Central skull base osteomyelitis as a complication of necrotizing otitis externa: Imaging findings, complications, and challenges of diagnosis

18F-FDG PET imaging for treatment response assessment and management guidance in patients with skull base osteomyelitis

OBJECTIVE

The objective of this study is to evaluate the role of hybrid 18F-FDG PET for treatment response assessment and management guidance in patients with skull base osteomyelitis.

MATERIALS AND METHODS

Retrospectively, 33 patients, with at least a baseline and follow-up PET (computed tomography/MRI) scan, were included. Parameters like standardized uptake value (SUV) max, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) (initial, follow-up, percentage change) were analysed and outcomes based on 18F-FDG PET reports were classified into resolution (a), partial response (b), progression (c) and stable disease (d). The clinical course and response on anatomical imaging were also compared with 18F-FDG PET.

RESULTS

There was mild correlation between initial SUV with ESR (0.338) and CRP (0.384). Moderate correlation was seen between follow-up SUV and CRP (0.619), percentage change in SUV max (PC SUV) with percentage change in ESR (0.456) and CRP (0.668). Mean PC SUV was 70% (a), 35% (b), -40% (c) and -18% (d), respectively. 48% (16/33) (resolution, progression, stable disease) patients had clear management change with 18F-FDG PET with either escalation or stopping of antibiotics/antifungals. Management decision in partial response group (52%, 17/33) was taken clinically. On retrospective PC SUV analysis, treatment continuation group (8 patients) showed 20% decrease, whereas the group that was only monitored further (9 patients) had 48% reduction in SUV.

CONCLUSION

18F-FDG PET showed a moderate association with clinical markers used in follow-up of patients with skull base osteomyelitis and is a reliable investigation for assessment of disease status. This can be used as a guide along with clinical evaluation for de-escalation of treatment.

Skull Base Osteomyelitis- Marauders of the Skull

Skull base osteomyelitis is a vicious infection of temporal bone associated with very high morbidity and mortality. But few studies have been undertaken recently for eliciting its increasing incidence. Hence this study aims to describe the clinical profile of skull base osteomyelitis and changes noted in the post-covid period, and encourage a uniform treatment policy globally. This descriptive study was conducted among 140 patients diagnosed with skull base osteomyelitis. Data was collected using semi-structured proforma, HRCT temporal bone findings, microbiological reports, histopathology of granulation tissue, ESR and House-Brackmann grading. Male patients in 61-70 age group were most commonly affected and all patients had uncontrolled diabetes mellitus, usually presenting with nocturnal otalgia, ear canal granulation and cranial nerve palsy. Pseudomonas aeruginosa was the most common isolate followed by Staphylococcus aureus. Among fungal pathogens, candida albicans were the most common. 29.3% patients had extensive disease according to Thakar et al. staging and on follow up, 43.75% patients showed a satisfactory response. Coronary artery disease and cerebrovascular accidents were the leading cause of death. More atypical organisms, extensive disease and changes in antibiotic sensitivity were noted in the post-covid period. Prolonged treatment with culture sensitive antibiotic is the main stay of treatment. A uniform treatment guideline is needed for proper management of such patients. Level of Evidence 4.

Imaging spectrum and complications of otogenic infections: insights into delayed diagnosis

Skull base osteomyelitis (SBO) is a late manifestation of complicated otogenic infections that presents a diagnostic challenge. Delayed or missed diagnoses lead to high morbidity and mortality and can be attributed to non-specific symptoms, subtle early radiologic findings, radiologic mimicry of nasopharyngeal carcinoma (NPC), and under-recognition from clinician and radiologists. This pictorial review aims to emphasize on early imaging recognition and distinction between SBO and NPC.

Skull base infections, their complications, and management

OBJECTIVE

Our review aims to summarize the current literature on skull base infections (SBIs) and retrospectively analyze any such cases encountered at our institution.

DESIGN

A literature search was conducted using online databases PubMed, MEDLINE, and ResearchGate with the terms "skull base osteomyelitis," "temporal bone osteomyelitis," "skull base infections," "necrotizing otitis media," and "SBO". References from the resulting manuscripts were reviewed for relevant articles. A search of our electronic health records using the same key terms was also performed to identify patients with a tissue biopsy-confirmed diagnosis of skull base infections. Patients with an indeterminate diagnosis or inaccessible/poor imaging were excluded.

SETTING

A level one trauma and major tertiary academic medical center.

PARTICIPANTS

All patients treated at the University of California Davis Health System with a confirmed diagnosis of skull base infections from January 2005 to November 2020.

MAIN OUTCOME MEASURES

Imaging results, symptoms, treatment, morbidity, and mortality.

RESULTS

Our literature search yielded 59 articles ranging from 1982 to 2021. A retrospective search of our electronic health records identified two cases of skull base infections.

CONCLUSION

Skull base infections have no pathognomonic findings. A multimodal approach with computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine is necessary to characterize the disease process in addition to a biopsy for definitive diagnosis. Other diagnoses can mimic SBI on imaging, such as nasopharyngeal carcinoma and inflammatory pseudotumor. Culture-guided antimicrobial treatment and surgery are mainstay therapies. Other adjuvant strategies currently lack the robust evidence necessary to characterize their risks and benefits.

68 Ga-Citrate PET/CT Imaging in the Diagnosis of Skull Base Osteomyelitis and Its Usefulness in the Assessment of Treatment Response

PURPOSE

68 Ga-citrate PET/CT imaging in the diagnosis of skull base osteomyelitis (SBO) and its usefulness in the assessment of treatment response.

METHODS

Eighteen patients underwent 68 Ga-citrate PET/CT scans for suspected SBO for diagnosis/assessment of treatment response.

RESULTS

Of 18 patients, 16 patients had a positive study for SBO, and 2 patients had a negative study. Scan findings were correlated with clinical, biochemical, microbiological, and radiological parameters.

