Differential Diagnosis for Fluctuant Painful Depression on the Top of the Skull
Single Most Likely Diagnosis
- Subgaleal hematoma or fluid collection: This condition is characterized by a collection of fluid or blood between the galea aponeurotica and the periosteum of the skull. It can occur after a head injury, which might not have been severe enough to cause significant concern at the time, and can present with a fluctuant mass. The absence of skin erythema does not rule out this condition.
Other Likely Diagnoses
- Epidermoid or sebaceous cyst: These are benign cysts that can become inflamed or infected, leading to pain and fluctuance. They are common on the scalp and can present with a painful, fluctuant mass.
- Folliculitis or furuncle (boil): Although the question mentions no skin erythema, early stages of folliculitis or a furuncle could present with a painful, fluctuant area that might not yet have significant surrounding erythema.
- Abscess: A scalp abscess could present similarly, although typically there would be more signs of infection such as erythema, warmth, and possibly pus.
Do Not Miss Diagnoses
- Osteomyelitis of the skull: This is an infection of the bone that can present with pain and swelling. It is less common but can be serious, especially if not treated promptly. The absence of erythema does not rule out this condition.
- Epidural or subdural hematoma: Although these conditions typically present with more severe symptoms such as altered mental status, severe headache, or neurological deficits, a small or slowly expanding hematoma might initially present with more subtle symptoms, including a fluctuant mass if it has eroded through the skull or is pressing against the scalp from beneath.
Rare Diagnoses
- Dermoid cyst: These are congenital cysts that can occur anywhere on the body, including the scalp. They can become infected or inflamed, leading to pain and fluctuance.
- Langerhans cell histiocytosis: This is a rare disorder that can cause lesions in the bones, including the skull, which might present as a painful, fluctuant mass.
- Metastatic disease to the scalp: Although rare, metastatic cancer can present with a wide range of symptoms, including a painful, fluctuant mass on the scalp.