Evaluating magnetic resonance imaging features in active thyroid eye disease

Dear Editor, Thyroid eye disease (TED), also referred to as thyroid-associated ophthalmopathy or Graves’ ophthalmopathy, is a condition characterized by lymphocytic orbital inflammation linked to thyroid dysfunction, particularly hyperthyroidism. This disease results from cross-reactivity between orbital and thyroid tissues, leading to the infiltration of lymphocytes, cytokine production, and subsequent glycosaminoglycan deposition. This deposition causes orbital fibrosis, muscle enlargement, and adipogenesis, which collectively contribute to symptoms such as ocular dysmotility, diplopia, and, in rare cases, compressive optic neuropathy. The European Group on Graves’ Orbitopathy (EUGOGO) provides guidelines on assessing TED activity through clinical activity scores (CAS). Despite existing literature on clinical and imaging assessments, a comprehensive review of radiological features of active TED, particularly through Magnetic resonance imaging (MRI) remains sparse. Our study aims to address this gap by identifying MRI-based radiological features of active TED and comparing these with clinical activity scores. Methodology: This study was conducted at a tertiary care center with institutional ethics approval. Patients with active TED, defined by a CAS of at least 3 out of 7, were included after informed consent. Exclusion criteria encompassed other ocular or orbital diseases and MRI contraindications. Clinical evaluations involved detailed ocular assessments, including Hertel’s exophthalmometry, visual acuity tests, and slit-lamp examinations. Blood tests measured baseline thyroid and lipid profiles. MRI was performed using a 1.5 Tesla machine, with protocols including T1, T2, and fat-saturated images. Radiological features analyzed included thickening of extraocular muscles (EOMs),[1,2] increased signal intensity[3], increased orbital fat and soft tissue,[2,4] apical crowding,[5,6] and optic nerve stretching[5] [Fig. 1]. Findings were assessed by a radiologist unaware of the clinical status.Figure 1: (a) T1-weighted MRI showing enlargement of extraocular muscles and (b) T2-weighted MRI showing increased signal intensity of extraocular musclesResults: Among 100 eyes from 50 participants screened, 60 eyes from 30 patients met the inclusion criteria. The age of participants ranged from 17 to 76 years, with a mean of 47.4 years. The majority were male (53.3%), and the most common symptoms were eye prominence (100%) and retrobulbar pain (90%). Notably, 73.3% of patients were hyperthyroid. MRI findings revealed thickening of EOMs in 90% of patients, increased signal intensity in 43.3%, and increased orbital fat in 33.3%. Apical crowding was observed in only 3.3%, and no patients exhibited optic nerve stretching. A significant association was found between CAS and EOM thickening, with increased signal intensity often accompanying thickening [Fig. 2]. However, increased fat was less frequently associated with high CAS. Notably, 10% of patients with active CAS had normal MRI findings.Figure 2: Clinical activity score and the number of MRI-detected radiological features in patients from our studyDiscussion: Our study highlights the utility of MRI in assessing TED, highlighting that muscle thickening and increased signal intensity are reliable indicators of disease activity. These findings align with the literature suggesting that MRI can enhance the sensitivity of detecting disease activity and response to treatment. While MRI excels in identifying tissue changes and muscle edema, limitations include its inability to detect early inflammation and the potential for variability in radiological features. The study supports MRI’s role in complementing clinical assessments of TED, offering a more nuanced understanding of disease activity and aiding in therapeutic decision-making. Future research with larger samples and controls will be essential for validating these findings and potentially developing refined radiological scoring systems. Overall, integrating MRI with clinical assessments could improve the management of TED, providing a comprehensive approach to monitoring and treatment planning. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.