Weber's syndrome, also known as superior alternating hemiplegia, is a form of stroke characterized by the presence of an ipsilateral oculomotor nerve palsy and contralateral hemiparesis or hemiplegia. It is caused by midbrain infarction as a result of occlusion of the paramedian branches of the posterior cerebral artery or of basilar bifurcation perforating arteries.
|Other names||Superior alternating hemiplegia|
|Midbrain cross section showing lesion|
This lesion is usually unilateral and affects several structures in the midbrain including:
|substantia nigra||contralateral parkinsonism because its dopaminergic projections to the basal ganglia innervate the ipsilateral hemisphere motor field, leading to a movement disorder of the contralateral body.|
|corticospinal fibers||contralateral hemiparesis and typical upper motor neuron findings. It is contralateral because it occurs before the decussation in the medulla.|
|corticobulbar tract||difficulty with contralateral lower facial muscles and hypoglossal nerve functions|
|oculomotor nerve fibers||ipsilateral oculomotor nerve palsy with a drooping eyelid and fixed wide pupil pointed down and out. This leads to diplopia|
Clinical findings mainly eyeball is down and out ipsilateral lateral squint. Ptosis present. Pupil dilated and fixed as LPS nerve supply is disrupted . Contralateral hemiplegia CT scan or MRI might help in delineating the cause or the vessel or region of brain involved in stroke.
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It carries the name of Sir Hermann David Weber, a German-born physician working in London, who described the condition in 1863. It is unrelated to Sturge-Weber syndrome, Klippel-Trenaunay-Weber syndrome or Osler-Weber-Rendu syndrome. These conditions are named for his son Frederick Parkes Weber.