Elsevier

World Neurosurgery

Volume 98, February 2017, Pages 873.e1-873.e7
World Neurosurgery

Case Report
Intra- and Extramedullary Dumbbell-Shaped Schwannoma of the Medulla Oblongata: A Case Report and Review of the Literature

https://doi.org/10.1016/j.wneu.2016.11.126Get rights and content

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.

Case Description

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.

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.

References (35)

  • M.T. Zagardo et al.

    Radiologic and pathologic findings of intracerebral schwannoma

    AJNR Am J Neuroradiol

    (1998)
  • M. Tanabe et al.

    Brainstem schwannoma–case report

    Neurol Med Chir (Tokyo)

    (1996)
  • B. Prakash et al.

    Schwannoma of the brain stem: case report

    J Neurosurg

    (1980)
  • R.A. Solomon et al.

    Intramedullary melanotic schwannoma of the cervicomedullary junction

    Neurosurgery

    (1987)
  • J. Aryanpur et al.

    Schwannoma of the medulla oblongata. Case report

    J Neurosurg

    (1988)
  • D. Ladouceur et al.

    Cystic schwannoma of the brainstem

    Can J Neurol Sci

    (1989)
  • V. Sharma et al.

    Schwannoma of the medulla oblongata

    Br J Neurosurg

    (1993)
  • Cited by (7)

    • Intramedullary Schwannoma of Cervical Spinal Cord Presenting Inconspicuous Enhancement with Gadolinium

      2019, World Neurosurgery
      Citation Excerpt :

      In the central type, the tumor may originate from Schwann cells associated with the perivascular nerve plexus, ectopia, aberrant nerve fibers, or multipotential mesenchymal cells.12 Tumors that arise posteriorly or posterolaterally may be explained by the dorsal root entry zone theory.11 Thus it is generally believed that the origin of intramedullary schwannomas in different locations differ from each other.

    • Isolated Pediatric Intramedullary Schwannoma: Case Report and Review of Literature

      2018, World Neurosurgery
      Citation Excerpt :

      Accordingly, many hypotheses have been formulated over their origin. It has been pointed out that the small peripheral nerves, surrounding intraspinal vessels, may represent a source for schwannoma origin.2,4 Also, some authors have suggested that IM schwannoma may be related to neural crest cells' dislocation into the parenchyma during the embryogenesis.4

    View all citing articles on Scopus

    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).

    View full text