Neuro-Ophthalmology — MCQs

A 63-year-old man is noticed to have asymmetric pupils. He is completely well and has no symptoms. On examination, the left pupil is small, round, and has a brisk response to light and near stimuli (accommodation). There is also ptosis of the left eyelid, but no other ocular movement abnormality or symptoms of double vision. For the above patient with a pupillary abnormality, select the most likely diagnosis.

Q16Easy

Lateral rectus palsy is characterized by which type of diplopia?

Q17Medium

Bilateral centrocaecal scotoma, more marked with red than white colour, is a feature of which condition?

Q18Medium

Which tumours are most common to cause early papilledema?

Q19Medium

A patient presented with complaints of diplopia. On examination, pupils were dilated and both direct and consensual light reflexes were lost. What is the most likely diagnosis?

Q20Medium

Which of the following is NOT true regarding the optic chiasma?

Neuro-Ophthalmology Indian Medical PG Practice Questions and MCQs

Question 11: A 50-year-old family physician presents with vertical diplopia, and feels unsure when descending stairs. He can eliminate the double vision by tilting his head toward the opposite side. Which of the following extraocular muscles is responsible for the ocular malalignment?

A. Inferior rectus
B. Inferior oblique
C. Lateral rectus
D. Superior oblique (Correct Answer)

Explanation: **Explanation:** The clinical presentation of **vertical diplopia** that worsens when looking down (e.g., descending stairs) and is relieved by a **contralateral head tilt** is the classic hallmark of **Superior Oblique (IV Nerve) Palsy**. **1. Why Superior Oblique is Correct:** The Superior Oblique (SO) muscle primarily acts as an **intorter**, depressor, and abductor. In SO palsy, the affected eye is hypertropic (elevated) because the antagonist (Inferior Oblique) acts unopposed. * **Descending stairs:** Diplopia worsens during downgaze because the SO is the primary depressor when the eye is adducted (the position used for reading or walking down stairs). * **Head Tilt (Bielschowsky Test):** Tilting the head to the *affected* side increases the vertical deviation (positive test). Conversely, tilting to the **opposite side** (as seen in this patient) minimizes the need for intorsion from the weak SO, thereby eliminating diplopia. **2. Why Other Options are Incorrect:** * **Inferior Rectus:** While it is a depressor, its weakness causes diplopia that worsens on looking down, but it does not typically present with a compensatory head tilt to the opposite shoulder. * **Inferior Oblique:** Palsy would cause a hypotropia (eye looking down) and diplopia that worsens on up-and-in gaze, not down-and-in gaze. * **Lateral Rectus:** This is supplied by the VI nerve. Its weakness causes **horizontal** (not vertical) diplopia, which worsens on abduction. **Clinical Pearls for NEET-PG:** * **Parks Three-Step Test:** Used to isolate the palsied vertical muscle. * **IV Nerve:** It is the only cranial nerve that exits **dorsally** and has the **longest intracranial course**, making it highly susceptible to trauma. * **Most common cause:** Congenital or Trauma (in adults). * **Rule of Thumb:** In SO palsy, the patient tilts their head **away** from the lesion to neutralize the extorsion.

Question 12: What type of visual field defect is typically seen in pituitary adenoma?

A. Bitemporal hemianopia (Correct Answer)
B. Binasal hemianopia
C. Quadrantanopia
D. Superior quadrantanopia ('Pie in the sky' defect)

Explanation: **Explanation:** **1. Why Bitemporal Hemianopia is correct:** The pituitary gland lies in the sella turcica, directly beneath the **optic chiasm**. A pituitary adenoma typically expands superiorly, compressing the central part of the chiasm. This area contains the **decussating (crossing) nasal retinal fibers**. Since the nasal retina receives light from the **temporal visual fields**, damage to these fibers results in a loss of the outer half of the vision in both eyes, known as **Bitemporal Hemianopia**. **2. Why other options are incorrect:** * **Binasal Hemianopia:** This occurs due to lateral compression of the chiasm, often by calcified internal carotid arteries or glaucoma; it is not typical for pituitary tumors. * **Quadrantanopia:** This usually indicates a lesion in the optic radiations (post-chiasmal). * **Superior Quadrantanopia ('Pie in the sky'):** This is characteristic of a lesion in **Meyer’s loop** within the **temporal lobe**. While a pituitary tumor can occasionally cause an asymmetrical superior defect if it compresses the chiasm from below, "Bitemporal Hemianopia" is the classic and most common presentation. **Clinical Pearls for NEET-PG:** * **Direction of Compression:** Pituitary tumors compress the chiasm from **below**, so the visual field defect often starts in the **upper temporal quadrants** before progressing to full hemianopia. * **Craniopharyngioma:** Conversely, these often compress the chiasm from **above**, leading to defects starting in the **inferior temporal quadrants**. * **Junctional Scotoma:** If a tumor compresses the junction of the optic nerve and chiasm, it causes a central scotoma in the ipsilateral eye and a superior temporal defect in the contralateral eye (due to involvement of **Wilbrand’s knee**).

