Magnetic Resonance Imaging. Vol. IO, pp. 8147, Printed in the USA. All rights reserved.
0730-725X/92 $5.00 + .lW Copyright 0 1992 Pergamon Press plc
1992
l Original Contribution
MR IMAGING IN RHINOCEREBRAL AND INTRACRANIAL MUCORMYCOSIS WITH CT AND PATHOLOGIC CORRELATION MICHAEL R. TERK, DAVID J. UNDERWOOD, CHI-SHING ZEE, AND PATRICK M. COLLETTI Department of Radiology, University of Southern California School of Medicine, 1200 N. State Street, Los Angeles, CA 90033, USA, LAC+USC Imaging Science Center, 1744 Zonal Avenue, Los Angeles, CA 90033, USA Three cases of mucormycosis, two in diabetics and one in an intravenous drug abuse patient, are presented. Mag netic resonance imaging proved to be useful in ail cases, as was computed tomography. In one case, extremely low signal was detected from the fungal mass. It is surmised that this appearance was a result of high concentrations of iron and manganese. The low-signal area simulated air in paranasal sinuses; however, CT displayed a mildly enhancing soft tissue mass and allowed the correct diagnosis to be made. In another patient, pontine infarction was demonstrated by MR. In the third case the MR findings of mucormycosis involving the basal ganglia are shown and correlated with CT. Subsequent imaging studies demonstrated reduction of the mass, corresponding
to clinical improvement.
Keywords: Mucormycosis; Fungus; Brain infection; Diabetes; Drug abuse; Magnetic resonance imaging.
different clinical syndromes including rhinocerebral, pulmonary, disseminated, gastrointestinal, focal cerebral, endocardial, and cutaneous involvement. 1,8The infection often progresses quickly, and detection at an early stage is crucial for survival.4 Several recent articles have demonstrated the ability of MRI to detect mucormycosis and elucidate the extent of its involvement, proving it a useful tool in diagnosis.6*9T’0Here we present three additional cases with MR and CT findings.
Mucormycosis is a rare and often deadly opportunistic fungal infection caused by members of the genera Rhizopus, Absidia, and Mucor belonging to the family Mucoracea, of the order Mucorales, within the class Zygomycetes. Species of Rhizopus are the organisms of this order most frequently associated with human rhinocerebral disease. ’ These fungi are common bread and fruit molds characterized microscopically by their broad, nonseptate (coenocytic) hyphae with near-right-angle branching. They thrive in nature and can commonly be found in soil, vegetable matter, and air.2p3 These organisms can frequently be cultured from the oronasal cavity, throat, and stool in healthy individuals, in whom they generally do not cause infection. 2*4In patients with specific conditions such as diabetes mellitus and intravenous drug abuse, as well as some immunosuppressed individuals, genera of Mucoracea can cause a rapidly progressive, severely debilitating and frequently lethal infection. Mucormycosis occurs most commonly in diabetics, but it can also be seen in drug abusers,’ in immunocompromised individuals (e.g., AIDS),‘j anemia, leukemia, uremia, and severe burns, and in those receiving corticosteroids or chemotherapy.’ It can present as a variety of
CASE REPORTS
Case 1 A 22-year-old insulin-dependent diabetic man presented with a 3-wk history of left-sided headache, left nasal stuffiness, and progressive loss of vision in the left eye. The patient also described one episode of epistaxis from the left nostril. A postcontrast head CT [Fig. l(A) and (C)] showed a large, midline, uniformly enhancing, soft tissue mass involving the nasal septum, and the ethmoid, sphenoid, and maxillary sinuses bilaterally. Bone erosion in the nasoantral portion of the maxillary sinus, the
RECEIVED 2/ 19/91; ACCEPTED 6/4/91. Address correspondence and reprint requests to Dr.
