Surgical Neurology 64 (2005) 221 – 225 www.surgicalneurology-online.com Spine Poor surgical technique in cervical plating leading to vertebral artery injury and brain stem infarction—case report Ki Hong Cho, MD, Yong Sam Shin, MD*, Soo Han Yoon, MD*, Se Hyuk Kim, MD, Young Hwan Ahn, MD, Kyung Gi Cho, MD Department of Neurosurgery, Ajou University School of Medicine, Suwon, Republic of Korea 443-721 Received 14 June 2004; accepted 13 September 2004 Abstract Background: Lateral mass plating is a safe fixating system for lower cervical fractures. Brain stem infarction after cervical lateral mass screw plating has not been reported in previous literature. We report a case of poor surgical technique leading to vertebral artery injury and brain stem infarction after cervical lateral mass plating. Case Description: A 41-year-old male patient was transferred to our hospital because of hemiparesis and dysarthria immediately after lateral mass plating for fracture and dislocation of the fifth and sixth cervical vertebrae. Brain magnetic resonance imaging showed infarction of the left posterior inferior cerebellar artery territory, and the vertebral artery angiography showed complete occlusion of the left vertebral artery. The cervical computed tomography revealed a left screw of the fifth and sixth cervical vertebrae penetrating the central portion of the transverse foramen. The patient was managed with anticoagulant and supportive therapy only, with subsequent improvement of hemiparesis and dysarthria. Conclusions: Poor surgical technique of lateral mass plating in the cervical spine could lead to vertebral artery injury and even brain stem infarction. Postoperative brain infarction in cervical fusion could be a complication of the usually safe lateral mass plating of the cervical spine. D 2005 Elsevier Inc. All rights reserved. Keywords: Cervical fracture; Lateral mass plating; Vertebral artery occlusion; Brain stem infarction 1. Introduction The surgical approaches for cervical fractures include anterior, posterior, and combined approaches. Lateral mass plating is widely accepted as one of the posterior fixation methods for the lower cervical spine fractures from the C3 through C7 vertebrae [2]. This approach is also useful for instability occurring after multiple-level anterior cervical fusion, multiple laminectomies due to myelopathy, cervical tumor removal, and surgery for degenerative diseases Abbreviations used in this paper: C, cervical vertebra; CT, computed tomography. * Corresponding authors. S.H. Yoon is to be contacted at tel.: +82 31 219 5233; fax: +82 31 219 5238. Y.S. Shin, tel.: +82 31 219 5235; fax: +82 31 219 5238. E-mail addresses: ee80@ajou.ac.kr (S.H. Yoon)8 khcho54@ajou.ac.kr (Y.S. Shin). 0090-3019/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2004.09.042 [1, 2, 25]. Although excellent results have been reported using lateral mass screw plating, neurovascular complications may potentially result from this approach because of its anatomic proximity to vital structures, such as the vertebral artery, cervical nerve root, and spinal cord [2, 24, 25]. However, brain complication of cerebellar or brain stem infarction is very rare, although the screwing procedure injures the vertebral artery during the operation. We present the first case of the left posterior inferior cerebellar artery territory infarction due to iatrogenic vertebral artery occlusion from screw compression after lateral mass screw plating for fracture and dislocation of the C5 through C6 vertebrae. 2. Case report A 41-year-old man had complained of neck pain after a traffic accident 12 days before the initial procedure, which 222 K.H. Cho et al. / Surgical Neurology 64 (2005) 221–225 Fig. 1. Initial cervical spine plain films show lateral mass plating and interspinous wiring between the C5 and C6 vertebrae because of fracture and dislocation. consisted of lateral mass plating and interspinous wiring for fracture and dislocation of the C5/C6 vertebra at another hospital (Fig. 1). After surgery, he suffered from dysarthria and right hemiplegia and was therefore referred to our department via the emergency department. Brain magnetic resonance imaging showed high signal intensities in the left cerebellum and pons on both T2- and diffusion-weighted images, revealing infarction of the left posterior inferior cerebellar artery territory (Fig. 2). To evaluate the posterior circulation infarction, we performed cerebral angiography, which showed complete occlusion of the left vertebral artery, and partial occlusion of the right vertebral artery at the C5/C6 level (Fig. 3). Cervical CT showed a left screw penetrating the central portion of the transverse foramen of C5 and C6 vertebrae, and therefore left vertebral artery occlusion due to malposition of the screw was suspected (Fig. 4). The inappropriate placement of the left screw during lateral mass screw plating between the C5 and C6 vertebrae had compressed the left vertebral artery, and the hemodynamic insufficiency resulted in infarction of the left posterior inferior cerebellar artery territory. Because removing the screw was very likely to cause further vascular injury, and would necessitate another operation for cervical stabilization, the patient was conservatively treated by anticoagulation therapy for the infarction of the left posterior inferior cerebellar artery territory. The patient recovered from symptoms of dysarthria and right hemiparesis completely, with bony fusion and no instability between the C5 and C6 vertebrae after a 10-month follow-up period. 