Imaging of Acute and Chronic Skull Base Infection

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.

Role of follow-up gallium scintigraphy in the evaluation of malignant external otitis (skull base osteomyelitis): A case report

Malignant otitis externa (skull base osteomyelitis) can be fatal and long-term antibiotic therapy is recommended. Despite being potentially fatal, this infection causes minor changes in inflammatory biomarkers (white blood cell count and C-reactive protein levels) upon blood testing. Computed tomography and magnetic resonance imaging changes persist over a long period. Therefore, it is difficult to determine the optimal time for the discontinuation of antibiotics. We present a 77-year-old male whose medical history included type 2 diabetes mellitus who suffered from chronic otitis media with Pseudomonas aeruginosa infection. His condition did not improve with proper treatment, and imaging revealed malignant otitis media. Intravenous cefepime treatment was administered. Antibiotic treatment was de-escalated to oral levofloxacin treatment after Gallium-67 scintigraphy showed less accumulation after 6 weeks of Cefepime administration; accumulation almost disappeared after 1 year. In this report, we describe the usefulness of gallium scintigraphy in the evaluation of malignant otitis externa.

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.

Pediatric Odontogenic and Paranasal Sinus Infections

Odontogenic and sinogenic infections are frequently encountered in the pediatric population. Although the diagnosis is often suspected clinically, imaging can play a significant role in localizing the site of infection, assessing for involvement of deep neck spaces, detection of abscess and other potentially life-threatening complications, and providing valuable information to help with treatment planning. This article reviews the general imaging considerations and anatomy relevant to odontogenic and paranasal sinus infections and describes the salient clinical and imaging features of infectious diseases of the dentition and sinuss.

Advanced imaging of head and neck infections

When head and neck infection is suspected, appropriate imaging contributes to treatment decisions and prognosis. While contrast-enhanced CT is the standard imaging modality for evaluating head and neck infections, MRI can better characterize the skull base, intracranial involvement, and osteomyelitis, implying that these are complementary techniques for a comprehensive assessment. Both CT and MRI are useful in the evaluation of abscesses and thrombophlebitis, while MRI is especially useful in the evaluation of intracranial inflammatory spread/abscess formation, differentiation of abscess from other conditions, evaluation of the presence and activity of inflammation and osteomyelitis, evaluation of mastoid extension in middle ear cholesteatoma, and evaluation of facial neuritis and labyrinthitis. Apparent diffusion coefficient derived from diffusion-weighted imaging is useful for differential diagnosis and treatment response of head and neck infections in various anatomical sites. Dynamic contrast-enhanced MRI perfusion may be useful in assessing the activity of skull base osteomyelitis. MR bone imaging may be of additional value in evaluating bony structures of the skull base and jaw. Dual-energy CT is helpful in reducing metal artifacts, evaluating deep neck abscess, and detecting salivary stones. Subtraction CT techniques are used to detect progressive bone-destructive changes and to reduce dental amalgam artifacts. This article provides a region-based approach to the imaging evaluation of head and neck infections, using both conventional and advanced imaging techniques.

Dynamic Contrast-Enhanced MRI Parameters and Normalized ADC Values Could Aid Differentiation of Skull Base Osteomyelitis from Nasopharyngeal Cancer

BACKGROUND AND PURPOSE

The skull base osteomyelitis sometimes can be difficult to distinguish from nasopharyngeal cancer. This study aimed to investigate the differences between skull base osteomyelitis and nasopharyngeal cancer using dynamic contrast-enhanced MR imaging and normalized ADC values.

MATERIALS AND METHODS

This study included 8 and 12 patients with skull base osteomyelitis and nasopharyngeal cancer, respectively, who underwent dynamic contrast-enhanced MR imaging and DWI before primary treatment. Quantitative dynamic contrast-enhanced MR imaging parameters and ADC values of the ROIs were analyzed. Normalized ADC parameters were calculated by dividing the ROIs of the lesion by that of the spinal cord.

RESULTS

The rate transfer constant between extravascular extracellular space and blood plasma per minute (Kep) was significantly lower in patients with skull base osteomyelitis than in those with nasopharyngeal cancer (median, 0.43 versus 0.57; P = .04). The optimal cutoff value of Kep was 0.48 (area under the curve, 0.78; 95% CI, 0.55-1). The normalized mean ADC was significantly higher in patients with skull base osteomyelitis than in those with nasopharyngeal cancer (median, 1.90 versus 0.87; P < .001). The cutoff value of normalized mean ADC was 1.55 (area under the curve, 0.96; 95% CI, 0.87-1). The area under the curve of the combination of dynamic contrast-enhanced MR imaging parameters (Kep and extravascular extracellular space volume per unit tissue volume) was 0.89 (95% CI, 0.73-1), and the area under the curve of the combination of dynamic contrast-enhanced MR imaging parameters and normalized mean ADC value was 0.98 (95% CI, 0.93-1).

CONCLUSIONS

Quantitative dynamic contrast-enhanced MR imaging parameters and normalized ADC values may be useful in differentiating skull base osteomyelitis and nasopharyngeal cancer. The combination of dynamic contrast-enhanced MR imaging parameters and normalized ADC values outperformed each measure in isolation.