Michael R. Terk, LAC+USC Imaging Science Center, 1744 Zonal Avenue, Los Angeles, CA !WO33,USA. 81
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(D) Fig. 1. Case 1. (A) Contrast-enhanced CT depicting a soft tissue density mass seen in the region of the ethmoid and sphenoid sinuses with destruction of the clivus posteriorly and posterior displacement of the basilar artery (arrow). (B) Corresponding 7”-weighted axial MR image (TR/TE, 2220/80) demonstrating low signal intensity within the ethmoid and sphenoid sinuses, corresponding to the enhancing soft tissue mass seen on CT. Note the posterior displacement of the basilar artery (arrow), (C) Coronal CT revealing a soft tissue mass in the sphenoid sinus with bony destruction of the planum sphenoidale and the tuberculum sella. Note destructive lesion in left sphenoid wing with associated soft tissue mass. (D) Corresponding T2weighted coronal MR image, (TR/TE, 1800/80) demonstrating a low-signal-intensity mass (arrows) in the sphenoid sinus with destruction of the planum sphenoidale and tuberculum sella.
planum sphenoidale, the floor of the sella turcica, and the cribriform plate was noted. MRI of the sinuses and orbits was performed on a Philips S15 Gyroscan imager (Philips Medical Systems, Inc., Shelton, CT) operating at 1.5 T [Fig. l(B) and (D)]. T, -weighted coronal images and multiecho axial and coronal images were obtained. All sequences obtained revealed signal void in the left anterior ethmoid, posterior ethmoid, and sphenoid sinuses; the lesion seen on MRI was of very low signal intensity on 7’r, T2, and fat-suppressed imaging and was not distinguishable from air on available images. Elevation of the planum sphenoidale extending dorsally to the sella turcica was noted, as was erosion of the clivus and displacement of the basilar artery posteriorly.
Final pathologic examination from this patient’s surgery confirmed mucor in the nasoethmoid mucosa. The patient recovered with near-normal return of vision. Case 2 A 2%year-old patient with a history of intravenous (IV) drug abuse presented complaining of headache and right-sided weakness. His symptoms began 2 wk prior to admission with an unsteady gait and manual clumsiness, which quickly progressed to frank right facial droop, right hemiparesis, and slurred speech. CT examination of the head was obtained with and without contrast [Fig. 2(A) and (B)], demonstrating an isolated, left-sided mass of mixed density, which en-
imaging in mucormycosis 0 M.R.
hanced irregularly. The mass involved the basal ganglia, thalamus, temporal lobe, and posterior portion of the frontal lobe, causing rightward shift of the midline and compression of the left lateral ventricle. No nasal or sinus involvement was noted. Four days later MR imaging was performed. T, -weighted sagittal and multiecho axial images were obtained in addition to gadolinium-DTPA enhanced, T, -weighted coronal and sagittal images [Fig. 2(C), (D), (E), and (F)]. These images demonstrated a mass in the left hemisphere involving the basal ganglia, thalamus, hypothalamus, and midbrain which enhanced intensely but irregularly with gadolinium. On Tz-weighted images, edema was noted to be extensive; there was compression of the foramen of Monro and the third ventricle, as well as dilatation of the contralateral lateral ventricle. Small scattered areas of high signal were noted on the precontrast Ti-weighted sagittal images [Fig. 2(E)] suggesting the presence of methemoglobin, implying some degree of hemorrhage. Stereotactic biopsy of the mass subsequently demonstrated nonseptate branching hyphae consistent with mucor species. Final culture grew genus Rhizopus. Amphotericin B was instituted, and symptoms improved over a 12-day course of IV therapy. Case 3 A 49-year-old non-insulin-dependent diabetic man with a history of cirrhotic alcoholic liver disease and portal hypertension presented with jaundice, ascites, and weakness. A head CT was obtained [Fig. 3(A)] which exhibited severe cerebral atrophy, but also demonstrated air-fluid levels in the sinuses and thinning of the medial and posterior walls of the left maxillary sinus. Over the course of 10 days of antibiotic therapy, the patient developed a left maxillary cellulitis, progressive left-sided cranial nerve VII palsy, and purulent discharge from the left eye. A follow-up CT was obtained 30 days following the prior study [Fig. 3(B)], demonstrating bony destruction of the medial and posterior lateral walls of the left maxillary sinus. Biopsy of sinus mucosa and fungal culture obtained at this time demonstrated mucormycosis. Following surgery, the patient was started on a regimen of amphotericin B and made a gradual recovery with the exception of residual left facial paresis. Several months later, facial cellulitis recurred. At this time MR of the head was obtained [Fig. 3(C)]. Ti-weighted sagittal images with axial and coronal multiecho images and gadolinium-enhanced Tl -weighted axial images were obtained. Preseptal soft tissue swelling was noted in the left facial and periorbital regions with no apparent intraconal involvement. On the T2weighted images, an area of increased signal intensity was noted in the central portion of the pons at the
TERK ETAZ.