CONCLUSION

68 Ga-citrate PET/CT is a promising tool in the diagnosis and management of skull base osteomyelitis.

Clinico-Radiological Evaluation for Longitudinal Assessment in Central Skull Base Osteomyelitis: Proposal of Novel Scoring System

This study aims to evaluate clinical, radiological and laboratory parameters for longitudinal assessment and prognostication in central skull base osteomyelitis (CSBO). Novel radiological score and cranial nerve assessment score (CNAS) have been proposed and analysed along with pain score (VAS), ESR, CRP, WBC count, and HbA1c for utility in disease-monitoring and predicting outcome in CSBO. CSBO cases managed in a tertiary care centre from January 2018 to November 2020, with a minimum follow-up of 6 months were included. The parameters were recorded at presentation, 3-month, 6-month postoperative follow-up, and at completion of therapy, for statistical analysis. Significant positive correlation was found amongst pain score, CNAS, radiological score, ESR, and CRP at different timelines. On longitudinal assessment, there was a statistically significant reduction in above-mentioned parameters, in the cases who recovered. Those with initial radiological score < 30, pain score ≤ 7, and CNAS < 10 showed early clinical improvement, required shorter duration of antimicrobial therapy, and exhibited higher probability of becoming disease-free at an earlier time, compared to those presenting with higher scores. We propose the use of pain score, a novel cranial nerve assessment score, and a novel radiological score for longitudinal assessment in CSBO. The trend in these parameters along with ESR and CRP are useful to monitor the disease process. The initial assessment scores can predict duration of antimicrobial therapy and probability of early recovery. WBC count and HbA1c were neither useful for disease-monitoring nor predicting outcome.

Atypical Skull-Base Osteomyelitis: Comprehensive Review and Multidisciplinary Management Viewpoints

Atypical skull-base osteomyelitis is a rare but fatal disease that usually involves infection of the ethmoid, sphenoid, occipital, or temporal bones that form the skull base. Unlike typical (so-called otogenic), atypical skull-base osteomyelitis has no otogenic cause. Instead, some authors call atypical skull-base osteomyelitis sinonasal, since the infection most often originates from the nose and paranasal sinuses. Diagnosing and treating this disease is challenging. To assist in managing atypical skull-base osteomyelitis, a review of the most recent literature, with patient cases and multidisciplinary perspectives from otolaryngologists, neurosurgeons, radiologists, infectious disease specialists, pathologists, and clinical microbiologists, is provided in this paper.

Cranial nerve palsy prevalence and associated factors in patients with malignant otitis externa

Objective

To identify the prevalence of cranial nerve (CN) palsy and its associated factors in malignant otitis externa (MOE).

Methods

In a retrospective study, records of MOE patients from 2011 to 2014 were reviewed. MOE and CN involvement were evaluated based on patient demographics, clinical, and paraclinical data.

Results

Overall, 119 MOE patients with a mean age of 65.9 ± 11.3 were included. 69.7% were male, and 63.0% had a history of diabetes. The most common symptoms and signs were otalgia (97.5%), otorrhea (44.5%), and ear canal erythema/edema (24.4%). Thirty-three patients (27.7%) had CN involvement. The facial nerve was mostly involved (26.1%). Skull base osteomyelitis (SBO) was present in 59 patients. When excluding patients younger than 30 and older than 80, age decade was correlated with CN palsy. 66.9% of patients with CN palsy and 65.6% without CN palsy were male, which was significantly different. The following factors were not significantly different between patients with and without CN palsy: Comorbidities, signs and symptoms, diagnostic delay, erythrocyte sedimentation rate level, fasting blood sugar, hemoglobin A1c level, antifungal therapy, hospitalization duration, and SBO on imaging. Tinnitus was correlated with SBO evidence on imaging (specificity: 96.7%).

Conclusion

CN involvement occurs in about three out of 10 MOE patients. Male gender and advanced age may be related to a higher incidence rate of CN palsy. Tinnitus can be a specific indicator of SBO. These findings could help in better decision-making for early interventions.

Level of Evidence

4.

Patients' experience of necrotising otitis externa: a qualitative study

BACKGROUND

Necrotising otitis externa is a serious infective condition. Patients are typically frail, diagnostic delay is common and severe pain is a key feature. This study aimed to qualitatively analyse patient-centred data to identify key themes in the patient's experience.

METHODS

Open-ended questionnaires were sent to 28 patients. Responses were qualitatively analysed using a grounded theory approach. Iterative cycles were used to develop codes using a constant comparison technique. Emerging categories were refined to identify core themes.

RESULTS

Four main themes emerged: severe pain, mental health, quality of life and diagnostic delays.

CONCLUSION

This is the first study to explore patients' perspectives in necrotising otitis externa. It indicates a need to raise awareness of necrotising otitis externa, and to improve symptom management, pain control and quality of life. This valuable information can be used to identify research priorities, guide service improvements, improve clinical care and feed into the development of a Core Outcome Set for necrotising otitis externa.

Skull base osteomyelitis with extensive bony erosion complicated by venous sinus thrombosis

Skull base osteomyelitis (SBO) mimics the presentation of various conditions, including solid tumors. Computed tomography-guided core biopsy for culture informs antibiotic selection, and with intravenous corticosteroids, may minimize chronic neurologic dysfunction. Although SBO predominantly affects individuals who are diabetic or immunocompromised, it is important to be able to recognize SBO presenting in an otherwise healthy individual.

A case of atlantoaxial instability following skull base osteomyelitis: Tips for diagnosis and management

Skull base osteomyelitis is a rare but dangerous consequence of untreated malignant otitis externa. Pseudomonas aeruginosa is responsible for most cases with typical presentation. Here, we discuss a diabetic 54-year-old female presented with malignant otitis externa and bilateral facial paresis followed by cervical spondylitis and C1-C2 instability. Skull base osteomyelitis confirmed by clinical presentation, imaging, and laboratory data. Fortunately, she responded well to antibacterial and antifungal therapy. Due to limited data, there is no confirmed standard of treatment for cervical instability secondary to SBO. It seems antibiotic therapy is the mainstay of treatment. In case of poor response to antibiotic therapy, surgical intervention is inevitable. This article introduces the first case of SBO-related AAI successfully managed with conservative treatment.

