Why Do I Have a Groove on the Back of My Head? Understanding the Causes

October 2, 2025 •

3 min read

Did you know that the human skull is made of several bony plates that are connected by fibrous joints called sutures, which can sometimes be felt as grooves? Understanding these anatomical features can help shed light on why you have a groove on the back of your head, a common phenomenon that is usually harmless but can sometimes point to an underlying issue.

Quick Summary

A groove on the back of the head can result from normal skull anatomy where sutures meet, or be caused by developmental issues in infants, such as positional plagiocephaly or craniosynostosis. In adults, less common causes include trauma, bone diseases, or age-related changes. A lifelong groove is typically benign, whereas a new or painful one warrants medical evaluation.

Key Points

Normal Anatomy: Many grooves are simply normal variations where skull sutures meet and are no cause for concern.
Infant Causes: In babies, a groove or flattening can be caused by positional plagiocephaly (flat head syndrome) or, more rarely, craniosynostosis.
Adult Causes: New grooves in adults may be related to age-related changes, old injuries, or very rare bone diseases.
New vs. Lifelong: A key factor is whether the groove is a new development or a lifelong feature that has only recently been noticed.
Seek Medical Advice When: Consult a doctor if a groove is new, painful, or accompanied by other symptoms like headaches or changes in vision.
Infant Evaluation: For infants, evaluation by a specialist is important to differentiate between benign plagiocephaly and potentially serious craniosynostosis.
Diagnosis is Key: While scary to discover, many grooves are harmless. A doctor can provide an accurate diagnosis and appropriate guidance.

Normal Anatomy and Lifelong Features

In many cases, a groove on the back of the head is simply a normal variation in skull anatomy. The skull is made of several bones joined by sutures. The lambdoid suture at the back connects the parietal and occipital bones. The area where these sutures meet, or near the external occipital protuberance, can sometimes be felt as a groove. This is typically harmless and present since birth. These natural contours might become more noticeable with aging, hair loss, or simply upon closer examination.

Causes Related to Infant Development

Grooves or flattened areas on an infant's head are often due to either deformational plagiocephaly or craniosynostosis. Since infant skull bones are soft and not yet fused, they can be easily shaped.

Deformational (Positional) Plagiocephaly

Often called "flat head syndrome," this is a common and treatable condition caused by repeated pressure on a baby's skull, typically from consistent sleeping positions on the back.

Craniosynostosis

This more serious condition occurs when one or more skull sutures fuse too early, affecting skull growth. Lambdoid synostosis, affecting the back of the head, is rare but can be mistaken for plagiocephaly. It may cause flattening on one side of the back of the head, ear displacement, or head tilting and requires specialist evaluation.

Potential Causes in Adulthood

New grooves in adults are less common but can arise from several factors.

Trauma and Injury

Depressed Fracture: A skull fracture can leave a permanent indentation.
Surgical Effects: Healing after head surgery may result in indentations.

Medical Conditions

Rare conditions affecting bone density can alter skull structure. Paget's Disease or Gorham's Disease may lead to indentations.

Skin Conditions

Changes in the scalp can sometimes mimic a groove, such as localized inflammation or hair loss revealing underlying bone structure.

Comparison of Skull Grooves


Feature	Normal Anatomical Groove (Lifelong)	Deformational Plagiocephaly (Infant)	Lambdoid Synostosis (Infant)
Timing	Noticed at any age, typically present since birth.	Develops in the first few months of life.	Present at birth or in early infancy.
Appearance	Subtle ridge or depression where skull sutures meet.	A flat spot on the back or side of the head.	Flatness on one side of the back of the head.
Cause	Genetic variations in skull bone formation.	Constant external pressure on the pliable skull.	Premature fusion of the lambdoid suture.
Additional Symptoms	Typically none, unless accompanied by other issues.	May be associated with muscular torticollis.	Can cause ear displacement or facial asymmetry.
Prognosis	Harmless; no treatment needed.	Often resolves with repositioning; can be treated with a helmet.	Requires surgical correction for proper brain growth.

When to See a Doctor

While most grooves are normal, seek medical advice if a groove is new, changing, painful, tender, red, or swollen. Consult a doctor if you had a head injury before noticing it, or if it's accompanied by headaches, vision changes, or other neurological symptoms. For infants with significant head shape asymmetry that doesn't improve with repositioning, see a doctor or craniofacial specialist. They may use imaging tests for diagnosis.

Conclusion

Often, a groove on the back of the head is a normal part of skull anatomy. In infants, it's frequently benign positional plagiocephaly, though craniosynostosis is a more serious consideration. For adults, new grooves can stem from age, injury, or rare medical issues. Observing when the groove appeared and any other symptoms is crucial to determine if medical evaluation is needed. An accurate diagnosis from a healthcare professional is always the best approach for any new or concerning head indentation.

For more information on infant head shape, the Children's Hospital of Philadelphia provides excellent resources.(https://www.chop.edu/conditions-diseases/deformational-plagiocephaly)

Frequently Asked Questions

Yes, it is often normal. Many people have a naturally occurring groove or ridge where the skull's bony plates connect at the lambdoid suture. For some, these features simply become more noticeable over time, especially with hair loss or age.

Yes, a severe head injury can cause a depressed skull fracture, which can leave a permanent indentation. If you notice a new groove after a head injury, it is important to see a doctor for evaluation.

Plagiocephaly is a common condition where an infant's head becomes flat from consistent external pressure, such as sleeping in one position. Craniosynostosis is a rarer and more serious birth defect where skull sutures fuse prematurely.

Yes, it's possible. As people age, the thinning of the skin and a reduction in subcutaneous fat can make the natural contours and sutures of the skull more prominent and easier to feel.

A new, painless groove is less urgent than one with pain, but it still warrants attention. A doctor can help determine if the change is a benign age-related effect or a sign of an underlying medical condition.

For deformational plagiocephaly, repositioning is the first step. This involves changing your baby's head position during sleep and playtime. Increasing "tummy time" is also highly recommended. In moderate to severe cases, a cranial orthotic helmet may be used.

In very rare cases, yes. Conditions like Paget's disease or Gorham's disease can affect bone health and density, potentially leading to irregularities or indentations in the skull.