Eye examination of a patient revealed lack of upward gaze and dilated pupils fixed to light. What is the MOST probable location of the lesion?
In a patient with lesion of the superior colliculus, there is loss of upward gaze associated with dilated pupils that are fixed to light. Lesions in the collicular region is caused by pressure and distoion of underlying structures in the midbrain and not by damaged to specific pathways traversing the colliculi. It can produce any combination of impaired upward gaze, impaired downward gaze, pupillary abnormalities or loss accommodation reflex can occur. The general name for the clinical picture produced is called Perinaud's syndrome. Ref: Textbook of Ophthalmology edited by Sunita Agarwal, page 284.
Optic chiasm
Inferior colliculus
Superior colliculus
Edinger Westphal nucleus