• Wai Wang Chau, Winnie C W Chu, Tsz Ping Lam, Bobby K W Ng, Linda L K Fu, and Jack C Y Cheng.
• *Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Shatin, Hong Kong †Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, Hong Kong ‡The Joint Scoliosis Research Centre of Chinese University of Hong Kong and Nanjing University, Shatin, Hong Kong.
• Spine. 2016 May 1; 41 (10): E598-604.

Study DesignA prospective cohort study.ObjectiveThe aim of this study was to compare the somatosensory-evoked potential (SEP) findings of adolescent idiopathic scoliosis (AIS) subjects of different curve severity with age- and gender-matched controls and to evaluate any correlation between the site of the SEP abnormality with cerebellar tonsillar level measured by magnetic resonance imaging (MRI).Summary Of Background DataOur previous studies showed that a higher percentage of SEP abnormality and cerebellar tonsillar ectopia was present in AIS patients than in normal controls. However, the relationship between the anatomical site of the neurophysiological abnormality and the severity in AIS patients has not been defined.MethodsSEP measurement was conducted on 91 Chinese AIS girls with major right thoracic curve of different curve severity (mild, moderate, severe) and 49 matched normal controls. Waveform characteristics (latency and amplitude) were compared among groups. Specific location of SEP abnormality was identified from tibial to cortical levels. Cerebellar tonsillar ectopia was defined by the previously established reference line between basion and opisthion on MRI.ResultsSignificant prolonged P37 latency was found on the right side between severe AIS patients and normal controls, while increased inter-side P37 latency difference was found between severe versus moderate, and severe versus normal controls. Cerebellar tonsillar ectopia was detected in 27.3% of severe group, 5.8% to 6.7% in mild and moderate group, but none in normal controls. Abnormal SEP occurred superior to C5 region in all surgical (severe) patients, of whom 58% had cerebellar tonsillar ectopia.ConclusionAIS patients showed significant prolonged latency and increased latency difference on the side of major curvature. The incidence of SEP abnormality increased with curve severity and occurred above the C5 level. The findings suggested that there was a subgroup of progressive AIS with subclinical neurophysiological dysfunction, associated with underlying neuromorphological abnormalities, which were only detectable by SEP and MRI.Level Of Evidence3.

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