Limited dorsal myeloschisis without extradural stalk continuity to coexisting congenital dermal sinus.

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural tethering stalk linking the skin lesion to the underlying spinal cord. LDM without an extradural stalk is rare. A full-term boy was noted at birth to have a dimple in the upper back (dorsal skin of the lower thoracic region). Computed tomographic scan showed spina bifida at the T9-12 vertebral level and osteochondral tissue at the T10 level. Magnetic resonance imaging (MRI) demonstrated a tiny dorsal lipoma at the T8 vertebral level, but the intradural tethering tract was not apparent. At 18 days of age, the congenital dermal sinus (CDS) tract started from the dimple and terminated at the osteochondral tissue, without continuity of the dura mater, and the osteochondral tissues were resected. At age 2 years 8 months, he developed spastic paresis of the right foot. On MRI, the tethering tract from the dorsal lipoma became apparent. During the second surgery at age 2 years 11 months, the intradural stalk started from the dorsal lipoma and joined the inner surface of the dura mater was untethering from the cord. Postoperatively, right spastic paresis was improved. Histological examination of the intradural stalk revealed the distribution of S100-immunopositive peripheral nerve fibers, which is one of the histopathological hallmarks of LDM. We speculated that the extradural stalk with coexisting CDS originally linked from the skin lesion subsequently regressed and was replaced by fibroadipose tissue with osteochondral tissue migration. Intradural exploration should always be seriously considered in these disorders of persisting neurocutaneous connection.