Subdural Empyema, an Intracranial Sinus Complication

Abstract

Subdural empyema is the most common intracranial complication in sinusitis, defined as an infection with purulent collection between the inner surface of the dura mater and the outer surface of the cerebral arachnoid. This condition is underestimated and neglected by physicians due to its low incidence. However, despite its rarity, it is a serious pathology, requiring early diagnosis and therapeutic management. The present work aims to emphasize sinusitis as the primary focus of subdural empyema and the importance of its eradication for treatment.

Scientific articles published in the past 15 years on PubMed, SciELO, and BVS databases were reviewed using the keywords sinusitis, subdural empyema, and intracranial complication, and selected according to the inclusion criteria: case reports and retrospective studies from 2008 to 2023. At last, 16 works were selected. According to the reviewed articles, sinusopathy should not be underestimated, and more attention should be given to clinical signs suggestive of intracranial infections.

In conclusion, despite being uncommon, subdural empyema resulting from sinusitis complications is a neurosurgical emergency that carries considerable morbidity and mortality rates. Therefore, physicians should be aware of its correct treatment. Lastly, it was observed that otorhinolaryngological procedures can be performed to eliminate the primary focus, while neurosurgical interventions can solve this pathology. Thus, it is impossible to deny the importance of new studies with clear analysis regarding the eradication of the primary focus.

Resumo

O empiema subdural se traduz como a complicação intracraniana mais comum da sinusite, sendo definido como uma infecção cuja coleção purulenta se localiza entre a superfície interna da dura-máter e a superfície externa da aracnoide cerebral. Essa condição é subestimada e negligenciada por médicos, devido a sua baixa incidência. Entretanto, apesar de rara, essa patologia é grave e requer um diagnóstico e uma abordagem terapêutica precoce. O objetivo do presente trabalho é reforçar a sinusite como foco primário do empiema subdural e a importância da sua erradicação para o tratamento.

Foram revisados os artigos científicos publicados nos últimos 15 anos nas bases de dados PubMed, SciELO e BVS, usando os descritores: sinusitis, subdural empyema e intracranial complication, e selecionando os estudos de acordo com os critérios de inclusão: relatos de caso e estudos retrospectivos de 2008 a 2023. Por fim, foram selecionados 16 trabalhos. Conforme os artigos estudados, não a sinusopatia não pode ser subestimada e os sinais clínicos sugestivos de infecções intracranianas devem receber mais atenção.

Conclui-se que, apesar de incomum, o empiema subdural advindo de complicações da sinusite é uma emergência neurocirúrgica com morbidade e mortalidade consideráveis. Assim, os médicos devem se atentar ao seu tratamento correto. Por fim, procedimentos otorrinolaringológicos podem ser feitos para erradicar o foco primário, enquanto intervenções neurocirúrgicas podem solucionar essa patologia. Portanto, é inegável a importância de novos estudos com uma análise esclarecedora referente à erradicação do foco primário.

Keywords

subdural empyema - sinusitis - intracranial complication

Palavras chaves

empiema subdural - sinusite - complicação intracraniana

Introduction

Sinusitis is a common medical condition from which most patients can recover with proper treatment. However, in rare cases, there are potentially lethal intracranial complications, such as subdural empyema, meningitis, venous sinus thrombosis, intracerebral and epidural abscesses, which develop as a result of the inflammation of frontal, ethmoidal, sphenoidal, and maxillary sinuses.[1] [2] [3] [4] [5]

Subdural empyema is the most common complication, and it can be defined as an infection with its purulent collection located between the inner surface of the dura mater and the outer surface of the cerebral arachnoid. Moreover, it should be noted that it is more frequent among male patients younger than 20 years of age.[2] [4] [5] [6] [7] [8] [9] [10] [11]

The mortality rate can be significantly reduced with antibiotics, and it varies from 4 up to 15%, while morbidity in survivors can reach up to 50% for residual neurological deficits, 15 to 35% for hemiparesis, and 12 to 37,5% for persistent seizures.[2] [4] [5] [6] [12]

