Otology & Neurotology 00:00Y00 Ó 2015, Otology & Neurotology, Inc.
Imaging Case of the Month
Imaging Characteristics of Cerebellopontine Angle Chloroma *Marsha S. Reuther, †Mahmood F. Mafee, and *Thomas H. Alexander *Division of OtolaryngologyYHead & Neck Surgery and ÞDepartment of Radiology, University of California, San Diego, California, U.S.A.
A 60-year-old woman presented to an emergency department with sudden left hearing loss, tinnitus, severe flu-like symptoms, fatigue, and a white blood count of 75,000/mm3. After further workup, she was diagnosed with acute myeloid leukemia (AML) and treated with chemotherapy. Magnetic resonance (MR) imaging revealed no abnormalities of the cochlea, internal auditory canal (IAC), or cerebellopontine angle (CPA) to explain the hearing loss (Fig. 1). After treatment, her symptoms improved, with the exception of the left hearing loss and tinnitus. She was deemed to be in complete remission. Two months after the completion of consolidation chemotherapy, the patient developed brief episodic vertigo and progressive disequilibrium. About 1 month later, she developed left facial weakness that rapidly progressed to complete paralysis. She was seen in an outside emergency department where a non-contrast computed tomography scan was reportedly negative and was treated for presumed Bell’s palsy. Two months later, a repeat MRI of the IAC was ordered and she was referred to the neurotology clinic. At the time of her consultation, she reported stable left hearing loss and tinnitus and the development of new intermittent left retro-orbital pain. Examination revealed complete left-sided facial paralysis (House-Brackmann Grade VI). MRI of the IAC showed interval development of a 2.2 1.1 1.8 cm mass of the left CPA with extension into the IAC (6 mo after her previous negative MRI). The mass was isointense to brain on T1- and T2-weighted MR images, enhanced with contrast, and showed diffusion restriction (Fig. 2, AYC). The cochlea, vestibule, and tympanic segment of the facial nerve all demonstrated abnormal enhancement with contrast. The mass abutted the cisternal component of the left trigeminal nerve, most likely causing the retro-orbital pain (not shown).
Analysis of her cerebrospinal fluid demonstrated blast cells and bone marrow biopsy was normal. She was diagnosed with isolated central nervous system relapse of AML. She underwent another course of chemotherapy followed by a stem cell transplant. Surveillance MRIs showed progressive decrease in size and enhancement of the mass. At her most recent MRI (11 mo post-diagnosis), there was minimal enhancement of the residual mass and resolution of enhancement of the cochlea and vestibule (Fig. 2D). Her facial nerve function improved to HouseBrackmann Grade III. DISCUSSION Extramedullary leukemic cells may rarely present as a focal mass lesion, known as a chloroma or granulocytic sarcoma. Chloroma occurs in 2.9 to 3.1% of patients with AML (1). A chloroma may develop in any location; however, only a small fraction involve the central nervous system. Five cases of CPA chloroma have previously been reported in the literature (2). Presenting symptoms have included acute onset facial weakness, SNHL, tinnitus, vertigo, and ataxia. MRI is the best imaging modality for demonstration of CPA chloromas and differentiation from other lesions. The MRI findings are characteristic of a dural-based infiltrative process, as seen in lymphoma, leukemia, dural metastases, neurosarcoidosis, and Langerhans histiocytosis. The presence of a dural tail helps exclude a neurogenic tumor. Chloromas share some imaging characteristics with meningiomas. Both typically are broad-based with a dural tail and are isointense or hypointense on T1-weighted MR imaging and hypointense to slightly hyperintense on T2weighted MR imaging. Both homogenously enhance with IV contrast. Labyrinthine involvement, as seen in the present case, would not be expected in a meningioma. Most importantly, diffusion-weighted imaging (DWI) with an apparent diffusion coefficient (ADC) map shows diffusion restriction in lymphoma and leukemic infiltration, which is not seen in the other lesions in the differential diagnosis
Address correspondence and reprint requests to Thomas H. Alexander, M.D., M.H.Sc., Division of OtolaryngologyYHead & Neck Surgery, University of California, San Diego, 200 W. Arbor Drive, MC 8895, San Diego, CA 92103, U.S.A.; E-mail: [email protected] The authors report no conflicts of interest.
1
Copyright © 2015, Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
2
M. S. REUTHER ET AL.
FIG. 1. MRI obtained after initial presentation with acute myeloid leukemia and sudden sensorineural hearing loss. A, Axial postgadolinium T1-weighted MR image reveals no abnormalities of IAC or CPA. B, Axial apparent diffusion coefficient (ADC) map demonstrating no restrictive lesions of the CPA or IAC.
