title: Intra- and Extramedullary Dumbbell-Shaped Schwannoma of the Medulla Oblongata: A Case Report and Review of the Literature.
abstract: BACKGROUND
  Brainstem intramedullary schwannomas (ISs) are extremely rare. Various theories have been suggested to explain its origin. It was first speculated that ISs arise from the region where the nerve roots lose their sheaths on penetrating the pia mater. Later, it was further predicted that ISs would contain both intra- and extramedullary parts and would be shaped like a dumbbell. However, no cases reported previously can support this assumption adequately.
  
  
  METHODS
  A 40-year-old woman presented with constant cervical pain, accompanied by progressive weakness of upper extremities and glove distribution numbness. Magnetic resonance imaging of the brain revealed a rare intra- and extramedullary dumbbell-shaped lesion of the medulla oblongata, which was partially removed via a midline suboccipital craniectomy. Histologic and immunohistochemical examinations confirmed the diagnosis of schwannoma. Routine imaging performed 20 months after the initial resection revealed a regrowth of the intramedullary part, which was subsequently partially removed through a far-lateral approach, with symptoms alleviated. At 2-year follow-up, there continued to be no radiologic or clinical evidence of regrowth.
  
  
  CONCLUSIONS
  To date and to our knowledge, there are only 16 reported cases of brainstem ISs, none of which contained both intra- and extramedullary components. We believe this is the first report of dumbbell schwannoma of the medulla oblongata with adequate radiologic evidence. The relevant literature is reviewed, and an assumption has been proposed that dumbbell or surfacing ISs arising near entry zones of sensory nerves, mixed cranial nerves, or ventral root may originate from the aberrant Schwann cells.
authors.affiliation: Department of Neurosurgery, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China; China National Clinical Research Center for Neurological Diseases, Beijing, China; Beijing Key Laboratory of Brain Tumor, Beijing, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Neurosurgery, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China; China National Clinical Research Center for Neurological Diseases, Beijing, China; Beijing Key Laboratory of Brain Tumor, Beijing, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Ni
authors.affiliation: Department of Neurosurgery, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China; China National Clinical Research Center for Neurological Diseases, Beijing, China; Beijing Key Laboratory of Brain Tumor, Beijing, China.
authors.forename: Wei-Ming
authors.initials: WM
authors.lastname: Liu
authors.affiliation: Department of Neurosurgery, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China; China National Clinical Research Center for Neurological Diseases, Beijing, China; Beijing Key Laboratory of Brain Tumor, Beijing, China.
authors.forename: Wang
authors.initials: W
authors.lastname: Jia
authors.affiliation: Department of Neurosurgery, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China; China National Clinical Research Center for Neurological Diseases, Beijing, China; Beijing Key Laboratory of Brain Tumor, Beijing, China. Electronic address: jiaguijun2013@163.com.
authors.forename: Gui-Jun
authors.initials: GJ
authors.lastname: Jia
authors.affiliation: Department of Neurosurgery, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China; China National Clinical Research Center for Neurological Diseases, Beijing, China; Beijing Key Laboratory of Brain Tumor, Beijing, China. Electronic address: zhangjunting2003@aliyun.com.
authors.forename: Jun-Ting
authors.initials: JT
authors.lastname: Zhang
mesh_terms: D000328:Adult; D018952:Antigens, CD34 / Q000378:metabolism; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008526:Medulla Oblongata / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D009442:Neurilemmoma / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D009418:S100 Proteins / Q000378:metabolism
chemical_list: D018952:Antigens, CD34; D009418:S100 Proteins
keywords: Brainstem tumor; Dumbbell shaped; Medulla oblongata; Schwannoma