7 Key Signs and Symptoms of Sacral Dimple You Should Know

A sacral dimple is a small indentation or pit in the skin located at the base of the spine, just above the buttocks in the sacral region. While most sacral dimples are harmless and require no treatment, some may indicate underlying spinal cord abnormalities. Understanding the signs and symptoms associated with sacral dimples can help parents and individuals know when medical evaluation is necessary. This condition is relatively common, occurring in approximately 3-8% of newborns, and is usually discovered during routine newborn examinations.

Most sacral dimples are considered “simple” or “typical” and pose no health concerns. However, certain characteristics may suggest a more complex condition that requires further investigation. Recognizing these warning signs early can ensure proper medical care and prevent potential complications.

1. Small Indentation Above the Buttocks

The primary and most obvious symptom of a sacral dimple is a visible small indentation or depression in the skin located in the sacral region, which is the area at the base of the spine just above the crease between the buttocks. This dimple typically appears as a small pit or hollow in the skin surface.

Characteristics of this indentation include:

• Size: Usually less than 5 millimeters in diameter for simple dimples
• Location: Positioned within 2.5 centimeters of the anal opening
• Appearance: The base of the dimple is clearly visible
• Depth: Typically shallow enough to see the bottom

Simple sacral dimples with these characteristics are generally benign and do not indicate any underlying problems. They are considered a normal anatomical variation and are often discovered during routine pediatric examinations or diaper changes in infants.

2. Presence of Hair Growth Around the Dimple

One concerning symptom that may indicate a more complex sacral dimple is the presence of abnormal hair growth in or around the dimple area. This can manifest as a tuft of hair, excessive hair, or unusually dark or coarse hair growing from or near the dimple site.

This symptom is significant because:

• It may suggest a connection between the skin surface and deeper spinal structures
• Hair growth can indicate a dermal sinus tract, which is an abnormal tunnel connecting the skin to the spinal canal
• This feature is considered an “atypical” characteristic that warrants further medical evaluation
• The presence of hair increases the likelihood of associated spinal cord abnormalities

If you notice hair growing in or around a sacral dimple, it is important to bring this to the attention of a healthcare provider who may recommend imaging studies to rule out underlying spinal cord issues.

3. Skin Discoloration or Birthmarks Near the Dimple

Another warning sign associated with sacral dimples is the presence of skin discoloration, birthmarks, or unusual pigmentation in the area surrounding the dimple. This may appear as red, purple, or darkened patches of skin, vascular marks, or hemangiomas near the sacral region.

Important aspects of this symptom include:

• Hemangiomas: Raised, red or purple marks caused by clusters of blood vessels
• Port-wine stains: Flat, pink, red, or purple discolorations
• Hyperpigmentation: Darkened areas of skin around the dimple
• Café-au-lait spots: Light brown patches in the sacral area

Skin discoloration near a sacral dimple can be a marker for underlying spinal dysraphism, which is a developmental abnormality of the spine and spinal cord. The combination of a sacral dimple with skin changes increases the need for medical assessment through imaging techniques such as ultrasound or MRI.

4. Mass or Swelling in the Sacral Area

The presence of a palpable mass, lump, or swelling in or around the sacral dimple is a significant symptom that requires immediate medical attention. This mass may be soft or firm to the touch and can vary in size from barely noticeable to quite prominent.

Characteristics of concerning masses include:

• A visible or palpable lump beneath or near the dimple
• Swelling that changes in size with activity or crying in infants
• A soft, compressible mass that may indicate a lipoma or fatty tissue connection to the spinal cord
• A firm or cystic structure that could represent a dermoid or epidermoid cyst

Masses associated with sacral dimples can indicate conditions such as tethered spinal cord, lipomyelomeningocele, or other spinal cord malformations. These conditions occur when spinal tissue or fatty tissue extends through the dimple, creating an abnormal connection. Early detection and evaluation are crucial for determining appropriate management and preventing neurological complications.

5. Drainage or Discharge from the Dimple

Any drainage, discharge, or fluid coming from a sacral dimple is an abnormal symptom that warrants prompt medical evaluation. This may appear as clear fluid, pus, blood, or any other type of secretion emanating from the dimple opening.

Types of concerning drainage include:

• Clear fluid: May indicate cerebrospinal fluid leakage through a sinus tract
• Purulent discharge: Suggests infection, which could potentially spread to the spinal canal
• Bloody discharge: Can indicate inflammation, infection, or trauma to the area
• Recurring moisture: Persistent wetness in the dimple area

Drainage from a sacral dimple is particularly concerning because it suggests a sinus tract or abnormal opening that connects the skin surface to deeper structures, potentially including the spinal canal. This creates a pathway for bacteria to enter, which can lead to serious infections such as meningitis. If any drainage is observed, immediate medical consultation is essential to prevent complications and determine if antibiotics or other interventions are necessary.