FIG. 2. AYC, MRI of the IAC obtained after onset of facial paralysis and vertigo (6 mo after previous MRI). A, Axial postgadolinium T1weighted MR image showing 2.2 1.1 1.8 cm left CPA enhancing mass (arrow) with extension into the IAC. Note abnormal enhancement of the cochlea, vestibule, and tympanic segment of the facial nerve. B, Axial T2-weighted MR image redemonstrates the left CPA mass, which is isointense. C, Axial apparent diffusion coefficient (ADC) map reveals that the mass is restrictive as it is hypointense on this image. D, MRI of the IAC obtained 9 months after treatment. Axial postgadolinium T1-weighted MR image displaying interval decrease in the size and enhancement of the left CPA and IAC with resolution of the enhancement of the cochlea, and vestibule (arrow). Otology & Neurotology, Vol. 00, No. 00, 2015
Copyright © 2015, Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CHARACTERISTICS OF CEREBELLOPONTINE ANGLE CHLOROMA mentioned above (meningiomas may show some restriction, but not to the extent of lymphoma or leukemia). Compared to lymphoma, leukemic infiltration is more likely to involve the labyrinth and dura, making chloroma the most likely diagnosis. Given the patient’s history of AML, the diagnosis was almost certain. This case highlights the importance of obtaining temporal bone imaging as part of the workup for otologic or cranial nerve symptoms in patients with a history of a hematologic malignancy. Additionally, this case emphasizes the use of DWI in the imaging of CPA lesions. Diffusion-weighted images characterize the diffusion of water molecules within intracellular and extracellular fluid compartments. Areas with decreased (restricted) diffusion appear bright on DWI series. However, most DWI series are T2-weighted and areas with high T2 signal also appear bright, a phenomenon known as ‘‘T2 shinethrough.’’ ADC maps quantify diffusion independent of
3
T2 signal, with areas of restricted diffusion appearing dark or hypointense. Therefore, it is important to compare DWI series and ADC maps to identify areas of true restriction. Tightly compacted cellular tumors such as lymphoma and leukemic infiltration usually demonstrate restriction on DWI. Other lesions that often demonstrate DWI restriction include acute stroke, cholesteatomas (epidermoid cysts), abscesses, and other highly cellular tumors such as medulloblastoma or retinoblastoma.
REFERENCES 1. Landis DM, Aboulafia DM. Granulocytic sarcoma: An unusual complication of aleukemic myeloid leukemia causing spinal cord compression. Leuk Lymphoma 2003;44:1753Y60. 2. Atalay B, Altino¨rs N, Yilmaz C, et al. Extraaxial chloroma of the cerebellopontine angle: Case report. Turk Neurosurg 2007;17:286Y8.
Otology & Neurotology, Vol. 00, No. 00, 2015
Copyright © 2015, Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
Imaging Case of the Month
Imaging Characteristics of Cerebellopontine Angle Chloroma *Marsha S. Reuther, †Mahmood F. Mafee, and *Thomas H. Alexander *Division of OtolaryngologyYHead & Neck Surgery and ÞDepartment of Radiology, University of California, San Diego, California, U.S.A.
A 60-year-old woman presented to an emergency department with sudden left hearing loss, tinnitus, severe flu-like symptoms, fatigue, and a white blood count of 75,000/mm3. After further workup, she was diagnosed with acute myeloid leukemia (AML) and treated with chemotherapy. Magnetic resonance (MR) imaging revealed no abnormalities of the cochlea, internal auditory canal (IAC), or cerebellopontine angle (CPA) to explain the hearing loss (Fig. 1). After treatment, her symptoms improved, with the exception of the left hearing loss and tinnitus. She was deemed to be in complete remission. Two months after the completion of consolidation chemotherapy, the patient developed brief episodic vertigo and progressive disequilibrium. About 1 month later, she developed left facial weakness that rapidly progressed to complete paralysis. She was seen in an outside emergency department where a non-contrast computed tomography scan was reportedly negative and was treated for presumed Bell’s palsy. Two months later, a repeat MRI of the IAC was ordered and she was referred to the neurotology clinic. At the time of her consultation, she reported stable left hearing loss and tinnitus and the development of new intermittent left retro-orbital pain. Examination revealed complete left-sided facial paralysis (House-Brackmann Grade VI). MRI of the IAC showed interval development of a 2.2 1.1 1.8 cm mass of the left CPA with extension into the IAC (6 mo after her previous negative MRI). The mass was isointense to brain on T1- and T2-weighted MR images, enhanced with contrast, and showed diffusion restriction (Fig. 2, AYC). The cochlea, vestibule, and tympanic segment of the facial nerve all demonstrated abnormal enhancement with contrast. The mass abutted the cisternal component of the left trigeminal nerve, most likely causing the retro-orbital pain (not shown).
