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Neuroradiology |
1 From the Departments of Radiology (J.M.M., B.G.A., J.H.G., N.M.A., J.C.) and Medicine (J.D.E., M.L.), Addenbrooke's Hospital and University of Cambridge, England. Received December 17, 1998; revision requested January 5, 1999; revision received March 10; accepted July 1. Address reprint requests to J.M.M., Department of Radiology, Sunnybrook Health Science Centre, 2075 Bayview Ave, North York, Toronto, Ontario, Canada M4N 3MS (e-mail: joemmurphy@hotmail.com).
| Abstract |
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MATERIALS AND METHODS: MR imaging studies in 19 patients with Wegener granulomatosis and possible central nervous system involvement were reviewed by two neuroradiologists. Intermediate-weighted and T2-weighted fast spin-echo MR images of the brain had been acquired in all patients, and spin-echo T1-weighted nonenhanced and gadolinium-enhanced images had been acquired in 18 patients.
RESULTS: MR imaging findings included diffuse linear dural thickening and enhancement (n = 6); focal dural thickening and enhancement contiguous with orbital, nasal, or paranasal disease (n = 5); infarcts (n = 4); nonspecific white matter areas of high signal intensity on intermediate-weighted and T2-weighted images (n = 10); enlarged pituitary gland with infundibular thickening and enhancement (n = 2); a discrete cerebellar lesion that was probably granulomatous in origin (n = 1); and cerebral (n = 8) and cerebellar atrophy (n = 2).
CONCLUSION: MR imaging demonstrated the wide spectrum of findings of central nervous system involvement in patients with Wegener granulomatosis and was particularly useful for the evaluation of direct intracranial spread from orbital, nasal, or paranasal disease.
Index terms: Brain, atrophy, 13.83, 153.83 Brain, diseases, 10.622 Brain, infarction, 13.78 Brain, MR, 10.121411, 10.121415, 10.12143 Gadolinium Meninges, 10.622 Wegener granulomatosis, 10.622
| Introduction |
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| MATERIALS AND METHODS |
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In 18 patients, transverse, coronal, or sagittal T1-weighted spin-echo MR images (500540/914 [repetition time msec/echo time msec]; field of view, 2022 x 2022; section thickness, 5 mm; matrix, 256 x 256; two signals acquired) also were obtained before and after intravenous administration of 0.1 mmol/kg gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany). Eleven examinations were performed with and seven were performed without spectral fat suppression.
Two consulting neuroradiologists (B.G.A., N.M.A.) independently reviewed all 19 studies at a workstation and used the standard postprocessing facilities available at the time. Each study was evaluated for the following features, which are recognized (58) as occurring in Wegener granulomatosis: meningeal thickening; direct spread from orbital, nasal, or paranasal disease; remote cerebral granulomatous lesions; infarcts; nonspecific white matter lesions; atrophy; pituitary gland enlargement; and infundibular thickening. A consensus was obtained when necessary.
The clinical history of each patient was subsequently reviewed with the consulting physician responsible for the patient's care, with specific reference to the following features: primary reason for referral for cranial MR imaging; extent of orbital, nasal, and paranasal disease; response to treatment; and presence of any other disease processes that may have contributed to the MR imaging appearance.
| RESULTS |
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Meningeal Enhancement
The meninges were considered to be abnormal if they showed either diffuse or focal thickening on contrast-enhanced MR images. Meningeal thickening and enhancement were found in 11 patients. Two distinct patterns of distribution were noted: (a) diffusely abnormal meninges unrelated to sinus or orbital disease and (b) focal dural thickening and enhancement adjacent to sinus or orbital disease.
Diffuse thickening and enhancement.Diffuse meningeal thickening and enhancement (Fig 1) were present in six patients (patients 16). In these six patients, enhancement was seen in the dura; in one patient, leptomeningeal enhancement also was present. Nodular enhancement was not found in any patient. Involvement of both the tentorium cerebelli and the dura overlying the convexity of the cerebrum was noted in five patients; the tentorium cerebelli was the sole site of involvement in one. One patient had asymmetric enhancement in which the right side of the tentorium cerebelli initially was more severely involved than the left, but the appearances were symmetric on subsequently obtained MR images. In one patient, there also was diffuse dural thickening and enhancement overlying the thoracic cord, with normal dura in the cervical region (Fig 2). In all six patients, severe headache was the reason for referral for MR imaging. No patient had cranial nerve palsy. In four patients, meningeal biopsy was performed, and histologic results were consistent with Wegener granulomatosis.
