Pott’s puffy tumor: a need for interdisciplinary diagnosis and treatment

A 6-year-old child was referred to our clinic from the pediatric department hospital with an unclear swelling of the forehead. The patient has already been treated in hospital with ampicillin/sulbactam for frontal sinusitis accompanied by fever for 6 days. After discharge, the boy presented with a discrete swelling of the forehead and was readmitted to hospital.

On physical examination, there were no additional symptoms apart of the non-tender painless forehead swelling. At readmission, fever was absent, but the parents described recurrent fever episodes over several weeks as well as a recurrent sinusitis, which had been treated over a long period with different antibiotics. Laboratory results showed an elevated C‑reactive protein (CRP) level of 61 mg/l (normal range: 0.0–5.0 mg/l) and white blood cells (WBC) of 20.6 (normal range: 4.8–12.0).

Ultrasound revealed a blurred clearly hypoechoic mass with thickening of the overlying tissue toward the skin. As far as it was detectable, the underlying bone was intact without any interruption of the corticalis intracranially. On suspicion of PPT, MRI and CT studies were initiated. The MRI examination revealed osteomyelitis of the right frontal bone with accompanying subperiosteal and subdural abscesses causing a local space-occupying effect and beginning meningoencephalitis. Furthermore, frontal sinusitis was described as the cause of the disorder and in the synopsis of all the findings, PPT was assumed (Fig. 1).

The patient underwent immediate surgery with frontolateral craniotomy. The destructed (small/less pneumatized) frontal sinus was opened to the ethmoid cells, with evacuation and drainage of the cranial, epidural, and subdural abscess. On endonasal inspection, no remnant abscess formations were found in the sinonasal cavities.

An additional ophthalmologic examination showed no pathological findings and no signs of visual impairment. Fever and pain were absent and laboratory chemical analysis showed a CRP level of 9.6 mg/l and a WBC of 9.9. Osteomyelitis was revealed at the CT examination as a low-grade frontal erosion of the bony skull base (Fig. 2). Conservative treatment was initiated with high-dose intravenous antibiotic therapy with ceftriaxone 4 g–0–4 g. Under this treatment, the symptoms improved significantly, and he was discharged from hospital after 4 days.

A 17-year-old male patient presented to our hospital with a history of fever, cough, and cephalgia for 2 days. The initial treatment was symptom-based with a mainly analgesic and antipyretic therapy. Due to a swelling of the forehead, the patient was referred to the clinic for otorhinolaryngology. Laboratory results revealed a highly elevated CRP level of 273.3 and a WBC of 15. On suspicion of PPT, MRI and CT examinations were initiated and confirmed the diagnosis of an acute pansinusitis. The CT scan additionally revealed two small encapsulated epidural abscesses in the frontal paramedic area with a connection to the left frontal sinus: 8 × 9 mm and 14 × 9 mm (Fig. 3). An intracerebral abscess could be excluded. The patient underwent immediate surgery of the frontal sinus. A transnasal type I drain according to Draf in combination with an endoscopic sinus surgery and an abscess relief through a cut in the corrugator fold was performed. Cranialization of the frontal sinus was also discussed but was postponed initially.

The patient received antibiotic therapy with ceftriaxone. On follow-up MRI and CT studies, no regression of the described epidural formations was seen, so that finally cranialization of the frontal sinus and evacuation of the epidural abscess were performed. The surgery was made as indicated, similar to the first case described here. The patient recovered without any neurological sequalae and was discharged in good general condition under further coverage with metronidazole and ceftriaxone for 2 weeks.

A 9-year-old girl presented to hospital with persistent and progressive cold symptoms for about 6 weeks. Upfront antibiotic treatment did not lead to an improvement of her symptoms and her overall condition.

On initial presentation, the patient’s parents described recurring episodes of fever of up to 40 °C and a newly developed forehead swelling. Laboratory results showed a slightly elevated CRP level of 30.3 mg/l and a WBC of 10.1. Both the MRI and CT studies revealed sinusitis with frontal osteomyelitis accompanied by an epidural and subgaleal abscess formation without intracranial involvement (Fig. 4). The patient underwent immediate surgery. In a combined ENT/neurosurgical intervention, endoscopic sinus surgery on the left side was performed followed by and an osteoplastic craniotomy with removal of the epidural abscess as well as a drilling out of the osteomyelitis duct. Antibiotic therapy with cefotaxime and clindamycin was initially started and switched to ampicillin/sulbactam after detection of S. intermedius. Antibiotic treatment was administered for 14 days. The epidural abscess formation and the soft tissue swelling completely resolved clinically and on follow-up imaging. The patient could be discharged home without neurological sequalae.

As described earlier, most cases of PPT occur during adolescence, most likely facilitated by developmental circumstances [9, 11]. The diameter and the flow rate in diploic veins that drain the frontal sinuses increases in adolescence, which promotes hematogenous spread of infections into the bone and intracranially [6, 21]. Additionally, the skull bone that limits the frontal sinus is much thinner in adolescents than in adults, and thus there is a shorter path between the infection and the bone contributing to a hematogenous spread of infections. Finally, pneumatization of the frontal sinuses is not completed before the age of 14–15 years [12, 19]. When the paranasal sinus system develops, the frontal sinuses grow from the ethmoid air cells continuously in a cranial direction. This explains the fact that small children are less likely to be affected by PPT due to an incomplete or less pneumatized frontal sinuses. Our cases, however, show that even younger children at the age of 6 and 9 years can develop a corresponding symptomatology (Table 1). Although the sinuses are not yet fully formed, infections of the anterior ethmoid can find their way across the frontal recess to the area of the later frontal sinus.

