Split cord malformations: A clinical study of 254 patients and a proposal for a new clinical-imaging classification

Abstract

Object. Split cord malformations (SCMs) are rare anomalies of the spinal cord. A total of 254 cases of SCM were treated surgically at the authors' center during a period of 16 years. Methods. Patients' demographic profiles, imaging studies, operative details, complications, and surgical outcomes were evaluated retrospectively. A new classification based on intraoperative findings is proposed. The mean age of the patients was 7.3 years (female/male 1.5:1). Type I SCM was seen in 156 patients (61.4%) and 98 patients (38.6%) had Type II SCM. Skin stigmata were present in 153 cases (60%); hypertrichosis, being the most common, was seen in 82 cases (32.3%). Asymmetrical lower-limb weakness and sphincter disturbances were present in 173 (68.1%) and 73 (33%) cases, respectively. Of the symptomatic cases, 39% (68 of 173) showed improvement in motor power, 57.9% (33 of 57) experienced sensory improvement, and 27.3% (20 of 73) regained continence. None of the 38 patients in the asymptomatic group had postoperative neurological deterioration. The neurological status was unchanged in 63% of the cases. A new subclassification of Type I SCM is proposed, based on intraoperative location of a bone spur causing the split, which may have a bearing on surgical dissection and outcome. Based on the authors' experience with 25 cases of Type I SCM, they have classified the disorder into four subtypes: Type Ia, bone spur located in the center with duplicated cord above and below the spur (12 cases); Type Ib, bone spur at the superior pole with no space above it (four cases); Type Ic, bone spur at the lower pole with large duplicated cord above (three cases); and Type Id, bone spur straddling the bifurcation with no space above or below the spur (six cases). The risk of injury to the hemicords is highest in the Id subtype (four of six patients in this group deteriorated neurologically in the present series, whereas none with subtypes Ia-c worsened). Conclusions. The authors present the largest series on SCMs so far reported in the world literature The risk of neurological deficits developing increases with age; hence, all patients with SCM should be surgically treated prophylactically even if they are asymptomatic. This new classification is easy to use and remember and takes into account the use of intraoperative findings that may have a bearing on surgical outcome.