3. Discussion Fig. 2. Axial T2-weighted magnetic resonance image shows a high signal intensity lesion in the pons and left cerebellum. The lateral mass plating technique is one of the most useful posterior cervical segmental instrumentation methods for cervical bony fractures [18]. Many surgeons have reported that the lateral mass plating technique requires less operative time and enhances stability. Nevertheless, this technique is expensive and has the potential to injure the nerve root and the vertebral artery [28]. To avoid such injury, surgeons should have a complete understanding of the anatomy of the articular mass, neural foramen, vertebral artery, and nerve roots. In particular, knowledge of the screw entry point, angle, and trajectory are critical for a safe approach. Several screw placement techniques have been previously described. The technique developed by Roy-Camille et al [21] places the screw halfway between the articular surfaces of the facets and halfway between the lamina facet line and the lateral margin of the lateral mass. The screw is placed at K.H. Cho et al. / Surgical Neurology 64 (2005) 221–225 223 Fig. 3. Anteroposterior view of conventional posterior circulation cerebral angiography shows patent flow of the right vertebral artery, but no flow of the left vertebral artery at the C5/C6 level. the midpoint of the lateral mass and angled 108 laterally. Magerl et al [15] described another technique, in which the entry point is 1 mm medial and 1 to 2 mm cephalic to the center of the lateral mass. The screw angles 258 laterally and 308 cephalic. In an anatomic and biomechanical study, the Magerl technique was observed to avoid neurovascular structures compared with the Roy-Camille technique [17]. Although the screw should angle laterally in both techniques, the screw paralleled the midline and was oriented 38 medially in our case. The screw malposition compressed Fig. 4. Computed tomography shows the anatomic relationship between screws and vertebral artery. The screw was malpostioned medially complete occlusion of the left vertebral artery and partial occlusion of the left vertebral artery at the level of the sixth cervical vertebra. the vertebral artery, causing infarction of the left posterior inferior cerebellar artery territory. Traynelis [24] reported that lateral mass plating results in successful arthrodesis in 98% of cases, with extremely low operative morbidity. The incidence of neurovascular injury was substantially less than 1%. Heller et al [10] performed the most complete analysis of complications after lateral mass plating. They found a 0.69% incidence of nerve root injury, 1.17% incidence of screw loosening, and 1.3% incidence of infection. Vertebral artery injury during lateral mass plating is very rare [24], and most cases of vertebral artery injury developed during pedicle screwing to involve arterial wall tearing, or rupture during drilling or screw insertion. The management of such an injury usually involves packing the drill hole with screw or bone wax, sometimes ligation, or rarely, direct repair of injured vertebral artery [5,12, 28]. Others have occluded the vertebral artery with intravascular embolization after surgery [3]. Pedicle screwing has been proven to be less safe than lateral mass plating. Even when the placement of the screw looks grossly accurate intraoperatively, in 65.5% of cases the screw was inserted into the critical area in a study of human cadavers [13]. Computer-assisted surgical guidance systems could enhance surgical accuracy from 34.1% to 89.4% in the above cadaver study, resulting in no misplacements of pedicle screws in all 19 cases [13, 20]. In our case, the initial operator did not notice that the screw was compressing the vertebral artery seriously because there was no hemorrhage due to vascular wall tearing or perforation. There have been no reports to date in previous literature regarding development of neurologic complications from vertebral artery occlusion by screwing of the lower cervical fixation plate, but it has been reported that 0% to 8.2% injuries of the vertebral artery occur during C1 through C2 224 K.H. Cho et al. / Surgical Neurology 64 (2005) 221–225 transarticular fixation with a screw [7,14, 23, 29]. However, neurologic complications from the first-second vertebral fixation with a screw occurred in only 0.2% to 1% of patients, which is more infrequent than the incidence of vertebral artery injury [5, 29]. Neurologic complications occurred in 0% to 6.25% patients because of occlusion of the unilateral vertebral artery during management of vertebral artery injuries [6,11 ,12 ,29 ,30], whereas brain infarction developed in 2.7% to 6.25% after ligation of unilateral vertebral artery during management of vertebral artery aneurysms [8, 22,29]. These results demonstrate that occlusion or ligation of the unilateral vertebral artery seldom results in neurologic complications when the contralateral vertebral artery or posterior communicating artery could preserve adequate blood supply. However, no case of brain infarction from lateral mass plating has been reported in comparison with previously reported neurologic complications resulting from pedicle screwing. The authors experienced a patient who unfortunately developed brain stem infarction with weakness because of a fixation screw directly compressing the unilateral vertebral artery, resulting in occlusion. No standard treatment has been established for vertebral artery injuries after nonpenetrating cervical trauma, but various options have been reported [9, 16]. Conservative care and/or anticoagulation with intravenous heparin, or oral antiplatelet agents is recommended for patients with vertebral artery injury who have evidence of posterior circulation stroke [9], as in our case. Extracranial-intracranial artery anastomosis or stent implantation to increase blood flow could also be considered for brain infarction resulting from vertebral artery occlusion, in addition to supportive management [4,19]. Removing the screw to improve posterior circulation hemodynamics is a controversial option, as the risk of secondary vertebral artery injury is high, and a secondary operation for cervical fracture fusion would have been necessary. Instead, we used anticoagulation treatment and the patient was observed. During the follow-up period, the patient’s symptoms improved, and bony fusion of the cervical fracture resulted. Ultimately, it was unnecessary for the screw to be removed. The proper diagnostic modality for vertebral artery injuries with ischemia is conventional angiography or magnetic resonance angiography [26, 27]. However, neither method revealed the cervical screws, whereas the anatomic relationship between the screws and vertebral artery was seen clearly in 3-dimensional reconstruction images using CT; thus, the latter is considered to be more valid for evaluating instrument-related problems. 4. 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Note that applications by men dropped 37%. — AAPS News, February 2005 www.aapsonline.org