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ANNA-1—Induced Encephalitis Associated with Noninvasive Thymoma

Lansing Radiology Associates, Sparrow Health System, Lansing, MI 48912
Michigan State University, East Lansing, MI 48824

A 34-year-old woman presented with leg paresthesias and subsequently developed focal seizures and nearly fixed pupils. An MR imaging examination of the patient's brain revealed multiple gray matter lesions as hyperintense foci on T2-weighted fast spin-echo and fluid-attentuation inversion recovery (FLAIR) images (Figs. 1A,1B,1C). No enhancement of the lesions occurred after the administration of gadolinium, and none of the lesions revealed a mass effect. Abnormal findings were most pronounced in regions of the temporal lobes, primarily in the limbic cortex, but were also seen in the frontal and occipital lobes. A chest radiograph and enhanced chest CT scan (Fig. 1D) revealed an anterior mediastinal mass. Results of a test for the ANNA-1 (type 1 antineuronal nuclear antibody, or anti-Hu antibody) were positive. A thoracotomy was performed, a typical noninvasive thymoma was removed, and the patient's symptoms improved. Findings of follow-up brain MR imaging 2 months later were normal, showing resolution of the brain lesions.

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —34-year-old woman who presented with diverse neurologic symptoms. Axial T2-weighted fast spin-echo MR image shows hyperintense lesions (arrows) distributed along insular cortex of right temporal lobe with dominant lesion (arrowhead) involving left temporal lobe.

View larger version (130K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —34-year-old woman who presented with diverse neurologic symptoms. Axial fluid-attenuated inversion recovery (FLAIR) image obtained at same level as A more clearly depicts dominant left temporal lesion (arrowhead) and lesions (arrows) along right insular cortex.

View larger version (136K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —34-year-old woman who presented with diverse neurologic symptoms. Axial FLAIR image reveals right occipital lesion (arrow). None of the lesions enhanced with administration of gadolinium.

View larger version (118K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1D. —34-year-old woman who presented with diverse neurologic symptoms. Enhanced CT scan of chest shows well-circumscribed soft-tissue mass (arrow) located in anterior mediastinum that proved to be noninvasive thymoma.

ANNA-1 is a marker of paraneoplastic neurologic diseases and is commonly associated with small cell lung carcinoma. The presence of the marker is sometimes caused by other malignancies, such as invasive thymoma, and is rarely associated with benign noninvasive thymoma [1,2,3]. The most common clinical manifestations related to ANNA-1 include peripheral neuropathy, cerebellar dysfunction, limbic encephalitis (including focal seizures), cranial neuropathy (typically affecting ocular motor functioning), and gastrointestinal symptoms (gut dysmotility). Myopathy and Lambert-Eaton syndrome are seen less frequently [2, 4]. The MR imaging appearance of ANNA-1 paraneoplastic syndrome varies. In cases in which ANNA-1 is associated with the clinical syndrome of limbic encephalitis, brain MR imaging has been reported to reveal abnormalities—typically involving only the temporal lobes—in approximately half of the patients imaged [5]. Enhancement occurs in up to 20% of patients, and extratemporal involvement is seen in fewer than 10% of patients. Biopsy of the cortical lesions has shown perivascular and parenchymal inflammatory cell infiltrates with neuronal loss, with no evidence of neoplasia [6].

Although the appearance of ANNA-1—induced encephalitis on MR imaging is not pathognomonic, findings of cortical-based non-enhancing lesions, most pronounced in the temporal lobes, are unique. A search for an ANNA-1-—associated malignancy, particularly in the mediastinum, should be considered. Unfortunately, the most common cause of the ANNA-1 marker is small cell lung carcinoma, which has a poor prognosis. In rare cases such as in this patient, a curable lesion, such as thymoma, is the source of the encephalitis.

References

1. Lucchinetti CF, Kimmel DW, Lennon VA. Paraneoplastic and oncologic profiles of patients seropositive for type 1 antineuronal nuclear autoantibodies. Neurology 1998;50:652 -657[Abstract/Free Full Text]
2. Evoli A, Lo Monaco M, Marra R, Lino MM, Batocchi AP, Tonali PA. Multiple paraneoplastic diseases associated with thymoma. Neuromuscul Disord 1999;9:601 -603[Medline]
3. Vernino S, Eggenberger E, Rogers L, Lennon VA. Paraneoplastic neurological autoimmunity associated with ANNA-1 autoantibody and thymoma. Neurology 2002 (in press)
4. Hinton RC. Paraneoplastic neurologic syndromes. Hematol Oncol Clin North Am 1996;10:909 -926[Medline]
5. Gultekin SH, Rosenfeld MR, Voltz R, Eichen J, Posner JB, Dalmau J. Paraneoplastic limbic encephalitis: neurological symptoms—immunologic findings and tumor association in 50 patients. Brain 2000;123:1481 -1491[Abstract/Free Full Text]
6. Alamowitch S, Graus F, René R, Bescansa E, Delattre JY. Limbic encephalitis and small cell lung cancer: clinical and immunologic features. Brain 1997;120:923 -928[Abstract/Free Full Text]

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This Article Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Buetow, M. P. Articles by Eggenberger, E. Search for Related Content PubMed Articles by Buetow, M. P. Articles by Eggenberger, E. Social Bookmarking                      What's this?