83
level of the brachia conjunctiva. There was no apparent mass effect associated with this lesion, and it did not enhance abnormally with gadolinium. This was felt to be most consistent with gliosis following inflammation or stroke. DISCUSSION The most common presentation of mucormycosis is rhinocerebral infection, 2*8which is the form typically seen in diabetics.2 The correlation of rhinocerebral mucormycosis with diabetes is so strong that it should be considered in any diabetic with symptoms of sinusitis, or facial or eye pain, regardless of the person’s state of chemical control.2.3*” Another form of cerebral mucormycosis is focal intracerebral infection in the absence of sinus disease or endocarditis. This is rare compared with the relatively more common rhinocerebral form and is most frequently encountered in IV drug users. Anatomically there is predilection for the basal ganglia.5 Stave et al.’ reviewed the literature and showed that of 22 cases with isolated cerebral involvement, 50% admitted to being IV drug abusers. The survey also showed that 82% of the IV drug abusers had involvement of the basal ganglia, while only 9% of non-drug users with focal cerebral disease presented with similar involvement. The suspected source of the infection is spores present in the injected street drugs or the chemicals used in diluting them.5 Other associations with focal cerebral disease include renal insufficiency, a history of head trauma, corticosteroid therapy, and hyperglycemia. Five percent of cases do not have any apparent predisposing factor.’ Case 2 in our series was an admitted IV drug abuser with focal cerebral mucormycosis, as seen on MR and CT. The T,-weighted contrast-enhanced MR of this patient demonstrated a mass of the left hemisphere involving the basal ganglia as well as the thalamus, hypothalamus, and midbrain. On T2-weighted imaging, massive edema with compression of the foramen of Monro and third ventricle was noted. MR and CT findings were largely complementary with irregularly enhancing masses seen. MR more clearly demonstrated hemorrhage with more obvious enhancement seen when imaged with gadolinium. Pathologically, the disease shows a remarkable predilection for the vasculature, in particular, arteries. It proliferates along the internal elastic lamina of the vessel walls, and hyphae may penetrate through the endothelium into the lumen causing thrombosis with subsequent infarction and necrosis of the infected tissue. 1-4,8 Cavernous sinus thrombosis is a frequent complication.2*8 If untreated, the infection eventually gains access to the cranium, either by direct extension
84
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992
(0 Fig. 2. Case 2. Pre- and postcontrast CT upon admission. (A) Precontrast scan revealing a large lesion of the left basal ganglia and thalamus with compression and displacement of the ipsilateral ventricle, midline shift, and obliteration of the third ventricle. (B) Postcontrast CT demonstrating patchy, irregular enhancement of the lesion. (C) Gadohnium-enhanced T,-weighted coronal image (TR/TE, 655/l@, obtained upon admision. Note the large enhancing lesion of the left basal ganglia and thalamus producing compression and shift of the third ventricle. (D) Tz-weighted axial image (TR/TE, 2000/80), obtained on admission. Note high signal extending laterally to the surface of the frontal and parietal lobes.
MR
imaging in mucormycosis 0 M.R. TERK ET AL.
85
(F) Fig. 2. continued. T,-weighted sagittal images. (E) Pregadolinium-DPTA T,-weighted (TRITE, W/18) sagittal image obtained upon admission demonstrating mass effect in the region of the left basal ganglia extending into the midbrain with sotie high signal, probably hemorrhage (arrow) in the midbrain. (F) Postgadolinium-DTPA T,-weighted (TR/TE, 544/l@ sagittal image demonstrating patchy, irregular enhancement of the central portion of the lesion with enhancement extending into the basal ganglia.
through the cribriform plate or orbital apex or by spread through the vascular system, such as the carotid artery and the cavernous sinus.2*3*8Such a mechanism may have been responsible for the suspected pontine infarction seen in case 3 [Fig. 3(C)]. In case 1, CT demonstrated a sinus mass that extended through the cribriform plate into the anterior cranial fossa. Magnetic resonance, however, showed this lesion to produce a near signal void (similar to air) on all imaging sequences such as to be nearly indistinguishable from normally aerated paranasal sinuses.
