Pott's puffy tumor

Introduction: This condition was first described by Sir Percival Pott in 1714. He was working in Bartholomew Hospital in London while he published his famous works. In his classic way he described this lesion as a puffy circumscribed lesion of scalp. He also discussed its Pathophysiology as classic separation of pericranium from the skull. In his original description he attributed this condition to head trauma. Later this condition became attributed as one of the possible complications of frontal sinusitis. Patients with subperiosteal abscess of frontal bone demonstrate focal necrosis of frontal bone as well thus causing Pott’s puffy tumor.

Applied anatomy: Frontal sinus is formed due to extension of anterior ethmoidal complex into the diploic space of frontal bone. The process of pneumatization of frontal sinus proceeds rather slowly and it becomes evident radiologically during the 6^th year of life. The whole process of pneumatization is complete by the age of 9. For this reason it is very rare for Pott’s puffy tumor to occur in young children. The anterior table of frontal sinus is composed of both compact and cancellous bone. Osteomyelitis can involve the anterior table of frontal sinus. The posterior table is formed completely by compact bone; hence osteitis may completely involve the posterior table of frontal sinus.

Infections from frontal sinus may progress beyond the confines of the sinus cavity by:

1. Focal osteitis / osteomyelitis – Osteitis involving the frontal inner table may cause extensive necrosis of bone followed by the spread of infection to the epidural space.
2. Via infectious thrombophlebitis – Venous drainage of frontal sinus passes through valveless diploic veins that extend posteriorly to the dura and anteriorly to the pericranium. Thrombophlebitis of anterior table can lead to infection of frontal pericranium and the development of Pott’s puffy tumor. As the pericranium is elevated off the underlying frontal bone by expansion of the abscess, the vascular supply to the frontal bone is further compromised causing necrosis and osteomyelitis.

Clinical features:

1. These patients may not give h/o chronic / recurrent frontal sinusitis
2. Symptoms of frontal sinusitis may be present for varying duration prior to the development of Pott’s puffy tumor.
3. H/o previous antibiotic therapy is common.
4. These patients have doughy / pitting forehead swelling due to the presence of subpericranial abscess. The tissue odema caused may extend to preseptal orbital tissues.
5. Headache
6. Fever
7. Nasal discharge
8. Frontal sinus tenderness

Males are commonly affected than females.

Complications: Include

1. Meningitis
2. Venous sinus thrombosis
3. Subdural abscess
4. Brain abscess

Role of imaging:

Imaging helps to delineate brain involvement. It also helps to assess the size of the abscess, extent of involvement. Orbit also should be scanned in the presence of preseptal cellulitis or in patients in whom vision / ocular movement is compromised. In order to clearly delineate bone infection nuclear scanning may have to be resorted to. Contrast CT may help in delineating brain involvement.

Treatment:

The source of infection should be addressed for the treatment to be effective. Appropriate antibiotics in adequate dosage should be administered.

Frontal sinus trephening can be performed to clear out the frontal sinuses. In patients with intracranial complications bifrontal craniotomy should be performed. With the advent of nasal endoscopes frontal sinus can easily be accessed through the nasal cavity and drained via its natural ostium.

Riedel’s procedure: This procedure is indicated in patients with intracranial complications. This procedure involves complete removal of posterior table of frontal sinus with cranialization of frontal sinus. This is followed by removal of anterior table, causing prolapse of forehead skin into the frontal sinus cavity.

Reconstruction of forehead can be performed using:

1. Split calvarial bone grafts
2. Polymethyl – methacrylate
3. Hydroxyapatite
4. Titanium mesh