Prone Position Magnetic Resonance Imaging and Transhiatal Approach to Filum Terminale Externum Sectioning in Adolescents with Occult Tethered Cord Syndrome: Report of Four Cases

<b><i>Introduction:</i></b> Occult tethered cord syndrome (OTCS) and its surgical treatment are controversial. A previous study with lumbar magnetic resonance imaging (MRI) in the prone position had found statistically significant differences in morphological parameters between pediatric OTCS patients and a control group. Filum terminale internum (FTI) sectioning is currently the gold standard for the treatment of OTCS. <b><i>Case Presentation:</i></b> We present four cases of adolescents with OTCS, of which three cases were associated with low-lying cerebellar tonsils (LLCT). The patients presented various symptoms of OTCS from pain to sensory disturbances to alterations in sphincter functions, but none had disorders belonging to all three categories. A T2-weighted axial MRI in the prone position supported the clinical diagnosis of OTCS. The patients were treated with minimal skin incision and filum terminale externum (FTE) sectioning through the sacral hiatus under local anesthesia. <b><i>Discussion:</i></b> We describe for the first time the association between lumbar MRI in the prone position and FTE sectioning in OTCS. The FTE sectioning has resulted in the disappearance of the pain and sensory disturbance symptoms. The results on the sphincter function are mixed. Three of our four patients with OTCS had LLCT, and all three also reported headache episodes, which, surprisingly, disappeared postoperatively. This minimally invasive surgery involves only minimal discomfort for the patient and minimizes the risks related to skin incision only. The postoperative lumbar MRI in the prone position has shown that there is no mobilization of the FTI or changes in the other preoperative morphological parameters.