The very low MR signal produced by the mass in case 1 was sufficiently hypointense as to simulate pneumatized paranasal sinuses creating a potential pitfall. The posterior displacement of the basilar artery was the principal detectable abnormality which, with knowledge of the patient’s clinical history and review of the CT examination, permitted the correct diagnosis to be made. Descriptions elsewhere of the MR appearance of rhinocerebral mucormycosis mention findings of hyperintense secretions and mucosal thickening of the
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09
Fig. 3. Case 3. (A) Initial CT performed demonstrating soft tissue density material within the nasal cavity extending to the maxillary sinus. There is minimal, irregular thinning (white arrows) of the medial wall and the posterior portion of the lateral wall of the left maxillary sinus. (B) CT obtained 3 wk later demonstrating a soft tissue mass in the left nasal cavity, Obvious bony destruction of the medial and lateral walls of the left maxillary sinus (arrows) can now be seen. (C) T,-weighted axial MR image (TRITE, 2000/80) after clinical suspicion of recurrent disease. The image depicts a high-signal-intensity lesion in the anterior aspect of the pons (arrow) suggesting infarction.
sinuses on proton and Tz-weighted images, sinus opacification, T, -weighted imaging. 6p9Our MR results in this patient were surprisingly different from those of the literature. A possible explanation is found in the paper by Zinreich et al., I2 which demonstrated markedly hypointense MRI images of fungal growths in seven patients with sinus infections caused by L)resch/era and Aspergilh species. This study showed decreased signal intensity on T,-weighted images and a very decreased signal intensity on T2-weighted images of fungal sinusitis, suggesting metallic susceptibility effect. Laboratory examination of the fungal elements
and concretions revealed levels of calcium, iron, and manganese that were much greater than levels found in mucus from bacterial sinusitis. Furthermore, a study by Kubicek et al. I3 demonstrated the importance of manganese uptake by the species Aspergillus niger and showed that it was necessary for normal growth of that fungus. Iron, manganese, and calcium are well known for their ability to disturb the magnetic field and reduce signal, creating a hypointense image. I4 The presence of these elements in significant levels in the fungal mass of case 1 was possibly responsible for the hypointense signal. The experience presented shows a spectrum of dis-
MR imaging in mucormycosis 0 M.R. TERK ET AL.
ease caused by Mucor. A potential pitfall in the interpretation of MR images in patients with the rhinocerebral form is discussed. REFERENCES Baker, R.D. The phycomycoses. Ann. NY Acad. Sci.
4. 5.
6.
7.
174592-605; 1970. Pillsbury, H.C.; Fischer, N.D. Rhinocerebral mucormycosis. Arch. Otolaryngol. 103:600-604; 1979. Meyers, B.R.; Wormser, G.; Hirschman, S.Z.; Blitzer, A. Rhinocerebral mucormycosis: Premortem diagnosis and therapy. Arch. Intern. Med. 139:557-560; 1979. Hauman, C.H.J.; Raubenheimer, E.J. Orofacial mucormycosis. Oral Surg. 68:624-627; 1989. Stave, GM.; Heimberger, T.; Kerkering, T.M. Zygomycosis of the basal ganglia in intravenous drug users. Am. J. Med. 86:115-117; 1989. Yousem, D.M.; Galetta, S.L.; Gusnard, D.A.; Goldberg, H. I. MR findings in rhinocerebral mucormycosis. J. Comput. Assist. Tomogr. 13:878-882; 1989. McNulty, J.S. Rhinocerebral mucormycosis: Predisposing factors. Laryngoscope 92:1140-l 143; 1982.
87
8. Eisenberg, L.; Wood, T.; Boles, R. Mucormycosis. Laryngoscope 87:347-356;
1977.
