Qualitative and Quantitative Magnetic Resonance Imaging in Bacterial Orbital Cellulitis

PURPOSE

To summarise the qualitative and quantitative parameters of bacterial orbital cellulitis (OC) on magnetic resonance imaging (MRI) and explore their clinical correlations.

METHODS

Multi-centre retrospective study with inclusion of patients of all ages with OC who underwent MRI. Patients with isolated pre-septal cellulitis, bilateral disease and poor-quality scans were excluded. An enlargement ratio for extraocular muscles (EOMs) was calculated by dividing maximal EOM measurements from the affected side by the contralateral side.

RESULTS

Twenty MRI scans from twenty patients (Mean age: 40.8 ± 24.3 years old, M: F = 15:5) between 2011 and 2022 were analysed. Three (15.0%) cases were paediatric patients (<18 years old). All cases had both pre-septal and orbital fat involvement. The EOM were affected in nineteen cases, with the superior muscle complex (18/19, 94.7%) most commonly affected. Mean enlargement ratio (1.30, Range: 1.04-1.82) was greatest for the medial rectus on axial views on T1 and fat-suppressed contrast-enhanced T1 (FS CE T1). Optic peri-neuritis was present in eleven (55.0%) patients, whilst two (9.5%) cases had optic neuritis. A greater degree of proptosis was observed in patients with optic neuropathy and those who underwent surgical intervention compared to those without (p = .002 and p = .002, respectively).

CONCLUSION

MRI remains an important imaging modality for evaluating complicated OC. However, qualitative features may lack accuracy and is not a reproducible means of analysis. Simple quantitative parameters, such as proptosis and EOM measurements, correlate with high-risk clinical features and may have utility in predicting clinical course.

Medication-associated orbital inflammation: A systematic review

We performed a comprehensive systematic review to identify medication-associated orbital inflammation and to characterize its clinico-radiological features. We reviewed English-language articles describing medication-associated orbital inflammation (i.e., orbital myositis, dacryoadenitis and orbital fat) published to June, 2023. Isolated inflammation of the intraocular structures or globe alone (i.e. uveitis, scleritis, optic neuritis and perineuritis) were excluded. In medication-associated orbital inflammation, the extraocular muscles are preferentially affected, occurring in isolation or in combination with other orbital and/or intraocular structures. Clinico-radiological manifestations may be non-specific; however, certain medications may be distinguished according to the presence of systemic prodrome, laterality, associated intraocular inflammation, and predisposition to involve certain orbital structures. Rapid identification, discontinuation of the provoking medication, and systemic corticosteroid therapy (if appropriate) typically achieves a favorable visual prognosis. As new medications become adopted by clinicians, rare adverse effects will be further delineated.Medication-associated orbital inflammation is an important diagnostic consideration in orbital inflammatory disease. A careful medication history and clinical assessment may be revealing, permitting timely discontinuation of the offending agent and initiation of appropriate management.

IgG4-related Orbital Disease Presenting as an Orbital Apex Lesion

IgG4-related disease is an uncommon multisystem inflammatory disease characterized by tissue infiltration by IgG4 plasma cells, extensive fibrosis, and sclerosing inflammation. Diffuse orbital involvement extending to the orbital apex and cavernous sinus has been reported, but a solitary well-circumscribed lesion at the apex has not been previously reported. Herein, we report a unique case of IgG4-related orbital disease presenting as a solitary well-circumscribed orbital apex lesion causing subacute visual decline in a 45-year-old male. MRI demonstrated bilateral lacrimal gland and infraorbital nerve enlargement and an 18 × 7 mm left orbital apex lesion demonstrating homogeneous contrast enhancement and isointense signal on T2. He was initially treated with tapering systemic corticosteroid therapy with improvement in his vision; however, he experienced visual deterioration 3 months later with recurrent inflammation. He subsequently commenced high-dose systemic corticosteroid therapy and rituximab infusions with improvement of left visual acuity to 6/7.5 + 2.

Magnetic Resonance Imaging of Idiopathic Orbital Myositis

PURPOSE

To characterize the qualitative and quantitative features of idiopathic orbital myositis (IOM) on MRI.

METHODS

This was a multicenter retrospective study of patients with active IOM with MRI. Patients with incomplete clinical records, poor-quality or interval scans without active myositis, and specific orbital myositis (i.e., orbital myositis secondary to an identified condition) were excluded. An enlargement ratio was calculated by dividing the diameters of the affected extraocular muscle (EOM) by the contralateral unaffected EOM.