It is widely known that subdural empyema is overlooked by physicians due to its low incidence. However, despite its rarity, this pathology is a serious condition and requires early diagnosis and therapeutic management, as sequelae are reported in up to 40% of cases and onset is related to late treatment and the duration of the symptoms prior to diagnosis.[11] [13]

Still, delays in diagnosis occur due to the absence of specific signs. Therefore, in cases with clinical suspicion, patients must be evaluated via computerized tomography (CT) or magnetic resonance imaging (MRI) to rule out intracranial infection. Empyema is considered a neurosurgical emergency due to the increase in intracranial pressure in the first 24 to 48 hours, which may lead to coma and death. Thus, physicians must be aware of its risks.[2] [5] [6]

In summary, this study aims to reaffirm sinusitis as the primary focus of subdural empyema and the importance of its eradication for treatment.

Materials and Methods

A systematic literature review was conducted. Articles were selected from the PubMed, SciELO, and BVS platforms, using the descriptors sinusitis, subdural empyema, and intracranial complication, followed by the Boolean operators “AND” and “OR” to combine keywords. All the references from the eligible studies were also reviewed in search of additional articles.

The inclusion criteria were case reports and retrospective studies from the past 15 years (2008–2023), available in full, were included in this study. We excluded unrelated articles, reviews, meta-analyses, and those without full text available. Following the criteria application, 16 articles remained.

Results

Out of the 16 selected articles ([Fig. 1]), 5 are retrospective studies, and the other 11 are case reports, which reinforce subdural empyema as a complication of sinusitis. Moreover, they highlight this condition as a neurosurgical emergency and highlight symptoms that raise clinical suspicion of related intracranial complications. Some studies also provide evidence for the recommendation of otolaryngological procedures, since sinusitis is the main focus and must be treated to eradicate the infection ([Table 1]).

Fig. 1 Study methodology.