9. Press, G.A.; Weindling, S.M.; Hesselink, J.R.; Ochi, J.W.; Harris, J.P. Rhinocerebral mucormycosis: MR manifestations. J. Comput. Assist: Tomogr. 12:744749; 1988.
10. McDevitt, G.R.; Brantley, M.J.; Cawthon, M.A. Rhinocerebral mucormycosis: A case report with magnetic resonance imaging findings. C/in. Imaging 13:317320; 1989.
11. Finn, D.G. Murcormycosis
of the paranasal
Ear, Nose, Throat J. 67:813-820;
sinuses.
1988.
12. Zinreich, S. J.; Kennedy, D.W.; Malat, J.; Curtin, H.D.; Epstein, J.I.; Huff, L.C.; Kumar, A.J.; Johns, M.E.; Rosenbaum, A.E. Fungal sinusitis: Diagnosis with CT and MR imaging. Radiology 169:439-444; 1988. 13. Kubicek, C.P.; Rohn, M. Metabolic effects of manganese deficiency in Aspergilfus niger: Evidence of increased protein degradation. Arch. Mcrobiol. 141:266-268; 1985.
14. Stark, D.D.; Bradley, W.G. Magnetic Resonance Imaging. St. Louis: C.V. Mosby Company; 1988: pp. 144-147.
0730-725X/92 $5.00 + .lW Copyright 0 1992 Pergamon Press plc
1992
l Original Contribution
MR IMAGING IN RHINOCEREBRAL AND INTRACRANIAL MUCORMYCOSIS WITH CT AND PATHOLOGIC CORRELATION MICHAEL R. TERK, DAVID J. UNDERWOOD, CHI-SHING ZEE, AND PATRICK M. COLLETTI Department of Radiology, University of Southern California School of Medicine, 1200 N. State Street, Los Angeles, CA 90033, USA, LAC+USC Imaging Science Center, 1744 Zonal Avenue, Los Angeles, CA 90033, USA Three cases of mucormycosis, two in diabetics and one in an intravenous drug abuse patient, are presented. Mag netic resonance imaging proved to be useful in ail cases, as was computed tomography. In one case, extremely low signal was detected from the fungal mass. It is surmised that this appearance was a result of high concentrations of iron and manganese. The low-signal area simulated air in paranasal sinuses; however, CT displayed a mildly enhancing soft tissue mass and allowed the correct diagnosis to be made. In another patient, pontine infarction was demonstrated by MR. In the third case the MR findings of mucormycosis involving the basal ganglia are shown and correlated with CT. Subsequent imaging studies demonstrated reduction of the mass, corresponding
to clinical improvement.
Keywords: Mucormycosis; Fungus; Brain infection; Diabetes; Drug abuse; Magnetic resonance imaging.
different clinical syndromes including rhinocerebral, pulmonary, disseminated, gastrointestinal, focal cerebral, endocardial, and cutaneous involvement. 1,8The infection often progresses quickly, and detection at an early stage is crucial for survival.4 Several recent articles have demonstrated the ability of MRI to detect mucormycosis and elucidate the extent of its involvement, proving it a useful tool in diagnosis.6*9T’0Here we present three additional cases with MR and CT findings.
Mucormycosis is a rare and often deadly opportunistic fungal infection caused by members of the genera Rhizopus, Absidia, and Mucor belonging to the family Mucoracea, of the order Mucorales, within the class Zygomycetes. Species of Rhizopus are the organisms of this order most frequently associated with human rhinocerebral disease. ’ These fungi are common bread and fruit molds characterized microscopically by their broad, nonseptate (coenocytic) hyphae with near-right-angle branching. They thrive in nature and can commonly be found in soil, vegetable matter, and air.2p3 These organisms can frequently be cultured from the oronasal cavity, throat, and stool in healthy individuals, in whom they generally do not cause infection. 2*4In patients with specific conditions such as diabetes mellitus and intravenous drug abuse, as well as some immunosuppressed individuals, genera of Mucoracea can cause a rapidly progressive, severely debilitating and frequently lethal infection. Mucormycosis occurs most commonly in diabetics, but it can also be seen in drug abusers,’ in immunocompromised individuals (e.g., AIDS),‘j anemia, leukemia, uremia, and severe burns, and in those receiving corticosteroids or chemotherapy.’ It can present as a variety of
CASE REPORTS
Case 1 A 22-year-old insulin-dependent diabetic man presented with a 3-wk history of left-sided headache, left nasal stuffiness, and progressive loss of vision in the left eye. The patient also described one episode of epistaxis from the left nostril. A postcontrast head CT [Fig. l(A) and (C)] showed a large, midline, uniformly enhancing, soft tissue mass involving the nasal septum, and the ethmoid, sphenoid, and maxillary sinuses bilaterally. Bone erosion in the nasoantral portion of the maxillary sinus, the
RECEIVED 2/ 19/91; ACCEPTED 6/4/91. Address correspondence and reprint requests to Dr.
