A 73-year-old male patient presented with a mesencephalic dorsal tegme
ntal haemorrhage involving the oculomotor nuclear complex. Clinically
the patient exhibited ipsilateral palsy of the third nerve associated
with internuclear ophthalmoplegia, transient upbeat nystagmus, bilater
al ptosis and paresis of the superior rectus muscle of the contralater
al eye, due to involvement of the subnucleus that mainly innervates th
e contralateral superior rectus muscle. No other neurological deficits
were seen. Isolated midbrain haemorrhages are very uncommon and they
usually produce combined supranuclear and nuclear disturbances of eye
movement. As documented by high resolution CT-scan, these exceptional
findings were caused by haemorrhage in the territory of a penetrating
branch from a long circumferential midbrain artery. The results of thi
s case are in accordance with Warwick's investigations on the organisa
tion of the oculomotor system in primates.