Table 1 Summary of selected articles

Author (year)	Title	Type of study	Sample	Points relevant to each study
Aljonas and Watanabe (2018)[6]	Subdural empyema following rhinosinusitis condition – case report	Case report	It reports a case regarding a 17-year-old male patient, diagnosed with rhinosinusitis. It evolved, however, to an SDE. The patient received antibiotic therapy treatment, but his condition ultimately led to death.	Complications of rhinosinusitis may come from acute or chronic infections. Although they occur more frequently in children, these infections may also impair adult patients. Among those of nasosinusal origin, SDE, cerebral, and extradural abscesses, as well as meningitis are mentioned as the most common. Treatment for empyemas is a neurosurgical emergency (burr holes or craniotomy) due to how quickly it can lead to coma or death as a consequence of the increase in intracranial pressure in the first 24 to 48 hours.
Sung et al. (2018)[1]	Bilateral subdural empyemas with meningitis secondary to acute barosinusitis	Case report	Healthy, immunocompetent 30-year-old man developed bilateral SDEs secondary to barosinusitis succeeding a plane trip abroad.	Intracranial complications of acute rhinosinusitis are not common, but may lead to extreme consequences, such as neurological morbidity or death.
Rasul et al. (2022)[12]	The Case for Early Antibiotic Commencement and Source Control in Pediatric Subdural Empyema: A Single-Centre Retrospective Case Series	Retrospective cohort study	Every patient admitted to their unit with a diagnosis of SDE over an 11-year period. A total of 36 patients received medical treatment throughout the inclusion period.	The contemporary series highlights some of the important changes regarding presentation and management of SDE over time. First, bimodal age distribution is in accordance with prior observations, with peaks in infancy, secondary to meningitis, and in older children, secondary to sinusitis or otitis media.
Belentani et al. (2008)[7]	Subdural Empyema: Complication of Acute Rhinosinusitis	Case report	13-year-old male patient.	SDE as an intracranial complication due to sinus disease, despite being infrequent, is still a reality. It is more common among male patients under 20-years-old, and presents considerable morbidity and lethality. It must be faced as a matter of urgency.
Barroso et al. (2019)[2]	Recurrent subdural empyema secondary to bacterial frontal sinusitis in an immunocompetent teenager: case report	Case report	16-year-old immunocompetent patient, with no associated comorbidities, who suffered an aggressive evolution to SDE from acute sinusitis. Urgent clinical-surgical approach was necessary.	Morbidity in SDE may reach 50% of the cases for residual neurological deficits, 15 to 35% for hemiparesis, and 12 to 37,5% for persistent seizures. In this case, the clinical picture had a satisfactory evolution, with no sequelae.
Hicks et al. (2011)[14]	Identifying and managing intracranial complications of sinusitis in children: a retrospective series	Retrospective cohort study	Every underage patient admitted to the Children's Hospital between January 1st, 2001, and December 31, 2009, with a diagnosis of sinusitis and intracranial suppuration or CVST.	Findings suggest that acute sinusitis, in combination with severe intractable headache, various degrees of altered level of consciousness, focal neurological deficits, and/or meningeal irritation signs, should raise clinical suspicion for potential sinusitis intracranial complications.
Pereira et al. (2018)[8]	Subdural empyema as a consequence of sinus diseases: considerations on 11 cases	Retrospective cohort study	11 cases of sinogenic SDE treated from January 1994 to August 1995 at the Department of Neurosurgery and Infectology from João Alves Filho Hospital (Aracaju, SE, Brazil) were studied.	It is worth noting the importance of conducting the specific procedure for the paranasal sinuses simultaneously to the SDE treatment. This approach aims to eradicate the infection's primary focus during the same surgical procedure, reducing the mortality rate.
Nicoli et al. (2016)[15]	Intracranial Suppurative Complications of Sinusitis	Retrospective cohort study	6 patients diagnosed with intracranial infection related to sinusitis; 4 patients with epidural abscess; 1 patient with both epidural abscess and SDE; 1 patient with SDE.	This study highlights the important clinical finding that patients with epidural abscess or SDE related to sinusitis usually present signs of elevated intracranial pressure instead of ordinary signs of sinusitis.
Gorman et al. (2018)[16]	Subdural empyema	Case report	69-year-old female patient on long-term immunosuppressive therapy for liver transplantation.	SDE is typically caused by prior neurosurgical procedure, sinusitis, otitis media, mastoiditis or meningitis. Its imaging characteristics may look subtle compared with its clinical severity. Thus, a high index of suspicion for diagnosis is required.
de Albuquerque Freitas et al. (2010)[9]	Intracranial complications of rhinosinusitis	Case report	15-year-old male patient, previously healthy, admitted to Risoleta Tolentino Neves Hospital in Belo Horizonte, MG, Brazil.	IEA and SDE are rare but highly lethal intracranial complications of sinusitis. They must be faced as a matter of urgency. In cases with clinical suspicion, CT is still the first exam in diagnostic investigation.
Mathon & Korinek (2018)[13]	Subdural empyema: an underestimated neurosurgical emergency	Case report	The study describes the clinical cases of three patients, aged 17, 21, and a 16-years.	SDE is an absolute neurosurgical emergency. Any delay in diagnostic and/or therapeutic management exposes the patient to a higher risk of death or neurological sequelae.
Szyfter et al. (2018)[3]	Simultaneous treatment of intracranial complications of paranasal sinusitis	Retrospective cohort	51 patients with intracranial complications of sinusitis, treated in the Department of Otorhinolaryngology and Laryngeal Oncology at the Poznán University of Medical Sciences from 1964 to 2016.	The most common intracranial complications of sinusitis develop as a result of inflammation of the frontal sinuses, ethmoid cells, sphenoid sinus and, less frequently, the maxillary sinuses.
Shen et al. (2018)[10]	Interhemispheric Subdural Empyema Secondary to Sinusitis in an Adolescent Girl	Case report	13-year-old female patient.	The most common cause of SDE is sinusitis, which represents 15% of hospitalized patients.
Varas et al. (2011)[11]	Subdural empyema secondary to sinusitis. A pediatric case report	Case report	9-year-old male patient.	For early diagnosis, it is important to search for any neurological complications in sinusitis cases with a negative clinical course. In view of clinical suspicion, imaging diagnosis is necessary to rule out complications.
Waseem et al. (2008)[4]	Subdural empyema complicating sinusitis	Case report	A case of sinusitis causing SDE in an immunocompetent, healthy teenage patient.	Despite improvements in antibiotic therapies, sinusitis still carries a risk of serious and potentially fatal complications. Physicians must consider SDE or brain abscess when evaluating a patient with severe headaches, especially if there is a recent history of sinusitis or ear infection.
Bruner (2012)[5]	Subdural empyema presenting with seizure, confusion, and focal weakness	Case report	16-year-old male patient.	Emergency neurosurgical consultation is essential, because surgical intervention (burr hole or craniotomy) is necessary in most cases to provide the best opportunity for neurological recovery. Similarly, otorhinolaryngological consultations are recommended because FESS can assist with drainage and recovery.

