Neuro-Ophthalmology Practice Questions

Q: Which type of visual defects are caused by a tumor of the pituitary gland pressing upon the optic chiasm?

Bitemporal hemianopia. ***Bitemporal hemianopia*** - A pituitary tumor typically arises from the **sella turcica** and grows upwards, impinging on the central aspect of the **optic chiasm**. [1] - This compression affects the crossing fibers from the **nasal retina** of both eyes, which perceive the **temporal (outer) visual fields**, leading to bitemporal hemianopia. [2] *Homonymous hemianopia* - This visual field defect involves the **same side of the visual field** in both eyes (e.g., right homonymous hemianopia means loss of the right visual field in both eyes). [2] - It usually results from a lesion **posterior to the optic chiasm**, such as in the **optic tract**, lateral geniculate body, optic radiations, or visual cortex. [2] *Heteronymous hemianopia* - This is a general term for visual field defects that involve **different parts of the visual field** in each eye. - While bitemporal hemianopia is a specific type of heteronymous hemianopia, this option is too broad and does not specify the characteristic pattern caused by a pituitary tumor. [2] *Binasal hemianopia* - This condition involves the loss of the **nasal (inner) visual fields** in both eyes. - It is a rare finding and typically results from bilateral lesions that interrupt the **uncrossed temporal fibers** of the optic nerves, such as from advanced glaucoma, hydrocephalus, or bilateral internal carotid artery aneurysms, rather than a pituitary tumor.

Q: A 26-year-old female presents with an insidious onset of diplopia on alternate cover test, exhibiting a right hypertropia that worsens on right head tilt and left gaze. Which muscle is paralyzed?

Right superior oblique. ***Right superior oblique*** - A paralyzed **right superior oblique** muscle causes a **right hypertropia** that worsens on **right head tilt** (positive Bielschowsky's head tilt test) and **left gaze**, which are classic signs of a **fourth nerve palsy**. - The superior oblique muscle is responsible for **intorsion**, **depression**, and **abduction** of the eye, and its weakness leads to characteristic vertical and torsional diplopia. - This presentation follows the **Parks-Bielschowsky three-step test**: hypertropia increases on contralateral gaze and ipsilateral head tilt. *Left superior rectus* - Paralysis of the **left superior rectus** would cause a **left hypotropia** (left eye lower than right), not a right hypertropia that worsens on right head tilt. - It would worsen on **left head tilt** and **left gaze** (ipsilateral to the affected muscle). - Its primary action is **elevation**, with secondary actions of **adduction** and **intorsion**. *Right inferior rectus* - Paralysis of the **right inferior rectus** would cause a **right hypertropia** that worsens on **right gaze** and **right head tilt**. - However, it would worsen on **downgaze** (not left gaze), which is a key differentiating feature from superior oblique palsy. - Its primary action is **depression**, with secondary actions of **adduction** and **extorsion**. *Left inferior oblique* - Paralysis of the **left inferior oblique** would cause a **left hypotropia** that worsens on **right gaze** and **right head tilt**. - This does not match the clinical presentation of right hypertropia worsening on left gaze and right head tilt. - Its primary action is **elevation**, with secondary actions of **abduction** and **extorsion**.

Question 1

Which type of visual defects are caused by a tumor of the pituitary gland pressing upon the optic chiasm?

Accepted Answer

Bitemporal hemianopia

Answer

Homonymous hemianopia

Answer

Heteronymous hemianopia

Answer

Binasal hemianopia

Question 2

A 26-year-old female presents with an insidious onset of diplopia on alternate cover test, exhibiting a right hypertropia that worsens on right head tilt and left gaze. Which muscle is paralyzed?

Accepted Answer

Right superior oblique

Answer

Left superior rectus

Answer

Right inferior rectus

Answer

Left inferior oblique

Neuro-Ophthalmology — MCQs

Neuro-Ophthalmology — MCQs

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