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Pott’s puffy tumor


Key points

  • Definition: Pott’s puffy tumor is an osteomyelitis with associated subperiosteal abscess collection usually related to frontal sinusitis or mastoiditis. It may extend into the orbit causing inflammation including cellulitis, subperiosteal abscess, orbital abscess (OA), and cavernous sinus thrombosis. It poses a potentially life-threatening emergency, often requiring surgery.

  • Synonym: Pott puffy tumor.

  • Classic clue: Teenage boy presents with slow saga of recurrent headache, fever, and scalp and eye swelling with purulent drainage from nose or eye. Not responding to “home remedies,” patient now complains of fluctuant supraorbital mass.

  • Although first described in 1768, Pott’s puffy tumor continues to be a lesser known, although potentially life-threatening, clinical entity.

Imaging

General imaging features

  • Regional osteopenia with decreased bone density.

  • Periosteal reaction can cause Codman’s triangle.

  • Focal bony lysis (see Figure 46-1 , C and D ).

    FIGURE 46-1 ■, A, Axial contrast-enhanced computed tomography (CECT) through orbits shows increased attenuation of right subcutaneous soft tissues extending over the nasion and lateral aspect of the orbit. There is also complete opacification of an anterior ethmoid air cell. B, Axial CECT through orbits shows cellulitis causing increased attenuation of right subcutaneous soft tissues, with nasal and temporal extension into anterior subcutaneous fat. The globe is displaced anteriorly (exopthalmos) and depressed caudally (hypoglobus), with a retrobulbar postseptal low attenuation due to phlegmon. C, Coronal CECT shows destruction of the inferior wall of the right frontal sinus with soft tissue phlegmon extending inferiorly from right frontal sinus into adjacent orbit causing inferior displacement of globe. D, Coronal bone algorithm nonenhanced CT shows opacified right frontal sinus with dramatic destruction of inferior wall/orbital roof. Oval low attenuation phlegmon superomedial to right globe with curvilinear collection extends along orbital floor caudal to globe.

  • Loss of bony trabeculation.

  • Sequestra are better seen on computed tomography (CT).

  • Magnetic resonance imaging (MRI) is the most sensitive and specific modality.

Computed tomography features

  • Typically see opacified frontal sinus with overlying scalp swelling (see Figure 46-1 , C ).

    FIGURE 46-2 ■, Sagittal (A and B) and axial (C) CECT show an enhancing rim around the abscess extending both anterior and posterior to frontal bone.

    FIGURE 46-3 ■, A , Axial T2 confirms abscess shown on CT with a relatively homogeneous signal similar to that of the cortical brain. T1 Gd axial (B) and sagittal (C) images show avid enhancement surrounding low signal abscess with irregular internal margins. Extensive abnormal enhancement of subcutaneous soft tissues and dura.

  • Bone algorithms often better demonstrate sinus wall defect (see Figure 46-1 , D ).

  • Often see obliteration of fat planes.

  • Cellulitis can display a diffuse homogeneously enhancing mass lesion.

  • Contrast can show focal abscess.

  • Eccentric globe displacement suggests subperiosteal OA.

  • Intraorbital gas or air-fluid level strongly suggests OA.

  • Inflammation of sinuses and adjacent structures is usually well demonstrated.

    • “Ring” enhancement or air bubbles herald the progression from cellulitis to suppuration and abscess development.

    • CT findings include sinusitis, cavernous sinus thrombosis, and subdural empyema.

    • CT is excellent to depict the full extent of bony involvement, and three-dimensional reconstructions have proven to be perfect presurgical roadmaps.

Magnetic resonance imaging features

Pott’s puffy tumor

  • Subtle intracranial involvement is best depicted by MRI.

  • Early in the disease process MRI can show linear dural enhancement, an extraaxial fluid collection, or a small area of cerebritis or cerebral abscess.

Pott’s puffy tumor and orbital inflammation

  • Imaging for the orbital inflammation component depends on the stage of infection when the diagnosis is made. 2 (Please refer to Chapter 44 : Orbital Abscess/Clinical Issues/Presentation)

  • Early T2 shows increased signal secondary to edema and later fluid in abscess cavity.

  • T1 orbital fat has loss of normal high signal.

  • T1 with gadolinium (Gd) shows ring enhancement around abscess periphery.

  • Contrast is crucial to separate edema, phlegmon, and abscess.

  • Diffusion-weighted images (DWIs) demonstrate restricted diffusion in OA:

    • OA restricts diffusion appearing bright on DWI with dark appearance on corresponding apparent diffusion coefficient (ADC) image.

    • DWI and contrast-enhanced imaging improved confidence of OA diagnosis by “blinded” readers.

    • For patients with renal insufficiency, readers relying on DWI (without Gd) made the diagnosis in most (but not all) cases of OA.

    • The minute required for the DWI sequence acquisition is time well spent when compared with its potential payoff.

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