Spinal dorsal dermal spinus tract:Case report and review of the literature

Introduction

Spinal dorsal dermal sinus is a rare entity and occurs in approximately one in every 2500 live births. This is supposed to results from failure of neuroectoderm to separate from the cutaneous ectoderm during the process of neurulation.^1-4

A congenital spinal dermal sinus consists of a tract lined by stratified squamous epithelium found on or near the midline and is thought to result from an abnormal adhesion (or incomplete disjunction) between the neuroectoderm (destined to form the neural tube) and the cutaneous ectoderm.^5,6

The squamous lining of spinal congenital dermal sinus may be encased in dermal and neurological tissue. Within the tract, one may find nerve or ganglion cells, fat, blood vessels, cartilage or meningeal remnants.^7,8 Congenital spinal dermal sinus may be associated with other abnormalities of the ectodermal, mesodermal or neural crest derivatives such as meningomyelocele or lipomeningomyelocele, reflecting it to be a common ontogenic disorder.^7,8

Sinus tracts can occur anywhere from occiput to sacrum. Different studies have shown that cervical area is least involved (<1% cases). Thoracic area is involved in 10% cases and lumbar and lumbosacral area in 40% and 12% of patients respectively. The involvement of sacrum is 23% and sacrococcygeal junction in 13% of cases.⁹

These tracts can be linked with tethering of the spinal cord, which limits the movement of the spinal cord in the spinal canal, and they may also be associated with aseptic meningitis, also known as chemical meningitis. Other potential problems include a benign dermoid cyst compressing the spinal cord or nerve roots, and diastematomyelia, where in there is splitting of the spinal cord by a bony, cartilaginous or fibrous septum in the central portion of the spinal canal.¹⁰

Case report

A 5 year old male child was brought with a history of fever, headache and intermittent discharge from a sinus in the mid-dorsal area. There was no history of seizure episodes, He had recurrent episodes of similar complaints since birth and the symptoms used to subside with antibiotic treatment each time.  On examination, he was febrile with normal motor power and intact sensations in all limbs and all neurological examination were normal.  Posterior aspect of mid-dorsal spine (D7) showed a dimple in the skin with pigmentation around and minimal active discharge at presentation (Fig 1).

Laboratory investigation showed raised leukocytes count and CRP. Antibiotics were started, USG showed Dermal sinus tract with suspected communication with Subarachnoid space. CT scan showed dorsal dermal sinus tract with bifid 7th dorsal vertebra (Fig 3 & 4). 

Whole spinal dermal sinus tract was excised and the tract disconnected from dural space and dura was repaired. (Fig 4 & 5). Postoperatively child made good recovery.

Histopathology suggestive of skin and sinus tract lined by granulation tissue and dense mixed inflammatory cell infiltrates with few foreign body giant cell and impacted hair follicles.

Discussion

Spinal dorsal sinus tract (DST) may have diverse and occasionally serious manifestations; in fact, many cases come to clinical attention by neurologic deficit and/or infectious complications including life-threatening conditions such as meningitis.9 In addition, DSTs are frequently associated with other anomalies of the central nervous system such as tethere cord, inclusion tumors, and split cord malformations (SCMs).^4,9  Inspite its benign external appearance, it may harbor great risks to the patients’ health. The neurological examination is reported to be normal in the early childhood. However, as the age increases, there is more chance of profound neurological deficit.

Dermal sinuses provide a portal of entry for bacterial agents into the intraspinal compartments that can cause meningitis or abscess formation that may be extradural, subdural, and intramedullary or infection of associated tumor. Also, aseptic meningitis can occur by spillage of inclusion tumor contents or other dermal elements into the cerebrospinal fluid.^11-13 In the study conducted by Jindal and Mahapatra only 1 patient presented with infection out of 26 patients (9). Ackerman and Menezes also had a low rate (10%) of infectious complications. In our case one child had infection which controlled by antibiotics.¹⁴

Nearly all children with spinal DSTs have intact neurological function at birth.^9,14 However, due to a relatively high rate of associated pathologies such as tethered cord, infection, and inclusion tumors, neurological deterioration becomes more common with increasing age. It has been shown that the chances of developing neurologic deficit are higher in patients who present in older ages.^9,14 However in our case child had no neurological symptoms.

These neurologic abnormalities may develop in up to 50% of children younger than 1 year of age and in 90% of children aged older than 1 year. Over time, children with these abnormalities may also have orthopedic abnormalities, which often include persistent toe walking and tight heel cords. Scoliosis and chronic back pain may also be observed.¹⁰

Clinical management of dysraphic spinal tract is generally determined on the basis of clinical history, examination findings, and results of MRI. While it is well recognized that infection (subcutaneous abscess, intraspinal abscess, and meningitis) can complicate a dermal sinus tract, it remains unclear which particular clinical or radiological factors predispose to this complication. The incidence of infection in a dermal sinus tract is not well characterized.¹⁴

Furthermore, in cases undergoing surgery, MRI may be unreliable in predicting the extent of the tract and the presence of associated pathology.¹⁵ Since none of the imaging modalities can accurately show intraspinal details, all dermal sinuses above the sacrococcygeal region should be explored operatively regardless of neuroimaging findings.^11,16,17 In our case we explored surgically where is a total excision of spinal dorsal sinus tract was done and dura repaired.

One should have a high index of suspicion for all dimples above the intergluteal fold, despite a normal examination or neuroradiologic finding. Midline should be carefully examined whenever a child suffers from meningitis, especially when an unusual organism is grown in the culture. Conservative treatment of spinal dermal sinus tract is not recommended. Surgery should be carried out prophylactically in advance of deficits, to maintain normal neurological function even in an asymptomatic child.^11,16,17

Conclusion

Spinal dorsal dermal sinus tract is an innocuousappearing spinal dysraphism that may contribute to devastating morbidities if not timely addressed. All patients with spinal dorsal dermal sinus tract should be offered aggressive surgical treatment in the form of total excision of sinus tract and correction of spinal malformation, as soon as diagnosis is made.