Trochlear palsies caused by isolated trochlear schwannomas

To describe clinical features and management of 4 patients suffering from unilateral superior oblique palsies due to MRI-documented trochlear nerve schwannomas.

Chart reviews of 4 patients seen at the departments of ophthalmogy and neurology at the University of Mainz.

All four patients were male, aged 36 to 72 years at initial presentation. None suffered from neurofibromatosis. The history of double vision prior presentation was 9 months to 13 years, follow-up time was 9 to 156 months. Two patients didn't receive any intervention: one remained stable over the follow-up time of 9 months. In patient #2, fourth nerve palsy was diagnosed 13 years prior to confirmation of a trochlear schwannoma by high-resolution MRI. In the third patient disturbing diplopia and head tilt were sufficiently corrected by strabismus surgery (combined oblique muscle surgery). The fourth patient had received stereotactic radiotherapy of an 8 mm schwannoma. He remained unchanged in the orthoptic measurements for 3,5 years. None of these patients developed any additional symptoms or signs of further cranial nerve or central nervous system involvement.

A trochlear nerve schwannoma is a possible cause of an isolated unilateral superior oblique palsy. MRI is a helpful tool for diagnosis and follow-up. Conservative management seems to be justified as patients can remain unchanged over years.