A Rare Case of Streptococcus Pneumoniae Causing Malignant Otitis Externa Complicated by Skull Base Osteomyelitis

Skull base osteomyelitis is an aggressive infection involving bones of the skull. It is a rare complication of malignant otitis externa, caused by the contiguous spread of the infection. Patients are mostly elderly with comorbidities that compromise immunity. It is atypical for Streptococcus species to be encountered in basilar skull osteomyelitis. Here we present the case of an 80-year-old male with multiple comorbidities including diabetes mellitus with a two-month history of right ear pain associated with occasional discharge and diminished hearing who was found to have bacteremia and basilar skull osteomyelitis with Streptococcus pneumoniae isolated from blood and otorrhea fluid cultures. This unusual presentation of S. pneumoniae related skull base osteomyelitis could be attributed to an undiagnosed pancreatic cancer at the time of presentation. Malignant otitis externa can progress into invasive disease in the head and neck; almost all cases tend to be caused by Pseudomonas aeruginosa but unusual cases, such as this, can be caused by Streptococcus pneumoniae.

The association between radiological spreading pattern and clinical outcomes in necrotizing external otitis

Objectives

Methods

Results

Conclusion

Level of evidence

Imaging of Acute and Chronic Skull Base Infection

Skull base infections are uncommon but can be life threatening without timely recognition. Imaging plays a crucial role because symptoms can be vague and nonlocalizing. Necrotizing otitis externa in diabetic or immunocompromised patients is the commonest cause of skull base osteomyelitis (SBO), followed by sinogenic infections and idiopathic central SBO. Multiparametric magnetic resonance (MR) and high-resolution CT are the mainstays for establishing a diagnosis and estimating disease extent, with MR being superior in ascertaining marrow and soft tissue involvement. Monitoring treatment response, of which imaging is a fundamental part, is challenging, with emerging promising imaging tools.

Skull base osteomyelitis imaging

PURPOSE OF REVIEW

Skull base osteomyelitis (SBO) is a challenging entity to diagnose and treat. The goal of this review is to summarize the imaging findings of SBO and present these in the context of recent studies on imaging of SBO.

RECENT FINDINGS

This review discusses the clinical presentation, pathophysiology and imaging appearances of SBO. The review further emphasizes the results of latest studies on imaging of SBO, and the role of different modalities in diagnosis and evaluation of disease course and treatment response. Brief discussion on differential diagnoses from an imaging standpoint is also included.

SUMMARY

Various imaging modalities play different and complimentary roles in diagnosis and management of SBO, which are discussed in this review.

Current management of skull base osteomyelitis

PURPOSE OF REVIEW

Skull base osteomyelitis (SBO) is a life-threatening condition. Due to an aging and increasingly multimorbid population, clinicians are more often challenged with this disease. Yet, there is no consensus on the optimal diagnostic and follow-up management. This review should aid clinicians in decision-making for their patients.

RECENT FINDINGS

Treatment-resistant otalgia or headache is suspicious of SBO. Pseudomonas aeruginosa remains the most common pathogen but clinicians are challenged with increasing rates of sterile or fungal cultures due to previously applied antibiotics/steroids. No single imaging modality is able to detect the full extent of the disease. Whereas functional nuclear imaging with gallium-67 or methylene diphosphonate-technetium-99m was once advocated, its actual benefit is questionable. Newer modalities such as fluoro-D-glucose-positron emission tomography (PET)/computed tomography, PET/magnetic resonance imaging (MRI), or diffusion-weighted MRI seem to be promising in diagnosis and follow-up. Finding the causative pathogen is of utmost importance followed by long-term intravenous antibiotics until the disease has completely resolved. Surgery plays a minor role in treatment but can be helpful in selected cases.

SUMMARY

The numerous challenges in SBO render management difficult, but with a clear work-up including regular clinical, laboratory and imaging examinations, outcome can be improved.

MRI of Emergent Intracranial Infections and Their Complications

Acute intracranial infections of the central nervous system and skull base are uncommon but time sensitive diagnoses that may present to the emergency department. As symptoms are frequently nonspecific or lack typical features of an infectious process, a high index of suspicion is required to confidently make the diagnosis, and imaging may not only serve as the first clue to an intracranial infection, but is often necessary to completely characterize the disease process and exclude any confounding conditions. Although computed tomography is typically the initial imaging modality for many of these patients, magnetic resonance imaging offers greater sensitivity and specificity in diagnosing intracranial infections, characterizing the full extent of infection, and identifying potential complications. The aim of this article is to serve as a review of the typical and most important imaging manifestations of these infections that can be encountered in the emergent setting.

Diagnosing necrotizing external otitis on CT and MRI: assessment of pattern of extension

BACKGROUND AND PURPOSE

Necrotizing external otitis (NEO) is a serious complication of external otitis. NEO can be classified according to-anterior, medial, posterior, intracranial, and contralateral-extension patterns. Currently there is no consensus on the optimal imaging modality for the identification of disease extension. This study compares NEO extension patterns on MR and CT to evaluate diagnostic comparability.

METHODS

Patients who received a CT and MR within a 3-month interval were retrospectively examined. Involvement of subsites and subsequent spreading patterns were assessed on both modalities by a radiologist in training and by a senior head and neck radiologist. The prevalence of extension patterns on CT and MR were calculated and compared.

RESULTS

All 21 included NEO cases showed an anterior extension pattern on CT and MR. Contrary to MR, medial extension was not recognized on CT in two out of six patients, and intracranial extension in five out of eight patients. The posterior extension pattern was not recognized on MR. Overall, single anterior extension pattern (62%) is more prevalent than multiple extension patterns (38%).

CONCLUSION

All anterior NEO extension pattern were identified on CT as well as MR. However, the medial and intracranial spreading patterns as seen on MR could only be identified on CT in a small number of patients. The posterior spreading pattern can be overlooked on MR. Thus, CT and MR are complimentary for the initial diagnosis and work-up of NEO as to correctly delineate disease extent through the skull base.

Malignant Otitis Externa: How to Monitor the Disease in Outcome Estimation?

Objective

Malignant otitis externa (MOE) is a serious disease affecting mainly the elderly diabetic patients that may result in mortality. It was aimed to evaluate the relationship between treatment responses and clinical and radiologic parameters among progress of the disease. Secondary aim was to present our clinical outcomes in the treatment of malignant otitis externa.

