www.e-neurospine.org 255 The Nuances of Occipitocervical Instability and Stenosis in Patients With Basilar Invagination and Atlantoaxial Dislocation The craniovertebral junction (CVJ) is a complex region with potential for instability and stenosis. The etiology of basilar invagination (BI) and atlantoaxial dislocation (AAD) may include congenital, traumatic, or rheumatioid arthritis related degeneration.1 The established, traditional treatment for dens related compressive stenosis in BI with AAD is transoral odontoidectomy plus posterior occipital-cervical fusion.2-4 Although the surgical results are excellent with odontoidectomy, it has some disadvantages including wound dehiscence, infection, velopharyngeal insufficiency, cerebral spinal fluid leak (with meningitis), and dysphagia. Recently, posterior surgery has gained in popularity for occipitocervical reduction and fixation done in a single stage prone position while avoiding the complications from odon- toidectomy.5 Chandra et al.6 demonstrate a single stage posterior surgery for reduction and re-alignment using the DCER (distraction, compression, extension, and reduction) tech- nique which combines usage of C1–2 spacers and occipitocervical fusion with custom in- strumentation. They reported a series of 148 patients and reported that 93.2% patients im- proved their nurick scale by a mean of 1.24 points. One major concern of this single stage posterior surgery is that the AAD and BI are fre- quently accompanied by osseous or vascular anomalies. The bony structure and vascular anatomy should be well studied before surgery using thin slice computed tomography (CT) with sagittal and coronal reconstruction views. In addition, a 3-dimensional printed model may also help to evaluate the bony structure preoperatively. Patients with BI and AAD have a reported higher incidence of vertebral artery (VA) anomalies than the normal popula- tion.7 Preoperative CT-angiogram is helpful to identify the course and dominant side of the VA. During surgery, instrumentation should be placed on the side with the nondominant VA first. If the nondominant VA is injured, the dominant side should not be instrumented and immediate angiogram for stenting or sacrifice is suggested. The authors did report four VA injuries in their series with a very high mortality rate (50%). In addition, it is not uncommon for BI/AAD patients to have coincidental osteoporosis (especially in rheumatoid arthritis patients who have had long-term steroid treatment). Pre- operative dual-energy X-ray absorptiometry is helpful to evaluate for osteoporosis in these patients. To achieve adequate reduction, a solid purchase of the fixation screws is essential. In osteoporotic patients, pretreatment with teriparatide is suggested to prevent screw pull- out, screw loosening and pseudarthrosis. In patients who have significant untreated osteo- porosis, odontoidectomy plus in situ occipital-cervical fusion with multiple anchor points Neurospine 2019;16(2):255-256. https://doi.org/10.14245/ns.19edi.011 Neurospine eISSN 2586-6591 pISSN 2586-6583 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecom- mons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright © 2019 by the Korean Spinal Neurosurgery Society Editorial Corresponding Author Praveen V. Mummaneni E-mail: Praveen.Mummaneni@ucsf.edu https://orcid.org/0000-0001-5501-7262 Department of Neurosurgery, University of California, San Francisco, CA, USA Chih-Chang Chang, Praveen V. Mummaneni Department of Neurosurgery, University of California, San Francisco, CA, USA http://crossmark.crossref.org/dialog/?doi=10.14245/ns.19edi.011&domain=pdf&date_stamp=2019-06-30 The Nuances of OC Instability and Stenosis in Patients With BI and AADChang CC, et al. https://doi.org/10.14245/ns.19edi.011256 www.e-neurospine.org is a viable option since a reduction maneuver may lead to hard- ware pullout. The key points of doing a successful single stage posterior re- duction and fixation include appropriate patient selection, iden- tification of osseous and vascular anomalies, and use of gentle reduction and solid fixation. We congratulate Dr. P. Sarat Chan- dra on the excellent clinical results for these patients. These pa- tients need to be followed for 1–2 years to ensure the bone graft heals. REFERENCES 1. Wu JC, Mummaneni PV, El-Sayed IH. Diseases of the odon- toid and craniovertebral junction with management by en- doscopic approaches. Otolaryngol Clin North Am 2011;44: 1029-42. 2. Chang PY, Yen YS, Wu JC, et al. The importance of atlanto- axial fixation after odontoidectomy. J Neurosurg Spine 2016; 24:300-8. 3. El-Sayed IH, Wu JC, Ames CP, et al. Combined transnasal and transoral endoscopic approaches to the craniovertebral junction. J Craniovertebr Junction Spine 2010;1:44-8. 4. Mummaneni PV, Haid RW. Transoral odontoidectomy. Neu- rosurgery 2005;56:1045-50, discussion 1045-50. 5. Deutsch H, Haid RW Jr, Rodts GE Jr, et al. Occipitocervical fixation: long-term results. Spine (Phila Pa 1976) 2005;30: 530-5. 6. Chandra PS, Bajaj J, Singh PK, et al. Basilar invagination and atlantoaxial dislocation: reduction, deformity correction and realignment using the DCER (distraction, compression, extension, and reduction) technique with customized in- strumentation and implants. Neurospine 2019;16:231-50. 7. Yamazaki M, Okawa A, Furuya T, et al. Anomalous verte- bral arteries in the extra- and intraosseous regions of the craniovertebral junction visualized by 3-dimensional com- puted tomographic angiography: analysis of 100 consecutive surgical cases and review of the literature. Spine (Phila Pa 1976) 2012;37:E1389-97. Title: On the Beach Artist: Pablo Picasso Year: 1937 On the Beach also draws upon aspects of Surrealism, here we are once more confronted with two female forms constructed from an assem- blage of peculiar biomorphic forms. The figures appear to be at the edge of the sea and one lowers a small toy boat into the water. Another, similar form rises above the horizon, as if watching the activity of the foreground figures. However, as this figure is represented as approxi- mately the same scale as the foreground figures, its presence on the horizon implies that it is a gigantic and threatening being. More information: https://www.pablopicasso.org/on-the-beach.jsp © 2019 - Succession Pablo Picasso - SACK (Korea)