Answer and Discussion of Quiz Set: N-001

Parinaud syndrome is characterized by paralysis of upward gaze, Pseudo-Argyll Robertson pupils, Convergence-Retraction nystagmus, Eyelid retraction (Collier sign), and Conjugate down gaze in the primary position ("sun-setting" sign). This syndrome is resulted from comprised function of which part of the brain?

A.  Medial and lateral genigulate nucleus

B.  Circuit of Papez

C.  Triangle of Guillain and Molaret

D.  Dorsal midbrain at the level of mesencephalic tectum (quadrigeminal plate)

E.  Hypothalamus-pituitary axis

Answer and Discussion: The answer is (D). Parinaud's syndrome is resulted from suppressed function of the dorsal midbrain due to compression, trauma, ischemia, or other pathologic process. The region involved is the mesencephalic tectum, including the superior colliculus adjacent oculomotor nuclei and Edinger-Westphal nuclei. Compression of this area leads to dysfunction of the eye. Since pineal gland is immediately above the mesencephalic tectum, pineal tumor can easily cause compression of the mesencephalic tectum. Other causes of Parinaud syndrome include obstructive hydrocephalus, space occupying lesions in this area such as arteriovenous malformation, and other causes such as trauma and infection.