Dermal sinus
A dermal sinus is a congenital defect arising from a closure failure of the neural tube that results in different degrees of communication between the skin and the central nervous system.
It is a scaly, multi-layered channel of tissue that is lined by epithelial cells and can end anywhere between subcutaneous planes to the thecal sac.
Localization
see Cranial dermal sinus.
A dermal sinus can occur anywhere from the root of the nose to the conus medullaris, and the occipital location is the second most common.
In about 66%, dermoid cysts are associated with some form of dermal sinus 1), or epidermoid cysts and less frequently with teratomas.
Pathophysiology
Embryologically, they result from a failure of the surface ectoderm and dermal elements to separate from the neuroectoderm. This process likely occurs between the 3rd and 8th weeks of gestation.
Clinical features
May appear as a dimple or a sinus (open tract), with or without hairs, usually very close to the midline, with an opening of only 1 to 2 millimeters. The surrounding skin may be normal, pigmented or distorted by an underlying mass.
The tract may end just below the skin surface or may extend to portions of the spinal cord, skull base or nasal cavity.
These tracts may be accompanied with other pathologies such as lipomyelomeningocele, myelomeningocele, split cord malformation, tethered cord, filum abnormality and inclusion tumors.
Congenital dermal sinus (CDS) and occult spinal dysraphism are suspected when a cutaneous marker overlies the spine of a newborn. CDS can have the appearance of a simple dimple and occur within the gluteal cleft without any skin markers.
Diagnosis
If the tract is seen following birth, a magnetic resonance imaging (MRI) scan should be obtained. Images may show the tract and its point of attachment. MRI also shows masses within the canal.
Complications
Treatment
Case reports
2015
A 15-month-old female presented with high fever, severe right hemiparesis, difficulty breathing and cranial nerve deficits. Magnetic resonance imaging (MRI) of the spine revealed a congenital dermal sinus tract at the Th6 level, an intramedullary collection extending up to the brainstem and a probable intramedullary cystic lesion. The child was operated acutely with ligation of the sinus tract, drainage of the abscess and partial removal of the intramedullary lesion. Due to abscess recurrence, she was reoperated with complete excision of the dermal sinus tract, abscess redrainage and subtotal excision of the dermoid cyst (retaining a part of its capsule). Pus culture isolated Corynebacterium species and Peptococcus species and histology of the lesion showed a dermoid cyst. Postoperatively, after an initial neurologic deterioration, she progressively improved. An MRI scan at 15 months neither showed recurrence of the collection nor regrowth of the lesion. Spinal dermal sinus tracts that remain unnoticed or untreated can result in serious complications and should be operated as soon as possible to prevent undesirable sequelae 2)
1995
A 16-month-old male infant presented with paraparesis and a high thoracic skin dimple. After myelography the child underwent complete surgical removal of the dermal sinus and of an abscessed tumor located within the cervicothoracic cord. Histological study showed that the lesion was an intramedullary epidermoid cyst. Only four descriptions have previously been published of dermal sinuses associated with intramedullary epidermoids, three of them complicated by intramedullary abscesses. This appears to be the first report in the current literature of the association of a dermal sinus and an infected intramedullary epidermoid occurring out of the confines of the lumbosacral region 3).