What is the dorsal midbrain syndrome?
Dorsal midbrain syndrome results from a lesion in the midbrain tegmentum caused by occlusion of paramedian branches of the basilar or posterior cerebral arteries or both. Its signs are:
- Ipsilateral oculomotor paresis, ptosis, and dilated pupil (damage to fascicle of cranial nerve III, including parasympathetic fibers as in Weber’s syndrome).
- Contralateral involuntary movements, such as intention tremor, ataxia, and chorea (damage to red nucleus).
- Contralateral hemiparesis may be present if the lesion extends ventrally.
- Contralateral hemianesthesia may be present if the lesion extends laterally, affecting the spinothalamic tract and medial lemniscus.