RESULTS

Twenty-four patients (mean age: 44.4 ± 17.8 years-old, male: 11) between 2011 and 2022 were included. One case (4.2%) was pediatric (17 years old), and 6 cases presented with recurrence. Active IOM was characterized by fusiform EOM enlargement, high T2 signal, and contrast enhancement. Average maximal EOM diameters ranged from 4.6 to 7.7 mm (enlargement ratio: 1.4-2.2). Eighteen (75%) patients had single EOM involvement, most commonly the medial rectus. Other ipsilateral structures affected included focal orbital fat (16/24, 66.7%) and lacrimal gland (8/24, 33.3%). Contralateral changes in the EOM and/or lacrimal gland were observed in 7 patients (29.2%). Patients presenting with recurrence were likely to develop ongoing recurrent episodes (p = 0.003).

CONCLUSIONS

Various radiological patterns of involvement described including EOM enlargement, contrast enhancement, abnormal signal, and involvement of other orbital structures are indicative of active IOM. IOM remains a heterogeneous spectrum of acute and chronic clinico-radiological presentations. Inflammation may involve other ipsilateral or contralateral orbital structures or may be bilateral despite presenting clinically as unilateral disease. Quantitative measurements may have utility in differentiating IOM from other causes of orbital myositis.

Methicillin-resistant Staphylococcus aureus-associated orbital cellulitis: a case series

PURPOSE

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) orbital cellulitis (OC) has drawn increasing clinical and public health concern. We present a case series of MRSA OC encountered at four Australian tertiary institutions.

METHODS

A multi-centre retrospective case series investigating MRSA OC in Australia from 2013 to 2022. Patients of all ages were included.

RESULTS

Nine cases of culture-positive non-multi-resistant MRSA (nmMRSA) OC were identified at four tertiary institutions across Australia (7 male, 2 female). Mean age was 17.1 ± 16.7 years (range 13-days to 53-years), of which one was 13 days old, and all were immunocompetent. Eight (88.9%) patients had paranasal sinus disease, and seven (77.8%) had a subperiosteal abscess. Four (44.4%) had intracranial extension, including one (11.1%) case which was also complicated by superior sagittal sinus thrombosis. Empirical antibiotics, such as intravenous (IV) cefotaxime alone or IV ceftriaxone and flucloxacillin, were commenced. Following identification of nmMRSA, targeted therapy consisting of vancomycin and/or clindamycin was added. Nine (100%) patients underwent surgical intervention. Average hospital admission was 13.7 ± 6.9 days (range 3-25 days), with two patients requiring intensive care unit (ICU) admission due to complications related to their orbital infection. All patients had favourable prognosis, with preserved visual acuity and extraocular movements, following an average follow-up period of 4.6 months (range 2-9 months).

CONCLUSION

NMMRSA OC can follow an aggressive clinical course causing severe orbital and intracranial complications across a wide demographic. However, early recognition, initiation of targeted antibiotics and surgical intervention when required can effectively manage these complications and achieve favourable visual outcomes.

Orbital inflammation following COVID-19 vaccination: A case series and literature review

PURPOSE

The purpose of the study was to report three cases of orbital inflammation following administration of the COVID-19 vaccination, manifesting as Tolosa-Hunt syndrome (THS) and orbital myositis.

METHOD

A retrospective case series and literature review of patients who developed orbital inflammation following a COVID-19 vaccination.

RESULTS

One patient presented with Tolosa-Hunt syndrome (THS) 14 days following her third (booster) COVID-19 vaccination, one patient developed orbital myositis 10 days following his first COVID-19 vaccination and one patient developed recurrent orbital myositis 1 and 7 days following her second and fourth COVID-19 vaccination. All patients received the Comirnaty vaccine (Pfizer-BioNTech). A thorough systemic autoimmune disease workup in both patients was unremarkable. Two patients had a prior history of orbital inflammation, with previous involvement of other different orbital structures. Characteristic MRI features for each pathology were observed, supporting the clinical presentation of THS and orbital myositis. There was complete resolution of THS following corticosteroids, with no recurrence at 2 months. Meanwhile, one case of orbital myositis self-resolved at 2 months without use of systemic corticosteroids, while the other patient with orbital myositis required treatment with intra-orbital steroid injections and oral corticosteroids.

