title: Clinical and Radiographical Differences Between Thoracic Idiopathic Spinal Cord Herniation and Spinal Arachnoid Cyst.
abstract: METHODS
  A retrospective, multicenter, case-controlled study.
  
  
  OBJECTIVE
  The aim of this study was to investigate the clinical and radiographical differences between thoracic idiopathic spinal cord herniation (ISCH) and spinal arachnoid cyst (SAC).
  
  
  BACKGROUND
  ISCH and SAC are relatively rare diseases. Preoperative misdiagnose was frequently reported in both; however, these clinical and radiographical differences remain unclear.
  
  
  METHODS
  Of 30,469 patients who underwent spinal surgery, 18 (0.059%) and 22 (0.072%) patients were diagnosed as ISCH or SAC at nine hospitals, respectively, and their clinical and radiographical data were retrospectively evaluated. The spinal cord kink angle was measured on magnetic resonance or computed tomography myelography sagittal images; the kink angle was the exterior angle formed between the two tangents to the dorsal-side inflection points at the maximally affected level.
  
  
  RESULTS
  There were no significant differences in age, gender, and duration of symptoms. Preoperative motor deficit was significantly higher (94.4%) and severer (manual muscle testing: 3.1 ± 1.1) in ISCH. Brown-Séquard syndrome was observed in 38.9% of ISCH, while no patients in SAC. In addition, leg sensory disorder and bladder rectal disorder were significantly more common in ISCH, while back pain was significantly frequent in SAC. With respect to radiographical findings, the length of disease (5.1 ± 2.7 levels) and altered cerebrospinal flow (CSF) (81.8%) in the lesion was significantly longer and more common in SAC. On the contrary, the kink angle was significantly greater in ISCH (54.0 ± 23.1°) than in SAC (14.1 ± 12.0°) (P < 0.001). The cut-off value of the kink angle to distinguish ISCH and SAC was 32.8°.
  
  
  CONCLUSIONS
  Patients with ISCH commonly had severe preoperative neurological deficit, Brown-Séquard syndrome, and higher kink angle, while patients with SAC had back pain, longer length of disease, and altered CSF in the lesion.
  
  
  METHODS
  4.
authors.affiliation: Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.|Department of Orthopedic Surgery, Konan Kosei Hospital, Aichi, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakashima
authors.affiliation: Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Imagama
authors.affiliation: Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Yagi
authors.affiliation: Department of Orthopedic Surgery, Chubu Rosai Hospital, Nagoya, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Kato
authors.affiliation: Department of Orthopedic Surgery, Konan Kosei Hospital, Aichi, Japan.
authors.forename: Tokumi
authors.initials: T
authors.lastname: Kanemura
authors.affiliation: Department of Orthopedic Surgery, Nagoya Daini Red Cross Hospital, Nagoya, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Sato
authors.affiliation: Department of Orthopedic Surgery, Meijo Hospital, Nagoya, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Kawakami
authors.affiliation: Department of Orthopedic Surgery, Aichi Medical University, Aichi, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kamiya
authors.affiliation: Department of Orthopedic Surgery, Toyohashi Municipal Hospital, Aichi, Japan.
authors.forename: Hisatake
authors.initials: H
authors.lastname: Yoshihara
authors.affiliation: Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Kenyu
authors.initials: K
authors.lastname: Ito
authors.affiliation: Department of Orthopedic Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Matsuyama
authors.affiliation: Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nishida
authors.affiliation: Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishiguro
mesh_terms: D000328:Adult; D000368:Aged; D016080:Arachnoid Cysts / Q000000981:diagnostic imaging* / Q000473:pathology; D001416:Back Pain / Q000000981:diagnostic imaging; D003951:Diagnostic Errors / Q000517:prevention & control; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods; D012189:Retrospective Studies; D013118:Spinal Cord Diseases / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed