Intrinsic brainstem schwannoma - A rare clinical entity and a histological enigma

Trigeminal Neuropathy Ascribed to a Probable Intrinsic Brainstem Schwannoma of the Pons: A Case Report

Brainstem schwannomas are very rare, only 11 cases have been reported in the literature so far. We report a small intraparenchymal brainstem schwannoma of the pons, in a 37-year-old female patient who presented with a four-day history of numbness at the mandibular division of the trigeminal nerve on the left side of her face. Trigeminal neuralgia was diagnosed, and magnetic resonance imaging (MRI) showed a small intraparenchymal lesion at the level of the nuclei of the left trigeminal nerve present at the junction between the pons and left brachium pontis. A biopsy wasn’t feasible in this small lesion. We discuss the keen radiological features that helped in the presumptive diagnosis of an intrinsic brainstem schwannoma, with both intra- and extra-axial components. Our case had the earliest presentation and the smallest probable brainstem schwannoma reported so far, as well as its unique symptomatology of trigeminal neuralgia related to both the nucleus and the nerve of the fifth cranial nerve (CN V).

Brainstem intraparenchymal schwannoma with genetic analysis: a case report and literature review

BACKGROUND

Schwannomas are neoplasms that typically arise from the myelin sheath of peripheral nerves and rarely originate within the brain parenchyma. Some case reports present schwannomas arising from the brainstem, but regrowth of the tumor and the efficacy of postoperative irradiation have not been examined. In addition, the genetic background of schwannomas arising from the brainstem has not been investigated.

CASE PRESENTATION

A 21-year-old male presented with diplopia, dysphagia, and left-sided hemiparesis, dysesthesia, and ataxia. Intracranial imaging showed a heterogeneous mass with a cystic lesion in the pontomedullary junction. Since the tumor caused obstructive hydrocephalus, the patient underwent subtotal tumor resection. A histopathologic evaluation aided a diagnosis of brainstem intraparenchymal schwannoma. Gradual postoperative mass regrowth was recognized. Three-dimensional conformal radiotherapy was performed on the residual mass and surgical cavity. No tumor regrowth was observed 4 years after surgery. To investigate the genetic background of the tumor, target sequences for 36 genes, including NF2, SMARCB1, and LZTR1, and microsatellite analysis for loss of 22q did not show any somatic variants or 22q loss.

CONCLUSIONS

We suggest that brainstem schwannomas might differ from conventional schwannomas in their genetic background.

Intramedullary schwannoma of cervicomedullary junction: A case report

BACKGROUND

Intramedullary schwannomas of brain stem and spinal cord are extremely rare. In almost all cases, homogeneous, asymmetrical or circular intensive gadolinium enhancement has been demonstrated. However, no cases reported previously with minimal contrast enhancement in cervicomedullary junction.

CASE DESCRIPTION

A 38-year old man presented with a one-month history of constant, radiative right shoulder and arm pain. There was no pathological finding in his neurological examination. Also, physical evidence or family history of neurofibromatosis was not found. Magnetic resonance imaging of brain and cervical spine showed intramedullary, solid-cystic lesion localized in the cervicomedullary junction with unobvious gadolinium enhancement. The mass was gross totally resected through a sub-occipital craniotomy via midline approach. Postoperative pathological examination confirmed diagnosis of schwannoma. No changes were detected in the neurological examination of the patient after the operation.

CONCLUSIONS

There are 3 previously reported intramedullary schwannomas of the cervicomedullary junction in the literature. To the best of our knowledge, this is the first case of unobvious contrast enhancing intramedullary schwannoma of the cervicomedullary junction. The possibility of schwannoma should not be excluded when a mass with slight contrast enhancement is detected in the intramedullary region of the cervicomedullary junction.