Neurosurgery Blog

J Neurosurg Spine 15:610–619, 2011. DOI: 10.3171/2011.7.SPINE1132
Iatrogenic injury of the V2 segment of the vertebral artery (VA) is a rare but serious complication and can be catastrophic. The purpose of this study was to characterize the relationship of the V2 segment of the VA to the surrounding anatomical structures and to highlight the potential site and mechanisms of injury that can occur during common neurosurgical procedures involving the subaxial cervical spine.
Methods. Ten adult cadaveric specimens (20 sides) were included in this study. Quantitative anatomical measurements between selected landmarks and the VA were obtained. In addition, lateral mass screws were placed bilaterally, from C-3 to C-7, reproducing either the Magerl technique or a modified technique. The safety angle, defined as the axial deviation from the screw trajectory needed to injure the VA, and the distance from the entry point to the VA were measured at each level for both techniques.
Results. The VA coursed closer to the midline at C3–4 and C4–5 (mean distance [SD] 14.9 ± 1.1 mm) than at C2–3 or C5–6. Within the intertransverse space it coursed closer to the uncinate processes of the vertebral bodies (1.8 ± 1.1 mm) than to the anterior tubercle of the transverse processes (3.4 ± 1.6 mm). The distance between the VA and the uncinate process was less at C3–6 (1.3 ± 0.7 mm) than at C2–3 (3.3 ± 0.8 mm). The VA coursed on average at a distance of 11.9 ± 1.7 mm from the anterior and 4.2 ± 2.6 mm from the posterior aspect of the intervertebral disc space. Lateral mass screw angles were 25° lateral and 39.1° cranial for the Magerl technique, and 36.6° lateral and 46.1° cranial for the modified technique. The safety angle was greater and screw length longer when using this modified technique.
Conclusions. The relation of the V2 segment of the VA to anterior procedures and lateral mass instrumentation at the subaxial cervical spine was reviewed in this study. A detailed anatomical knowledge of the V2 segment of the VA combined with careful preoperative imaging is mandatory for safe cervical spine surgery.

Neurosurgery 67[ONS Suppl 1]:ons00-ons00, 2010. DOI: 10.1227/01.NEU.0000382971.63877.DD

Anterolateral meningiomas of the foramen magnum (FMMs) represent a neurosurgical challenge because they grow in close contact with osteoarticular, nervous, and vascular structures that cannot be sacrificed or retracted. OBJECTIVE: To evaluate our strategy and results in 26 patients with FMMs and analyze factors affecting the decision-making process, resection, and outcome. METHODS: Among 26 consecutive symptomatic FMM (10 anterior, 16 lateral) patients (16 women, 10 men, ages 28-82 years), 4 older than 70 years of age were untreated. Twentytwo were operated on using a posterolateral approach, with the vertebral artery transposed in 19 and the occipital condyle drilled in 10. We analyzed the characteristics and outcome of untreated cases, the utility of THE occipital condyle drilled, the difficulties of microdissection, morbidity and total removal rates, the outcome of tumor residues, and the literature on radiosurgery. RESULTS: Three of 4 untreated patients remained clinically stable at 2 to 5 years. After systematic vertebral artery medial transposition and occipital condyle drilled in 6 cases, our technique evolved with experience in the next 16 (vertebral artery transposed in 13 of 16; occipital condyle drilled in 4 of 13) for dissecting anteriorly beyond midline (anterior FMMs). Retrocondylar access was sufficient for lateral FMMs. Tumors were totally removed in 16 of 22 (73%). One patient died, and 4 had permanent deficits. Follow-up of more than 5 years in 12 patients showed no C0-1 instability, and slight increase of tumor residue size 7 years after surgery. In the literature, 15 FMMs treated with radiosurgery are reported, 13 at diagnosis and 2 at recurrence, with short-term clinical and radiological safety and efficacy. CONCLUSION:We currently recommend (1) aiming for subtotal removal in difficult cases, (2) remaining conservative in asymptomatic or elderly patients with mild symptoms, and (3) considering radiosurgery at diagnosis for small (<30 mm) symptomatic FMMs or as an adjunct for evolving residues/recurrences in poor candidates for resection.

