THS has an extensive list of differentials, with many other disease entities having a similar clinical presentation. These include metastases, aspergillosis, sarcoidosis, carotid-cavernous fistulae, vasculopathic cranial neuropathy, Wegener granulomatosis, lymphoma, and ophthalmoplegic migraine. The diagnosis is mainly clinical, based on history and examination, and is essentially one of exclusion. Pertinent laboratory investigations may be done to eliminate other processes. Laboratory workup requires a complete blood picture, ESR, electrolytes, blood glucose levels, thyroid function tests, ANAs, antineutrophil cytoplasmic antibodies (ANCAs), serum protein electrophoresis, Lyme titre, ACE level, and HIV titre to exclude other conditions, which can have significant morbidity associated. Anti-GQ1b antibodies may be helpful in distinguishing THS from Miller Fisher syndrome. Various CSF studies may also be required to eliminate conditions that mimic THS.
Neuroimaging must be done to rule out malignancies, vascular pathologies, and non-THS forms of inflammation in the region of the cavernous sinus and/or superior orbital fissure. Contrast-enhanced MRI should be the initial diagnostic study performed. Multiple views must be obtained, particularly coronal sections, which are important in visualizing the area of the cavernous sinus. In some patients with THS, an area of abnormal soft tissue in the region of the cavernous sinus is visualized, with intermediate signal intensity on T1- and intermediate-weighted images; this may show postcontrast enhancement suggestive of an inflammatory process.[12,13,14,15,16,17,18,19] Abnormal convexity of the wall of the cavernous sinus may be seen. At times, focal narrowing of the intracavernous internal carotid artery may be found. However, MRI findings in THS lack specificity, which is a drawback; at times, the MRI scan may even be normal, as in this particular patient.[20,21]
The International Headache Society (IHS) formulated specific diagnostic criteria for THS in 1988; the most recent criteria are available in the third edition of the International Classification of Headache Disorders (ICHD-3).[3,22] According to the society, characteristics of THS include the following:
Unilateral orbital or periorbital pain that is ipsilateral to granulomatous inflammation
Paresis of CN III, IV, and/or VI and demonstration via MRI or biopsy of granulomas present in the cavernous sinus, superior orbital fissure, or orbit
Development of cranial nerve palsy/palsies within two weeks of the onset of orbital pain or with onset of pain
Exclusion of other causes by appropriate investigation
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