An Unusual Presentation of Congenital Dermal Sinus
An Unusual Presentation of Congenital Dermal Sinus
The authors present the first report of spinal congenital dermal sinus with paramedian dual ostia leading to 2 intradural epidermoid cysts. This 7-year-old girl had a history of recurrent left paramedian lumbosacral subcutaneous abscesses, with no chemical or pyogenic meningitis. Admission MRI studies demonstrated bilateral lumbar dermal sinus tracts and a tethered spinal cord. At surgery to release the tethered spinal cord the authors encountered paramedian dermal sinus tracts with dual ostia, as well as 2 intradural epidermoid cysts that were not readily apparent on MRI studies. Congenital dermal sinus should be considered in the differential diagnosis of lumbar subcutaneous abscesses, even if the neurocutaneous signatures are located off the midline.
Congenital dermal sinus tracts of the spine are a rare form of spinal dysraphism, and are hypothesized to be the result of incomplete separation of the neuroectoderm from the cutaneous ectoderm during neurulation. The incidence of CDS has been estimated to be approximately 1 in every 2500 live births. The stratified squamous epithelium–lined sinus originates at the skin surface and may terminate superficially within the subcutaneous layers, or it may extend deep through the fascia through normal vertebrae or a bifid spine to communicate directly with the dura mater or intradural compartment. The CDS tracts can be associated with several pathological findings, including inclusion tumors (for example, epidermoid, dermoid, and teratoma), split-cord malformations, and tethered spinal cords. An epidermoid or dermoid cyst may arise at any point along the course of the CDS tract. There have been only 5 reported cases of CDS with dual paramedian ostia, 2 of them associated with dermoid cysts. Association of these multiple paramedian CDS ostia with lumbosacral lipomas and vertebral anomalies such as hemivertebrae, block vertebrae, and accessory hemivertebrae are reported by Lee et al.
Spinal congenital epidermoid cysts arise from epithelial inclusion during neural tube formation between the 3rd and 5th weeks of embryological development. Acquired intraspinal epidermoid cysts may occur iatrogenically following lumbar puncture. Congenital epidermoid cysts are uncommon, but occur more frequently than iatrogenic epidermoid cysts. The incidence of intracranial epidermoids varies from 0.2% to 1%, and is even less frequent in the spine. Epidermoids are classically noted to occur intracranially in a paramedian location such as the parasellar region or cerebellopontine angle. They are typically hypo- to isointense on T1-weighted MRI and hyperintense on T2-weighted MRI studies. Because their signal intensity on MRI is similar to CSF, epidermoids can sometimes be difficult to diagnose. Some of these tumors appear iso- to hyperintense on T1-weighted MRI due to high lipid content, and hence are called "white epidermoids," whereas those tumors having reduced lipid content on spectroscopy are called "black epidermoids." Rarely, these epidermoid tumors have been reported to have varying signal intensities (for example, hyperintensity on T1-weighted images and hypointensity to mixed intensity on T2-weighted images).
The DW and FLAIR techniques are commonly used in MRI studies to differentiate epidermoid cysts from arachnoid cysts. Most epidermoid cysts do not suppress completely on FLAIR images and restrict well on DW images, showing high signal intensity. Arachnoid cysts on the other hand commonly do not restrict on DW images. The CSF component of arachnoid cysts demonstrates a low or suppressed signal on FLAIR imaging. Chen et al. compared conventional MRI sequences to fast-FLAIR and echo planar DW MRI studies, and concluded that FLAIR was superior to other conventional MRI sequences in detecting epidermoids. However, some arachnoid cysts may also contain blood or proteinaceous material that can further complicate the radiological diagnosis. Likewise, rare white epidermoids are dense lesions with high protein content showing a reversal of signal intensity on MRI studies, with hyperintensity on T1-weighted and hypointensity on T2-weighted images.
Spinal epidermoid cysts may be asymptomatic or may produce a varied range of symptoms such as radiculopathy, motor deficit, or sphincter dysfunction. Gradual worsening of symptoms may suggest enlargement of the cyst with mass effect on abutting neural structures. A sudden onset of symptoms, especially headache, is often suggestive of cyst rupture. The rupture of an epidermoid cyst may introduce its inflammatory contents (keratin, cholesterol crystals, and desquamated squamous cells) into the CSF, resulting in chemical meningitis.
We report a child with 2 paramedian skin dimples and recurrent soft-tissue infections that were drained by general surgeons over 7 years. An MRI sequence of the lumbar spine showed a tethered cord, but 2 intradural epidermoid cysts were noted at surgery. We highlight the importance of CDSs with intradural extension in the differential diagnosis of recurrent lumbosacral soft-tissue infections, even in the absence of chemical or pyogenic meningitis.