Analysis of her cerebrospinal fluid demonstrated blast cells and bone marrow biopsy was normal. She was diagnosed with isolated central nervous system relapse of AML. She underwent another course of chemotherapy followed by a stem cell transplant. Surveillance MRIs showed progressive decrease in size and enhancement of the mass. At her most recent MRI (11 mo post-diagnosis), there was minimal enhancement of the residual mass and resolution of enhancement of the cochlea and vestibule (Fig. 2D). Her facial nerve function improved to HouseBrackmann Grade III. DISCUSSION Extramedullary leukemic cells may rarely present as a focal mass lesion, known as a chloroma or granulocytic sarcoma. Chloroma occurs in 2.9 to 3.1% of patients with AML (1). A chloroma may develop in any location; however, only a small fraction involve the central nervous system. Five cases of CPA chloroma have previously been reported in the literature (2). Presenting symptoms have included acute onset facial weakness, SNHL, tinnitus, vertigo, and ataxia. MRI is the best imaging modality for demonstration of CPA chloromas and differentiation from other lesions. The MRI findings are characteristic of a dural-based infiltrative process, as seen in lymphoma, leukemia, dural metastases, neurosarcoidosis, and Langerhans histiocytosis. The presence of a dural tail helps exclude a neurogenic tumor. Chloromas share some imaging characteristics with meningiomas. Both typically are broad-based with a dural tail and are isointense or hypointense on T1-weighted MR imaging and hypointense to slightly hyperintense on T2weighted MR imaging. Both homogenously enhance with IV contrast. Labyrinthine involvement, as seen in the present case, would not be expected in a meningioma. Most importantly, diffusion-weighted imaging (DWI) with an apparent diffusion coefficient (ADC) map shows diffusion restriction in lymphoma and leukemic infiltration, which is not seen in the other lesions in the differential diagnosis
Address correspondence and reprint requests to Thomas H. Alexander, M.D., M.H.Sc., Division of OtolaryngologyYHead & Neck Surgery, University of California, San Diego, 200 W. Arbor Drive, MC 8895, San Diego, CA 92103, U.S.A.; E-mail: [email protected] The authors report no conflicts of interest.
1
Copyright © 2015, Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
2
M. S. REUTHER ET AL.
FIG. 1. MRI obtained after initial presentation with acute myeloid leukemia and sudden sensorineural hearing loss. A, Axial postgadolinium T1-weighted MR image reveals no abnormalities of IAC or CPA. B, Axial apparent diffusion coefficient (ADC) map demonstrating no restrictive lesions of the CPA or IAC.
FIG. 2. AYC, MRI of the IAC obtained after onset of facial paralysis and vertigo (6 mo after previous MRI). A, Axial postgadolinium T1weighted MR image showing 2.2 1.1 1.8 cm left CPA enhancing mass (arrow) with extension into the IAC. Note abnormal enhancement of the cochlea, vestibule, and tympanic segment of the facial nerve. B, Axial T2-weighted MR image redemonstrates the left CPA mass, which is isointense. C, Axial apparent diffusion coefficient (ADC) map reveals that the mass is restrictive as it is hypointense on this image. D, MRI of the IAC obtained 9 months after treatment. Axial postgadolinium T1-weighted MR image displaying interval decrease in the size and enhancement of the left CPA and IAC with resolution of the enhancement of the cochlea, and vestibule (arrow). Otology & Neurotology, Vol. 00, No. 00, 2015
Copyright © 2015, Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CHARACTERISTICS OF CEREBELLOPONTINE ANGLE CHLOROMA mentioned above (meningiomas may show some restriction, but not to the extent of lymphoma or leukemia). Compared to lymphoma, leukemic infiltration is more likely to involve the labyrinth and dura, making chloroma the most likely diagnosis. Given the patient’s history of AML, the diagnosis was almost certain. This case highlights the importance of obtaining temporal bone imaging as part of the workup for otologic or cranial nerve symptoms in patients with a history of a hematologic malignancy. Additionally, this case emphasizes the use of DWI in the imaging of CPA lesions. Diffusion-weighted images characterize the diffusion of water molecules within intracellular and extracellular fluid compartments. Areas with decreased (restricted) diffusion appear bright on DWI series. However, most DWI series are T2-weighted and areas with high T2 signal also appear bright, a phenomenon known as ‘‘T2 shinethrough.’’ ADC maps quantify diffusion independent of
3
T2 signal, with areas of restricted diffusion appearing dark or hypointense. Therefore, it is important to compare DWI series and ADC maps to identify areas of true restriction. Tightly compacted cellular tumors such as lymphoma and leukemic infiltration usually demonstrate restriction on DWI. Other lesions that often demonstrate DWI restriction include acute stroke, cholesteatomas (epidermoid cysts), abscesses, and other highly cellular tumors such as medulloblastoma or retinoblastoma.
REFERENCES 1. Landis DM, Aboulafia DM. Granulocytic sarcoma: An unusual complication of aleukemic myeloid leukemia causing spinal cord compression. Leuk Lymphoma 2003;44:1753Y60. 2. Atalay B, Altino¨rs N, Yilmaz C, et al. Extraaxial chloroma of the cerebellopontine angle: Case report. Turk Neurosurg 2007;17:286Y8.
Otology & Neurotology, Vol. 00, No. 00, 2015
Copyright © 2015, Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
