title: Utility of the clivo-axial angle in assessing brainstem deformity: pilot study and literature review.
abstract: There is growing recognition of the kyphotic clivo-axial angle (CXA) as an index of risk of brainstem deformity and craniocervical instability. This review of literature and prospective pilot study is the first to address the potential correlation between correction of the pathological CXA and postoperative clinical outcome. The CXA is a useful sentinel to alert the radiologist and surgeon to the possibility of brainstem deformity or instability. Ten adult subjects with ventral brainstem compression, radiographically manifest as a kyphotic CXA, underwent correction of deformity (normalization of the CXA) prior to fusion and occipito-cervical stabilization. The subjects were assessed preoperatively and at one, three, six, and twelve months after surgery, using established clinical metrics: the visual analog pain scale (VAS), American Spinal InjuryAssociation Impairment Scale (ASIA), Oswestry Neck Disability Index, SF 36, and Karnofsky Index. Parametric and non-parametric statistical tests were performed to correlate clinical outcome with CXA. No major complications were observed. Two patients showed pedicle screws adjacent to but not deforming the vertebral artery on post-operative CT scan. All clinical metrics showed statistically significant improvement. Mean CXA was normalized from 135.8° to 163.7°. Correction of abnormal CXA correlated with statistically significant clinical improvement in this cohort of patients. The study supports the thesis that the CXA maybe an important metric for predicting the risk of brainstem and upper spinal cord deformation. Further study is feasible and warranted.
authors.affiliation: Doctor's Community Hospital, Lanham, MD, USA. Henderson@FraserHendersonMD.com.|The Metropolitan Neurosurgery Group, LLC, 8401 Connecticut Avenue, Suite 220, Chevy Chase, MD, 20815, USA. Henderson@FraserHendersonMD.com.
authors.forename: Fraser C
authors.identifier: http://orcid.org/0000-0001-9479-2368
authors.initials: FC
authors.lastname: Henderson
authors.affiliation: Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Fraser C
authors.initials: FC
authors.lastname: Henderson
authors.affiliation: The Metropolitan Neurosurgery Group, LLC, 8401 Connecticut Avenue, Suite 220, Chevy Chase, MD, 20815, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Wilson
authors.affiliation: University of Maryland Medical Center, Baltimore, MD, USA.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Mark
authors.affiliation: Doctor's Community Hospital, Lanham, MD, USA.
authors.forename: Myles
authors.initials: M
authors.lastname: Koby
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001933:Brain Stem / Q000473:pathology*; D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000473:pathology*; D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000150:complications / Q000175:diagnosis* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010865:Pilot Projects; D011446:Prospective Studies; D013123:Spinal Fusion; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
keywords: Basilar invagination; Brainstem deformation; Cervical medullary syndrome; Clivo-axial angle; Craniocervical instability; Dynamic MRI