Pseudo-dermal sinus tract or spinal dermal-sinus-like stalk?

Abstract

Dear Editor,We read with great interest the paper “Spinal dermal sinusand pseudo-dermal sinus tracts: two different entities” byMartinez-Lage et al. [1]. In fact, the term “sinus” may beused for (chronically) infected tracts connecting a deep-seated infection to the skin, and discharging pus to thesurface, except for those tracts connecting two epithelial-ized surfaces, which are called “fistula”.A spinal dermal sinus (DS) is a developmental anomalyof the dorsal midline axis, in which a hollow, epithelium-lined tract extends inward from the skin surface for avariable distance [1–3]. A key feature of a DS is an openskin defect; however, this may be minute and, as such,easily overlooked during routine neonatal examination [1].Occasional discharge from this orifice is a common finding,however, even in case of connection with the spinal cord,this never is cerebrospinal fluid [3, 4]. Another key featureof a DS is the accumulation of (epi)dermoid remnants,often presenting as tumors inside the tract or even insidethe spinal cord. Such tumors may produce manifestationsof spinal cord or cauda equina compression [1]. Moreover,due to an open connection with the skin surface, manycases present with meningitis and intraspinal, intramedul-lary, or more superficial intra-epidermoid abscesses, apotentially life-threatening condition, rather than with cordtethering (recurrent cases no longer connected to the skinsurface) [1, 3].A spinal dermal-sinus-like stalk (DSS) [4] or pseudo-dermal sinus tract as proposed by Martinez-Lage et al. [1]isa developmental anomaly of the dorsal midline axis, inwhich a solid tract extends outward from the intraduralspace to the skin. Key features of a DSS are a closed skindefect (a dimple, cigarette burn, or blister, all without anorifice) usually more obvious than in case of a DS, theabsence of a lumen, and the absence of (epi)dermoidremnants inside the tract [1, 4]. Consequently, a DSS willnever present with meningitis, but rather with cord tethering[1, 4]. To illustrate this point, we have included severalphotographs highlighting the essential surgical steps in caseof a DSS, which, in this particular case, was attached to alow-lying conus medullaris (Fig. 1a–f).In case of a DS, stratified squamous epithelium insidethe lumen, surrounded by dermal tissue, suggests anondisjunction of cutaneous and neural ectoderm withinward dragging of the epidermis. In case of a DSS,however, mesenchymal and neural elements inside the stalksuggest an embryologic development in the oppositedirection (inside-out rather than outside-in). This wouldexplain the absence of a skin orifice, the occasional dorsaltenting of the dura, and the presence of glioneural tissueinside the stalk. Thus, a DSS would represent an atrophicmesodermal-neural stalk [4] and, as suggested by Martinez-Lage et al., may indeed represent the spinal counterpart ofan atretic encephalocele [1].