Keywords
cervical dermal sinus tract - rudimentary meningoceles - tethered spinal cord
Introduction
Rudimentary meningoceles arise from involution and scarring from incomplete neural
tube closure during pregnancy. In the setting of spinal cord tethering, surgery is
indicated to prevent future neurologic sequelae. Rudimentary meningoceles are rare
congenital spinal malformations that typically present with solid cutaneous masses
and carry the risk of future neoplastic growth.[1]
[2] This entity is typically present at birth with cutaneous deformities and is characteristically
on the scalp or midline spine.[3] Intradural rudimentary meningoceles are infrequently reported and carry operative
challenges that are not well established in the literature. To date, there have been
three reported cases of intradural rudimentary meningoceles in the spine.[2]
[3]
[4] Here we present the surgical management of an asymptomatic infant with a rudimentary
meningocele and tethered spinal cord.
Case Report
History and Preoperative MRI
The patient presented at birth with a midline cervical and posterior right shoulder
dimple. The patient was born at 40 weeks, 4 days to a 29-year-old primigravida whose
pregnancy was complicated by a prenatal ultrasound showing possible amniotic band
syndrome. The patient underwent a total spinal ultrasound that was inconclusive for
a dermal sinus tract.
At the age of 4 months, the patient underwent a total spine magnetic resonance imaging
(MRI). The MRI revealed what appeared to be a dorsal dermal sinus tract with intraspinal
extension to C2-3 and external opening at level of spinous process C5 ([Fig. 1]). There was a small (5 × 8 mm) subcutaneous nodule in the soft tissue at the C5
level felt to represent an epidermoid cyst. The MRI also showed a hypoplastic C3-4
intervertebral disc with vertebral segmentation abnormality and spinal laminar nonfusion
of C4 vertebra ([Fig. 1]). The scan was negative for hydromyelia. We recommended surgical resection of the
dermal sinus tract and suspected dermoid cyst and tethered cord release.
Fig. 1 Preoperative magnetic resonance imaging scan. T2 sagittal scan shows dorsal dermal sinus tract and external opening at the level
of spinous process C5.
Surgical Management
At the time of surgery, the patient was 5 months old and had a normal neurological
examination. She underwent general anesthesia for excision of dermal sinus tract,
en bloc resection of the presumed subcutaneous epidermoid and associated tract, and
release of the tethered cervical cord via intradural exploration. At the time of surgery,
the patient was placed in the prone position and somatosensory-evoked potential and
motor-evoked potential neuromonitoring were initiated. An ellipse incision allowed
for en bloc removal of the dermal sinus tract and exposed the intradural attachment
([Fig. 2A]). The team performed C2-4 laminectomies to obtain adequate dural exposure and complete
dermal sinus tract excision. A small tract remnant at the level of the dura was left
and was tied off with a silk suture. The excised tract appeared bubbled in nature
with a distinct white cutaneous nodule and was sent to pathology for evaluation ([Fig. 2B]).
Fig. 2 Intraoperative pictures. (A) Preoperative image of skin lesion. (B) Excised dermal sinus tract with prominent white nodule on skin surface. (C) Microsurgical intradural exploration and detethering.
An operating microscope was used to facilitate the intradural microdissection for
the remainder of the tethered cord release. The dura was opened caudally to the insertion
point of the tract and extended cranially around this point to visualize the fibrous
stalk that penetrated the dura and attached to the spinal cord ([Fig. 2C]). The spinal cord was completely detethered and the dura was closed in standard
running fashion. Neuromonitoring signals remained stable throughout the duration of
the case. 11 days postoperatively, the patient underwent revision surgery for wound
dehiscence and presumed cerebrospinal fluid leak, although no discrete leak site was
observed. Cultures from the surgical site were negative. A lumbar drain was placed,
and plastic surgery assisted with a two-layer muscle closure over the dura. The patient
has had an uneventful recovery since.