Method

This study was retrospectively conducted in a single center. Reviewed data included history of complaints, duration of symptoms, addition of hyperbaric oxygen treatment, presence of surgical intervention, pathological findings, culture positivity and microorganism, laboratory findings, scintigraphy, imaging modalities and outcome of disease.

Result

A total of 26 cases with malignant external otitis including 17 females (65.4%) and nine males (34.6%) patients were included in our study. Duration of symptoms before the initiation of treatment, and hyperbaric oxygen treatment did not positively influence the outcome. Inflammatory markers and Peleg staging significantly reflected the treatment response.

Conclusion

Close monitoring of inflammatory parameters is the key point in the prediction of prognosis. Planning the management and predicting the outcomes rely on proper radiological and clinical assessment of the extent of disease. In the assessment of MOE, universal scoring systems should be preferred for pooling the data in comparable manner.

Skull Base Osteomyelitis: A Comprehensive Imaging Review

Skull base osteomyelitis is a relatively rare condition, generally occurring as a complication of advanced otologic or sinus infection in immunocompromised patients. Skull base osteomyelitis is generally divided into 2 broad categories: typical and atypical. Typical skull base osteomyelitis occurs secondary to uncontrolled infection of the temporal bone region, most often from necrotizing external otitis caused by Pseudomonas aeruginosa in a patient with diabetes. Atypical skull base osteomyelitis occurs in the absence of obvious temporal bone infection or external auditory canal infection. It may be secondary to advanced sinusitis or deep face infection or might occur in the absence of a known local source of infection. Atypical skull base osteomyelitis preferentially affects the central skull base and can be caused by bacterial or fungal infections. Clinically, typical skull base osteomyelitis presents with signs and symptoms of otitis externa or other temporal bone infection. Both typical and atypical forms can produce nonspecific symptoms including headache and fever, and progress to cranial neuropathies and meningitis. Early diagnosis can be difficult both clinically and radiologically, and the diagnosis is often delayed. Radiologic evaluation plays a critical role in the diagnosis of skull base osteomyelitis, with CT and MR imaging serving complementary roles. CT best demonstrates cortical and trabecular destruction of bone. MR imaging is best for determining the overall extent of disease and best demonstrates involvement of marrow space and extraosseous soft tissue. Nuclear medicine studies can also be contributory to diagnosis and follow-up. The goal of this article was to review the basic pathophysiology, clinical findings, and key radiologic features of skull base osteomyelitis.

Skull base osteomyelitis: Comprehensive analysis and a new clinicoradiological classification system

OBJECTIVE

Skull baseosteomyelitis (SBO) is a rare phenomenon that typically occurs in diabetic or immunocompromised patients, causing significant morbidity and mortality. This study aimed to analyze a single institution's treatment results in SBO patients and propose anew integrated clinicoradiological classification system.

METHODS

The medical records of 32 SBO patients that were treated at a tertiary care center between 2006 and 2017 were retrospectively reviewed. A scoring system based on anatomical involvement according to MRI was created. Subsequently, the scoring system was integrated with cranial nerve dysfunction status and a clinical grading system (CGS) was proposed.

RESULTS

Among the 32 patients, 78.1% were diabetic and 63% had cranial nerve dysfunction at presentation. Bone erosion based on CT was greater in the patients without regression (P = 0.046). The regression rate decreased from clinical grade (CG)1 to CG3 (P = 0.029). Duration of hospitalization increased as CG increased (P = 0.047). Surgery had no effect on regression status at the time of discharge (P = 0.41). The 1-year, 2-year, and 5-year overall survival rates were 82.2%, 70.8%, and 45.8%, respectively. CG was significantly correlated with overall survival but not with disease-specific survival (log-rank; P = 0.017, P = 0.362, respectively).

CONCLUSION

SBO continues to pose a challenge to clinicians, and causes significant morbidity and mortality. The proposed new classification system can be an option for grouping SBO patients according to clinical and radiological findings, helping clinicians estimate prognosis.

In the evaluation of patients with skull base osteomyelitis, does 18F-FDG PET CT have a role?

PURPOSE

To evaluate the diagnostic performance of regional fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography-computed tomography (PET-CT) in patients with skull base osteomyelitis (SBO) and to compare with magnetic resonance imaging (MRI) whenever available.

MATERIALS AND METHODS

A total of 77 patients (male:female = 56:21; mean age 66.4 ± 9.4 years) with clinically suspected SBO, who underwent regional F-FDG PET-CT were included in this retrospective study. F-FDG PET-CT images were analyzed for presence, localization and intensity of FDG uptake. Diagnostic performance of F-FDG PET-CT was analyzed based on histopathology, culture, and clinical/imaging follow-up. The agreement analysis between F-FDG PET-CT and MRI findings was performed in 56 patients.

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of F-FDG PET-CT for diagnosing SBO were 96.7, 93.3, 98.3, 87.5, and 96.1%, respectively. The average SUVmax of the lesions was 5.9 ± 3.5. The SUVmax of the fungal lesions was lower than that of bacterial lesions with P-value of <0.001. On comparing variables like C-reactive protein, erythrocyte sedimentation rate, and SUVmax for prediction of recurrence/progression, by plotting an ROC curve, the SUVmax was found to be an independent prognostic marker. 56 out of 77 patients had undergone both F-FDG PET-CT and MRI. The agreement analysis between the modalities showed almost perfect agreement for delineation of soft tissue and bony involvement with κ values of 0.82 and 0.81, respectively.

CONCLUSION

F-FDG PET-CT is a sensitive tool in evaluation of patients with SBO. It shows a very good agreement with the MRI. It plays a critical role in treatment response evaluation.

The challenging diagnosis and follow-up of skull base osteomyelitis in clinical practice

PURPOSE

The disease activity of skull base osteomyelitis can be challenging to assess by means of conventional imaging methods and renders monitoring of the disease difficult, especially in areas with restricted access to nuclear medicine imaging. Here, we provide clinically relevant data on the management of skull base osteomyelitis including assessment, treatment, and follow-up strategies with regards to the role of imaging.

