The human skull has a natural back of the head bump called an ‘inion.’ It is the point where the bottom of the skull attaches to the neck muscle. But sometimes, bumps and lumps on the head occur for a varied number of reasons and because of a plethora of causes. For example, some head injuries are not very serious and can lead to bruising or back of head bump. Some bumps occur under the skin, on the skin, or in the bone.
You should seek a medical opinion if you detect any lump or back of head bump which appears suddenly, is painful or seems to change its appearance. The medical health expert will examine and monitor the bump. If necessary, your clinician will investigate it further through medical imaging tests or biopsies.
Common causes of back of head bump
Here are some common causes of a bump on the back of the head.
Head injury: Head injuries occur in people of all ages and are very common. Minor head injury is not severe and will not cause any permanent damage. But traumatic brain injury (TBI) can lead to a back of head bump. Possible causes of traumatic brain injury include falling in a backward direction, collisions or impacts while playing contact sports, an act of violence, accidents, etc.
Generally, the apparent cause is a scalp hematoma that is bleeding and swelling beneath the skin because of the trauma. A blow to the back of the head thus leads to the formation of a semisolid bump, which some people refer to as ‘goose eggs.’ However, these kinds of back head bump ease gradually over some time.
Epidermal cysts: As the name suggests, these cysts are slow developing and affect the skin’s epidermis layer. Generally, the epidermal cysts are made of fat and keratin and can be triggered by mild injuries. They are not cancerous and disappear without treatment or with the help of antibiotics, steroids, or excision.
Sebaceous cysts: Epidermoid cysts and pilar cysts affect the skin. Pilar cysts are more prevalent in women than in men. It is a type of cyst that develops on the scalp but can also occur on the neck. Sometimes, it is also referred to as ‘trichilemmal cysts.’ These cysts are smooth and dense lumps. It contains a build-up of the protein called ‘keratin.’ Usually, these cysts grow slowly and vary between 0.5 and 5 cm in diameter. Epidermoid cysts are also caused by keratin build-up, but they are generally small because they are formed because of trauma or disruption to the skin or a hair follicle.
Bony growth: Generally, it is called ‘Exostosis’ and is a benign bone tumour. It is rare and seen on the skull area as a bump in the back of the head. Long-term irritations, infection, osteoarthritis, or traumatic brain injury causes bony growth.
Folliculitis: A bump on the back of the head occurs because of folliculitis if there is inflammation of the hair follicles. They appear in clusters of red bumps or look like white-headed pimples around the hair follicles. Folliculitis is caused by an infection of the follicles by fungi, bacteria, viruses, or inflammation from ingrowing hairs.
Pilomatrixoma: Although uncommon and harmless, pilomatrixoma is a tumor of the hair follicle. It occurs because of an overproduction of matrix hair cells. It appears as a purple lesion or single skin-colored bump.
Lipoma: Lipoma is a kind of bump on the back of the head which occurs under the skin and internally in the body. Usually, it is harmless and looks like a soft, fatty, moveable bump. If these bumps grow larger and become firmer to touch, then they should be further investigated. The doctor will examine the bump on the back of the head to eliminate the origin of cancerous cells.
Seborrhoeic keratosis: It is a type of benign skin tumor and looks like scaly brown plaque that may appear greasy. Such tumors need a clinical investigation to rule out the presence of cancerous cells.
Treatment of back of head bump
For the back of the head bump due to minor head injuries, you can apply ice to reduce swelling. Open wounds should be cleaned and then dressed. To relieve pain, use pain-killers like paracetamol and use them as directed by your doctor. After traumatic brain injury or head injury leading to the back of head bump, watch for signs and symptoms of concussions like memory loss, nausea, passing out, drowsiness, etc. Seek medical attention if the symptoms persist for more than a few weeks or get worse.
For bumps because of infection, improving cleanliness is the key treatment. Your doctor may prescribe antibiotics and antifungal agents. For certain types of back of the head bump like a cancerous growth, treatment involves biopsy and removal of the lesion or even cryotherapy.