Histological Diagnosis
Histologically, the specimen had two epidermal openings that formed two blunt sinus
tracts lined with squamous epithelium. The specimen had dilated irregular vessels
forming a cord around fibrous tissue and epithelial membrane antigen immunostaining
was positive for meningothelial cells. The findings were consistent with rudimentary
meningocele.
Discussion
Dermal sinus tracts are a rare spinal dysraphism that typically presents in approximately
0.04% of neonates with skin abnormalities, neurologic deficits, or infection.[5] Cervical dermal sinus tracts are rare (<1% of dermal sinus tracts) and surgical
outcomes are widely absent from present literature.[5] Rudimentary meningoceles of the spine are exceedingly rare and only 18 cases have
been reported; of these 18 patients, only three cases had intradural rudimentary meningocele
extension.[1]
[2]
[3]
[4] Given the rarity of both cervical dermal sinus tracts and rudimentary meningoceles,
there is a need to report surgical outcomes to inform future management of these conditions.
Dermal sinus tracts and rudimentary meningoceles are thought to be of similar embryogenic
origin and require surgical intervention.[3]
[5] The presence of dermal sinus tracts raises the risk of hydrocephalus, meningitis,
and other infections.[5] Rudimentary meningoceles carry the risk of nerve damage and can manifest bladder
and bowel dysfunction and muscle paralysis.[3] The rare nature of rudimentary meningoceles has complicated a definitive understanding
of the origin and pathogenicity of this condition. Recent reports have questioned
if rudimentary meningoceles carry the risk of neoplastic growth. A recent study has
shown that a neoplastic cutaneous meningioma can grow within a rudimentary meningocele.
Histopathological analysis in these cases (n = 4) reported meningeal whorl formations, psammoma bodies, and collagen bundles in
addition to the meningothelial cells of the rudimentary meningocele.[2]
Current understanding defines rudimentary meningoceles as spinal dysraphisms and type
I cutaneous meningiomas as neoplasms. Rudimentary meningoceles do not always have
features of meningioma and are not synonymous with type I cutaneous meningiomas.[2] Our patient's histopathological analysis was negative for indications of cutaneous
meningioma. Nevertheless, the risk of neoplastic growth from rudimentary meningoceles
warrants surgical intervention to prevent neurological dysfunction and potential meningioma
growth.
Tethered spinal cords have been reported in up to 63% of dermal sinus tract cases.[1]
[5] Tethered spinal cords are associated with sensory loss, motor weakness, and urinary
tract dysfunction.[2] Although some cases may present asymptomatically, diagnosis of a tethered spinal
cord requires prompt treatment to prevent future sequelae. In total, the risk of future
infection, neoplastic growth, and sensory and motor deficits call for prompt surgical
treatment of intradural rudimentary meningoceles in infants.
Presently, there are three reported cases of intradural rudimentary meningoceles in
the spine that were surgically managed.[2]
[3]
[4] In a case similar to our patient, a 14-month-old female presented with a cutaneous
skin dimple and MRI confirmed a cervical dermal sinus tract with spinal cord tethering.[3] In other related cases, a 9-month-old male presented with a congenital skin-covered
hump in the thoracolumbar region with intradural attachment via vascular stalk and
a 15-year-old male presented with a protuberant skin lesion that penetrated the dura
and attached to the phylum terminale.[2]
[4] The second two cases were not associated with an identifiable tract and at presentation
had outward skin protrusions from the meningocele. No cases of recurrence or neurological
deficit after surgery have been reported. Taken together, these cases suggest surgical
excision is an appropriate treatment option for intradural rudimentary meningoceles
in the spine.
Conclusion
Cervical dermal sinus tracts and rudimentary meningoceles are extremely rare spinal
conditions. Surgical intervention can prevent future neurologic deficits. Here we
present the case of an asymptomatic infant with a midline cervical dimple at birth.
MRI confirmed the presence of a cutaneous tract with intraspinal extension. Our study
supplements the current literature on intradural rudimentary meningoceles and reports
the successful surgical management of this condition in an infant presenting with
a tethered cervical cord.
