Objective:

To increase awareness of an uncommon diagnosis by detailing the clinical and radiographic characteristics of isolated trochlear nerve schwannomas (TNS).

Background:

Schwannomas without evidence of neurofibromatosis are rare. Due to limited literature about treatment outcomes for TNS, evidence-based approaches to management are lacking.

Design/Methods:

We describe four patients presenting to neuro-ophthalmology clinic with binocular diplopia ultimately found to have TNS.

Results:

1. A 35-year-old male with seven months of vertical binocular diplopia. Exam revealed an incomitant right hypertropia worse with right head tilt. MRI revealed an 8x4x4 mm extra axial homogeneously enhancing mass abutting the right aspect of the pons and traversing the 4^th cranial nerve. He was treated with gamma knife radiosurgery.

2. A 50-year-old female with four months of binocular diplopia and images appearing diagonally out of place. Exam revealed an incomitant left hypertropia worse with left head tilt, a mild deficit in depression of the left eye, and a slight esotropia in primary gaze. MRI revealed a lobulated area of abnormal enhancement in the left ambient cistern measuring approximately 8x3mm. She was followed with serial imaging.

3. A 73-year-old male with nine months of intermittent binocular diplopia. Exam revealed an incomitant left hypertropia worse with left head tilt and near vision. MRI revealed a 3x2x2mm enhancing lesion in the left perimesencephalic cistern. He was followed with serial imaging.

4. A 54-year-old male with eighteen months of vertical binocular diplopia. Exam revealed an incomitant left hypertropia worse with left head tilt. MRI revealed a 3x8mm enhancing focus along the intracranial course of the left trochlear nerve, adjacent to the midbrain. He was followed with serial imaging.

Conclusions:

Isolated trochlear nerve schwannomas should be included in the differential for patients experiencing isolated superior oblique palsies.