Syringobulbia associated with posterior fossa meningioma: a review of the literature

Upper end of the central canal of the human spinal cord: Quantitative anatomical study and 3D modeling

The upper end of the central canal of the human spinal cord has been repeatedly implicated in the pathogenesis of various diseases, yet its precise normal position in the medulla oblongata and upper cervical spinal cord remains unclear. The purpose of this study is to describe the anatomy of the upper end of the central canal with quantitative measurements and a three-dimensional (3D) model. Seven formalin-embalmed human brainstems were included, and the central canal was identified in serial axial histological sections using epithelial membrane antigen antibody staining. Measurements included the distances between the central canal (CC) and the anterior medullary fissure (AMF) and the posterior medullary sulcus (PMS). The surface and perimeter of the CC and the spinal cord were calculated, and its anterior-posterior and maximum lateral lengths were measured for 3D modeling. The upper end of the CC was identified in six specimens, extending from the apertura canalis centralis (ACC) to its final position in the cervical cord. Positioned on the midline, it reaches its final location approximately 15 mm below the obex. No specimen showed canal dilatation, focal stenosis, or evidence of syringomyelia. At 21 mm under the ACC in the cervical cord, the median distance from the CC to the AMF was 3.14 (2.54-3.15) mm and from the CC to the PMS was 5.19 (4.52-5.43) mm, with a progressive shift from the posterior limit to the anterior third of the cervical spinal cord. The median area of the CC was consistently less than 0.1 mm2. The upper end of the CC originates at the ACC, in the posterior part of the MO, and reaches its normal position in the anterior third of the cervical spinal cord less than 2 cm below the obex. Establishing the normal position of the upper end of this canal is crucial for understanding its possible involvement in cranio-cervical junction pathologies.

Posterior Cranial Fossa Meningioma Causing Tonsillar Herniation and Giant Cervicothoracic Syringomyelia: Case Report and Review of Literature

Syringomyelia is a fluid-filled cyst within the spinal cord and is usually associated with conditions that obstruct the cerebrospinal fluid (CSF) (flow at the foramen magnum or spinal levels such as Chiari malformations, arachnoiditis, and basilar invaginations). Very rarely, posterior cranial fossa tumors can lead to tonsillar herniation and secondary syringomyelia. There are only nine reported cases in the literature. We report a rare case of a 56-year-old female with posterior cranial meningioma and secondary syringomyelia, admitted with headache, nausea, vomiting, and ataxic gait. Magnetic resonance imaging (MRI) demonstrated a large posterior fossa lesion causing early ventriculomegaly and a giant cervicothoracic syrinx within the upper spinal cord extending from the hindbrain inferiorly to the level of T8. She underwent a posterior fossa craniectomy with left C1 hemilaminectomy and complete excision of the tumor. In 6 months following her procedure, an MRI scan showed a significant reduction in the caliber of the syringomyelia throughout its length, and there was a significant improvement in symptoms. Although the pathophysiology of syrinx formation is still poorly understood, the alteration of CSF dynamic flow has been implicated. A common unifying cause appears to be increased transcranial difference in intracranial pressure across the foramen magnum causing tonsillar herniation, irrespective of location in the posterior fossa. With high syrinx pressure, mechanical stress-induced structural change of the spinal cord occurs, allowing the persistence and progression of the syrinx in the spinal cord. Syringomyelia appears to be resolved partially or completely after craniotomy and excision of the posterior fossa lesion.

Iatrogenic syringomyelia postcranial surgery in pediatric patients: systematic review and illustrative case

INTRODUCTION

Iatrogenic syringomyelia has previously been described preoperatively due to space occupying lesions and postoperatively predominantly postspinal CSF drainage. Iatrogenic syringomyelia after cranial surgery is a rare entity. The purpose of this study is to review the current literature for iatrogenic syringomyelia following cranial surgery in children.

MATERIAL AND METHODS

We performed a systematic review in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and meta-analyses) guidelines. Using keywords "de novo," "acquired," "iatrogenic," "postoperative development," and "syringomyelia," we searched PubMed and Scopus databases. We paid particular attention to type of surgery, clinical presentation, management, and outcome. We also present a relevant case report, operated on at John Radcliffe Hospital, Oxford.

RESULTS

The systematic literature review provided 19 cases of iatrogenic syringomyelia postcranial surgery in pediatric patients, in addition to our case report, resulting in a total of 20 cases reported. The patients' mean age at surgery preceding syringomyelia was 8.1 years (range 0.1-17) with a female sex predilection (2.7:1). The mean time of manifestation of the iatrogenic syringomyelia after surgery was 5.7 years (range 0.1-51), and the median time to presentation was 1.7 years. Nine children had surgery for Chiari I malformation before formation of the syrinx, 8 patients underwent shunt surgery, 2 children had intracranial tumor surgery, and 1 patient had lambdoid and sagittal suturectomy for scaphocephaly before developing a syrinx. Surgery after the manifestation of the iatrogenic syrinx resolved the symptoms in 9 patients; in 8 patients, the symptoms partially resolved; and in 1 patient, the symptoms persisted. After surgery addressing the syrinx, it resolved in 5, decreased in size in 10, and remained unchanged in 2 of the patients.

CONCLUSION

Iatrogenic syringomyelia after cranial surgery in pediatric patients occurs mainly after decompressive surgery for Chiari I malformation, shunt surgery, and less frequently following intracranial tumor surgery. Risk factors are postoperative intracranial scarring, shunt malfunction, and mass effect on the foramen magnum. Surgery addressing the iatrogenic syrinx seems to be effective in the majority of the patients in terms of clinical and radiological outcome.