Abbreviations: CT, computed tomography, CVST, cerebral venous sinus thrombosis; FESS, functional endoscopic sinus surgery; IEA, intracranial epidural abscess; SDE, subdural empyema.

Discussion

Sung et al.[1] and Belentani et al.[7] argued that intracranial complications in consequence of rhinosinusitis conditions occur through direct extension due to a defect in the anterior cranial base, or hematogenously through retrograde thrombophlebitis of veins which interlink face and skull sinuses.[1] [7]

Aljonas and Watanabe[6] reported a clinical case regarding a 17-year-old male patient diagnosed with rinosinusitis who underwent outpatient, antibiotic treatment. His symptoms regressed temporarily but evolved again after discontinuing medication. Thus, the patient underwent outpatient treatment again. Subsequently, the patient had changes to his clinical condition, such as seizures and decreased levels of consciousness. An MRI scan was performed, leading to clinical suspicion of subdural empyema. However, his condition ultimately led to brain death.[6]

The authors note that the most common symptoms are headaches, altered mental status, seizures, focal deficits, vomit, orbital swelling, fever, rhinorrhea, nasal obstruction, neck stiffness, and Kerning's sign. Moreover, they insist on the need for imaging exams in any case of sinusitis with neurological signs, failure from a previous treatment, or associated orbital cellulitis, to ensure rapid diagnosis and avoid outcomes such as the reported one.[6]

Barroso et al.[2] state that imaging exams are mandatory for patients diagnosed with frontal sinusitis who persistently demonstrate fever, frontal edema, or failure to resolve symptoms, even if their condition lacks neurological signs.[2]

Belentani et al.[7] and Pereira et al.[8] emphasize that subdural empyema diagnosis is based on clinical suspicion. Therefore, physicians must be vigilant in cases that show a symptom evolution with fever, headaches, or neurological manifestations. Lastly, these authors highlight the importance of specific procedures for paranasal sinuses, along with the endoscopic submucosal dissection (ESD), to eradicate the primary focus infection during the same surgical procedure. This also brings the advantage of reducing mortality rates. Similarly, antibiotic treatment associated with otorhinolaryngological, and neurological surgical approaches result in good prognosis.[8]

Rasul et al.[12] conducted a retrospective study regarding 36 patients and demonstrated an increase in the occurrence of sinusitis and related intracranial complications. The cause of this increase, however, remained unclear. Furthermore, in their study, none of the patients who underwent simultaneous otorhinolaryngological procedures needed repeated surgery, emphasizing the importance of controlling the primary focus infection.[12]

According to Hicks et al.,[14] laboratory data such as leukocytosis, polymerase chain reaction (PCR), and elevated sedimentation levels in a sinusitis scenario can be used to raise suspicion of possible intracranial complications. Even though those are nonspecific markers of infection and inflammation, a comparison among 12 patients suggests that individuals diagnosed with uncomplicated sinusitis have lower PCR and sedimentation levels than those with intracranial abscesses. However, the small sample size is one of the study's limitations.[14]

Pereira et al.[8] concluded that sinusitis, when it is not adequately treated, may lead to intracranial complications such as subdural empyema. They also observed that headaches and fever are often found prior to more specific symptoms, such as neck stiffness, dizziness, vomit, seizures, altered consciousness, and focal neurological signs.