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Nonspecific White Matter Lesions
Ten patients had nonspecific white matter lesions with high signal intensity on intermediate-weighted and T2-weighted images. These lesions, which were multiple in all cases, were seen in the periventricular and subcortical regions, the basal ganglia, and the mesencephalon and pons (Fig 5). The mean age of these 10 patients was 53 years 6 months (range, 17 years to 71 years 5 months). Three patients had clinical symptoms suggestive of cerebral vasculitis, and two of these patients had symptoms of paraesthesia, loss of vision, and internuclear ophthalmoplegia consistent with cerebral ischemia and infarct. Three of the 10 patients had coexistent hypertension.
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| DISCUSSION |
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Because cerebral and meningeal involvement by Wegener granulomatosis is rare, with a reported prevalence of 2%8% (1,4,6), there are few reports of small series (7,8) in which the MR imaging appearances were described. Asmus et al (7) reported the MR imaging findings in seven patients: Six patients had small, sometimes multiple, focal areas of increased signal intensity in the white matter on T2-weighted images, and one had an infarct. Provenzale and Allen (8) reported the computed tomographic (two patients) and MR imaging (five patients) findings in seven patients, which included dural thickening and contrast enhancement in three patients, infarcts in two, areas of high signal intensity in the white matter on T2-weighted MR images in two, and abnormal high signal intensity in the brainstem on T2-weighted MR images in two. Direct intracranial spread from nasal, paranasal, or orbital disease or remote, discrete granulomatous lesions in brain parenchyma were not reported in either series.
Remote granulomatous involvement of the meninges in Wegener granulomatosis is rare (46,10). At postmortem examination in one of 104 patients in Drachman's review (5), meningeal involvement by a necrotic and granulomatous process was observed. Nishino et al (6,10) reported that only one of 324 patients with Wegener granulomatosis had thickening and enhancement of the right tentorium cerebelli, which caused multiple cranial neuropathies and severe headaches. None of 85 patients described by Fauci et al (4) had meningeal involvement with Wegener granulomatosis. In our series, the typical MR imaging appearance was that of bilateral diffuse symmetric linear dural thickening and enhancement. Similar findings were described by Provenzale and Allen (8) in three patients, although focal and nodular thickening have also been previously reported (11). Large areas of high signal intensity in the white matter underlying thickened meninges on T2-weighted images have been previously noted (11,12) but were not present in any of the patients in our series.
One patient in our series had diffuse dural thickening and enhancement both intracranially and overlying the thoracic cord. To our knowledge, such MR imaging findings have not previously been reported. There is one previous report (10) of dural thickening overlying the thoracic cord in a case of Wegener granulomatosis, and this resulted in a subacute myelopathy. There was no evidence of myelopathy in the patient in our series.
One patient had leptomeningeal thickening and enhancement overlying the sulci in addition to dural enhancement. To our knowledge, this radiologic finding has not previously been reported, although thickening, fibrosis, and numerous granulomas that often surrounded and involved blood vessels, as seen at histologic examination of the pia-arachnoid, have been reported (11).
The differential diagnosis for diffuse symmetric linear meningeal thickening is broad and includes neurosarcoid, primary dural tumors such as lymphoma and meningioma, metastases, infectious meningitis, neurosyphilis, and hypertrophic cranial pachymeningitis. In neurosarcoid, the pia is involved more frequently than the dura (13). Clinical evaluation and laboratory and radiologic investigations help the radiologist determine the most likely diagnosis, although biopsy may be necessary for confirmation.
Direct intracranial invasion from adjacent extracranial disease has been reported (5,14) to be the most common means by which the central nervous system is involved with Wegener granulomatosis. There was extensive nasal, paranasal, or orbital disease in all five patients in our series who had evidence of direct spread. Two patients showed a poor response to chemotherapy at these sites, and one patient had refused treatment for 45 years, which resulted in advanced disease.
The ability to acquire multiplanar images without irradiating the eyes makes MR imaging an excellent modality for demonstration of subtle intracranial spread from nasal, paranasal, or orbital disease. Because thickened dura can be difficult to differentiate from cerebrospinal fluid on T2-weighted images, we advocate the use of fat-suppressed T1-weighted MR imaging with gadolinium enhancement when direct spread is suspected.
