Neuro-Ophthalmology Practice Questions

Q: Which nerve, when affected, results in the loss of medial/nasal movement during eye action?

3rd nerve. ### Explanation **Correct Answer: C. 3rd nerve (Oculomotor Nerve)** The **3rd Cranial Nerve (Oculomotor)** supplies the majority of the extraocular muscles, including the **Medial Rectus**. The primary action of the Medial Rectus is **adduction**, which moves the eye medially toward the nose. Therefore, a palsy of the 3rd nerve results in the inability to move the eye nasally. In a complete 3rd nerve palsy, the eye typically deviates "down and out" due to the unopposed action of the Superior Oblique (4th nerve) and Lateral Rectus (6th nerve). **Analysis of Incorrect Options:** * **A. 4th nerve (Trochlear):** This nerve supplies the **Superior Oblique** muscle. Its primary action is depression in the adducted position and intorsion. Damage leads to vertical diplopia and a compensatory head tilt, not a loss of medial movement. * **B. 6th nerve (Abducens):** This nerve supplies the **Lateral Rectus** muscle, which is responsible for **abduction** (moving the eye away from the nose). A 6th nerve palsy results in a loss of lateral movement and an inward (esotropic) deviation. * **D. 7th nerve (Facial):** This nerve supplies the muscles of facial expression, including the **Orbicularis Oculi**, which is responsible for closing the eyelids. It does not control extraocular muscle movements. **High-Yield Clinical Pearls for NEET-PG:** * **Rule of 3s:** The 3rd nerve supplies 4 out of 6 extraocular muscles (MR, SR, IR, IO) plus the Levator Palpebrae Superioris (LPS) and the sphincter pupillae. * **Pupil Involvement:** In 3rd nerve palsy, a **dilated pupil** suggests external compression (e.g., PCom artery aneurysm), while **pupillary sparing** often suggests a microvascular cause (e.g., Diabetes Mellitus). * **Mnemonic for Nerve Supply:** **LR6 (SO4) 3** — Lateral Rectus (6th), Superior Oblique (4th), and all others (3rd).

Q: What is not a feature of a carotico-cavernous fistula?

Can lead to spontaneous intraorbital hemorrhage. **Explanation:** A **Carotico-cavernous fistula (CCF)** is an abnormal communication between the carotid arterial system and the cavernous sinus. High-pressure arterial blood flows into the low-pressure venous sinus, leading to venous engorgement and characteristic clinical signs. **Why Option D is correct:** While CCF causes significant venous congestion, it **does not typically lead to spontaneous intraorbital hemorrhage**. The increased pressure is transmitted to the orbital veins, causing them to dilate, but the primary complications are related to ocular ischemia, secondary glaucoma, and cranial nerve palsies. Intraorbital hemorrhage is usually a result of direct trauma (which may also cause the CCF) rather than a spontaneous feature of the fistula itself. **Why the other options are incorrect:** * **A. Pulsatile exophthalmos:** This is a hallmark feature. The transmission of arterial pulsations through the fistula to the ophthalmic veins causes the globe to pulsate in sync with the heartbeat. * **B. Generally post-traumatic:** Direct CCFs (high-flow) are most commonly caused by basal skull fractures (70-80% of cases), making them predominantly post-traumatic. * **C. Dilated superior ophthalmic vein:** This is a classic radiological finding on CT or MRI. The reversal of blood flow from the cavernous sinus into the orbital veins leads to significant dilation of the superior ophthalmic vein. **Clinical Pearls for NEET-PG:** * **Classic Triad:** Pulsatile exophthalmos, conjunctival chemosis (corkscrew vessels), and an orbital bruit (heard over the eye). * **Dandy’s Sign:** Disappearance of the bruit upon compression of the ipsilateral carotid artery. * **Gold Standard Investigation:** Digital Subtraction Angiography (DSA). * **Treatment:** Endovascular embolization (detachable balloons or coils) is the treatment of choice.

Q: Which visual field defects are seen in a lesion at the tip of the lateral geniculate body?