6. Large or Deep Dimple

While most sacral dimples are small and shallow, larger or unusually deep dimples may indicate a higher risk of underlying spinal abnormalities. The size and depth of the dimple are important factors in determining whether further investigation is needed.

Concerning features include:

• Size: Dimples larger than 5 millimeters in diameter
• Depth: Deep dimples where the base cannot be clearly visualized
• Location: Dimples located more than 2.5 centimeters above the anal opening
• Appearance: Dimples with an irregular or atypical shape

Large or deep sacral dimples are more likely to be associated with spinal dysraphism or other congenital spinal cord anomalies. These atypical dimples may represent the opening of a dermal sinus tract that extends deeper into the tissues and potentially connects to the spinal canal. The inability to see the bottom of the dimple is particularly concerning as it suggests significant depth and warrants imaging evaluation to assess for underlying abnormalities.

7. Neurological Symptoms in the Lower Body

Although rare, some individuals with sacral dimples associated with underlying spinal cord abnormalities may develop neurological symptoms affecting the lower body. These symptoms typically become more apparent as a child grows and the spinal cord becomes tethered or compressed.

Neurological symptoms to watch for include:

• Weakness in the legs: Decreased muscle strength or difficulty with movement
• Sensory changes: Numbness, tingling, or altered sensation in the legs or feet
• Gait abnormalities: Unusual walking patterns, toe-walking, or limping
• Bowel or bladder dysfunction: Incontinence, constipation, or urinary retention
• Foot deformities: Development of high arches, flat feet, or asymmetric feet
• Back pain: Persistent or recurring pain in the lower back or sacral region

These neurological symptoms suggest that a sacral dimple may be associated with tethered cord syndrome or other spinal cord malformations. In tethered cord syndrome, the spinal cord is abnormally attached to surrounding tissues, limiting its movement within the spinal canal. As a child grows, this tethering can cause stretching and damage to the spinal cord, leading to progressive neurological deficits. Early recognition and surgical intervention can prevent permanent neurological damage in many cases.

Main Causes of Sacral Dimple

Understanding the causes of sacral dimples helps in recognizing when they may be associated with more serious conditions. The development of sacral dimples occurs during fetal development and can be attributed to several factors:

Congenital Development: The most common cause of simple sacral dimples is a normal variation in fetal development. During embryonic development, as the neural tube closes and the spine forms, small indentations can occur in the skin overlying the sacral region. These simple dimples are considered a benign anatomical variant with no underlying cause for concern.

Incomplete Neural Tube Closure: In some cases, sacral dimples may be associated with incomplete closure of the neural tube during early fetal development. The neural tube is the embryonic structure that eventually becomes the brain and spinal cord. When closure is incomplete in the lower spinal region, it can result in conditions such as spina bifida occulta, where there is a small gap in the vertebrae, or more complex spinal dysraphism. These conditions may present with atypical sacral dimples along with other cutaneous markers.

Dermal Sinus Tract Formation: Some sacral dimples are caused by the formation of a dermal sinus tract, which is an abnormal tunnel-like structure that extends from the skin surface toward deeper tissues. This occurs when epithelial cells become trapped during neural tube closure, creating a pathway that may connect the skin to the spinal canal. Dermal sinus tracts can occur sporadically without a clear hereditary pattern.

Genetic Factors: While most sacral dimples occur sporadically, there may be some genetic predisposition to spinal dysraphism and associated cutaneous markers. Certain genetic syndromes and chromosomal abnormalities have been associated with increased rates of spinal malformations, though these are relatively rare. Family history of neural tube defects may slightly increase the risk.

Environmental Factors During Pregnancy: Certain environmental factors during pregnancy have been associated with increased risk of neural tube defects, which may present with atypical sacral dimples. These include maternal folic acid deficiency, certain medications (such as valproic acid), maternal diabetes, and maternal obesity. However, it is important to note that most sacral dimples, even atypical ones, occur without any identifiable risk factors.

Prevention Strategies

While simple sacral dimples cannot be prevented as they are a normal anatomical variation, there are steps that can be taken to reduce the risk of neural tube defects and associated spinal abnormalities during pregnancy:

Folic Acid Supplementation: Taking adequate folic acid before conception and during early pregnancy is one of the most effective ways to reduce the risk of neural tube defects. Healthcare providers recommend that women of childbearing age take 400-800 micrograms of folic acid daily, starting at least one month before conception and continuing through the first trimester. Women with a previous pregnancy affected by a neural tube defect or those taking certain medications may require higher doses as recommended by their healthcare provider.