Michael R. Terk, LAC+USC Imaging Science Center, 1744 Zonal Avenue, Los Angeles, CA !WO33,USA. 81
82
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992
(D) Fig. 1. Case 1. (A) Contrast-enhanced CT depicting a soft tissue density mass seen in the region of the ethmoid and sphenoid sinuses with destruction of the clivus posteriorly and posterior displacement of the basilar artery (arrow). (B) Corresponding 7”-weighted axial MR image (TR/TE, 2220/80) demonstrating low signal intensity within the ethmoid and sphenoid sinuses, corresponding to the enhancing soft tissue mass seen on CT. Note the posterior displacement of the basilar artery (arrow), (C) Coronal CT revealing a soft tissue mass in the sphenoid sinus with bony destruction of the planum sphenoidale and the tuberculum sella. Note destructive lesion in left sphenoid wing with associated soft tissue mass. (D) Corresponding T2weighted coronal MR image, (TR/TE, 1800/80) demonstrating a low-signal-intensity mass (arrows) in the sphenoid sinus with destruction of the planum sphenoidale and tuberculum sella.
planum sphenoidale, the floor of the sella turcica, and the cribriform plate was noted. MRI of the sinuses and orbits was performed on a Philips S15 Gyroscan imager (Philips Medical Systems, Inc., Shelton, CT) operating at 1.5 T [Fig. l(B) and (D)]. T, -weighted coronal images and multiecho axial and coronal images were obtained. All sequences obtained revealed signal void in the left anterior ethmoid, posterior ethmoid, and sphenoid sinuses; the lesion seen on MRI was of very low signal intensity on 7’r, T2, and fat-suppressed imaging and was not distinguishable from air on available images. Elevation of the planum sphenoidale extending dorsally to the sella turcica was noted, as was erosion of the clivus and displacement of the basilar artery posteriorly.
Final pathologic examination from this patient’s surgery confirmed mucor in the nasoethmoid mucosa. The patient recovered with near-normal return of vision. Case 2 A 2%year-old patient with a history of intravenous (IV) drug abuse presented complaining of headache and right-sided weakness. His symptoms began 2 wk prior to admission with an unsteady gait and manual clumsiness, which quickly progressed to frank right facial droop, right hemiparesis, and slurred speech. CT examination of the head was obtained with and without contrast [Fig. 2(A) and (B)], demonstrating an isolated, left-sided mass of mixed density, which en-
imaging in mucormycosis 0 M.R.
