Trochleitis is inflammation of the superior oblique tendon trochlea apparatus characterized by localized swelling, tenderness, and severe pain. This condition is an uncommon but treatable cause of periorbital pain. The trochlea is a ring-like apparatus of cartilage through which passes the tendon of the superior oblique muscle. It is located in the superior nasal orbit and functions as a pulley for the superior oblique muscle. Inflammation of the trochlear region leads to a painful syndrome with swelling and exquisite point tenderness in the upper medial rim of the orbit. A vicious cycle may ensue such that inflammation causes swelling and fraying of the tendon which then increases the friction of passing through the trochlea which in turn adds to the inflammation. Trochleitis has also been associated with triggering or worsening of migraine attacks in patients with pre-existing migraines (Yanguela, 2002). Symptoms Patients with trochleitis typically experience a dull fluctuating aching over the trochlear region developing over a few days. Some may also feel occasional sharp pains punctuating the ache. In patients with migraines, trochleitis may occur simultaneously with headache. Presentation is usually unilateral with palpable swelling over the affected area supranasal to the eye. The trochlear region is extremely tender to touch. Pain is exacerbated by eye movements looking down and inwards, and especially in supraduction (looking up) and looking outwards, which stretches the superior oblique muscle tendon. Notably, there is no restriction of extraocular movements, no diplopia, and often no apparent ocular signs such as proptosis. However, occasionally mild ptosis is found. The absence of generalized signs of orbital involvement is helpful in eliminating other more common causes of periorbital pain. Cause The cause of trochleitis is often unknown (idiopathic trochleitis), but it has been known to occur in patients with rheumatological diseases such as systemic lupus erythematosus, rheumatoid arthritis, enteropathic arthropathy, and psoriasis. In his study, Tychsen and his group evaluated trochleitis patients with echography and CT scan to demonstrate swelling and inflammation. Imaging studies showed inflammation of superior oblique tendon/ trochlear pulley. It was unclear whether the inflammation involved the trochlea itself, or the tissues surrounding the trochlea. Diagnosis Trochleitis is diagnosed based on three criteria: 1) demonstration of inflammation of superior oblique tendon/ trochlea region, 2) periorbital pain and tenderness to palpation in the area of the sore trochlea, and 3) worsening of pain on attempted vertical eye movement, particularly with adduction of the eye. It