Prenatal Care: Regular prenatal care allows for early detection of potential spinal abnormalities through ultrasound examinations and maternal serum screening. Early prenatal visits enable healthcare providers to assess risk factors and provide appropriate counseling and monitoring throughout pregnancy.

Medication Management: Women who are pregnant or planning pregnancy should consult with their healthcare provider about any medications they are taking. Certain medications, particularly some anti-seizure drugs, have been associated with increased risk of neural tube defects. Healthcare providers can help adjust medications or dosages when possible to minimize risks while managing underlying health conditions.

Blood Sugar Control: For women with diabetes, maintaining optimal blood sugar control before conception and throughout pregnancy can reduce the risk of congenital abnormalities, including spinal malformations. Working closely with healthcare providers to manage diabetes during pregnancy is essential.

Avoiding Harmful Substances: Avoiding alcohol, recreational drugs, and excessive heat exposure (such as hot tubs or saunas) during pregnancy may help reduce the risk of developmental abnormalities. Maintaining a healthy lifestyle with proper nutrition and avoiding known teratogens supports normal fetal development.

Early Newborn Examination: While not prevention per se, thorough examination of newborns for cutaneous markers of spinal dysraphism, including sacral dimples, allows for early detection and management of associated conditions before complications develop. This early identification enables timely imaging and intervention when necessary.

Frequently Asked Questions

When should I worry about a sacral dimple?

You should be concerned about a sacral dimple if it exhibits atypical features such as: being larger than 5mm, located more than 2.5cm above the anus, having hair growth around it, showing skin discoloration, having drainage or discharge, being accompanied by a mass or swelling, or if the base cannot be seen. Additionally, if any neurological symptoms such as leg weakness, bowel or bladder problems, or gait abnormalities develop, immediate medical evaluation is necessary.

Are sacral dimples and pilonidal dimples the same thing?

No, sacral dimples and pilonidal dimples are related but distinct conditions. Sacral dimples are typically present at birth and located in the lower sacral region, most often benign. Pilonidal dimples or sinuses are usually located higher, in the cleft between the buttocks, and are more commonly associated with pilonidal cysts or infections. Pilonidal conditions often develop during adolescence or young adulthood and are more likely to cause symptoms such as pain, swelling, and infection.

Can a sacral dimple close on its own?

Simple sacral dimples typically do not close on their own as they are a permanent anatomical feature. However, they usually do not increase in size or depth. The appearance may become less noticeable as a child grows and the surrounding tissue develops. Atypical dimples with underlying sinus tracts will not close spontaneously and may require medical intervention if they are associated with spinal abnormalities.

What tests are done to evaluate a sacral dimple?

For atypical sacral dimples or those with concerning features, healthcare providers may recommend imaging studies. Ultrasound is typically the first-line imaging modality for infants under 3-4 months of age, as it can effectively visualize the spinal cord through the incompletely ossified spine. For older infants and children, MRI (magnetic resonance imaging) is the gold standard for evaluating the spinal cord and detecting any abnormalities such as tethered cord, lipomas, or dermal sinus tracts.

Is a sacral dimple hereditary?

Simple sacral dimples are not typically hereditary and occur sporadically as a normal anatomical variation. However, certain spinal malformations associated with atypical dimples may have a genetic component. Families with a history of neural tube defects or spina bifida may have a slightly increased risk of recurrence, though this remains relatively low overall.

Do all babies with sacral dimples need imaging?

No, not all babies with sacral dimples require imaging studies. Simple sacral dimples that are small (less than 5mm), shallow (with visible base), located close to the anus (within 2.5cm), and without any associated abnormal features do not typically require further investigation. However, atypical dimples with any concerning features should be evaluated with ultrasound or MRI as recommended by a healthcare provider to rule out underlying spinal cord abnormalities.

Can sacral dimples cause back pain later in life?

Simple sacral dimples themselves do not cause back pain. However, if a sacral dimple is associated with underlying spinal cord abnormalities such as tethered cord syndrome or spinal lipomas, these conditions can potentially cause back pain, leg pain, or neurological symptoms as a child grows or later in life. This is why proper evaluation of atypical dimples during infancy is important for early detection and management of associated conditions.

References:

• Mayo Clinic – Sacral Dimple Information
• National Center for Biotechnology Information – PubMed Central
• American Academy of Pediatrics – Clinical Guidelines
• Boston Children’s Hospital – Neurosurgery Department
• HealthyChildren.org – AAP Patient Education
• UpToDate – Clinical Decision Support