10-year-old girl with back pain, myelopathy and neuropathy due to thoracic spine mass
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A 10-year-old girl with no significant past medical history presented to the ED for evaluation of 6 months of progressively worsening back pain.
During the preceding month, she began experiencing worsening numbness and weakness to her lower extremities resulting in difficulty ambulating and frequent falls. She also endorsed worsening constipation but did not have saddle anesthesia. She underwent an MRI of her spine, which demonstrated a large thoracic spine mass.
On exam, she was noted to have bilaterally diminished strength in hip flexion, knee extension, ankle dorsiflexion and hallux extension, and diminished sensation to light touch in the L2-S1 nerve distributions. MRI on this presentation demonstrated a large multiloculated cystic lesion centered at T10 with extension into T9 and T11 and involvement of posterior soft tissue structures and paraspinal soft tissue, as well as associated central stenosis with fluid-fluid levels (Figures 1a and 1b). CT spine demonstrated an osteolytic lesion centered at T10 (Figure 1c).
Source: Dhruv Shankar, MD; Pooja Prabhakar, MD; Scott Yang, MD;
She was admitted to the ICU on day of presentation for neuromonitoring and administration of dexamethasone. An open incisional biopsy was performed that same day and specimens were sent to pathology. She was kept on bedrest for the next 8 days pending results. However, her neurological exam gradually declined during this period with increasing weakness and diminished sensation to her lower extremities, prompting the team to intervene more urgently.
What are the best next steps in management of this patient?
See answer below.
Posterior spinal decompression and tumor resection with instrumentation and fusion
There were several challenges in managing this patient’s thoracic spine mass, namely the rapid growth of the mass resulting in progressive myelopathy secondary to spinal cord compression, as well as the lack of final pathology results at the time of this rapid worsening of symptoms. In the absence of significant neurologic decline, it would be prudent to wait on pathology findings before planning any further intervention. A malignant lesion may require medical treatment prior to surgical resection, whereas an aggressive benign lesion could proceed directly to resection. If the mass were found to be an aneurysmal bone cyst, sclerotherapy could be a viable nonoperative treatment.
However, given the high concern for progressive loss of neurological function in this patient, more urgent surgical intervention was warranted. If the pathology were to come back as osteosarcoma or another malignancy, neoadjuvant chemotherapy may not be able to shrink the tumor in time to prevent further loss of neurological function. Therefore, surgical resection of the tumor was indicated to reliably decompress the spinal cord and improve neurological function.
Surgical resection presents several risks for this patient including neurologic injury, dural tear, bleeding, hardware-associated infection and mortality in the perioperative setting. In addition, true en bloc resection or margin-free resection may not be possible given the proximity of the mass to the spinal cord and the extent of posterior involvement. The decision was made to proceed with T8-T12 and possible L1 posterior decompression with instrumentation and fusion. The day prior to surgery, interventional radiology-guided embolization of the mass was performed to reduce the risk of severe intraoperative bleeding.
Surgical procedure
The patient was placed in supine for administration of general anesthesia. Baseline preoperative neuromonitoring was performed which confirmed no motor function to the bilateral lower extremities in all muscle groups. She was then flipped to the prone position, and her back was prepped in the usual sterile fashion. Fluoroscopy was used to mark the appropriate levels and a midline incision was made incorporating her previous biopsy incision, with care taken not to cut into the soft tissue overlying the mass at the level of T10. The dissection commenced from the levels of T11-L1 and continued in subperiosteal fashion to expose the posterior elements. Levels T8/9 were incised, dissected down to the posterior elements and retracted in a similar fashion. Once bony exposure was complete, a BoneScalpel (Bioventus Surgical) ultrasonic instrument was used to perform facetectomies at T8/9, T11/12 and T12-L1. Pedicle screws, all 4.35 mm x 35 mm, were placed bilaterally at T8/9, T12 and L1.
Resection of the tumor was performed starting with a laminectomy at T11 to identify normal dura. Once this plane was identified, the dissection proceeded superiorly to separate the tumor from the posterior dura. The tumor was able to be excised from T11 to T9 without dural invasion using a combination of bone rongeurs, pituitary rongeurs and curettes. The laminectomy was continued up to T9. At the level of T10, any visible tumor was resected along the left and right pedicles all the way to the vertebral body, and multiple specimens were sent to pathology. At T11, all posterior elements (laminae, transverse processes and facets bilaterally), the right pedicle and most of the left pedicle were removed. Pedicle screws were placed bilaterally into the T11 vertebral body. A 5.5-mm titanium rod was placed on the left side and locked into the pedicle screws before proceeding with further anterior column resection.
A partial corpectomy of the T10 vertebral body was performed through a posterolateral approach. The T10 nerve roots were tied off bilaterally to access the vertebral body in its entirety. All visible tumor was resected from the vertebral body and anterior to the spinal cord using bone rongeurs. Egg-shelling and decancellation of the vertebral body was performed with a burr from the right side via posterolateral approach and left side via transpedicular approach. Once the spinal cord was confirmed to be adequately decompressed circumferentially, discectomies were performed at T9/10 and T10/11.