CONCLUSION

Orbital inflammation has been recognised as a rare adverse effect following COVID-19 vaccination. We present a case series of THS and orbital myositis as varied presentations of this entity.

Microbiology of bacterial orbital cellulitis-tertiary institutional experiences in South Australia: a multi-centre retrospective study

PURPOSE

This study describes the microbiology of bacterial orbital cellulitis (OC) over an 11-year period and its clinical associations at three tertiary institutions in Adelaide, South Australia.

METHODS

Multi-centre retrospective study of the microbiology of bacterial OC between January 2012 and August 2022. Pre-septal cellulitis was excluded. Differences in means were determined by the Independent Samples t-test, and categorical data was analysed via Pearson's Chi square. A P-value < 0.05 was statistically significant.

RESULTS

99 patients (male: 69, mean age: 22.0 ± 23.8 years old), of which 70.7% were aged ≤ 18 years. Sinus and orbital abscess cultures had the greatest positive yield (73.7%). Frequency of organisms: Streptococcus species (34.3%), Staphylococcus aureus (28.3%), Haemophilus species (5.1%), mixed anaerobes (3.0%), Enterobacter cloacae (2.0%), Moraxella catarrhalis (1.0%), Pseudomonas aeruginosa (1.0%), Corynebacterium species (1.0%), Klebsiella pneumoniae (1.0%), Proteus mirabilis (1.0%), Citrobacter koseri (1.0%), and Enterococcus species (1.0%). Streptococcus species predominated in the paediatric population, with a statistically significant difference in mean age between Streptococcus species and Staphylococcus aureus (14.1 ± 16.5 vs 27.6 ± 24.6 years old, respectively) (P = 0.028). No organism was cultured in 32.3% of cases. Methicillin-resistant Staphylococcus aureus (MRSA) accounted for 28.6% of all Staphylococcus aureus isolates, with 50% occurring between 2021 and 2022.

CONCLUSION

Yearly microbiological trends have remained largely constant in South Australia. The causative organism was not identified in 32.3% of cases, further emphasising appropriate empirical antibiotics, and obtaining microbiology from various sources. MRSA OC remains of increased clinical and public health concern and may be associated with a more aggressive disease course.

Evaluation of orbital lesions with DCE-MRI: a literature review

PURPOSE

To provide a major review on the applications of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in evaluating orbital lesions. This review also outlines selected scenarios where DCE-MRI may be helpful.

METHODS

A comprehensive retrospective literature review of all English language publications on PubMed, EMBASE, and Google Scholar between 1994 and 2022. This literature review examined the specific applications and clinical scenarios surrounding the utility of DCE-MRI in orbital lesions and various findings that have been presented in the current literature.

RESULTS

DCE-MRI provides information on tissue physiology and permeability, beyond the anatomical features displayed on static imaging. Various measured parameters (qualitative, semi-quantitative, and quantitative) obtained by DCE-MRI have been used to differentiate between benign and malignant lesions, specific orbital lymphoproliferative diseases (OLPD), lacrimal gland lesions, and various rare orbital tumours. DCE-MRI has a limited role as an initial diagnostic imaging modality. However, DCE-MRI may prove to have benefit in predicting and monitoring treatment response in orbital lymphoma as a critical imaging study, but literature specific to orbital malignancies remains limited.

CONCLUSION

The value of DCE-MRI may be in situations of diagnostic uncertainty, where it may be an additional imaging aid following conventional imaging techniques. It may also act as a critical imaging modality for monitoring of orbital tumour treatment response, but the literature remains limited. Standardisation of imaging protocol, measured parameters, and statistical analysis remain limitations of this imaging technique.

Functional assessment of military aircrew applicants in a hypobaric chamber

Background

Aircrew are exposed to environmental pressure changes. In the Republic of Singapore Air Force (RSAF), applicants assessed to be at intermediate risk of otic barotrauma undergo a hypobaric chamber assessment [“trial of chamber” (TOC)] to functionally evaluate their suitability for military aircrew vocations.

Aims

To identify factors associated with TOC failure among applicants with otorhinolaryngological conditions.

Methods

All applicants to RSAF aircrew vocations who were assessed to be at intermediate risk of otic barotrauma over a 3-yr period were identified using the RSAF Aeromedical Centre’s electronic database. Their medical records, as well as the TOC assessment records of the subset of applicants who underwent TOC, were reviewed for demographic data, clinical findings, and TOC outcomes.