METHOD

A chart review was performed including 30 patients treated for SBO from 1993 to 2015. Clinical findings, treatment procedures, and complication rates were assessed. Special attention was paid to imaging procedures.

RESULTS

The overall mortality rate was 36.7% and increased to 45% when cranial nerve palsies were present. An initial computed tomography (CT) scan was performed in all patients, MRI in 60% and nuclear imaging in 33%. CT scans failed to detect progression or regression in up to 80% after four to nine months. MRI examinations could reveal changes at a higher rate compared to CT. Nuclear medicine functional imaging was most likely to assess disease activity.

CONCLUSION

A combination of different imaging modalities is recommended for diagnosing SBO. For the follow-up, MRI is preferable to CT as changes can be detected more readily with MRI. If available, nuclear medicine imaging should guide the decision of treatment discontinuation.

Diagnosis of Skull Base Osteomyelitis

Skull base osteomyelitis (SBO) is an infection of the temporal, sphenoid, or occipital bone that can be a challenge to diagnose because of its nonspecific symptoms, long clinical course, and radiologic findings that mimic those of other entities. The authors review this unusual infection on the basis of six proven cases. The diagnosis of SBO should be made according to four points: a high index of clinical suspicion, radiologic evidence of infection, repeated biopsies that are negative for malignancy, and positive results of microbiologic tests. SBO typically manifests clinically in patients with diabetes and recurrent otitis externa; the infection usually extends inferiorly to the compact bone of the infratemporal fossa, affecting the lower cranial nerve foramina. Several image-based techniques should be used to diagnose SBO. CT is the best option for evaluating bone erosion and demineralization, MRI can help delineate the anatomic location and extent of disease, and nuclear imaging is useful for confirming bone infection with high sensitivity. However, the standard diagnostic procedure for SBO is for patients to undergo repeated biopsies to rule out malignancy, with histopathologic signs of infection and detection of microorganisms in the biopsied bone or soft tissue indicating SBO. The ability to diagnose SBO can be increased by identifying patients at risk, recognizing the most important causes and routes of infection, describing the main radiologic findings, and always considering the differential diagnosis. ^©RSNA, 2021.

From Uncommon Infection to Multi-Cranial Palsy: Malignant External Otitis Insights

Purpose:

The progression of the otitic infectious process toward diseases of particular severity is often unpredictable, just as it is challenging to manage the patient over time, even after the apparent resolution of the disease. We aim to define a radiological reading key that allows us to correctly and promptly treat the disease, avoiding the possible severe complications.

Methods:

We conducted a retrospective study of 13 cases of basal cranial osteomyelitis (SBO) due to malignant external otitis, by the ENT Department of the University of Catania. Through a standardized approach and following the latest guidelines, we have evaluated all patients performing a standardized and personalized radiological protocol according to the stage of the patient’s pathology and modulating the treatment consequently.

Results:

Clinical signs have been observed such as otorrhea (100%), otalgia in 13/13 patients (100%), granulations in external auditory canal (100%), preauricular cellulitis in 9/13 patients (69%) headache 6/13 cases (46%), dysphonia 4/13 cases (31%). HRCT of the temporal bone proved useful in identifying even minimal bone lesions in 13/13 (100%) while improving MRI in vascular and nervous involvement, although in 1/13 patient with nerve palsy clinical symptomatology preceded radiological evidence. The 99mTc 3-phase planar bone scintigraphy was positive for SBO in 9/13 cases (69%) during the initial phase and, in 100% of the cases in images delayed to 2-3 hours. Subsequent checks up to 1 year, using the Ga 67 scintigraphy, excluded the presence of recurrences in 100% of patients.

Conclusion:

The osteomyelitis of the base of the skull is a severe complication of malignant external otitis, often not always easily diagnosed. Recurrence can occur up to 1 year after stopping therapy. Imaging techniques such as Tc and MRI are relevant for the initial diagnostic approach and the staging of the pathology and its complications. Nuclear medicine imaging plays a fundamental role in the evaluation of related osteoblastic activity, especially in the remission phase of the disease.

Nontraumatic Head and Neck Emergencies

Head and neck imaging is an intimidating subject for many radiologists because of the complex anatomy and potentially serious consequences of delayed or improper diagnosis of the diverse abnormalities involving this region. The purpose of this article is to help radiologists to understand the intricate anatomy of the head and neck and to review the imaging appearances of a variety of nontraumatic head and neck conditions that bring patients to the emergency department, including acute infectious and inflammatory diseases and acute complications of head and neck neoplasms. These conditions are presented in five sections on the basis of their primary location of involvement: the oral cavity and pharynx, neck, sinonasal tract, orbits, and ears. Important anatomic landmarks are reviewed briefly in each related section.Online supplemental material is available for this article.^©RSNA, 2019.

Prediction of skull base osteomyelitis in necrotising otitis externa with diffusion-weighted imaging

OBJECTIVE

To predict skull base osteomyelitis in patients with necrotising otitis externa using diffusion-weighted imaging.

METHODS

A retrospective analysis was conducted of 25 necrotising otitis externa patients with skull base osteomyelitis (n = 10) or without skull base involvement (n = 14) who underwent a single-shot diffusion-weighted imaging of the skull base.

RESULTS

The respective mean apparent diffusion coefficient values of the skull base, as determined by two reviewers, were 0.851 ± 0.15 and 0.841 ± 0.14 ×10-3mm2/s for the skull base osteomyelitis patients, and 1.065 ± 0.19 and 1.045 ± 0.20 ×10-3mm2/s for the necrotising otitis externa patients without skull base involvement. The difference in apparent diffusion coefficients between the groups was significant, for both reviewers (p = 0.008 and 0.012). The optimal threshold apparent diffusion coefficient for predicting skull base osteomyelitis in necrotising otitis externa patients was 0.945 ×10-3mm2/s and 0.915 ×10-3mm2/s, with an area under the curve of 0.825 and 0.800, accuracy of 87.5 and 83.3 per cent, sensitivity of 85.7 and 90.0 per cent, and specificity of 90.0 and 78.6 per cent, for each reviewer respectively.