Mathon and Korinek[13] emphasize the delay in therapy as the main factor for bad subdural empyema prognosis. They also bring attention to the importance of entry point surgical treatment, especially when draining sinusitis, to increase bacterial isolation and improve the effectiveness of antibiotic therapy.[13]

According to Szyfter et al.,[3] neurological signs associated with intracranial complications have been less frequent in recent years, when compared with the usual symptoms of paranasal sinusitis. They further emphasize that simultaneous treatment of inflammation along with intracranial complications is quite effective.[3]

Similarly, Herrero et al.[11] describe that the therapeutic approach includes not only surgical intervention of empyema but also drainage of the original focus.[11]

Building on other studies, Waseem et al.[4] suggest that subdural empyema is one of the most common complications of sinusitis and that the similarity of its symptoms with those of sinusitis can make it difficult to differentiate. The authors also noted that acute or progressive headaches are the most important indicator of intracranial complications. They further report that, despite antibiotic treatment, infections can still progress rapidly and might require surgical drainage, which is the most important factor in determining a favorable outcome.[4]

Contrary to other studies, Nicoli et al.[15] say that patients with intracranial complications related to sinusitis often present signs of elevated intracranial pressure rather than usual sinusitis signs. Moreover, in accordance with other studies, they advise drainage of both the source of infection and the intracranial suppuration, in combination with antibiotic therapy, to limit morbidity, mortality, and recurrence. In addition, these authors emphasize the need for multidisciplinary management by neurosurgeons and otorhinolaryngologists.[15]

According to Bruner et al.,[5] complications historically occurred secondary to middle ear infection, but currently are more frequent as a consequence of bacterial sinusitis. The authors also highlight that otolaryngological and emergency neurosurgical consultations are essential, since a functional endoscopic sinus surgery (FESS) can assist in drainage and recovery.[5]

In summary, sinusitis is the most common cause of subdural empyema, and the aforementioned articles reinforce the need to raise suspicion for intracranial complications whenever there is a poor clinical course, to obtain better therapeutic response and to reduce the risk of morbidity and mortality.

Additionally, sinus disease ought not to be underestimated, and physicians should pay attention to clinical signs suggestive of intracranial infections, as subdural empyema is a neurosurgical emergency that requires rapid recognition for appropriate intervention. With the analyzed data, it becomes evident there is a great diversity of symptoms, so imaging tests should be performed in cases with headaches, fever, or if the treatment fails, even if they show no neurological signs.

Furthermore, it has been observed that antibiotic therapy shows better results and prognosis when associated with otorhinolaryngological and neurological surgical approach, since these contribute to the eradication of the primary focus. For this reason, Rasul et al.[12] reported no repeated surgeries among their 36 patients, all of whom underwent these simultaneous procedures. Therefore, we emphasize the importance of further research addressing this topic and thoroughly examining the relationship between both interventions.

This work presents some limitations, as it did not address empyema treatment, except for surgical intervention simultaneous to otorhinolaryngological treatment to eradicate the primary focus. Furthermore, there were few studies on the relationship between both interventions. Finally, most of the included studies are case reports, so the final sample size is considerably small. There is a scarcity of studies measuring the neglect from both doctors and patients regarding sinusitis.

Despite this limitation, the present study reinforced sinusitis as the primary focus of empyema to raise awareness regarding this matter and highlighted the main symptoms that lead to early diagnosis. Finally, we discussed otorhinolaryngological treatments aimed at eradicating sinusitis being managed simultaneously to surgical intervention.

Conclusion

In light of this discussion, we can conclude that sinusitis is indeed one of the primaries focuses of subdural empyema. However, its treatment is still neglected. Despite being infrequent, subdural empyema resulting from sinusitis complications is a neurosurgical emergency with significant morbidity and mortality rates. This should be enough to encourage careful monitoring of patients diagnosed with sinusitis.

Additionally, we discussed how otorhinolaryngological procedures can eradicate the primary focus, and neurosurgical interventions may be conducted to resolve subdural empyema. However, there is limited data regarding these approaches, preventing a comprehensive and widespread understanding of the subject. Thus, a larger sample of patients would provide more precise information on how to prevent and treat this condition.

Furthermore, the importance of new studies providing a clear analysis of these issues cannot be denied.

Conflict of Interests

The authors have no conflict of interests to declare.

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Publication History

Received: 17 September 2023

Accepted: 23 October 2024

Article published online:
27 March 2025