LAUSR

Dear Editor: The concurrence of posterior fossa medulloblastoma and Chiari 1 malformation with syringomyelia in a paediatric patient is extremely rare. At present, the existence of a pathophysiological relationship between these two conditions remains unknown. We report a case of a previously well 9-year-old male who was admitted for progressive symptoms of headache, nausea and vomiting. There was no history of neck pain or dissociated sensory loss. A magnetic resonance imaging (MRI) scan of the brain and spine reported a 4.0 × 4.2 × 5.1 cm intraventricular midline posterior fossa mass associated with obstructive hydrocephalus. Simultaneously, cerebellar tonsillar herniation resulting in crowding of the foramen magnum was observed. There was also a long segment central cord syrinx extending from the level of C2 to T6 vertebral level causing cord expansion (Fig. 1a–c). The patient underwent a posterior fossa decompression, partial removal of C1 arch and removal of the tumour. A thickened, fibrous epidural band was found at the craniocervical junction after paraspinal muscle dissection. This structure was released prior to dura opening. Intradurally, there was congestion of bilateral cerebellar tonsils and caudal herniation via the foramen magnum. The tonsils were surgically shrunk to treat the herniation, allowing adequate space within the foramen magnum. Next, the intra-axial lesion underwent resection. Final histological diagnosis confirmed the lesion to be a medulloblastoma (classic type). Molecular interrogation using NanoString nCounter assay demonstrated the tumour to be a group 4 subtype. (Fig. 2a–c). Post-operatively, the patient was commenced on adjuvant chemo-radiation treatment as per institutional protocol. Medulloblastoma is the most common paediatric brain tumour. Most commonly arising in the posterior fossa, it causes symptoms of raised intracranial pressure and, or cerebellar dysfunction. Conversely, Chiari malformations encompass a broad spectrum of neurodevelopmental disorders, some of which are unlikely to share a common pathophysiology [1]. It is characterized by caudal herniation of the cerebellar tonsils exceeding 5 mm below the foramen magnum. Up to 70% of affected patients have concurrent syringomyelia—cystic cavitation of the spinal cord [2]. There is no universally accepted theory explaining Chiari 1 malformation and its associated anomalies [2]. At present, there are only a small number of reported cases of Chiari 1 malformation with syringomyelia associated with posterior fossa medulloblastoma, as previously summarized by Qi et al. [3]. * Sharon Y. Y. Low [email protected]