Case ReportIntra- and Extramedullary Dumbbell-Shaped Schwannoma of the Medulla Oblongata: A Case Report and Review of the Literature
Introduction
Intraparenchymal schwannomas of the brainstem are extremely rare. Only 16 cases have been reported previously. Several theories have been proposed to explain the intramedullary growth of schwannomas. Mason and Keigher1, 2, 3, 4, 5 first speculated that intramedullary schwannomas (ISs) arise from the region where the nerve roots lose their sheaths on penetrating the pia mater. According to this theory, Wood et al.1 predicted that ISs would contain both intra- and extramedullary portions and would be shaped like a dumbbell. However, none of the reported cases can offer adequate radiologic evidence. A case of dumbbell schwannoma of the brainstem, encountered with both intra- and extramedullary components, is reported in a 40-year-old woman. To our knowledge, no such cases have been reported previously. The radiographic and pathologic characteristics of this lesion are discussed, the natural history of brainstem ISs is better defined, and the relevant literature is reviewed.
Section snippets
History and Examination
A 40-year-old woman presented with a 1-year history of constant, nonradiative cervical pain, accompanied by gradually progressive weakness of the upper extremities and glove distribution numbness. Neurologic examination revealed mild weakness of the stemocleidomastoid and trapezius muscle. Diminished muscle strength (grade 4/5) and hypomyotonia were detected in the right upper extremity. Sensory examination showed decreased light touch, temperature, and pinprick sensation over the entire right
Epidemiology and Clinical Features
Schwann cells are not normally found in the brain or spinal cord parenchyma; therefore, intraparenchymal schwannomas are quite rare. The most common site of it is the spinal cord, followed by the cerebral hemisphere (especially in the frontal and temporal lobes), and other locations, including the sellar and cerebellar regions and the brainstem. Intracranial intraparenchymal schwannomas are more likely to occur in children and young adults before the age of 30 years.6 A reported male
Conclusions
The present brainstem intra- and extramedullary schwannoma with regrowth, which is extremely rare, may play an essential role in reconciling the previous theories and give a new insight into the tumor genesis. The natural history of brainstem ISs is better defined, which may help improving the accuracy of initial diagnosis and selecting proper therapeutic method and timing.
Acknowledgments
The authors are grateful to Gui-Lin Li and Yun Cui for their contributions to the tissue preparation and immunohistochemical support. The authors also thank Xiao-Xu Shi for providing the photomicrographs of the tumors.
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Conflict of interest statement: This work was supported by the Beijing Natural Science Foundation (General Program) (grant number 7152050); the Research Special Fund for Public Welfare Industry of Health (grant number 201402008); and the National High Technology Research and Development Program of China (863 Program) (grant number 2014AA020610).