Slender Stalk with Combined Features of Saccular Limited Dorsal Myeloschisis and Congenital Dermal Sinus in a Neonate

In utero Diagnosis of Spinal Dermal Sinus

INTRODUCTION

Congenital dermal sinus (CDS) is an open neural tube defect (NTD) that occurs in 1 in 2,500 births a year and often goes undetected until patients present with complications like infection and neurological deficits. Early diagnosis and repair of CDS may prevent formation of these complications. In utero diagnosis of these lesions may improve long-term outcomes by enabling referral to specialty services and planned postnatal repair; however, only 2 such cases have been reported in the literature. We present a third case of in utero diagnosis of CDS with a description and discussion of findings from surgical exploration and pathology.

CASE PRESENTATION

Routine prenatal ultrasound scan detected a tethered cystic structure arising from the back of the fetus at 20 weeks of gestation. Dedicated fetal ultrasound confirmed the presence of a cystic lesion protruding through a lamina defect, while fetal magnetic resonance imaging showed an intact spinal cord and meninges, suggesting a diagnosis of CDS. Neurosurgery followed along closely and took the child for surgical exploration on day 2 of life. A fibrous stalk with an intradural component and associated cord tethering was excised. Histology showed fibrous tissue without an epithelial-lined lumen.

CONCLUSION

CDS is a form of NTD that occurs from nondisjunction of the cutaneous ectoderm and neuroectoderm during formation of the neural tube. Slight differences in how this error occurs can explain variations seen in this spectrum of disease, including CDS without an epithelial-lined lumen as seen in this case. Newborns with CDS can go undiagnosed for years and present with long-term complications. Fetal imaging can assist in early recognition and surgical excision of CDS in newborns.

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.

Spinal cord deformity with aggravation of tethering in saccular limited dorsal myeloschisis during the first 2 months of life

Background

Although the optimal timing of prophylactic untethering surgery for limited dorsal myeloschisis (LDM) with intact or subtle neurological findings diagnosed at birth remains undetermined, intentional delayed surgery is commonly used for flat and tail-like LDM. Conversely, for saccular LDM, early surgery is indicated during the postnatal period because it prevents rupture of the sac. We treated a saccular LDM patient, in whom intentional delayed surgery was selected because the sac was thickly covered with normal skin. We describe the clinical course of the case and discuss the optimal timing of the surgery.

Case Description

The patient had a dorsal midline sac in the upper lumbar region. Initial magnetic resonance imaging (MRI) after birth revealed a tethering tract that began at the dome of the sac and joined the lumbar cord. Dorsal bending of the cord at the stalk-cord union and invagination of the cord into the sac were noted. At 2 months, he was neurologically normal; however, the second MRI examination revealed that the cord tethering was aggravated. The cord was markedly displaced dorsally and to the left, with deviation of the cord to the sac out of the spinal canal. Following untethering surgery, the spinal cord deformity markedly improved.

Conclusion

Early surgery may be recommended for saccular LDM when tethering is present, including dorsal bending of the cord at the stalk-cord union and invagination of the cord into the sac observed on detailed MRI examination, even if the sac has no risk of rupture.

Saccular Limited Dorsal Myeloschisis with Spinal Cord Deviation out of the Spinal Canal to the Sac

Saccular limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the saccular skin lesion to the underlying spinal cord. Since untethering surgery during the early postnatal period is often indicated to prevent sac rupture, saccular LDM should be distinguished from myelomeningocele (MMC) during the perinatal period. We treated two patients with the spinal cord deviation from the spinal canal to the sac, which mimicked a prolapse of the neural placode into the MMC sac. In patient 1, pre- and postnatal magnetic resonance imaging (MRI) revealed that the spinal cord was strongly tethered to the thick stalk. During surgery, the dorsally bent cord and stalk were united, and the border between these two was determined with intraoperative neurophysiological mapping (IONM). In patient 2, the spinal cord was tethered to two slender stalks close to each other, which was visible with the combined use of sagittal and axial postnatal three-dimensional heavily T2-weighted imaging (3D-hT2WI). The preoperative MRI hallmark of saccular LDM is the visualization of a stalk that links the bending cord and sac. Complete untethering surgery to return the cord into the spinal canal and correct its dorsal bending is recommended.