Abstract and Introduction
Abstract
The authors present the first report of spinal congenital dermal sinus with paramedian dual ostia leading to 2 intradural epidermoid cysts. This 7-year-old girl had a history of recurrent left paramedian lumbosacral subcutaneous abscesses, with no chemical or pyogenic meningitis. Admission MRI studies demonstrated bilateral lumbar dermal sinus tracts and a tethered spinal cord. At surgery to release the tethered spinal cord the authors encountered paramedian dermal sinus tracts with dual ostia, as well as 2 intradural epidermoid cysts that were not readily apparent on MRI studies. Congenital dermal sinus should be considered in the differential diagnosis of lumbar subcutaneous abscesses, even if the neurocutaneous signatures are located off the midline.
Introduction
Congenital dermal sinus tracts of the spine are a rare form of spinal dysraphism, and are hypothesized to be the result of incomplete separation of the neuroectoderm from the cutaneous ectoderm during neurulation. The incidence of CDS has been estimated to be approximately 1 in every 2500 live births. The stratified squamous epithelium–lined sinus originates at the skin surface and may terminate superficially within the subcutaneous layers, or it may extend deep through the fascia through normal vertebrae or a bifid spine to communicate directly with the dura mater or intradural compartment. The CDS tracts can be associated with several pathological findings, including inclusion tumors (for example, epidermoid, dermoid, and teratoma), split-cord malformations, and tethered spinal cords. An epidermoid or dermoid cyst may arise at any point along the course of the CDS tract. There have been only 5 reported cases of CDS with dual paramedian ostia, 2 of them associated with dermoid cysts. Association of these multiple paramedian CDS ostia with lumbosacral lipomas and vertebral anomalies such as hemivertebrae, block vertebrae, and accessory hemivertebrae are reported by Lee et al.
Spinal congenital epidermoid cysts arise from epithelial inclusion during neural tube formation between the 3rd and 5th weeks of embryological development. Acquired intraspinal epidermoid cysts may occur iatrogenically following lumbar puncture. Congenital epidermoid cysts are uncommon, but occur more frequently than iatrogenic epidermoid cysts. The incidence of intracranial epidermoids varies from 0.2% to 1%, and is even less frequent in the spine. Epidermoids are classically noted to occur intracranially in a paramedian location such as the parasellar region or cerebellopontine angle. They are typically hypo- to isointense on T1-weighted MRI and hyperintense on T2-weighted MRI studies. Because their signal intensity on MRI is similar to CSF, epidermoids can sometimes be difficult to diagnose. Some of these tumors appear iso- to hyperintense on T1-weighted MRI due to high lipid content, and hence are called "white epidermoids," whereas those tumors having reduced lipid content on spectroscopy are called "black epidermoids." Rarely, these epidermoid tumors have been reported to have varying signal intensities (for example, hyperintensity on T1-weighted images and hypointensity to mixed intensity on T2-weighted images).
The DW and FLAIR techniques are commonly used in MRI studies to differentiate epidermoid cysts from arachnoid cysts. Most epidermoid cysts do not suppress completely on FLAIR images and restrict well on DW images, showing high signal intensity. Arachnoid cysts on the other hand commonly do not restrict on DW images. The CSF component of arachnoid cysts demonstrates a low or suppressed signal on FLAIR imaging. Chen et al. compared conventional MRI sequences to fast-FLAIR and echo planar DW MRI studies, and concluded that FLAIR was superior to other conventional MRI sequences in detecting epidermoids. However, some arachnoid cysts may also contain blood or proteinaceous material that can further complicate the radiological diagnosis. Likewise, rare white epidermoids are dense lesions with high protein content showing a reversal of signal intensity on MRI studies, with hyperintensity on T1-weighted and hypointensity on T2-weighted images.
Spinal epidermoid cysts may be asymptomatic or may produce a varied range of symptoms such as radiculopathy, motor deficit, or sphincter dysfunction. Gradual worsening of symptoms may suggest enlargement of the cyst with mass effect on abutting neural structures. A sudden onset of symptoms, especially headache, is often suggestive of cyst rupture. The rupture of an epidermoid cyst may introduce its inflammatory contents (keratin, cholesterol crystals, and desquamated squamous cells) into the CSF, resulting in chemical meningitis.
We report a child with 2 paramedian skin dimples and recurrent soft-tissue infections that were drained by general surgeons over 7 years. An MRI sequence of the lumbar spine showed a tethered cord, but 2 intradural epidermoid cysts were noted at surgery. We highlight the importance of CDSs with intradural extension in the differential diagnosis of recurrent lumbosacral soft-tissue infections, even in the absence of chemical or pyogenic meningitis.
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