The resection cavity was carefully inspected and additional bone and surrounding soft tissue that was abnormal in appearance was debrided. After confirming resection of all visible pathologic tissue, a 14-mm expandable interbody fusion cage (DePuy Synthes) was placed into the corpectomy space and expanded to approximately 25 mm. A 5.5-mm titanium rod was placed on the right side and the pedicle screws were used to compress across the cage. Satisfactory pedicle screw and cage placement were confirmed fluoroscopically.
Prior to closure, the posterior elements were decorticated with a drill and cancellous autograft bone was placed followed by 1g of vancomycin powder. The fascia and skin were closed in layers. The patient was flipped supine and transferred back to the ICU in stable condition.
Follow-up
Following surgery, she was placed into a thoracic-lumbar-sacral orthosis brace to be worn while out of bed and upright for at least 3 months after surgery. She exhibited gradual improvement in her neurological exam starting on postoperative day 1 with increasing strength to her bilateral lower extremities. On postoperative day 6, she was transferred to the inpatient rehabilitation medicine unit.
At 6-week follow-up, she was noted to have full motor strength in both lower extremities and was ambulating without a walker, but still endorsed diminished sensation in the L2-S1 distributions. Upright spine radiographs showed no evidence of change in alignment of the interbody cage, pedicle screws or spine (Figure 2). By this time, final pathology results were available and had identified her mass as an aneurysmal bone cyst.
Her brace was discontinued at 3-month follow-up. At 6-month follow-up, she reported that her lower extremity sensation had normalized and denied any new or persistent neurological symptoms. Repeat radiographs confirmed intact hardware and maintained alignment (Figure 3). She was permitted to return to select noncontact sports, with additional exclusion of tumbling, cheer and gymnastics.
Discussion
Aneurysmal bone cyst is an expansile, multiloculated lesion that contains multiple blood-filled cystic spaces surrounded by thin cortical bone. Aneurysmal bone cysts are non-neoplastic and benign but can be locally aggressive and commonly involve the posterior elements of the thoracic and lumbar vertebrae. They comprise about 1.4% of all primary bone tumors and 15% of all primary spine tumors and are more common among the pediatric population, with more than two-thirds of all cases presenting in patients younger than 20 years. Though the most common presenting symptom is pain at the site of the lesion, neurological symptoms may be the initial complaint in about 70% of cases. Aneurysmal bone cysts appear as osteolytic lesions on radiographs and may contain fluid-fluid levels on CT and MRI.
Management of spinal aneurysmal bone cysts is a controversial topic given the absence of treatment guidelines. Nonoperative modalities include arterial embolization, radiation therapy, sclerotherapy and intralesional injection of steroid and calcitonin. Operative modalities include curettage with or without bone grafting, complete excision or partial excision. Complete en bloc resection confers the lowest risk of recurrence and is the treatment of choice for patients who are good surgical candidates presenting with progressive neurological deficits, but incomplete resection has been associated with a 50% to 60% rate of disease progression. Preoperative arterial embolization is a useful adjunct to surgical treatment as it can decrease the vascularity of the lesion and reduce intraoperative blood loss. Spinal reconstruction and stabilization, such as with interbody cages and posterior instrumentation, is indicated in patients requiring extensive tumor resection that can result in instability and/or deformity.
Key points:
- Aneurysmal bone cysts of the spine can be locally aggressive and present significant risk of spinal cord compression, so urgent decompression is indicated in the setting of worsening neurological function, even when definitive pathology results are not available.
- Preoperative arterial embolization may help to reduce intraoperative bleeding given the vascularity of aneurysmal bone cyst lesions.
- References:
- Aljoghaiman MS, et al. Interdiscip Neurosurg. 2019;doi:10.1016/j.inat.2018.11.004.
- Jaiswal A, et al. BMJ Case Rep. 2013;doi:10.1136/bcr-2013.009265.
- Liu K, et al. Neurosurg Focus. 2003;doi:10.3171/foc.2003.15.5.4.
- Zilei M, et al. Eur Spine J. 2013;doi:10.1007/s00586-012-2510-x.
- For more information:
- John Bartoletta, MD; Pooja Prabhakar, MD; Dhruv Shankar, MD; and Lara Shefelbine, MD, can be reached at the department of orthopaedics and sports medicine at the University of Washington Medical Center. Scott Yang, MD, can be reached at the department of orthopedic surgery at Seattle Children’s Hospital. Bartoletta’s email: jjbarto@uw.edu. Prabhakar’s email: prabhaka@uw.edu. Shankar’s email: shankd02@uw.edu. Shefelbine’s email: shefel@uw.edu.
- Edited by Andrew Bi, MD, and Pooja Prabhakar, MD. Bi is a chief resident in the department of orthopedic surgery at NYU Langone. He will pursue a fellowship in sports medicine at Rush University Medical center following residency completion. Prabhakar is a chief resident in the department of orthopaedic surgery at the University of Washington. She will pursue a fellowship in foot and ankle surgery at Baylor University Medical Center following residency completion. For more information on submitting Orthopedics Today Grand Rounds cases, please email orthopedics@healio.com.
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