Frontocutaneous Fistula Secondary to Pott’s Puffy Tumor

Pott’s puffy tumor (PPT) is currently defined as a forehead-localized swelling with overlying subperiosteal abscess and osteomyelitis of the frontal bone. ¹ It has become an uncommon disease entity due to the widespread use of antibiotics and it is even more rarely reported with a frontocutaneous fistula, also known as sinocutaneous fistula. ² We present a case involving a fistula formed between the frontal sinus and the medial eyebrow area misdiagnosed as an infected sebaceous cyst.

A 49-year-old male presented with an erythematous skin lesion suspected with cutaneous inflammation which was sized 0.5 cm on the medial area of the left eyebrow that had developed 3 months ago (Figure 1). He had no other previous medical history and he only complained of cutaneous discomfort. He did not have any other symptoms, such as visual disturbance, headache, or nasal symptoms. Initially, he presented to the dermatologist at a local clinic with painful swelling in the same area which had first appeared 6 months earlier. After an incision had been made on the swelling area under the provisional diagnosis of infected sebaceous cyst, the lesion had occurred repeatedly in the same location. The patient underwent computed tomography (CT) scans for the head and neck area. Frontal sinusitis destructing the anterior skull base and combined subperiosteal abscess was suspected by CT scans (Figure 2) and he was transferred to our department. We performed endoscopic sinus surgery, and polypoid inflammatory lesions in the left frontal sinus was identified and radically removed. During surgery, a metal probe inserted from the external skin lesion was observed in the frontal sinus suggesting the cutaneous fistula originated from the frontal sinus (Figure 3). After the operation, the patient was treated with oral antibiotics for 4 weeks and the skin lesion then healed spontaneously. During a follow-up period of 1 year after the surgery, there was no recurrence.

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Figure 1.

The 0.5 cm-sized erythematous skin lesion (arrow) suspected with cutaneous inflammation was observed on the medial area of the left eyebrow.

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Figure 2.

An axial CT demonstrates left frontal sinusitis destructing the anterior wall of the frontal sinus and contiguous abscess of the soft tissues. CT indicates computed tomography.

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Figure 3.

During surgery, a metal probe (arrow) inserted from the external skin lesion was observed in the left frontal sinus suggesting frontocutaneous fistula.

Pott’s puffy tumor is a rare complication which occurs as a result of the spread of infection through venous drainage of the frontal sinus or from direct extension of the infection through the bone. The resulting osteomyelitis of the frontal bone can then lead to formation of an abscess. ³ A frontocutaneous fistula may develop in the frontal or orbital area because the anterior wall or floor of the frontal sinus, respectively, is frequently the pathways of least resistance for the infection. ⁴ In addition, it may be accompanied by complications such as neurologic emergencies (meningitis: subdural, epidural, or intracerebral abscesses; and sagittal sinus thrombosis), and systemic sepsis. ⁵ Thus, early diagnosis and appropriate treatment can improve the clinical outcome and reduce the possibility of intracerebral complications. Once the diagnosis of PPT is suspected, appropriate imaging including CT or MRI should be performed to evaluate the possible life-threatening complications of neurologic emergencies such as subdural, epidural, or intracerebral abscesses. ⁴

The differential diagnosis of PPT includes hematoma, skin and soft-tissue infections (furuncle and infected epidermal cyst), and soft-tissue tumors. ⁶ Treatment of PPT usually consists of long-term antibiotics, with surgical drainage, debridement, and reconstruction, depending on disease severity. ⁷

In conclusion, we present an extremely rare case of a frontocutaneous fistula secondary to PPT, a complication of underlying frontal sinusitis, and clinicians should keep in mind the possibility of underlying frontal sinus lesions in patients with intractable skin inflammatory pathology located in the forehead or periorbital area.