Terminal syringomyelia associated with lumbar limited dorsal myeloschisis

PURPOSE

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural tethering stalk linking the skin lesion to the underlying spinal cord. Terminal syringomyelia, which is located at the lower third of the cord, is often associated with a tethered cord caused by various spinal dysraphisms; however, terminal syringomyelia has not been documented in LDM. The purpose of this study was to clarify the pathophysiological mechanisms of syringomyelia in LDM.

METHODS

In our 16 patients with lumbar LDM, three patients had terminal syringomyelia. We retrospectively analyzed the clinical, neuroradiological, intraoperative, and histopathological findings for these patients, with particular attention to the clinical course of the syrinx.

RESULTS

Patient 1 had a saccular skin lesion and patients 2 and 3 had flat lesions. In all patients, the syringomyelic cavity was located in the lower thoracolumbar cord, immediately rostral to the stalk-cord attachment at the lumbar level. The caudal pole of the syrinx extended to the thickened stalk at the attachment instead of at the caudal cord. Patient 3 had another syrinx in the stalk itself. The longitudinal axis of the syrinx and central canal coincided with the traveling angle of the LDM stalk at the stalk-cord attachment. In patient 1, histology revealed an ependyma-lined central canal in both the LDM stalk and meningocele sac. Patients 1 and 2 underwent syringostomy, but long-term effects were not obtained. Preoperative spontaneous resolution occurred in patient 3.

CONCLUSIONS

The histological findings in patient 1 supported the idea that segmental myelocystocele is involved in the development of saccular LDM. The hydromyelic central canal herniates and distends the stalk, resulting in the formation of the myelocystocele. It is possible that the hydromyelic central canal also distends the stalk of flat LDM lesions. The syrinx in patient 3 differed from that in patients 1 and 2, in that the syrinx resolved spontaneously. Further studies are needed to clarify the outcomes of syrinxes associated with LDM stalks.

Retained medullary cord with sacral subcutaneous meningocele and congenital dermal sinus

BACKGROUND

A retained medullary cord (RMC) is a rare closed spinal dysraphism with a robust elongated cord-like structure extending continuously from the conus medullaris to the dural cul-de-sac that is caused by late arrest of secondary neurulation. Five patients with RMC extending to an associated sacral subcutaneous meningocele have been reported.

CASE PRESENTATION

We report an additional patient with RMC, in whom a congenital dermal sinus (CDS) was found in the caudal portion of the RMC. At the age of 3 days, the patient underwent surgery consisting of meningocele excision and cord untethering, and CDS was noted histologically in the proximal cut end of the RMC. During a second surgery at the age of 5 months, after determining the exact border of the nonfunctional RMC and the true conus by neurophysiological mapping, we removed the entire length of the remnant RMC, including newly developed epidermoid cysts in the CDS.

CONCLUSION

Although the exact pathoembryogenesis of concurrent RMC and CDS is unknown, an associated subcutaneous meningocele, caused by failure of primary neurulation, could be involved. Surgeons should be aware of the possibility of the coexistence of CDS when dealing with RMCs that extend out to the extradural space.

Neurosurgical Pathology and Management of Limited Dorsal Myeloschisis Associated with Congenital Dermal Sinus in Infancy

BACKGROUND

Because of the shared origin of limited dorsal myeloschisis (LDM) and congenital dermal sinus (CDS), CDS elements may be found within the fibroneural LDM stalk. When part of the CDS invested in the intradural stalk is left during untethering surgery, inclusion tumors such as dermoid cysts may develop. However, the most appropriate surgical strategy for LDM with CDS is still under debate.

METHODS

Of 19 patients with LDM, 3 (15.8%) had histologically verified CDS elements. We retrospectively analyzed the clinicopathological findings of these patients.