CONCLUSION

Apparent diffusion coefficient is a non-invasive imaging parameter useful for predicting skull base osteomyelitis in necrotising otitis externa patients.

The role of imaging in skull base osteomyelitis - Reviewed

PURPOSE

Skull base osteomyelitis (SBO) is difficult to diagnose due to a wide array of clinical presentations. It can be life threatening if not treated promptly. The objective of this study is to identify the various neck spaces involved in skull base osteomyelitis, correlate them with the possible source of infection and identify the related complications.

METHODS

Eighty nine consecutive either culture proven cases of skull base osteomyelitis, or culture negative cases with inflammation on histopathology responding to antibiotic therapy, presenting at a single non-government hospital in south India between January 2016 and December 2018 were included in this study. Images were reviewed by two radiologists and imaging findings were documented by consensus.

RESULTS

Involvement of the parotid space, retromastoid space and (temporomandibular) TM joint was associated with otogenic source of infection (p value < 0.05); while, retropharyngeal/prevertebral involvement was associated with sphenoid and nasopharyngeal sources (p value < 0.05). Complications such as cavernous sinus thrombosis (p value = 0.023) and ICA involvement (p value = 0.014) were more commonly seen with central skull base osteomyelitis. Abscess formation was seen in all three groups of patients without a significant difference between the groups.

CONCLUSION

Imaging plays an important role in determining the possible source of infection by identifying the involved neck spaces and this in turn can guide the clinician to a site for biopsy. Complications related to SBO can also be identified on imaging and can guide appropriate management.

Stenotrophomonas skull base osteomyelitis presenting as necrotizing otitis externa: Unmasking by CT and MRI-case report and review

Necrotizing or malignant otitis externa in patients presenting with mild clinical findings can pose as a tip of the iceberg; computed tomography (CT) and/or magnetic resonance imaging (MRI) unveils the clinical-imaging discrepancy and unmasks the presence of skull-base osteomyelitis (SBO). Pseudomonas aeruginosa is the most common causative pathogen of SBO, followed by fungal and other rare bacterial organisms. This report presents a rare case in an elderly diabetic patient, where the pathogen Stenotrophomonas maltophilia was isolated. There have been no previous reported cases in the literature of SBO caused by this pathogen. The hallmark of SBO on computed tomography or magnetic resonance imaging is soft tissue inflammatory changes under the central skull base with associated bone erosion. This may result in the peculiar appearance of the "Ovoid Gap" sign. SBO can be due to nonotogenic sources, namely: sinogenic, rhinogenic, pharnygogenic, or odontogenic infections. Low threshold for imaging is advised in immunosuppressed and elderly diabetic patients.

Severe Daily Headache as an Uncommon Manifestation of Widespread Skull Base Osteomyelitis

Temporal bone osteomyelitis has been recognized for decades as a complication of otitis externa, specifically in elderly patients with diabetes. A much less prevalent form is skull base osteomyelitis. We report a 70-year-old man with diabetes who presented to our outpatient clinic with severe chronic daily complaints of headache. The headache was located frontoparietally and kept him awake at night. Imaging (nonenhanced computed tomography [CT], magnetic resonance imaging, and positron emission tomography/CT) showed a hypermetabolic mass on the right side of the skull base, in the middle ear, and in the mastoid process, with invasion and partial destruction of the surrounding elements of the petrous bone, the occipital bone, and the sphenoid bone on the right, with extension by way of the clivus into the apex of the left petrous bone. Diagnostic puncture revealed Streptococcus pneumoniae. The final diagnosis was severe daily headache due to central skull base osteomyelitis. Our case emphasizes the need for proper clinical and radiological investigation keeping the diagnosis of skull base osteomyelitis in mind with patients with diabetes or otherwise immunocompromised status who present with chronic daily headache and otalgia.

Skull base osteomyelitis secondary to Scedosporium apiospermum infection

Scedosporium apiospermum is a common environmental mold which is increasingly reported in the literature as a cause of infection, particularly in the immunocompromised patient population. We present a case of malignant otitis externa due to S apiospermum, complicated by spread of infection causing skull base osteomyelitis, internal carotid artery vasculitis and subsequent stroke. Despite the multiple complications encountered, prompt diagnosis and initiation of appropriate antifungal treatment resulted in patient survival. Multiple imaging modalities were used to aid the establishment of the diagnosis in this complex case and highlight the radiological findings associated with skull base osteomyelitis and its possible complications.

99mTc-HMPAO-leukocyte scintigraphy for diagnosis and therapy monitoring of skull base osteomyelitis

Objective

Skull base osteomyelitis (SBO) is a rare but life‐threatening disease observed in elderly diabetic patients, with high risk of recurrence and difficult therapeutic management. The diagnosis is ascertained from a set of clinical, biological, and imaging findings. CT and MRI allow initial diagnosis, but are not accurate to affirm healing at the end of therapy. 99mTc‐HMPAO‐Leucocyte Scintigraphy (LS) is highly sensitive and specific for the detection of infection. The aim of this study was to evaluate LS i) for initial diagnosis, and ii) to confirm healing at the end of antibiotherapy in SBO.

Study design

We retrospectively reviewed from November 2011 to September 2015 all patients with confirmed SBO who underwent LS twice, at diagnosis and at the end of antibiotic therapy in our nuclear medicine department (n = 27).

Methods

Clinical, biological, CT, LS, and follow‐up data were recorded in all patients. LS images (planar and tomographic performed 4 hours and 24 hours after intravenous injection of autologous Tc‐99m‐HMPAO‐leucocytes) were visually assessed and quantified.

Results

At initial diagnosis, 25 of 27 patients had a positive LS. At the end of antibiotic therapy (3 ± 1 months duration), 26 of 27 patients had a negative LS. During subsequent follow‐up (= or >6 months), the disease recurred in four patients including three with a negative postantibiotherapy LS scan.

Conclusion

In this retrospective study, LS was powerful for initial diagnostic of SBO and for healing assessment at the end of antibiotic therapy. We conclude it is a useful technique for therapeutic monitoring of SBO.

