Pott's Puffy Tumor

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Diagnosis and reasoning

The pediatric patient with a facial swelling is a more common presentation than one might imagine; it is also a highly concerning presentation for both healthcare provider and parents. As a diverse array of diseases can present in this manner, an appreciation of the clinical manifestations and common sites of occurrence of each is essential for a timely and accurate diagnosis. First and foremost, note that facial swellings can be classified into 4 broad groups by clinical manifestation; these are: - acute swellings with inflammation - nonprogressive swellings - slowly progressive swellings - rapidly progressive swellings It is fairly self-evident that this patient's presentation falls into the first category. Inflammatory swellings are the most common type of facial mass in children; when the frontal (forehead) location in this patient is taken into consideration, key possibilities include: - A soft tissue infection such as an infected sebaceous cyst or carbuncle - Pott's puffy tumor (i.e. frontal osteomyelitis secondary to chronic sinusitis) - A frontal hematoma, with subsequent secondary infection. A hematoma is the most remote possibility, give the absence of an antecedent history of trauma, or signs suggestive of a coagulopathy. A sebaceous cyst is also unlikely, as this would have been present for some time before being infected. Note also that a carbuncle is unlikely in a healthy person; furthermore, examination usually demonstrates multiple openings discharging pus. Pott's puffy tumor is a strong possibility here, particularly given the presence of signs and symptoms suggestive of sinusitis. Note also the presence of periorbital edema; this is an extremely worrisome finding, which in this context is suspicious of periorbital cellulitis due to local spread. Urgent imaging should be the next step in her workup; while both contrast-enhanced computerized tomography (CT) and magnetic resonance imaging (MRI) are viable modalities here, note that CT is superior to MRI for depiction of bony pathology, and is probably a better choice in this clinical context. The CT scan in turn confirms the presence of frontal osteomyelitis in association with subperiosteal and epidural abscesses, pansinusitis, and left-sided periorbital cellulitis. Thus the diagnosis is Pott's puffy tumor indeed. Note that Pott's puffy tumor may be complicated by meningitis (particularly as an epidural abscess is already present); fortunately, CSF analysis is unremarkable. Pott's puffy tumor is a neurosurgical emergency; urgent surgical drainage in conjunction with antibiotic therapy are key aspects of the management. Antituberculous therapy should never be commenced without significant proof of tuberculosis; chemotherapy is not indicated here.


Discussion

Pott’s puffy tumor was first described by Sir Percival Pott in 1760; it is not a tumor per se, but rather, a subperiosteal abscess of the frontal bone secondary to frontal osteomyelitis. Note that it is the subperiosteal location which gives rise to the typical 'well-circumscribed' and 'puffy' appearance of the lesion. Pott’s puffy tumor is most often a complication of frontal sinusitis; the infection spreads to the frontal bone via one of two mechanisms: hematogenous (venous) spread, or direct extension. Hematogenous spread is the most common pathway for extension of infection; this occurs via the thin-walled, valveless diploic veins which drain the frontal sinuses. Direct extension of frontal sinusitis usually occurs when there is a history of trauma or malignancy. The infection may further erode through the bony cortex, resulting in the classical subperiosteal abscess; it may also erode inward causing meningitis, epidural or subdural empyema, a frontal lobe abscess, or cavernous sinus thrombosis. If the inferior wall of the frontal sinus is involved, infection may spread toward the orbit, leading to an intraorbital abscess or orbital cellulitis. Pott’s puffy tumor has become a clinical rarity, due to the widespread use of antibiotics; while the exact incidence is unclear, it is believed to be more common in the pediatric population (particularly adolescents) possibly because the vascularity of the diploic system and growth of the frontal sinuses peaks at this age. Affected patients usually present with an erythematous, tender swelling of the forehead, in association with headache, purulent rhinorrhea, and little or no fever. Worsening symptoms, or the presence of seizures, lethargy, vomiting, or focal neurologic deficits suggest the development of intracranial complications. Early diagnosis is critical to prevent neurological sequelae; a high index of suspicion should be entertained in all patients presenting with a fluctuant, tender, erythematous swelling of the scalp or forehead. Basic investigations may show a leukocytosis along with elevated markers of inflammation, reflecting the bacterial origin of the disease. Imaging of the brain, bone and sinuses with contrast computerized tomography (CT) or magnetic resonance imaging (MRI) is essential for diagnosis. Note that contrast CT is the current study of choice for diagnosing the intracranial as well as extracranial complications of frontal sinusitis; it is superior to MRI in its depiction of bone. In both CT and MRI, imaging findings suggestive of Pott’s puffy tumor include erosions of the anterior wall, along with a pericranial fluid collection; where present, these may also detect epidural, subdural or frontal lobe abscesses, or periorbital cellulitis. Pott's puffy tumor is a neurosurgical emergency; urgent surgery should be performed, aiming to drain the abscess and debride the infected bone where necessary. Cultures of the infected site should be taken during surgery, to adjust antibiotic therapy. Empirical antibiotic therapy should be commenced as soon as the diagnosis is suspected; this should cover the most common causative agents (i.e. Staphylococcus aureus, streptococci spp, and anaerobes), and adequately penetrate the central nervous system. Once culture results are available, the antibiotics should be changed as necessary; most patients require antibiotic therapy for 6 to 8 weeks in total.


Take home messages

  1. Pott's puffy tumor is a rare clinical entity where there is osteomyelitis of the frontal bone in association with a subperiosteal abscess.
  2. The disease should be suspected in all patients with a fluctuant, tender, erythematous swelling of the scalp or forehead, particularly if antibiotics have not been administered before.
  3. Contrast enhanced CT imaging is the diagnostic study of choice in these patients.
  4. Early treatment is critical for prevention of neurological sequelae; this involves a combined surgical and medical approach.

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