Vasculitis most frequently affects the peripheral nervous system, causing mononeuritis multiplex or polyneuritis; it involves the brain or meninges in 0%6% of patients, causing intracerebral hemorrhage, subarachnoid hemorrhage, and cerebral arterial or venous thrombosis (46). These hemorrhagic complications are thought to be secondary to weakening of blood vessel walls by means of an inflammatory vasculitis, resulting in vessel rupture and bleeding. Four patients in our series had symptoms suggestive of vasculitis, such as altered consciousness or altered affect, or symptoms suggestive of ischemic episodes, such as paraesthesia, blackouts, or internuclear ophthalmoplegia. In three of these patients, nonspecific areas of high signal intensity were seen in the white matter on intermediate-weighted and T2-weighted MR images, and two of these patients had infarcts. There are several other possible causes of infarct in cases of Wegener granulomatosis: arterial occlusion secondary to a granulomatous mass that extends from nasal or paranasal sites into the skull base (15), emboli from marantic endocarditis (8), infarct secondary to renal failureinduced hypertension, and other causes unrelated to Wegener granulomatosis.
Remote granulomatous lesions in brain parenchyma are the least common form of central nervous system involvement with Wegener granulomatosis (5), although there have been a few reported cases (1618). Patients may present with seizures, and the lesions may be single or multiple (17,18). Homogeneous and ring enhancement have been demonstrated, and the lesions have high signal intensity on T2-weighted MR images and have been shown to either decrease in size or disappear with treatment (17). Cerebral granulomas have been found to be dark brown, scarred, indurated, and poorly demarcated at surgery and to contain plasma cells, lymphocytes, histiocytes, and giant cells at histologic examination (18).
Multiple nonspecific lesions with increased signal intensity on intermediate-weighted and T2-weighted MR images are seen in the white matter in many conditions, including postinfectious encephalitis, viral infections, sarcoidosis, multiple sclerosis, Behçet syndrome, and the leukodystrophies, and are commonly seen in the elderly. Although there was possible coexistent vasculitis in three of the 10 patients with such lesions in our series, the exact etiology in relation to Wegener granulomatosis was unclear. Similar white matter lesions in cases of Wegener granulomatosis have also been reported by Provenzale and Allen (8) and Asmus et al (7). Asmus et al reported that these areas represented areas of microinfarct, and Drachman (5) reported the postmortem examination finding of small (<4 x 6-mm) areas of infarct in the thalamus, cortex, mesencephalon, pons, and subcortical white matter in a patient with cerebral vasculitis secondary to Wegener granulomatosis.
The pituitary and infundibulum may be involved in Wegener granulomatosis by means of distant granulomas or direct spread. Four patients in Drachman's series (5) had involvement of the pituitary gland due to direct extension from nasal, paranasal, or orbital disease that caused diabetes insipidus. Czarnecki and Spickler (19) reported a case of diabetes insipidus and hyperprolactinemia; this was probably secondary to remote granulomatous involvement with Wegener granulomatosis because there was no evidence of direct extension from extracranial disease. MR imaging demonstrated a sellar mass, absence of the posterior pituitary high-signal-intensity spot, and thickening and enhancement of the infundibulum, with almost complete resolution of findings at repeat imaging performed 2 months after treatment with high-dose steroid therapy (19). In the two patients in our series with diffuse enlargement of the pituitary gland and infundibular thickening, it is impossible to be certain whether this represented distal granulomatous involvement with Wegener granulomatosis or direct spread from extensive inflammatory changes in the sphenoid sinus, although the floor of the pituitary fossa appeared to be intact in both patients.
Finally, the exact etiology of brain atrophy in cases of Wegener granulomatosis is unclear, but possible explanations include cerebral vasculitis, drugs used in treatment (eg, steroids), and other unrelated causes such as senile atrophy. Yamashita et al (20) reported the development of cerebral atrophy over 6 months in a patient with cerebral vasculitis secondary to Wegener granulomatosis.
In summary, in patients with cerebral and meningeal involvement with Wegener granulomatosis, there is a wide spectrum of MR imaging findings, which reflect the three means by which the central nervous system can be affected in this disease: vasculitis; direct spread from adjacent disease in the nasal, paranasal, or orbital region; and remote granulomatous lesions. MR imaging, with which it is possible to acquire multiplanar images without radiation, is an excellent modality for demonstration of these abnormalities, especially for evaluation for direct spread to the meninges from orbital, nasal, or paranasal disease.
| Footnotes |
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| References |
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