Level of Evidence

4

Advanced Imaging Techniques in Skull Base Osteomyelitis Due to Malignant Otitis Externa

PURPOSE OF REVIEW

To give an up-to-date overview of the strengths and weaknesses of current imaging modalities in diagnosis and follow-up of skull base osteomyelitis (SBO).

RECENT FINDINGS

CT and MRI are both used for anatomical imaging, and nuclear techniques aid in functional process imaging. Hybrid techniques PET-CT and PET-MRI are the newest modalities which combine imaging strengths.

SUMMARY

No single modality is able to address the scope of SBO. A combination of functional and anatomical imaging is needed, in the case of newly suspected SBO we suggest the use of PET-MRI (T1, T2, T1-FS-GADO, DWI) and separate HRCT for diagnosis and follow-up.

A Comprehensive Review of Skull Base Osteomyelitis: Diagnostic and Therapeutic Challenges among Various Presentations

Skull base osteomyelitis (SBO) is a complex and fatal clinical entity that is often misdiagnosed for malignancy. SBO is commonly a direct complication of otogenic, sinogenic, odontogenic, and rhinogenic infections and can present as central, atypical, or pediatric clival SBO. This review describes the clinical profile, investigational approach, and management techniques for these variants. A comprehensive literature review was performed in PubMed, MEDLINE, Research Gate, EMBASE, Wiley Online Library, and various Neurosurgical and Neurology journals with the keywords including: SBO, central or atypical SBO, fungal osteomyelitis, malignant otitis externa, temporal bone osteomyelitis, and clival osteomyelitis. Each manuscript's reference list was reviewed for potentially relevant articles. The search yielded a total of 153 articles. It was found that with early and aggressive culture guided long-term intravenous broad-spectrum antibiotic therapy decreases post-infection complications. In cases of widespread soft tissue involvement, an early aggressive surgical removal of infectious sequestra with preferentially Hyperbaric Oxygen (HBO) therapy is associated with better prognosis of disease, less neurologic sequelae and mortality rate. Complete resolution of the SBO cases may take several months. Since early treatment can improve mortality rates, it is paramount that the reporting radiologists and treating clinicians are aware of the cardinal diagnostic signs to improve clinical outcomes of the disease. It will decrease delayed diagnosis and under treatment of the condition. However, due to rarity of the condition, complete prognostic factors have not fully been analyzed and discussed in the literature.

Skull base osteomyelitis secondary to malignant otitis externa mimicking advanced nasopharyngeal cancer: MR imaging features at initial presentation

PURPOSE

Skull base osteomyelitis (SBOM) is an inflammatory process which often arises from malignant otitis externa (MOE); the diffuse skull base and adjacent soft tissue involvement may be mistaken at initial imaging for advanced nasopharyngeal carcinoma (NPC), especially if there is no prior knowledge of MOE, direct spread from the sphenoid sinus or in atypical presentations of MOE. This study aims to evaluate imaging features on MR that may differentiate SBOM from NPC.

MATERIALS AND METHODS

The MR examinations of 26 patients diagnosed with SBOM between January 1996 and January 2013 were retrospectively reviewed. Comparison was also made with the MR images of 22 consecutive patients with newly diagnosed advanced T3 and T4 NPC between July 2011 and August 2012. Imaging features in both conditions were compared, including the presence of a nasopharyngeal bulge, nasopharyngeal mucosal irregularity, lateral extension, architectural distortion (or lack thereof), increased T2 signal and enhancement patterns.

RESULTS

The most prevalent findings in SBOM were lateral extension, increased T2 signal in adjacent soft tissues, lack of architectural distortion and enhancement greater than or equal to mucosa. The combination of these 4 findings was found to best differentiate SBOM from advanced NPC, and found to be statistically significant (p<0.001).

CONCLUSION

We suggest that the combination of lateral extension, increased T2 signal, lack of architectural distortion and enhancement greater than or equal to mucosa is helpful in differentiating SBOM from advanced NPC.

Severe skull base osteomyelitis caused by Pseudomonas aeruginosa with successful outcome after prolonged outpatient therapy with continuous infusion of ceftazidime and oral ciprofloxacin: a case report

Background

Skull base osteomyelitis is an uncommon disease that usually complicates a malignant external otitis with temporal bone involvement. It affects predominantly diabetic and immunocompromised males and has a high mortality rate. Pseudomonas aeruginosa is the most common causative organism. Currently, there is no consensus about the best therapeutic option. Here we describe a case of severe skull base osteomyelitis caused by Pseudomonas aeruginosa with progressive palsy of cranial nerves that was successfully managed with prolonged outpatient continuous infusion of ceftazidime plus oral ciprofloxacin.

Case presentation

A 69-year-old Caucasian man presented with dysphagia, headache, and weight loss. He complained of left earache and purulent otorrhea. Over the following weeks he developed progressive palsy of IX, X, VI, and XII cranial nerves and papilledema. A petrous bone computed tomography scan showed a mass in the left jugular foramen with a strong lytic component that expanded to the cavum. A biopsy was then performed and microbiological cultures grew Pseudomonas aeruginosa. After 6 weeks of parenteral antibiotic treatment, our patient was discharged and treatment was continued with a domiciliary continuous infusion of a beta-lactam through a peripherally inserted central catheter, along with an oral fluoroquinolone for 10 months. Both radiological and clinical responses were excellent.

Conclusions

Skull base osteomyelitis is a life-threating condition; clinical suspicion and correct microbiological identification are key to achieve an accurate and timely diagnosis. Due to the poor outcome of Pseudomonas aeruginosa skull base osteomyelitis, prolonged outpatient parenteral antibiotic therapy administered by continuous infusion could be a valuable option for these patients.

