What is a spinal sinus? A comprehensive guide

September 21, 2025 •

4 min read

Approximately 1 in 2500 live births involves a congenital dermal sinus, a rare birth defect commonly referred to as a spinal sinus. This condition presents as an abnormal tract connecting the skin's surface to the deeper tissues around the spine, posing a significant risk if not properly managed.

Quick Summary

A spinal sinus, or congenital dermal sinus tract (DST), is a rare congenital condition and a type of spinal dysraphism, characterized by a narrow, hollow channel that extends inward from a tiny skin opening along the midline of the back toward the spinal cord and its protective coverings.

Key Points

Congenital Origin: A spinal sinus is a rare birth defect resulting from incomplete embryonic separation of the skin and nervous system, forming an abnormal tract.
Visible Signs: It often appears as a small dimple, pit, hair patch, or skin tag along the midline of the back, most commonly in the lumbosacral region.
Risk of Infection: The open tract can allow bacteria to enter the spinal canal, leading to severe complications such as meningitis and spinal abscesses.
Associated Problems: The tract can be associated with other issues like tethered cord syndrome, which can cause neurological deficits as a child grows.
MRI is Key for Diagnosis: An MRI scan is the gold standard for diagnosis, revealing the full depth of the tract and any associated cysts or spinal anomalies.
Early Surgical Treatment: Surgical removal of the entire sinus tract is the standard treatment to prevent serious infections and other complications, with the best outcomes achieved when performed early.

Understanding the Congenital Dermal Sinus

A congenital dermal sinus is a type of occult spinal dysraphism, meaning a hidden or closed spinal cord malformation. The condition arises from an incomplete separation of the cutaneous ectoderm (which forms the skin) and the neuroectoderm (which forms the spinal cord) during early embryonic development. The result is an epithelium-lined tract that creates a direct connection from the outside skin to the inside of the spinal canal.

While a spinal sinus can occur anywhere along the midline neuroaxis, from the nasal bridge to the tailbone, approximately 90% are found in the lumbosacral region, followed by the thoracic and cervical areas. The length of the tract varies, potentially ending just under the skin or extending all the way to the spinal cord or thecal sac, the membrane containing the spinal cord.

Recognizing the Signs and Symptoms

Identifying a spinal sinus is crucial for early intervention, as external appearances can be deceptive. A physical examination is the first step, where a healthcare provider looks for telltale cutaneous abnormalities along the spine's midline.

Common External Signs:

A dimple or pit: Often, the sinus appears as a small, pinpoint opening in the skin, only 1-2 millimeters wide.
Abnormal hair growth: A patch of excess hair, known as hypertrichosis, may surround the sinus opening.
Skin discoloration: The skin around the tract might be abnormally pigmented or a red spot (angioma).
Skin tag or subcutaneous mass: A small, benign growth of skin or a fatty lump may be present.
Recurrent local infection: The area may become red, swollen, or tender, indicating an infection of the tract itself.

Potential Neurological Symptoms:

For cases where the sinus extends deep into the spinal canal, symptoms related to infection or cord tethering may appear later in life and include:

Fever and symptoms of meningitis
Chronic pain or weakness in the legs
Bladder or bowel dysfunction
Loss of sensation
Scoliosis

Potential Complications of an Untreated Spinal Sinus

The most significant danger of a spinal sinus is its role as a potential gateway for infection. Because the tract provides an open pathway, bacteria from the skin's surface can travel directly into the spinal canal. This can lead to serious and life-threatening complications.

Meningitis: This is an inflammation of the membranes (meninges) surrounding the brain and spinal cord. Bacterial meningitis is a medical emergency and can cause permanent neurological damage or be fatal if left untreated.
Spinal abscess: An infection can lead to an abscess (a collection of pus) forming either within the spinal cord (intramedullary) or outside it but within the spinal canal (intradural).
Tethered Cord Syndrome: As a child with a deep-seated sinus tract grows, the spinal cord may become abnormally stretched and anchored, or 'tethered', by the tract or associated masses. This can lead to progressive neurological deficits, including weakness, sensory changes, and incontinence.
Dermoid or Epidermoid Cysts: The cells lining the sinus tract can shed and accumulate, forming benign cysts filled with skin cells, hair, and other debris. These cysts can grow over time, compressing the spinal cord and nerves, leading to neurological problems.