hanced irregularly. The mass involved the basal ganglia, thalamus, temporal lobe, and posterior portion of the frontal lobe, causing rightward shift of the midline and compression of the left lateral ventricle. No nasal or sinus involvement was noted. Four days later MR imaging was performed. T, -weighted sagittal and multiecho axial images were obtained in addition to gadolinium-DTPA enhanced, T, -weighted coronal and sagittal images [Fig. 2(C), (D), (E), and (F)]. These images demonstrated a mass in the left hemisphere involving the basal ganglia, thalamus, hypothalamus, and midbrain which enhanced intensely but irregularly with gadolinium. On Tz-weighted images, edema was noted to be extensive; there was compression of the foramen of Monro and the third ventricle, as well as dilatation of the contralateral lateral ventricle. Small scattered areas of high signal were noted on the precontrast Ti-weighted sagittal images [Fig. 2(E)] suggesting the presence of methemoglobin, implying some degree of hemorrhage. Stereotactic biopsy of the mass subsequently demonstrated nonseptate branching hyphae consistent with mucor species. Final culture grew genus Rhizopus. Amphotericin B was instituted, and symptoms improved over a 12-day course of IV therapy. Case 3 A 49-year-old non-insulin-dependent diabetic man with a history of cirrhotic alcoholic liver disease and portal hypertension presented with jaundice, ascites, and weakness. A head CT was obtained [Fig. 3(A)] which exhibited severe cerebral atrophy, but also demonstrated air-fluid levels in the sinuses and thinning of the medial and posterior walls of the left maxillary sinus. Over the course of 10 days of antibiotic therapy, the patient developed a left maxillary cellulitis, progressive left-sided cranial nerve VII palsy, and purulent discharge from the left eye. A follow-up CT was obtained 30 days following the prior study [Fig. 3(B)], demonstrating bony destruction of the medial and posterior lateral walls of the left maxillary sinus. Biopsy of sinus mucosa and fungal culture obtained at this time demonstrated mucormycosis. Following surgery, the patient was started on a regimen of amphotericin B and made a gradual recovery with the exception of residual left facial paresis. Several months later, facial cellulitis recurred. At this time MR of the head was obtained [Fig. 3(C)]. Ti-weighted sagittal images with axial and coronal multiecho images and gadolinium-enhanced Tl -weighted axial images were obtained. Preseptal soft tissue swelling was noted in the left facial and periorbital regions with no apparent intraconal involvement. On the T2weighted images, an area of increased signal intensity was noted in the central portion of the pons at the
TERK ETAZ.
83
level of the brachia conjunctiva. There was no apparent mass effect associated with this lesion, and it did not enhance abnormally with gadolinium. This was felt to be most consistent with gliosis following inflammation or stroke. DISCUSSION The most common presentation of mucormycosis is rhinocerebral infection, 2*8which is the form typically seen in diabetics.2 The correlation of rhinocerebral mucormycosis with diabetes is so strong that it should be considered in any diabetic with symptoms of sinusitis, or facial or eye pain, regardless of the person’s state of chemical control.2.3*” Another form of cerebral mucormycosis is focal intracerebral infection in the absence of sinus disease or endocarditis. This is rare compared with the relatively more common rhinocerebral form and is most frequently encountered in IV drug users. Anatomically there is predilection for the basal ganglia.5 Stave et al.’ reviewed the literature and showed that of 22 cases with isolated cerebral involvement, 50% admitted to being IV drug abusers. The survey also showed that 82% of the IV drug abusers had involvement of the basal ganglia, while only 9% of non-drug users with focal cerebral disease presented with similar involvement. The suspected source of the infection is spores present in the injected street drugs or the chemicals used in diluting them.5 Other associations with focal cerebral disease include renal insufficiency, a history of head trauma, corticosteroid therapy, and hyperglycemia. Five percent of cases do not have any apparent predisposing factor.’ Case 2 in our series was an admitted IV drug abuser with focal cerebral mucormycosis, as seen on MR and CT. The T,-weighted contrast-enhanced MR of this patient demonstrated a mass of the left hemisphere involving the basal ganglia as well as the thalamus, hypothalamus, and midbrain. On T2-weighted imaging, massive edema with compression of the foramen of Monro and third ventricle was noted. MR and CT findings were largely complementary with irregularly enhancing masses seen. MR more clearly demonstrated hemorrhage with more obvious enhancement seen when imaged with gadolinium. Pathologically, the disease shows a remarkable predilection for the vasculature, in particular, arteries. It proliferates along the internal elastic lamina of the vessel walls, and hyphae may penetrate through the endothelium into the lumen causing thrombosis with subsequent infarction and necrosis of the infected tissue. 1-4,8 Cavernous sinus thrombosis is a frequent complication.2*8 If untreated, the infection eventually gains access to the cranium, either by direct extension
84
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992
(0 Fig. 2. Case 2. Pre- and postcontrast CT upon admission. (A) Precontrast scan revealing a large lesion of the left basal ganglia and thalamus with compression and displacement of the ipsilateral ventricle, midline shift, and obliteration of the third ventricle. (B) Postcontrast CT demonstrating patchy, irregular enhancement of the lesion. (C) Gadohnium-enhanced T,-weighted coronal image (TR/TE, 655/l@, obtained upon admision. Note the large enhancing lesion of the left basal ganglia and thalamus producing compression and shift of the third ventricle. (D) Tz-weighted axial image (TR/TE, 2000/80), obtained on admission. Note high signal extending laterally to the surface of the frontal and parietal lobes.