RESULTS

In patient 1, the entire stalk including a tiny dermoid cyst at the intradural stalk could be resected through two-level laminectomy during untethering at 6 months of age. In patients 2 and 3, the stalk appeared to be a typical LDM stalk during the initial surgery at 18 and 7 days, respectively; however, CDS was histologically diagnosed in the proximal severed end of the stalk. Postoperative three-dimensional heavily T2-weighted imaging demonstrated spherical enlargement of the remnant stalk, and the entire length of the remnant stalk including newly developed dermoid was resected during the second surgery at 3 years 11 months and 11 months, respectively. Histopathologically, glial fibrillary acidic protein-immunopositive neuroglial tissues and CDS elements were mainly located at the proximal and distal sites of the stalk, respectively, supporting the "dragging down and pulling up" theory. In patients 2 and 3, however, the proximal head of the dermoid cyst passed the distal head of the neuroglial tissues and located at the stalk-cord attachment.

CONCLUSION

Surgeons should be aware of the approximately 10% possibility of the coexistence of CDS when managing infant LDM. However, the recommendation for excision of the entire length of the LDM stalk in all patients should be more carefully made because such a strategy may result in an unnecessary extent of laminotomy/laminectomy for most patients with pure LDM. However, once the postoperative histological examination reveals coexistence of CDS in the resected proximal part of the stalk, the entire length of the remnant stalk should be excised as soon as possible.

Congenital Dermal Sinus Elements in Each Tethering Stalk of Coexisting Thoracic Limited Dorsal Myeloschisis and Retained Medullary Cord

INTRODUCTION

The embryogenesis of limited dorsal myeloschisis (LDM) likely involves impaired disjunction between the cutaneous and neural ectoderms during primary neurulation. Because LDM and congenital dermal sinus (CDS) have a shared origin in this regard, CDS elements can be found in the LDM stalk. Retained medullary cord (RMC) is a closed spinal dysraphism involving a robust, elongated, cord-like structure extending from the conus medullaris to the dural cul-de-sac. Because the RMC is assumed to be caused by impaired secondary neurulation, concurrent RMC and CDS cannot be explained embryologically. In the present article, we report a case in which CDS elements were noted in each tethering stalk of a coexisting LDM and RMC.

CASE PRESENTATION

A 2.5-month-old boy with left clubfoot and frequent urinary and fecal leakage had 2 tethering tracts. The upper tract, which ran from the thoracic tail-like cutaneous appendage, had CDS elements in the extradural stalk and a tiny dermoid cyst in the intradural stalk immediately after the dural entry. In the lower tract, which ran from the lumbosacral dimple, the CDS as an extradural stalk continued to the RMC at the dural cul-de-sac. Both stalks were entirely resected through skip laminotomy/laminectomy at 1 stage to untether the cord and resect the CDS elements.

CONCLUSION

Surgeons should be aware that CDS elements, in addition to LDM, may coexist with RMC that extends out to the extradural space.

Human tail-like cutaneous appendage with a contiguous stalk of limited dorsal myeloschisis

PURPOSE

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the skin lesion to the underlying spinal cord. On account of the external skin lesion, all LDMs are either flat (nonsaccular) or saccular, and a human tail-like cutaneous appendage has not been reported.

METHODS

In our 14 LDM patients, 2 had tail-like appendages. We retrospectively analyzed the relationship between the appendage and the LDM tract from the clinicopathological findings of these 2 patients.

RESULTS

Preoperative magnetic resonance imaging including three-dimensional heavily T2-weighted images demonstrated an intradural tethering tract, but failed to reveal the precise communication with the appendage. However, surgery revealed the extradural and intradural slender stalk, starting at the base of appendage and running through the myofascial defect. Histological examination demonstrated that there was a tight anatomical relationship between the fibroadipose tissue of the appendage and the fibrocollagenous LDM stalk.

CONCLUSION

When there is potential for an LDM stalk in patients with an appendage, a meticulous exploration of the stalk leading from an appendage is required. Clinicians should be aware of possible morphological variations of skin lesions associated with LDM.