Diagnosis and Treatment

Prompt and accurate diagnosis is critical to prevent complications associated with a spinal sinus. While physical examination can identify external markers, imaging is necessary to determine the tract's full extent.

Diagnostic Imaging

Magnetic Resonance Imaging (MRI): A full-spine MRI is considered the gold standard for diagnosing a spinal sinus. It provides detailed images of the spinal cord and surrounding structures, allowing neurosurgeons to visualize the tract, its termination point, and any associated issues like cysts, tethering, or abscesses.
Ultrasonography: For infants, an ultrasound may sometimes be used as a screening tool, but MRI is definitive, especially for deeper tracts.

Treatment

For most cases of a congenital dermal sinus, surgical excision is the recommended treatment. The goal of surgery is to completely remove the tract and any associated masses or cysts to prevent future infection or neurological damage. The results of treatment are significantly better when surgery is performed before infection or neurological symptoms develop. The specific surgical approach depends on the sinus's location and depth. For more medical information, consult a resource like UCLA Health.

Spinal Sinus vs. Pilonidal Sinus

While both involve a tract near the tailbone, a spinal sinus (or congenital dermal sinus) and a pilonidal sinus are distinct conditions with different origins and risks. Confusing them can lead to inappropriate management.


Feature	Spinal Sinus (Congenital Dermal Sinus)	Pilonidal Sinus (Pilonidal Disease)
Origin	Congenital; a birth defect from incomplete embryonic separation of skin and nervous system.	Acquired; an inflammatory condition involving hair follicles, often occurring after puberty.
Location	Along the midline of the spine, most commonly lumbosacral.	In the crease between the buttocks, near the tailbone.
Tract Extent	Can extend deep into the spinal canal to the dura or spinal cord.	Extends under the skin in the fat tissue.
Associated Risks	Serious risks of meningitis, spinal abscess, and tethered cord.	Risks of local abscesses and infection, but does not connect to the spinal canal.
Typical Patient	Usually diagnosed in infancy or early childhood.	More common in young men after puberty.
Appearance	May have a tiny pit, skin tag, or hair tuft.	Can include a small pit, abscess, or cyst with pus drainage.

Conclusion

A spinal sinus is a serious congenital condition that should be evaluated by a healthcare professional immediately upon discovery. Though externally appearing as a minor dimple or pit, the underlying tract poses a significant risk of infection and neurological damage. With early diagnosis, particularly through MRI, and timely surgical intervention, the chances of preventing long-term complications are excellent. Public awareness and careful physical examination of newborns and infants are paramount for prompt identification and optimal outcomes.

Frequently Asked Questions

A spinal sinus is a congenital birth defect connecting the skin to the spinal canal, posing a risk of infection inside the spine. A pilonidal cyst is an acquired inflammatory condition, usually in the buttock crease, that involves hair follicles and is not connected to the spine.

Diagnosis begins with a physical examination of the spine for external markings. A magnetic resonance imaging (MRI) scan is then used to confirm the diagnosis, visualize the tract's depth, and identify any associated spinal problems.

Yes, an untreated spinal sinus can be very dangerous. It creates a pathway for infection, which can lead to serious conditions like bacterial meningitis or a spinal abscess. It can also cause tethered cord syndrome over time.

The first signs can be a small dimple or pit on the back, a patch of hair, or a skin tag along the midline. If it becomes infected, signs can include localized redness, swelling, and drainage, or more severe symptoms like fever and neurological issues.

The standard treatment is surgical removal of the entire sinus tract. Early surgical excision is recommended, ideally before any infections or neurological symptoms occur, to prevent complications.

While some shallow sacral dimples may spontaneously resolve, a true spinal sinus tract that poses a risk for deeper infection will not close on its own and requires surgical intervention. It is always best to have it evaluated by a neurosurgeon.

Since a spinal sinus is a congenital birth defect that occurs during embryonic development, it cannot be prevented. However, early detection and treatment are key to preventing serious complications.

Not necessarily, but the risk is significant, especially if the sinus is deep. If the tract becomes infected or causes tethered cord syndrome, it can lead to progressive neurological deficits over time. Early surgical removal greatly minimizes this risk.