MR
imaging in mucormycosis 0 M.R. TERK ET AL.
85
(F) Fig. 2. continued. T,-weighted sagittal images. (E) Pregadolinium-DPTA T,-weighted (TRITE, W/18) sagittal image obtained upon admission demonstrating mass effect in the region of the left basal ganglia extending into the midbrain with sotie high signal, probably hemorrhage (arrow) in the midbrain. (F) Postgadolinium-DTPA T,-weighted (TR/TE, 544/l@ sagittal image demonstrating patchy, irregular enhancement of the central portion of the lesion with enhancement extending into the basal ganglia.
through the cribriform plate or orbital apex or by spread through the vascular system, such as the carotid artery and the cavernous sinus.2*3*8Such a mechanism may have been responsible for the suspected pontine infarction seen in case 3 [Fig. 3(C)]. In case 1, CT demonstrated a sinus mass that extended through the cribriform plate into the anterior cranial fossa. Magnetic resonance, however, showed this lesion to produce a near signal void (similar to air) on all imaging sequences such as to be nearly indistinguishable from normally aerated paranasal sinuses.
The very low MR signal produced by the mass in case 1 was sufficiently hypointense as to simulate pneumatized paranasal sinuses creating a potential pitfall. The posterior displacement of the basilar artery was the principal detectable abnormality which, with knowledge of the patient’s clinical history and review of the CT examination, permitted the correct diagnosis to be made. Descriptions elsewhere of the MR appearance of rhinocerebral mucormycosis mention findings of hyperintense secretions and mucosal thickening of the
86
Magnetic Resonance Imaging 0 Volume 10, Number 1, 1992
09
Fig. 3. Case 3. (A) Initial CT performed demonstrating soft tissue density material within the nasal cavity extending to the maxillary sinus. There is minimal, irregular thinning (white arrows) of the medial wall and the posterior portion of the lateral wall of the left maxillary sinus. (B) CT obtained 3 wk later demonstrating a soft tissue mass in the left nasal cavity, Obvious bony destruction of the medial and lateral walls of the left maxillary sinus (arrows) can now be seen. (C) T,-weighted axial MR image (TRITE, 2000/80) after clinical suspicion of recurrent disease. The image depicts a high-signal-intensity lesion in the anterior aspect of the pons (arrow) suggesting infarction.
sinuses on proton and Tz-weighted images, sinus opacification, T, -weighted imaging. 6p9Our MR results in this patient were surprisingly different from those of the literature. A possible explanation is found in the paper by Zinreich et al., I2 which demonstrated markedly hypointense MRI images of fungal growths in seven patients with sinus infections caused by L)resch/era and Aspergilh species. This study showed decreased signal intensity on T,-weighted images and a very decreased signal intensity on T2-weighted images of fungal sinusitis, suggesting metallic susceptibility effect. Laboratory examination of the fungal elements
and concretions revealed levels of calcium, iron, and manganese that were much greater than levels found in mucus from bacterial sinusitis. Furthermore, a study by Kubicek et al. I3 demonstrated the importance of manganese uptake by the species Aspergillus niger and showed that it was necessary for normal growth of that fungus. Iron, manganese, and calcium are well known for their ability to disturb the magnetic field and reduce signal, creating a hypointense image. I4 The presence of these elements in significant levels in the fungal mass of case 1 was possibly responsible for the hypointense signal. The experience presented shows a spectrum of dis-
MR imaging in mucormycosis 0 M.R. TERK ET AL.
ease caused by Mucor. A potential pitfall in the interpretation of MR images in patients with the rhinocerebral form is discussed. REFERENCES Baker, R.D. The phycomycoses. Ann. NY Acad. Sci.
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