Keyhole visual field defect. **Explanation:** The **Lateral Geniculate Body (LGB)** is the primary relay station for visual information traveling from the optic tract to the optic radiations. It has a unique tonotopic arrangement and a dual blood supply, which dictates the specific field defects seen in vascular lesions. **Why "Keyhole visual field defect" is correct:** The LGB is supplied by two main arteries: the **Anterior Choroidal Artery (AChA)** and the **Lateral Posterior Choroidal Artery (LPChA)**. * The **AChA** supplies the lateral and medial aspects of the LGB. * The **LPChA** supplies the central wedge-shaped area (the "hilum" or "tip"). A lesion or infarct involving the **LPChA** results in a loss of the central visual fibers while sparing the periphery, or vice versa, creating a characteristic **horizontal sectoranopia** or a **"keyhole" shaped defect** (specifically, a wedge-shaped sector defect that respects the horizontal meridian). **Analysis of Incorrect Options:** * **Pie in the sky (Superior Quadrantanopia):** This occurs due to a lesion in **Meyer’s Loop** (temporal lobe), which carries fibers from the inferior retina. * **Pie on the floor (Inferior Quadrantanopia):** This occurs due to a lesion in **Baum’s Loop** (parietal lobe), which carries fibers from the superior retina. * **Homonymous hemianopia:** While a total destruction of the LGB would cause a complete contralateral homonymous hemianopia, a lesion specifically at the **tip/hilum** (vascular territory) results in the sectorial "keyhole" pattern. **High-Yield Clinical Pearls for NEET-PG:** 1. **Dual Blood Supply:** Remember AChA (Lateral/Medial) vs. LPChA (Central/Hilum). 2. **Wernicke’s Pupil:** Seen in optic tract lesions, but **absent** in LGB lesions (since pupillary fibers leave the tract before reaching the LGB). 3. **LGB Layers:** Layers 1, 4, 6 receive contralateral (crossed) fibers; Layers 2, 3, 5 receive ipsilateral (uncrossed) fibers.

Q: Enophthalmos is an uncommon feature of Horner's syndrome. Enophthalmos is due to palsy of which muscle?

Orbitalis muscle. **Explanation:** **Horner’s Syndrome** is caused by a lesion in the sympathetic pathway supplying the eye. The classic triad includes miosis, partial ptosis, and anhidrosis. While **enophthalmos** (the backward displacement of the eyeball) is often described as a clinical feature, it is frequently an "apparent" enophthalmos caused by the narrowing of the palpebral fissure rather than true displacement. **Why Orbitalis Muscle is Correct:** The **Orbitalis muscle (Müller’s orbital muscle)** is a rudimentary smooth muscle that bridges the inferior orbital fissure. It is innervated by **sympathetic fibers**. In Horner’s syndrome, the loss of sympathetic tone leads to the relaxation of this muscle, which can result in a slight sinking of the globe into the orbit (true enophthalmos). **Analysis of Incorrect Options:** * **Levator palpebrae superioris (LPS):** This is a skeletal muscle innervated by the **Oculomotor nerve (CN III)**. Its paralysis causes complete ptosis, not enophthalmos. * **Superior tarsal muscle (Müller’s muscle):** This is a smooth muscle in the upper lid innervated by sympathetic fibers. Its palsy causes the **partial ptosis** seen in Horner’s, but it does not affect the position of the globe. * **Inferior tarsal muscle:** This is the sympathetic smooth muscle in the lower lid. Its palsy leads to "upside-down ptosis" (slight elevation of the lower lid), contributing to the narrowed palpebral fissure. **High-Yield Clinical Pearls for NEET-PG:** * **Apparent vs. True:** Most enophthalmos in Horner’s is "apparent" due to ptosis and lower lid elevation. * **Cocaine Test:** Confirms the diagnosis of Horner's; a Horner's pupil will **not** dilate. * **Apraclonidine Test:** Causes **reversal of anisocoria** (the Horner's pupil dilates while the normal pupil remains unchanged). * **Hydroxyamphetamine Test:** Used to differentiate preganglionic from postganglionic lesions.

Q: Which of the following signs is not typically associated with Horner's syndrome?

Mydriasis (pupil dilation). **Explanation:** Horner’s syndrome results from a lesion in the **oculosympathetic pathway** (a three-neuron chain). Since the sympathetic nervous system is responsible for pupillary dilation, its disruption leads to the clinical features of the syndrome. **1. Why Mydriasis is the Correct Answer:** Mydriasis refers to pupil dilation, which is mediated by the sympathetic system (dilator pupillae muscle). In Horner’s syndrome, sympathetic activity is lost, leading to unopposed parasympathetic action. This results in **Miosis** (constriction of the pupil), not mydriasis. Therefore, mydriasis is the "odd one out." **2. Analysis of Incorrect Options:** * **Ptosis:** Occurs due to paralysis of **Müller’s muscle** (superior tarsal muscle), which provides 2mm of eyelid elevation. This results in a "partial ptosis." * **Anhidrosis:** Loss of sympathetic supply to the sweat glands of the face leads to decreased sweating. Note: This is usually absent in post-ganglionic (third-order) lesions. * **Enophthalmos:** This is often an **apparent enophthalmos** caused by the narrowing of the palpebral fissure (due to upper lid ptosis and lower lid "upside-down ptosis"). **Clinical Pearls for NEET-PG:** * **Cocaine Test:** A classic diagnostic test; a Horner’s pupil will **not dilate** with cocaine drops. * **Apraclonidine Test:** Causes **reversal of anisocoria** (the Horner’s pupil dilates while the normal one does not). * **Heterochromia Iridis:** Seen in **congenital** Horner’s syndrome (the affected eye is lighter/blue). * **Pancoast Tumor:** A common cause of pre-ganglionic Horner’s syndrome due to involvement of the sympathetic chain at the lung apex.