A Case of Skull Base Osteomyelitis with Multiple Cerebral Infarction

Skull base osteomyelitis is classically documented as an extension of malignant otitis externa. Initial presentation commonly includes aural symptoms and cranial nerve dysfunctions. Here we present a case that emerged with multiple infarctions in the right cerebrum. A male in his 70s with diabetes mellitus and chronic renal failure presented with left hemiparesis. Imaging studies showed that blood flow in the carotid artery remained at the day of onset but was totally occluded 7 days later. However, collateral blood supply prevented severe infarction. These findings suggest that artery-to-artery embolization from the petrous and/or cavernous portion of the carotid artery caused the multiple infarctions observed on initial presentation. Osteomyelitis of the central skull base was diagnosed on the basis of the following findings taken together: laboratory results showing high levels of inflammation, presence of Pseudomonas aeruginosa in the otorrhea and blood culture, multiple cranial nerve palsies that appeared later, the bony erosion observed on CT, and the mass lesion on MRI. Osteomyelitis was treated successfully by long-term antibiotic therapy; however, the patient experienced cefepime-induced neurotoxicity during therapy. The potential involvement of the internal carotid artery in this rare and life-threatening disease is of particular interest in this case.

Can computed tomography and magnetic resonance imaging differentiate between malignant pathology and osteomyelitis in the central skull base?

BACKGROUND

Central skull base osteomyelitis is clinically difficult to distinguish from malignancy.

METHOD

The computed tomography and magnetic resonance imaging scans of six patients with central skull base osteomyelitis were compared with scans from patients with a range of skull base conditions.

RESULTS AND CONCLUSION

Computed tomography scans of central skull base osteomyelitis show much less bony destruction relative to the magnetic resonance imaging changes, whereas malignancy cases were associated with similar bony destruction on computed tomography and magnetic resonance imaging. In magnetic resonance imaging scans, it was possible to confirm previous findings of clival hypointensity on T1-weighted images relative to normal fatty marrow. In addition, there were signs of pre- and para-clival soft tissue infiltration, with the obliteration of normal fat planes and frank soft tissue masses in all six central skull base osteomyelitis patients. Signal intensity on T2-weighted images of the clivus was high in five central skull base osteomyelitis patients. With intravenous contrast, fascial plane anatomy appeared restored in central skull base osteomyelitis cases, almost in keeping with that of non-involved areas. This was not a feature in any of the malignant conditions.

Temporomandibular joint involvement as a positive clinical prognostic factor in necrotising external otitis

Objective:

Necrotising otitis externa is associated with high morbidity and mortality rates. This study investigated whether temporomandibular joint involvement had any prognostic effect on the course of necrotising otitis externa in patients who had undergone hyperbaric oxygen therapy after failed medical and sometimes surgical therapy.

Methods:

A retrospective case series was conducted of patients in whom antibiotic treatment and surgery had failed, who had been hospitalised for further treatment and hyperbaric oxygen therapy.

Results:

Twenty-three patients with necrotising otitis externa were identified. The temporomandibular joint was involved in four patients (17 per cent); these patients showed a constant gradual improvement in C-reactive protein and were eventually discharged free of disease, except one patient who was lost to follow up. Four patients (16 per cent) without temporomandibular joint involvement died within 90 days of discharge, while all patients with temporomandibular joint involvement were alive. Three patients (13 per cent) without temporomandibular joint involvement needed recurrent hospitalisation including further hyperbaric oxygen therapy; no patients with temporomandibular joint involvement required such treatment.

Conclusion:

Patients with temporomandibular joint involvement had lower rates of recurrent disease and no mortality. Therefore, we suggest considering temporomandibular joint involvement as a positive prognostic factor in necrotising otitis externa management.

[Clinical Study of Skull Base Osteomyelitis]

Typical osteomyelitis is reportedly caused by Pseudomonous aeruginosa in elderly diabetic patients after malignant external otitis. Recently, complications have arisen due to the emergence of atypical osteomyelitis. We have experiensed 5 cases of skull base osteomyelitis at our hospital. All patients were male with a mean age of 75.2 years. Four patients had diabetes. Regarding the clinical and radiographic findings, patients 1, 2, and 3 had typical osteomyelitis after malignant external otitis, whereas patients 4 and 5 had atypical osteomyelitis without temporal bone findings. Sample culturing revealed Pseudomonas aeruginosa in 4 cases and Aspergillus in one. Intravenous antibiotics were administered to all patients. Two patients responded positively and survived, while 3 died. Typical osteomyelitis is reportedly caused by P. aeruginosa in elderly diabetic patients after malignant external otitis. Recently, complications have arisen due to the emergence of atypical osteomyelitis. The prognosis of skull base osteomyelitis is still poor in Japan. Early diagnosis and long-term antibiotic administration is required to improve outcome.

Nonotogenic Skull Base Osteomyelitis in Children: Two Cases and a Review of the Literature

Skull base osteomyelitis is a rare condition in childhood and can be described according to whether it is associated with spread of infection from the middle ear (otogenic) or not (nonotogenic). Early recognition of this serious disease and prompt treatment are key to preventing extension to adjacent vascular and nervous system structures. Diagnosis can be challenging due to the variable presentation of the disease and potentially subtle radiological appearances. We present 2 cases of nonotogenic skull base osteomyelitis in childhood both affecting the clivus and review the 6 cases previously described. Both children presented with fever, headache and neck stiffness and responded well to medical management alone; detailed imaging was key to making a diagnosis.

Central skull base osteomyelitis: a rare but life-threatening disease

We present the case of a 70-year-old non-diabetic patient who presented to the emergency department with unrelenting otalgia. A severe otitis externa (OE) and mastoiditis were treated with broad spectrum antibiotics and surgical drainage. No bacteria was isolated from surgical samples. Because the otalgia persisted, a magnetic resonance (MR) was performed and showed an infiltrating process at the skull base. Biopsies failed to prove malignancy or granulomatosis. The patient's neurological state deteriorated. The suspicion of a skull base osteomyelitis (SBO) was raised and proven by CT-guided biopsies that grew Pseudomonas aeruginosa. Meropenem and ciprofloxacin, given for 8 weeks, lead to a fast clinical improvement and a full recovery. SBO is uncommon, often complicating severe OE. Pseudomonas aeruginosa is the main pathogen. Prompt diagnosis and adequate antibiotherapy are required to lower mortality and morbidity. The diagnosis may be delayed because of unawareness and large differential diagnosis including solid neoplasic tumours, malignant hemopathies and granulomatosis.