Spine 2010;35:1136–1143

Use of magnetic resonance imaging (MRI) with Constructive Interference in Steady State (CISS) sequence and isometric voxels to demonstrate the anatomic variations of vertebral artery in C2 vertebra. Objectives. To determine the transarticular screw trajectory on CISS MRI and to identify patients with anatomic variations of vertebral artery in C2 vertebra. Summary of Background Data. Atlantoaxial transarticular screw fixation has been reported to be biomechanically superior to other posterior techniques for atlantoaxial arthrodesis. Vertebral artery injury can be associated with catastrophic sequelae. Anatomic variation of vertebral artery is well recognized and computed tomography scan is the traditional preoperative assessment. However, no report has evaluated the use of MRI in preoperative assessment for the screw trajectories and the anatomic variation of vertebral artery. Methods. The 3-dimensional (3D) CISS MRI with isometric voxels was performed in 30 local Chinese patients. The 3D reconstruction images were created to determine the proposed screw trajectories and their relationship with the vertebral arteries. Results. In 12 patients (40%), the vertebral arteries were lying within the screw trajectories prohibiting transarticular screw fixation on at least one side. Bilateral variations with high risk of vertebral artery injuries were found in 6 patients. The remaining 6 patients had unilateral variations prohibiting the insertion of transarticular screws on one side. Conclusion. The 3D CISS MRI with isometric voxels is a safe and simple imaging technique to outline the vertebral arteries in C2. Reconstruction images are easily created and undistorted. It is one of the useful imaging in preoperative planning of transarticular screw fixation and determination of anatomy of vertebral artery.

INTRODUCTION:We evaluated the feasibility, usefulness, and limitations of near-infrared indocyanine green (ICG) videoangiography during procedures involving the extracranial vertebral artery (VA).

METHODS: Nine patients (2 women, 7 men; mean age, 55 years) were evaluated at 2 neurosurgical centers. Near-infrared ICG videoangiography was applied during transposition and rerouting of the first segment of VA (V1; n = 6) and during resection of neurinomas near the second (V2; n = 1) and third (V3; n = 2) segments of VA.

RESULTS: Early after ICG injection, V1 fluoresced homogenously. The fluorescence of V2 and V3 varied. Without extrinsic compression, these segments appeared as noncontiguous hot spots because the VA runs freely in a periosteal sheath surrounded by a venous plexus that attenuates the fluorescent light. Hot spots corresponded to areas where the artery neared the surface. With extrinsic compression, VA enhanced homogenously because it was pushed against the periosteal layer. During the late phase, the V1 signal was attenuated, whereas the venous plexus surrounding V2 and V3 enhanced homogeneously, thereby masking the VA itself. Near-infrared ICG videoangiography helped to confirm VA patency during transposition and rerouting but was not helpful during VA exposure because the periosteal sheath must already be exposed to detect the VA or its surrounding plexus. After exposure, videoangiography can help to determine the position of the VA within its periosteal sheath.

CONCLUSION: Videoangiography can be used to provide information about the patency of the VA and its location within the periosteal sheath to prevent injury during resection of tumor adherent to the periosteal sheath.

The Spine Journal 9 (2009) 822–829. doi:10.1016/j.spinee.2009.06.023

Removal of cervical dumbbell tumors can be particularly challenging because of unique exposure requirements and proximity of the vertebral artery (VA). There are no reports describing the treatment of giant cervical spine dumbbell tumors (CSDTs).

PURPOSE: To introduce an extensive posterolateral approach to CSDTs involving total lateral mass resection and laminectomy.

STUDY DESIGN: Prospective study of all the patients with multilevel CSDTs treated by  this new procedure between December 2002 and March 2006.

PATIENT SAMPLE: Sixteen patients (3 men and 13 women) with CSDTs underwent the procedure we describe. The follow-up periods ranged from 9 to 51 months (average 9 months). Average age at surgery was 45 years (range 23–68 years).

OUTCOME MEASURES: Axial symptoms and Japanese Orthopedic Association scores were recorded. Pre- and postoperative ranges of neck motion were measured on lateral flexion and extension radiographs.

METHODS: After making a midline incision, we preferred exposing the extraforaminal component of the tumor before performing a semilaminectomy and lateral mass resection. Any lateral extensión of a tumor can be attained by detachment of the adjacent three or more segments of the lateral mass muscle insertion. The most lateral portion can be separated beneath the tumor’s superficial muscle flap, and then when the tumor is retracted medially, the whole portion of the lateral component can be totally exposed. We then performed total lateral mass resection and laminectomy to expose the tumor at the foramina and cervical canal.

RESULTS: We were able to completely resect the tumors in every patient. The average duration of surgery was 150 minutes. Blood loss was minimal (average 400 mL). All patients were monitores for a minimum of 9 months (range 9–51 months; mean 28 months). The follow-up period was uneventful, and no patients developed spinal instability.

CONCLUSIONS: Extensive posterolateral exposure enables surgeons to reach the lateralmost portion of CSDTs and also facilitates septation of the VA and resection of vertebral body encroachment of the tumor.