Teaching Case

A 12-year-old female patient arrived at the emergency room with a fever up to 39ºC and vomiting. Three days before she had an episode of a common cold with mucus.

At the physical exploration mild palpebral oedema was detected so orbital cellulitis was suspected. 

Emergency CT showed signs of acute diffuse paranasal sinusitis as soft tissue swelling of the frontal, ethmoid and maxillary sinus (Fig. 1-2). Follow-up MRI confirmed the findings, showing hyperintense sinus content (Fig. 3), peripheral enhancement (Fig. 4) and diffusion restriction signs (Fig. 5-8).

Signs of bilateral post septal orbital cellulitis were identified as extraconal fat infiltration (white arrow Fig. 9-10) with an intraorbital abscess at the superoextern margin of the orbit causing proptosis (pink arrow Fig. 10-11).

Frontal sinus infection complicated with frontal osteomyelitis and subperiosteal abscess as a Pott’s puffy tumour (orange arrow at Fig. 12).

There were also intracranial complications as superior sagittal and transverse sinus vein thrombophlebitis (red arrow in Fig. 13-17) and voluminous subdural empyema at the falx cerebri and cerebellar tentorium (green arrow in Fig. 13-17). The empyema showed a deposit of purulent content (Fig. 18-20).

A. Background

Acute bacterial rhinosinusitis can spread to orbital and intracranial compartments.

Early identification is crucial to avoid life-threatening conditions. [1]

B. Clinical perspective

There is considerable overlap between the symptoms and clinical findings of uncomplicated upper respiratory infections and acute bacterial rhinosinusitis, like the case exposed. 

In this patient, orbital cellulitis manifested as the first sign of acute sinusitis.

C. Imaging perspective 

This case illustrates the life-threatening orbital and intracranial complications that can occur due to bacterial rhinosinusitis. When suspected, cross-sectional imaging techniques are mandatory since early identification is essential for avoiding dreaded complications. [1]

These complications occur due to the anatomic relationship of the paranasal sinuses with orbital and intracranial compartments:

• Infection can spread from the ethmoid sinus to the orbit through the lamina papyracea. This typically occurs in young children (age <5 years) presenting with acute ethmoiditis. [2, 3]
• Frontal sinusitis can spread intracranially to the anterior cranial fossa through dehiscences or osteomyelitis. This commonly affects adolescent patients. Intracranial complications are less common but have a higher mortality and morbidity rate. [1]

Bacterial thrombophlebitis can be caused either by contiguous spread to the cavernous sinus or by direct extension through osteomyelitis.

D. Outcome

At the first emergency CT no intracranial involvement was seen. After 24-48 hours the patient had a poor evolution, with irritation meningeal signs and facial hypoesthesia. Due to clinical-radiological dissociation, further imaging evaluation was performed and CT was repeated, showing subdural empyema and thrombophlebitis signs that were confirmed at MRI.

An urgent surgical resection of the frontal bone and drainage of the empyema were performed. The evolution was not favourable, with the persistence of the empyema in the posterior part of the falx cerebri (the anterior part was drained through the frontal approach), and up to four surgical interventions were needed.

Prompt diagnosis and treatment could have had probably avoided the complications in this patient.

E. Take home message

Acute bacterial rhinosinusitis is a common diagnosis in the daily practice at the emergency room so radiologists need to be aware of the specific imaging findings of its orbital and intracranial complications, especially in an early stage.

Written informed patient consent for publication has been obtained.