. .1. E. Magnetic resonance imaging reveals microhaemorrhage in the feel of diabetic patients with a history of ulceration. Diabet. Med. 13(1996)973-978.
5. Craig, J. G.. Amin, M. B.. Wu, K., Eyler, W. R.. van Holsbeeck. M. T., Bouffard, J. A. and Shirazi. K. Osteomyelitis of the diabetic foot: MR imaging-palhologie correlation. Radiology 203(1997)849-855.
6. Faber, W. R.. Hoeksma, A. F.. van der Kleu, A. J., Maas. M. and Dijkstra. P. F. Diagnostic procedures for suspected osteomyelitis in neuropathic feet of leprosy patients. (Abstract) Int. J. Lepr. 66(1998)29A.
7. Hoeksma, A. F. and Faber, W. R. Assessment of skin temperature by palpation in leprosy patients: interobserver reliability and correlation with in frared thermometry. Int. J. Lepr. 68(2000)65-67.
8. Maas. M.. Dijkstra, P. F. and Akkerman, E. M. Uniform fat suppression in hands and feet through the use of twopoint Dixon chemical shift MR imaging. Radiology 210(1999)189-193.
9. Marcus, C. D., Ladam-Marcus, V. J., Leone, J.. Malgrange, D.. Bonnet-Grausserand, F. M. and Mentaneau, B. R MR imaging of osteomyelitis and neuropathic osteoarthropathy in the feet of diabetics. Radiographics 16(1996)1337-1348.
10. Moore,T. E., Yuh, W.T. C. Kathol. M. H. Elkhoury, G. Y. and Corson, J. D. Abnormalities of the foot in patients with diabetes mellitus: findings on MR imaging. AJR 157(1991)813-816.
11. Morrison, W. B., Schweitzer, M. E., Bock, G. W., Mitchell. D. G., Hume. E. L.. Pathria. M. N. and Resnick, D. Diagnosis of osteomyelitis: utility of fatsuppressed contrastenhanced MR imaging. Radiology 189(1993)251-257.
12. Morrison, W. B., Schweitzer, M. E., Wapner. K. L., Hecht, P. J., Gannon, F. H. and Behm, W. R. Osteomyelitis in feet of diabetics: clinical accuracy, surgical utility, and costeffectiveness of MR imaging. Radiology 196(1995)557-564.
13. Patil., K. M. and Jacob, S. Mechanics of tarsal disintegration and plantar ulcers in leprosy by stress analysis in three-dimensional foot models. Indian J. Lepr. 72(2000)69-86.
14. Peterfy, C. G., Linares, R. and Steinbach, L. S. Recent advances in magnetic resonance imaging of the musculoskeletal system. Rad. Clin. North Am. 32(1994)291-311.
15. Resnick, D. and Niwayama, G. Osteomyelitis, septic arthritis and soft tissue infection: organisms. In: Diagnosis of Bone and Joint Disorders. 3rd edn. Philadelphia: W.B. Saunders Company. 1995. pp. 2486-2492.
16. Schon. L. C, Easley, M. E. and Weineeld, S. B. Charcot neuroarthropathy of the foot and ankle. Clin. Orthopaed. Rel. Res. 349(1998)116-131.
17. Tomas. M. B., Patel, M., Marwin, S. E. and Palestro, C. J. The diabetic foot. Br. J. Radiol. 73(2000)443-450.
18. Yuh, J. S. Diabetic foot and neuroarthropathy magnetic resonance imaging evaluation. Top. Magn. Reson. Imaging 9(1998)295-310.
1. M.D., Department of Radiology, Suite GI-231, Academic Medical Center, Meihergdreef 9, 1105 AZ Amsterdam Zuidoost, The Netherlands.
2. M.D., Department of Radiology, Suite GI-231, Academic Medical Center, Meihergdreef 9, 1105 AZ Amsterdam Zuidoost, The Netherlands.
3. Ph.D., Department of Radiology, Suite GI-231, Academic Medical Center, Meihergdreef 9, 1105 AZ Amsterdam Zuidoost, The Netherlands.
4. M.D., Ph.D., Department of Dermatology. Academic Medical Center, Amsterdam, The Netherlands.
Reprint requests to M. Maas, M.D., at the above address or FAX 31-20-5669119: e-mail: m.maas@amc.uva.nl
Received for publication on 1 May 2001.
Accepted for publication in revised form on 23 July 2001.