Results

Of the 483 identified applicants, 374 (77%) had abnormal otoscopic findings, 103 (21%) had rhinitis symptoms, and 6 (1%) had previous ENT surgery. 123 (25%) underwent TOC, of which 20 (16%) failed. Holding other predictor variables constant, the odds of TOC failure increased by 0.79 per unit decrease in BMI (95% CI 0.63–0.99), and the odds of TOC failure increased by 0.93 per kg decrease in body weight (95% CI 0.87–1.00). An abnormal tympanogram was not a statistically significant predictor of TOC failure (OR 1.96, 95% CI 0.59–6.42). Of the 47 applicants who passed TOC and were eventually recruited, none subsequently developed otic barotrauma (mean follow-up, 3.3 yr ± 1.5 yr).

Conclusions

Applicants with lower weight and BMI are more likely to develop otic barotrauma with environmental pressure change. Tympanometry cannot be reliably used to identify applicants who would more likely pass TOC.

Systemic inflammatory markers differentiate between orbital cellulitis and non-specific orbital inflammation

PURPOSE

Bacterial orbital cellulitis (OC) and diffuse non-specific orbital inflammation (DNSOI) may be challenging to differentiate clinically. This study investigates the utility of systemic inflammatory markers, namely white cell count (WCC) and C-reactive protein (CRP), in differentiating between OC and DNSOI.

METHODS

A single-centre retrospective study of patients diagnosed with OC or DNSOI, between 2003 to 2021, who had WCC and/or CRP obtained at presentation. The mean levels of these factors and the proportion of positivity were compared between OC and DNSOI. A receiver operating characteristic (ROC) analysis was conducted to calculate the specificity and sensitivity of WCC or CRP in each group.

RESULTS

49 patients were included in this study. The mean age was 56 ± 20 years, and 21 patients were females. 26 (53.1%) patients had OC, and 23 (46.9%) patients had DNSOI. Mean WCC for OC and DNSOI were 14.5 × 10³/μL and 9.27 × 10³/μL, respectively (P = 0.001). Mean CRP for OC and DNSOI were 104.4 mg/L and 10.0 mg/L, respectively (P < 0.001). The optimal CRP cut-off value of 20.2 mg/L demonstrated 90.9% sensitivity and 90.5% specificity (AUC = 0.946, P < 0.001) for differentiating between OC and DNSOI. CRP was more predictive of OC than WCC (P = 0.017). 7/26 (26.9%) OC patients with fever also had an elevated CRP, while 1/23 (4.3%) of DNSOI with fever had a normal CRP.

CONCLUSIONS

An elevated WCC is suggestive of OC. However, a normal WCC can neither exclude nor differentiate between OC and DNSOI. CRP may be a more accurate predictor of OC compared to WCC.

Autoimmune markers in screening for orbital inflammatory disease

PURPOSE

Immunogenic causes of inflammation may be difficult to differentiate in the work-up of orbital inflammatory disease. The study aims to investigate the utility of autoimmune markers in the screening for orbital inflammation. Markers studied included angiotensin-converting enzyme (ACE), antinuclear antibody (ANA), anti-neutrophilic cytoplasmic autoantibodies (ANCA), extractable nuclear antigen (ENA), anti-cyclic citrullinated peptide (Anti-CCP) and anti-double stranded DNA antibody (Anti-dsDNA antibody).

METHODS

A retrospective single-centre study of consecutive patients with non-infective orbital inflammation screened for autoimmune markers at presentation. Serology was interpreted alongside clinical course and other investigations (e.g. radiographic features and histopathology). Tabulated data and Pearson's Chi-square allowed analysis of trends between serology, diagnosis and the decision to biopsy.

RESULTS

79 patients, between 1999 and 2021, were included (50 females, mean age was 50.4 ± 17.4 years). 28 (34.6%) patients had specific orbital inflammation and 53 (65.4%) patients had non-specific orbital inflammation (NSOI). Of the 12 patients with positive serology and a specific diagnosis, only 5 (41.7%) patients had concordant serological results. There was no association between serology results and the patient undergoing biopsy (P = 0.651). Serology was unable to exclude nor differentiate NSOI from other specific conditions and ANA had limited discriminatory value between specific conditions and NSOI.

CONCLUSION

Serological testing alone may not provide a clear direction for further investigation of orbital inflammation and a biopsy may occur independently of the serological results. The value of autoimmune markers may lie in subsequent follow-up as patients may develop suggestive symptoms after an indeterminate positive result or initially seronegative disease.