Q: Optic nerve meningioma arises from which layer?

Arachnoid. ### Explanation **Correct Option: D. Arachnoid** Optic Nerve Sheath Meningiomas (ONSM) are benign tumors that arise from the **cap cells of the arachnoid villi** located within the optic nerve sheath. Since the optic nerve is an embryological extension of the central nervous system (diencephalon), it is encased by all three layers of the meninges (dura, arachnoid, and pia). The proliferation of these arachnoid cells leads to a tumor that grows circumferentially around the nerve, often resulting in the classic "tram-track" sign on imaging. **Analysis of Incorrect Options:** * **A. Pia mater:** This is the innermost vascular layer closely adherent to the optic nerve. While it provides nourishment, it is not the site of origin for meningiomas. * **B. Dura mater:** This is the tough, outermost layer. While the tumor eventually compresses the dura and may be contained by it, it does not originate here. * **C. Astrocytes:** These are glial cells within the nerve parenchyma. Proliferation of astrocytes leads to an **Optic Nerve Glioma**, not a meningioma. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad (Hoyt-Spencer Triad):** 1. Visual loss, 2. Optic atrophy, and 3. Optociliary shunt vessels (collaterals). * **Radiology:** Contrast-enhanced CT or MRI shows the **"Tram-track sign"** (calcified or enhancing tumor sheath surrounding the non-enhancing optic nerve). * **Demographics:** Most common in middle-aged women. * **Management:** Observation or Radiotherapy (Surgery is usually avoided as it often leads to immediate blindness due to damage to the pial blood supply).

Question 1

Which nerve, when affected, results in the loss of medial/nasal movement during eye action?

Accepted Answer

3rd nerve

Answer

4th nerve

Answer

6th nerve

Answer

7th nerve

Question 2

What is not a feature of a carotico-cavernous fistula?

Accepted Answer

Can lead to spontaneous intraorbital hemorrhage

Answer

Pulsatile exophthalmos

Answer

Generally post-traumatic

Answer

Dilated superior ophthalmic vein

Question 3

Which visual field defects are seen in a lesion at the tip of the lateral geniculate body?

Accepted Answer

Keyhole visual field defect

Answer

Pie in the sky

Answer

Pie in the floor

Answer

Homonymous hemianopia

Question 4

Enophthalmos is an uncommon feature of Horner's syndrome. Enophthalmos is due to palsy of which muscle?

Accepted Answer

Orbitalis muscle

Answer

Levator palpebrae superioris

Answer

Superior tarsal muscle

Answer

Inferior tarsal muscle

Question 5

In papilledema, all of the following are true except?

Accepted Answer

Sudden loss of vision

Answer

Blurring of the disc

Answer

Congestion of retinal veins

Answer

Soft white exudates around the disc

Question 6

Which of the following signs is not typically associated with Horner's syndrome?

Accepted Answer

Mydriasis (pupil dilation)

Answer

Ptosis (drooping eyelid)

Answer

Anhidrosis (decreased sweating)

Answer

Enophthalmos (recession of the eyeball)

Question 7

A Marcus Gunn pupil is associated with a lesion in which of the following locations?

Accepted Answer

Cortex

Answer

Cerebellum

Answer

Midbrain

Answer

Pons

Question 8

Which of the following best describes the visual loss associated with optic neuritis?

Accepted Answer

Sudden painful loss of vision

Answer

Gradual painless loss of vision

Answer

Sudden painless loss of vision

Answer

Gradual painful loss of vision

Question 9

Methanol toxicity primarily affects which part of the retina?

Accepted Answer

Ganglion cells

Answer

Cones

Answer

Rods

Answer

Germinal cell layer

Question 10

Optic nerve meningioma arises from which layer?

Accepted Answer

Arachnoid

Answer

Pia mater

Answer

Dura mater

Answer

Astrocytes

Neuro-Ophthalmology — MCQs

Neuro-Ophthalmology — MCQs

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