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Neuroradiology Case of the Week

Case 198

Devang Butani, MD and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: Patient is an 81-year-old female with chronic left eye paralysis presented increasing confusion and falls for the past 2 months. The patient also complained of increasing left facial pain.

Radiological Findings: There is diffuse enlargement of the extraocular eye-muscles bilaterally. Major differential diagnoses for this finding include pseudo-tumor and Grave's opthalmopathy, less likely sarcoidosis, lymphoma or metastatic disease.

Diagnosis: Grave's disease.

Discussion: The CT findings of pseudotumor and Grave's disease overlap and are best viewed as a continuous spectrum at both ends of which characteristic patterns can be identified. Massive swelling of ocular muscles, involvement of several muscles, usually without density changes of the orbital fat, are diagnostic for Graves' disease. More or less circumscribed masses of soft tissue density surrounding the globe, eye muscles or the optic nerve, severe diffuse increase of density in the retrobulbar space masking orbital structures and calcifications indicate orbital pseudotumor.
     With Grave's disease, there is a fairly specific relative sparing of the tendons of the muscles, with hypertrophy of the muscle belly. Involvement of muscles in descending order are inferior, medial, superior, lateral and oblique ("I'M SLOW"). Associated findings also include increased orbital fat, which when prolapsed, can cause optic nerve compression.
     Localization of the swelling within a muscle, enhanced contrast, moderate density changes of the orbital fat, and involvement of the lacrimal gland are of minor differential diagnostic value. CT shows the extent and degree of the pathologic changes and indicates the optimal approach for tissue biopsy, if clinically indicated.
     Optimal imaging for suspected diagnosis has included thin sections, preferably in a direct coronal aquisition plane. Recent advances in imaging technology which enables acquisition of isovolumetric data allows multi-planar re-formats without patient discomfort.

References:

1. Harnsberger HR, et al. Diagnostic Imaging: Head and Neck. Amirsys, 2004; II:1-70.
2. Mancuso AA, Ojiri H, Quisling RG. Head and Neck Radiology. A Teaching File. Lippincott Williams & Wilkins, 2002:25-26.
3. Mafee MF, Valvassori GE. Becker M. Imaging of the Head and Neck. Thieme, 2nd ed, 2004: 230-241.
4. Yen MT, Lin R, Yen KG. Ophthalmopathy, Thyroid. http://www.emedicine.com/radio/topic485.htm
5. www.learningradiology.com - Case of the Week 168 - Neuroradiology: Thyroid Ophthalmopathy.