Revisiting role of Intra-operative ultrasound in Spine surgery for extradural pathologies. Review and clinical usage

Minimally Destabilizing Corridor for Resection of Dumbbell Nerve Sheath Tumors: A Novel Surgical Technique

BACKGROUND AND OBJECTIVES

Current surgical strategies for dumbbell nerve sheath tumors (DNSTs) with cord compression have primarily involved wide spinal exposures with total laminectomy and unilateral facetectomy, often leading to spinal destabilization and requiring fusion, or staged procedures separately addressing the intraspinal and extraforaminal tumor components. This study highlights technical nuances of a novel approach for DNST resection to minimize spinal destabilization and avoid fusion while facilitating safe, single-stage complete resection.

METHODS

A retrospective chart review was conducted on patients undergoing DNST resection. Using unilateral subperiosteal dissection, hemilaminotomy and medial facetectomy procedures are performed. The extradural tumor component is resected, followed by internal decompression of the intradural tumor. A small horizontal incision at the origin of the nerve root sleeve releases the underlying dural stricture, facilitating delivery of the remaining intradural tumor and allowing section of the nerve root of origin. Ultrasonography confirms complete tumor resection and return of cord pulsation, and excludes intradural hemorrhagic complications. The dura is reconstructed using a dural substitute bolstered with fat graft and sealant.

RESULTS

Twelve consecutive patients undergoing this approach from 2014 to 2021 were included. Mean patient age was 53.5 years, and 58.3% were male. Nine tumors were cervical and 3 were lumbar. Five patients presented with myelopathy, 4 with radiculopathy, and 4 with axial pain. Two cases had transient intraoperative neuromonitoring signal changes. Eleven tumors were diagnosed as schwannomas and 1 as neurofibroma. All patients had complete resection of the intraspinal component; 2 had far distal extraforaminal residual. No patient has had recurrence, progression of residual, or signs of spinal instability during follow-up (median 28.5 months, range 6-66 months).

CONCLUSION

This study highlights technical considerations for DNST resection, focusing the approach at the center of the tumor, with minimal bone removal and ligamentous disruption. Intraoperative ultrasound is instrumental in the safety of this approach.

How to Apply Intraoperative Ultrasound when Spinal Trauma Surgery Is Performed in the Lateral Decubitus Position?

OBJECTIVE

At present, intraoperative ultrasound was widely used in spinal surgery. But there have been no reports on the use of intraoperative ultrasound in lateral decubitus position spinal surgery. The authors' research objective was to describe the applications of intraoperative ultrasound in spinal trauma surgery when performed in the lateral decubitus position.

METHODS

Six patients with polytrauma who underwent surgery for spinal trauma between June 2020 and March 2022 and could not be operated on using a posterior approach in the prone position. All six patients underwent surgery in the lateral decubitus position. During surgery, a capsular bag had been designed and surgical field can be filled with normal saline for acoustic coupling, and then ultrasound was used to observe and guide decompression, and assess injuries of the neural elements such as the spinal cord. The data of preoperative and postoperative (12 months) American Spinal Injury Association impairment scale (AIS), follow-up time, operation time, blood loss, ultrasound signal change of spinal cord, ultrasound guide decompression, internal fixation (12 months), and fracture healing(12 months) were collected.

RESULTS

The study included four males and two females whose ages ranged from 19 to 56 years old (41.5 ± 13.06 years old). Follow-up times ranged from 12 to 20 months (14.33 ± 2.75 months). The operation times ranged from 195 to 248 mins (222.16 ± 16.86 mins). The estimated volume of blood loss ranged from 280 to 450 mL (383.33 ± 55.58 mL). The six cases' AIS (preoperative vs. postoperative) were A versus A, C versus D, A versus B, B versus B, B versus C, and B versus C. Intraoperative ultrasound was performed successfully in all patients using our designed method. Intraoperative ultrasound observation revealed varying degrees of changes in spinal cord echo in all patients. Intraoperative ultrasound provided excellent assistance in spinal cord decompression during surgery. The surgery was completed successfully with no surgery-related complications till the last follow-up. At the time of last follow-up (median time of 12 months) satisfactory fracture reduction and good internal fixation was confirmed on postoperative computed tomography scans and radiographs.

CONCLUSIONS

The authors represented the technology of intraoperative ultrasound in spinal trauma surgery when performed in the lateral decubitus position. This technology solves how to apply intraoperative ultrasound in lateral decubitus position.

Case report: High-resolution, intra-operative µDoppler-imaging of spinal cord hemangioblastoma

Surgical resection of spinal cord hemangioblastomas remains a challenging endeavor: the neurosurgeon's aim to reach total tumor resections directly endangers their aim to minimize post-operative neurological deficits. The currently available tools to guide the neurosurgeon's intra-operative decision-making consist mostly of pre-operative imaging techniques such as MRI or MRA, which cannot cater to intra-operative changes in field of view. For a while now, spinal cord surgeons have adopted ultrasound and its submodalities such as Doppler and CEUS as intra-operative techniques, given their many benefits such as real-time feedback, mobility and ease of use. However, for highly vascularized lesions such as hemangioblastomas, which contain up to capillary-level microvasculature, having access to higher-resolution intra-operative vascular imaging could potentially be highly beneficial. µDoppler-imaging is a new imaging modality especially fit for high-resolution hemodynamic imaging. Over the last decade, µDoppler-imaging has emerged as a high-resolution, contrast-free sonography-based technique which relies on High-Frame-Rate (HFR)-ultrasound and subsequent Doppler processing. In contrast to conventional millimeter-scale (Doppler) ultrasound, the µDoppler technique has a higher sensitivity to detect slow flow in the entire field-of-view which allows for unprecedented visualization of blood flow down to sub-millimeter resolution. In contrast to CEUS, µDoppler is able to image high-resolution details continuously, without being contrast bolus-dependent. Previously, our team has demonstrated the use of this technique in the context of functional brain mapping during awake brain tumor resections and surgical resections of cerebral arteriovenous malformations (AVM). However, the application of µDoppler-imaging in the context of the spinal cord has remained restricted to a handful of mostly pre-clinical animal studies. Here we describe the first application of µDoppler-imaging in the case of a patient with two thoracic spinal hemangioblastomas. We demonstrate how µDoppler is able to identify intra-operatively and with high-resolution, hemodynamic features of the lesion. In contrast to pre-operative MRA, µDoppler could identify intralesional vascular details, in real-time during the surgical procedure. Additionally, we show highly detailed post-resection images of physiological human spinal cord anatomy. Finally, we discuss the necessary future steps to push µDoppler to reach actual clinical maturity.