The Most Common Cause: Your External Occipital Protuberance
One of the most frequent and entirely normal reasons for a bump at the back of the head is the external occipital protuberance (EOP), a naturally occurring bony feature of the skull. This bump, also called the inion, is a point of attachment for muscles and ligaments in the neck and is not a cause for concern.
What is an EOP and Why Does it Vary?
The EOP is located at the base of the skull, where the head joins the neck. It serves as an anchor for the nuchal ligament, which supports the head and spine. The size of this bony knob can vary significantly from person to person due to genetics and musculature. It is generally larger in males, who tend to have greater muscle mass in the neck area. For some, it is barely noticeable, while for others, it is quite prominent, feeling like a distinct lump of bone.
Can Technology Cause a Larger Bump?
A 2019 study, published in scientific journals including Nature, noted an increase in larger occipital spikes, particularly in younger adults. This growth, a type of bone spur, is possibly linked to poor posture resulting from technology use, like frequent phone and tablet usage. The constant forward tilting of the head strains neck muscles, causing the bony attachment points to enlarge over time. While interesting, this phenomenon is generally considered benign.
Other Common Benign Causes of Lumps on the Skull
Beyond the natural bone structure, several other harmless growths can appear on or under the scalp, contributing to a bumpy sensation. These are typically non-cancerous and may not require treatment unless they cause discomfort.
Cysts and Lipomas
- Pilar cysts: These are smooth, dense lumps that form around hair follicles, most often on the scalp. They contain a buildup of keratin, the protein that makes up hair and nails, and are generally harmless and slow-growing. They can sometimes run in families and are more common in women.
- Epidermoid cysts: Similar to pilar cysts, these are small, hard lumps under the skin, though they can occur on the face or scalp. They are usually painless unless they become infected. They are caused by a buildup of keratin and may resolve on their own.
- Lipomas: A lipoma is a soft, rubbery, fatty tumor that grows slowly beneath the skin. While they can occur anywhere on the body, they are rarely found on the head but are possible. They are harmless and painless and often only removed for cosmetic reasons or if they become large.
Bone Spurs (Exostosis)
This is an overgrowth of bone on an existing bone, and while more common around joints, it can also happen on the skull. These hard, immovable lumps can be discovered during childhood and, while often symptomless, may cause pain if they press on nearby tissues or nerves.
Acne and Folliculitis
On the back of the head, particularly near the hairline, skin conditions like scalp acne or folliculitis can cause inflamed, pimple-like bumps. This is caused by clogged or infected hair follicles. Folliculitis can cause soreness and itching and may require medicated washes or antibiotic creams if persistent.
Understanding Different Skull Bumps
| Feature | Occipital Protuberance (EOP) | Pilar Cyst | Lipoma | Bone Spur (Exostosis) |
|---|---|---|---|---|
| Type | Bony prominence | Keratin-filled sac | Fatty tumor | Bony overgrowth |
| Feel | Hard, immovable, part of skull | Smooth, firm, under skin | Soft, rubbery, movable | Hard, immovable, part of bone |
| Location | Midline back of skull | Scalp, around hair follicles | Anywhere, rarely head | Any bone, can be on skull |
| Cause | Normal anatomy, genetics | Keratin buildup, genetics | Fat tissue overgrowth | Bone formation, injury |
| Symptoms | None normally, some pain possible if enlarged | Usually painless, can become infected | Painless | Can be painful if pressing on nerves |
When to Seek Medical Attention
While most bumps on the back of the head are harmless, it is wise to consult a doctor if you experience any of the following symptoms:
- The bump is causing severe or increasing pain.
- The size or shape of the bump changes noticeably.
- The area leaks pus, discharge, or bleeds.
- The bump feels warm to the touch or is accompanied by discoloration.
- You experience other neurological symptoms, such as persistent headaches, vision problems, or balance issues.
- The bump appears following a significant head injury, and you experience confusion, dizziness, or vomiting.
Conclusion: How to Reassure Yourself about a Bumpy Skull
The discovery of a bump at the back of your skull can be disconcerting, but it is very likely the external occipital protuberance, a perfectly normal part of your anatomy. Other common causes like cysts, lipomas, or skin irritations are also typically harmless. The key to knowing whether you should be concerned is to monitor the bump for changes and observe any accompanying symptoms.
Most bumps are benign and won't require medical intervention. However, if you are concerned, seeking a professional medical opinion is always the best course of action. Consulting a healthcare provider, such as a family doctor or dermatologist, can provide peace of mind and an accurate diagnosis. For more information on general health concerns, the World Health Organization is an excellent resource.