In ethmoidal or frontal sinusitis, the infection spreads via the diploic veins or through the thinnest bone, in case of the frontal sinus, it is via the floor and the frontal wall. If the infection spreads into the bone, it leads to demineralization with necrosis, resulting in osteomyelitis [23]. An infection can spread via retrograde thrombophlebitis; in the case of destruction of the anterior wall of the frontal sinus, a subperiosteal abscess can be formed and by destruction of the posterior wall an epidural abscess can be formed. If the inferior wall of the sinus is affected, the infection can spread to the orbit and form the clinical picture of an orbital complication with preseptal cellulitis up to an orbital abscess. The spread of the infection is further promoted by the lack of venous valves in the diploic veins.

The diagnosis of PPT is made on the basis of a clinical examination. Most patients show a frontal swelling in the forehead area partially reaching the orbit. Many patients experience frontal headache, clear or purulent rhinorrhea, and/or fever [2, 8]. The differential diagnosis of such a forehead swelling includes, beside acute sinusitis, an infected atheroma, a carbuncle, or a condition after a head trauma with hematoma [12, 20]. The blood count is in many cases increased WBC as well as an elevated erythrocyte sedimentation rate and CRP level [1]. The medical history of a head trauma or acute and chronic sinusitis may be helpful for the diagnosis. If there is intracranial involvement, patients may also show signs of increased intracranial pressure indicated by nausea, focal or neurological deficits, and even loss of consciousness [2, 15]. An ultrasound examination can more precisely differentiate the entity of the forehead swelling. Here, liquid components such as pus in the swelling can be revealed and structures of the frontal bone can be assessed more precisely [16]. As a less invasive method, ultrasound should be favored especially for children instead of MRI and/or CT [18]. To identify the destruction of the frontal bone and subperiosteal fluid collection, contrast-enhanced CT is considered most effective [5]. In addition, CT is crucial for upfront surgical intervention, indicating whether other paranasal sinuses in addition to the frontal sinus are affected or if there is involvement of the orbits [11, 14]. If there is any suspicion of intracranial and/or intracerebral involvement, MRI should be performed in time to prove the necessity of intracranial interventional treatments. In addition to the meninges, the intraorbital structures can be evaluated and a sinus vein thrombosis may be excluded or confirmed [11]. To plan the procedure further, especially with regard to a transnasal drainage of the focus in the sense of FESS, a CT examination should always be performed to carry out a navigated endonasal sinus surgery and to reduce the intraoperative risk.

Since in the majority of cases PPT is associated with an upper respiratory tract infection, Streptococcus (alpha- and beta hemolytic streptococci), Haemophilus influenzae, Staphylococcus aureus and other anaerobes (Fusobacterium and Bacteroides species) play a crucial role [12]. In our cases, Streptococcus intermedius was found in three of four patients, Staphylococcus capitis was detected in one (Table 1). Streptococcus intermedius is known for its high pathogenic potential and is reported to be associated with intracranial abscesses in patients with concurrent sinusitis and patients with multiple risk factors [22]. In contrast to this, all our patients were young, healthy, and immunocompetent. Early and calculated antibiotic therapy makes the complication of acute sinusitis ever rarer and a prolonged antibiotic therapy should be administered after resistance testing, especially in difficult anatomical conditions and up to 6 weeks after the surgical intervention [22]. The antibiotic susceptibility testing of Streptococcus intermedius showed an antimicrobial susceptibility against penicillin, ampicillin, cefotaxime, ceftriaxone, and vancomycin. For Staphylococcus capitis, antibiotic sensitivity to flucloxacillin, vancomycin, ciprofloxacin, doxycycline, and co-trimoxazole was found.

The gold standard in the therapy of PPT is calculated antibiotic therapy in combination with an operative drainage of the infection. A rapid and effective treatment is of crucial importance to prevent further complications such as an epidural or intracerebral complication. In this case, the antibiotic treatment should already be started when there is clinical suspicion of PPT and should be adapted to the corresponding pathogen spectrum after obtaining microbiological material. Initial treatment should be commenced by a broad-spectrum antibiotic with good blood–brain barrier passage, such as ceftriaxone, which was used in our cases [14]. Nonetheless, the key pillar of therapy is surgical drainage of the abscess. The approach to should be chosen depends on the individual anatomy and extent of the infection. There is the possibility of an endonasal approach and even an open frontal sinus access or the combination of both. Intracranial abscess formation needs additional neurosurgical treatment [12]. Here, external drainage has the distinct advantage that the entire area of the frontal sinus can be overseen and the bone that is affected by osteomyelitis can be removed [11]. In many cases, frontal sinus trepanation represents the access of choice [4]. By contrast, FESS is a minimally invasive technique and represents the possibility of tissue-preserving drainage. Here, in contrast to an open external access, the osteomeatal complex, which is the narrowest point of drainage of the frontal sinus, can be viewed and treated. In addition to the advantage of lacking external scars, patients after FESS, in contrast to an open approach, have a significantly shortened convalescence and thus a much shorter hospitalization time. Only single drainage of the subperiosteal abscess also appears to be associated with an increased recurrence rate or further complications [11, 13]. According to these findings, surgical therapy and rehabilitation should be carried out in close cooperation between the participating disciplines of ENT, neurosurgery, radiology, ophthalmology, microbiology/infectious diseases, and pediatrics. Sole antibiotic therapy without any operative treatment seems to be associated with a high rate of recurrences and—according to the current state of research—cannot replace surgical therapy [16]. In the four cases described here, drainage of the frontal sinus was solely endonasal in two cases whereas the other two patients had a craniotomy in combination with external access for the treatment of the subgaleal and epidural as well as intradural abscess formations (Table 1).