Intraspinal Neural Axis Abnormalities And Cervical Abnormalities In Severe Spinal Deformity

Objective:Documents indicated that the average prevalence of intraspinal neural axis abnormalities(INAAs)in presumed idiopathic scoliosis(PIS)patients was about 11.4%and average prevalence of cervical anomalies(CAs)in scoliosis was 26.9%.However,paucity study focuses on the incidence of INAAs in severe spinal deformity(SSD).In this study,we investigate the incidence of INAAs and/or CAs to reveal clinical relevance in SSD patients at a single center.Methods:All the patients with SSDs admitted for spinal surgery were evaluated from 2003-2015.Inclusion criteria:patients who present with coronal Cobb over 90 °(and/or the sagittal cobb?90°);had completed preoperative data of iconography(whole spine MRI,CT,cervicle X ray:postero-anterior,lateral,dynamic and open-mouth);patients with documented clinical findings preoperatively.Exclusion criteria:ankylosing spondylitis,adult onset scoliosis,scoliosis secondary to bone destruction.Results:108 patients fulfilled the criteria were included.44 patients were detected with INAAs(44/108,40.7%).The most common INAAs was syrinx(S)(16/44,36.4%).Of which,43.7%(7/16),37.5%(6/16),and 18.8%(3/16)were spindle,slit,and swelling types,respectively.Most of them were located in thoracic(6/16,37.5%)and cervical(5/16,31.3%)region.MRI revealed Chiari malformation with syringomyelia(C+S)in 10 patients(10/44,22.7%),Chiari malformation(C)in 7 patients(7/44,15.9%)and others in 11 patients(11/44,25.0%).As to the etiology,most patients with INAAs were PIS(34/44,77.3%).On clinical examination,17 of 108 patients(17/108,15.7%)had abnormal neurologic signs.15 of 17 patients(15/17,88.2%)with abnormal neurologic signs had INAAs on MRI.On the other hand,29 of 44 patients(29/44,65.9%)with INAAs on MRI presented neurologically intact.29 of 91 patients(29/91,31.9%)with neurologically intact were detected with INAAs on MRI.There were significant different in abnormal neurologic signs between SSD with INAAs and SSD without INAAs(15/44,34%vs 2/64,3.1%)(P=0.000).56 patients were detected with CAs(51.9%,56/108),including cervical INAAs(CINAAs)(25.9%,28/108),cervical osseous abnormalities(COAs)(32.4%,35/108)and combined of the two(6.5%,7/108).The most common CINAAs was S(11/28,39.3%).There were 23(23/45,51.1%)different OAs in 17(17/35,48.6%)patients,in upper cervical region.There were 22(22/45,48.9%)different OAs in 13(13/35,37.1%)patients,in subaxial cervical region(C3-C7).As to the etiology,OAs had much more weight in CS compared to PIS(45.5%vs 28,1%).9 of 17 patients(9/17,52.9%)with abnormal neurologic signs had CAs on imaging examinations,CINAAs(3/9,33.3%),CINAAs+COAs(2/9,22.2%)andCOAs(4/9,44.4%),respectively.About the study of CINAAs with COAs,5(5/35,14.3%)patients whose OAs was detected in upper and subaxial cervical region both,1(1/5,20%)of them with CINAAs.For subaxial COAs,13(13/35,37.1%)patients were detected,all of them without CINAAs,including 2 vertebral failures of formation,1 vertebral failures of segmentation and 1 mixed of the two.In upper cervical region,17(17/35,48.6%)patients with COAs were detected,6(6/17,35.3%)of them were detected with CINAAs.The 6 patients were 3 with mutiple COAs,3 with one type COAs.Conclusions:The incidence of INAAs in SSD was 40.7%(44/108),most of them present intact neurologic status;abnormal neurologic signs rate in SSD with INAAs was higher than in SSD without INAAs;most common INAAs was S.The incidence of CAs in SSD was 51.9%(56/108);most of them present intact neurologic status;the most common CAs was S and BI.The patient with mutiple COAs in upper cervicle region who was easier to be dectected with CINNAs.To reduce the neurologic injured risks,preoperative imaging MRI assessment of the whole spine must be beneficial for SSDs and focus on CAs,even in the absence of neurological findings.