Clinical History
A 37-year-old male patient presented with discharge arising from a defect on the left side of the forehead for 8 months. The patient gave a history of chronic frontal headaches with a low grade fever and rhinorrhoea for 2 years.
On examination, purulent discharge was noted from an orifice overlying the left frontal sinus.
Imaging Findings
Computed tomography (CT) of face and paranasal sinuses was performed and showed a heterogeneous soft tissue mass filling the left frontal sinus with osteitis and erosion of the anterior bony wall. There was extension into surrounding soft tissues and increased density of subcutaneous fat with no evidence of a collection or cold abscess (Fig. 1, 2, 3).
Both maxillary antra were hazy with no signs of osteolysis (Fig. 4).
Contrast-enhanced axial and coronal CT did not demonstrate any spread of disease to the extradural space, meninges or brain parenchyma (Fig. 5 and 6).
Discussion
Paranasal sinus tuberculosis (TB) is a rare entity [1]. Facial bones are unusual sites of involvement and it is extremely rare in the frontal sinus. Very few cases have been reported to date [2].
In our case, the diagnosis of TB of the frontal sinus was suspected due of the endemic nature of tuberculosis in Morocco and after no response to conventional courses of antibiotics (amoxicillin-clavulanic acid, quinolones).
A bacteriological examination with Ziehl-Neelsen staining for acid-fast bacilli (AFB) of the purulent material from frontal fistula demonstrated the presence of acid-fast bacilli. A tissue biopsy from the margins of the bony defect was performed by an ENT surgeon and showed the presence of an inflammatory process composed of epithelioid granulomas without giant cells, but with caseating necrosis. This was consistent with TB as caseous necrosis is not found in Wegener’s granulomatosis or sarcoidosis.
The patient was treated with the standard Moroccan antituberculosis regimen for 12 months: 3 months of a combination of four drugs: Rifampicin, Pyrazinamide, Ethambutol and Isoniazid according to body weight, followed by Rifampicin and Isoniazid for the next nine months with resolution of purulent secretions after 4 weeks of starting treatment. No local treatment was performed.
In such cases inoculation occurs directly via infected microdroplets or, more rarely, from primary pulmonary tuberculosis [3]. Our patient had no associated pulmonary tuberculosis. Radiological investigations include X-ray of the paranasal sinuses which showed diffuse opacity of the frontal sinus with expansion. Chest X-ray can indicate pulmonary TB. Computed tomography (CT) of the paranasal sinuses may show a heterogeneous soft tissue mass in the sinus with bone erosion and extension into surrounding tissues. Opacification with air fluid levels or a hazy appearance in others sinuses can also be demonstrated. Signs of osteomyelitis or infection of the orbit may be associated. CT may also reveal spread of infection to the extradural space, meninges, and brain parenchyma. MRI may delineate soft tissue involvement better [4].
There is no specific CT/MRI sign to differentiate TB from other aggressive inflammatory diseases of the paranasal sinuses. Bacteriological and histopathological examination are necessary to confirm the diagnosis.
Prognosis depends upon the tissues involved. Mucosal lesions respond well to a full course of treatment. Bone involvement and fistula formation have a poor prognosis [5].
It is important for the radiologist to bear tuberculosis of paranasal sinuses in mind especially in presence of a fistula associated with osteitis.
Differential Diagnosis List
Tuberculosis of the frontal sinus
Syphilis
Parasitic infestations such as leishmaniasis
Fungal infections
Wegener’s granulomatosis
Sarcoidosis
Final Diagnosis
Tuberculosis of the frontal sinus
