Central Trochlear Nerve Palsy due to Stroke: Report and Clinical Correlation of Two Cases.

An elderly lady, 80 years of age, with a past medical history of high blood pressure was admitted to the emergency department after sudden onset of dizziness and binocular diplopia. Dizziness improved in the next 24 hours but diplopia did not change. She was discharged from the hospital with medical treatment. She was initially checked two months later because of persistence of binocular diplopia. Diplopia was vertical when she focused downwards. She did not present any other neurological symptom. On examination, mild left hypertropia was observed in primary gaze, which increased with left head tilt (positive Bielschowsky’s test); the hypertropia was more evident in the right down gaze. According to the patient, diplopia was vertical and it was maximal in the right down gaze. Examination on the rest of the oculomotor nerves was normal. Pupils were equal, normally reacting to light. No other cranial nerves were affected. There were no motor, cerebellar or sensory abnormalities in the limbs. All clinical findings were compatible with left isolated trochlear nerve palsy. Brain MRI revealed a T2-weighted hyper intensity within the right dorsal midbrain at the level of colliculus inferior, suggestive of an ischemic event. A schematic drawing representing the stroke location is also shown (Figure 1). Magnetic resonance imaging angiogram was normal. Treatment was initiated with Clopidogrel, and prisms to improve diplopia were prescribed by the ophthalmologist. The diplopia completely resolved over the following six months.