An anatomical study of the foramen of Monro: implications in management of pineal tumors presenting with hydrocephalus.
BACKGROUND: For pineal tumors presenting with hydrocephalus, simultaneous endoscopic third ventriculostomy (ETV) and tumor biopsy is commonly used as the initial step in management. To analyze the restriction which the foramen of Monro poses to this procedure, one must start with a detailed description of the microsurgical anatomy of the foramen in living subjects. However, the orientation and shape of the foramen of Monro make this description difficult with conventional imaging techniques.
METHOD: Virtual reality technology was applied on MRIs on living subject without hydrocephalus, as well as patients with hydrocephalus, to generate precise anatomical models with sub-millimeter accuracy. The morphometry of the foramen of Monro was studied in each group. In addition, displacement of the margins of the foramen was studied in detail for simultaneous ETV and pineal tumor biopsy through a single burr hole.
RESULTS: In 30 normal subjects, the foramen of Monro had oval-shaped openings averaging 5.23 mm
CONCLUSIONS: The foramen of Monro is an oval-shaped cylinder that changes in size and orientation in the hydrocephalic patient. If universally applied to all patients regardless of foramen and tumor size, ETV/biopsy can displace structures around the Foramen of Monro up to 1 cm, which can potentially lead to neurological damage. Careful pre-operative assessment is critical to determine if a single burr hole approach is safe.
Published In/Presented At
Jean, W. C., Tai, A. X., Hogan, E., Herur-Raman, A., Felbaum, D. R., Leonardo, J., & Syed, H. R. (2019). An anatomical study of the foramen of Monro: implications in management of pineal tumors presenting with hydrocephalus. Acta neurochirurgica, 161(5), 975–983. https://doi.org/10.1007/s00701-019-03887-4
Medicine and Health Sciences
Department of Surgery