Surgical consideration of the intraspinal component in extradural dumbbell tumors

The dumbbell tumor is considered a distinct group of tumors of the spinal nerve sheath owing to its intriguing clinical and radiological characteristics. More than half of dumbbell tumors are completely restricted to the extradural space, although preoperative MRI in some cases suggests the presence of intradural/extradural tumors. The aim of this retrospective investigation is to elucidate the clinical features and to suggest the surgical strategy to reduce the operating time and prevent additional complications in extradural type.

The medical records and radiological studies of 7 consecutive cases (4 male, 3 female, mean age 40.4 years) who underwent removal of the intraspinal component of their extradural dumbbell tumors between January 1996 and December 2005 were analyzed. Diagnosis and preoperative evaluation were performed with MRI and myelogram/CTs.

The relationship of the tumor mass to dural sac in preoperative MRIs was so indistinct as to suggest an intradural mass in 5 cases. We found that extradural portion was covered with an attenuated dura and that the dural ring was invaginated into the intradural portion in these cases. Therefore, the author began with the epidural removal of the intraspinal and extraspinal component, followed by carefully extracting the intradural-like mass.

In conclusion, we suggest that invagination of the dural ring is the anatomical feature that may be confused with an intradural/extradural tumor during operations for extradural dumbbell tumors. Initial epidural mass removal, extraction of intradural/extradural tumors subsequent to dural opening, and affirmation of presence of intradural tumor remnant could save time during dumbbell tumor surgery.