Combined microneurosurgical and thoracoscopic resection for thoracic spine dumbbell tumors

WANG Zhen-yu, LIANG Zheng, LIU Bin, CHENG Xiao-dong, ZHANG Jia

Dumbbell tumors have both intraspinal and anterior paraspinal components connected through an intervertebral foramen. Most of these tumors are neurogenic and include schwannomas, neurofibromas, ganglioneuromas and neuroblastomas.¹ Fortunately, more than 90% of these tumors are benign.² Dumbbell tumors of the thoracic spine are particularly difficult to expose and remove by virtue of their location and relationship with vital structures of the thoracic cavity. The traditional surgical approach for removing these tumors has been using either combined anterior thoracotomy and posterior neurosurgical procedures or the lateral extracavitary approach.^3-5 We present our experience with resection of three dumbbell tumors with a combined microneurosurgical and thoracoscopic procedures in a single stage.

Patients

Between May 2002 and September 2007, three patients with thoracic spine dumbbell tumors were treated with combined laminectomy and thoracoscopic surgery in our hospital. Our patients consisted of one man and two women. The age range was 39–71 years (mean age, 44.9 years). The duration of preoperative symptoms ranged from 6 to 32 months (mean duration, 18 months). All patients presented with thoracic back pain, dyspnea, cough, weakness and numbness of the lower extremity. Preoperatively, all patients had computed tomographic (CT) and magnetic resonance imaging (MRI) scans to localize and define the nature of the tumor. A particular effort was made to identify dumbbell tumors preoperatively to enable these tumors to be resected in a single stage combined operation. Preoperative MRI scans enabled identification of tumor extension into the spinal canal, the presence of cystic components within the tumor and the relationship of the tumor to vital structures within the chest cavity. CT and MRI revealed that the tumors were located at the T4–T5 level in two patients and at the T6–T7 level in one patient. These tumors extended to the spinal canal and paravertebral through an enlarged intervertebral foramen. Sizes of the tumors varied from 3 to 6 cm. The spinal cord was compressed and displaced (Figure 1).

Surgical procedure

Under general anesthesia the patients were intubated with a double-lumen endotracheal tube and were placed in a lateral position. A posterior midline incision was made. The muscles were retracted off the spine and laminae bilaterally at the selected levels and self-retaining retractors were placed. At the selected level a hemilaminectomy of two adjacent laminae of the tumor was performed, carrying the bone removal laterally to the foramen on the appropriate side. The extradural tumor was removed, and the root was amputated in a preganglionic location (in the thoracic spine, T4–T11, the associated nerve root can be generally sacrificed without significant deficit) using an operating microscope and cavitron ultrasonic surgical aspirator. The dura was opened when the tumor was intradural. This component of the tumor was removed. The dura was primarily closed and the root and root sleeve were tied off if feasible. The remaining tumor with the distal stump of the nerve was pushed into the chest cavity via the enlarged foramen. The intervertebral foramen was then packed with fatty tissue and fibrin glue to seal the spinal canal from the thoracic cavity. The posterior wound was then closed in routine fashion.

After the neurosurgical procedure, a thoracoscopic resection of the thoracic part of the tumor was performed. Three thoracoscopic ports were introduced dependent on the location of the tumors alone the thoracic spine. The ports include an endoscopic port, a working port and a suction port. The tumor was found to be egg-shaped, smooth surfaced and positioned lateral to the thoracic vertebrae. No adhesion or invasion to adjacent structures was found. The parietal pleura was carefully excised around the remaining tumors. The intercostal vessels were safely separated from the tumor or clipped. The tumor was then dissected from the thoracic wall laterally to medially toward to the orifice of the intervertebral foramen. The lesion continued to the foramen with a stalk-like structure. After careful dissection of the tumor to the root of the stalk-like structure at the entrance to the intervertebral foramen, the tumor was removed at the foraminal orifice. A chest tube was placed through thoracoscopic port.

Outcome and follow-up data

Three dumbbell tumors of the thoracic spine were resected with combined microneurosurgical and thoracoscopic surgery, with no conversions to open thoracotomy. Gross total resection was achieved in all cases (Figure 2). The operative time was 4–6 hours. The estimated blood loss ranged from 100 to 300 ml. The hospital stay was 12–14 days. There were no operative complications. The postoperative period was uneventful in all three patients. The back pain disappear and neurological deficit symptoms were improved after operation. Final pathology included two schwannomas and one angiolipoma. Patients' follow-up MRI scans ranged from 10 to 36 months. No patients showed signs of tumor regrowth at the time of follow-up visit.

DISCUSSION

Tumors with both spinal canal and paravertebral components that communicate via an intravertebral foramen are defined as dumbbell tumors. The majority of these tumors are neurogenic in origin arising from the nerve sheath, autonomic ganglia or paraganglionic system. Perineural or direct proximal extension of tumors arising in the anterior paraspinal region or adjacent visceral structures (e.g., lung, kidney) may also gain spinal canal entrance via an intervertebral foramen. These include primary paraspinal sarcomas, hemopoietic neoplasms and primary or secondary pulmonary or renal neoplasms. In these tumors, the spinal canal component usually remains extradural.^5,6

Surgical removal of dumbbell tumors is challenging because of the well-separated intraspinal and anterior paraspinal components, which are connected through an intervertebral foramen. It is generally agreed that it is unsafe to remove a paravertebral tumor, such as a schwannoma, from an anterior approach without first separating it from its attachment to the spinal cord.^3-6 As in our study, the intraspinal and foraminal tumor component was removed first by a hemilaminectomy of the thoracic spine. Then, an anterior approach with thoracoscopic surgery is used to remove the paravertebral tumor. It avoided spinal cord injury from retraction.

Previously, dumbbell tumors of the thoracic spine have been removed either through combined anterior thoracotomy and posterior procedures or through a single stage lateral extracavitary approach which may be destabilizing.^3-5 This open approach results in significant postoperative pain, muscle dysfunction and sometimes, long-term pain syndromes.⁷ With advances in endoscope technology since the early 1990s, thoracoscopic technique is rapidly becoming the procedure of choice for removal of posterior mediastinal tumors.^8,9 Our experience demonstrates that a combined microneurosurgical and thoracoscopic surgery can b