Object: The author studied the specific issue of ventral tethering in cases of type II split cord malformation (SCM). He also discussed the issue of ventral tethering in patients with type I SCM in whom a bony septum and dural sleeve have been resected.
Methods: Eleven (21%) of 52 patients with type II SCM were found to have a ventral fibrous septum tethering the hemicords to the ventral dura. Four categories of ventral septa were noted: 1) pure ventral intradural septa (three patients); 2) complete dorsoventral intradural septa (three patients); 3) dorsoventral septa continuous with a dermal sinus tract (two patients); and 4) ventral or complete septa continuous with ventral intestinal bands causing intestinal malrotation or diverticulum (three patients). Excluding one autopsy case, all 10 patients had symptoms or progressive neurological syndromes at diagnosis. Magnetic resonance imaging was completely ineffective, and computerized tomography (CT) myelography was only partially effective in detecting ventral tethering in 50% of cases. The only other positive predictor of ventral tethering is the association of dermal sinus tract and intestinal malformations. Combining this predictor with CT myelography, only 60% of the cases of ventral tethering could be suspected before surgery.
Conclusions: The author recommends examining all patients with type II SCM, and at surgery the ventral surface of the split length and reunion site should be thoroughly inspected to reveal a ventral band.