Question 13: Eye examination of a patient revealed lack of downward gaze and loss of convergence but has normal pupillary reactions to light. What is the MOST probable location of the lesion?

A. Optic chiasm
B. Inferior colliculus (Correct Answer)
C. Superior colliculus
D. Edinger Westphal nucleus

Explanation: **Explanation:** The clinical presentation of **impaired downward gaze** and **loss of convergence** with **sparing of the pupillary light reflex** is characteristic of a lesion in the **Inferior Colliculus** (or the periaqueductal gray matter at that level). 1. **Why Inferior Colliculus is correct:** While the Superior Colliculus is traditionally associated with upward gaze (Parinaud Syndrome), the centers for **downward gaze** and **convergence** are located more caudally in the midbrain, specifically near the level of the inferior colliculus. Lesions here disrupt the efferent pathways for downward saccades and the convergence neurons, while the light reflex remains intact because its pathway enters the midbrain higher up at the pretectal nucleus. 2. **Why other options are incorrect:** * **Optic Chiasm:** Lesions here typically cause visual field defects (bitemporal hemianopia) and afferent pupillary defects, not ocular motility issues like gaze palsy. * **Superior Colliculus:** Lesion here leads to **Parinaud Syndrome**, characterized by loss of *upward* gaze, lid retraction (Collier’s sign), and light-near dissociation. * **Edinger-Westphal Nucleus:** This is the parasympathetic nucleus for the 3rd nerve. A lesion here would cause a **fixed, dilated pupil** (loss of light reflex) and loss of accommodation, which contradicts the "normal pupillary reaction" in the question. **Clinical Pearls for NEET-PG:** * **Parinaud Syndrome (Dorsal Midbrain Syndrome):** Loss of upward gaze + Light-near dissociation + Convergence-retraction nystagmus. Most common cause: Pineal gland tumors. * **Downward Gaze Palsy:** Often seen in **Progressive Supranuclear Palsy (PSP)** or localized lower midbrain/pretectal lesions. * **Light-Near Dissociation:** Pupil reacts to accommodation (near) but not to light. Seen in Neurosyphilis (Argyll Robertson Pupil) and Parinaud Syndrome.

Question 14: All of the following are true about the trochlear nerve (CN IV) EXCEPT:

A. It is the only cranial nerve to emerge from the dorsal aspect of the brainstem.
B. It is the only cranial nerve that completely crosses to the opposite side before emerging from the brainstem.
C. It is the thickest cranial nerve. (Correct Answer)
D. It has the fewest axons of any cranial nerve.

Explanation: **Explanation:** The **Trochlear Nerve (CN IV)** is unique among cranial nerves due to several anatomical peculiarities. The correct answer is **Option C** because the trochlear nerve is actually the **thinnest** (slenderest) cranial nerve, not the thickest. The thickest cranial nerve is the Trigeminal nerve (CN V). **Analysis of Options:** * **Option A (True):** It is the only cranial nerve that exits from the **dorsal (posterior)** aspect of the brainstem (specifically, below the inferior colliculus). All other cranial nerves emerge ventrally or ventrolaterally. * **Option B (True):** It is the only cranial nerve where **all fibers decussate** (cross) within the superior medullary velum before emerging. Therefore, the right trochlear nucleus innervates the left Superior Oblique muscle. * **Option D (True):** Despite having the longest intracranial course (approx. 7.5 cm), it contains the **fewest number of axons** (around 2,400) compared to any other cranial nerve, correlating with its small diameter. **Clinical Pearls for NEET-PG:** * **Longest Intracranial Course:** Because of its long, thin path, it is highly susceptible to **shearing injuries** during head trauma. * **Action:** It innervates the **Superior Oblique (SO4)** muscle, which primarily depresses the eye in adduction. * **Clinical Presentation:** A CN IV palsy presents with **vertical diplopia** (worse on downgaze) and a compensatory **head tilt** to the opposite side (Bielschowsky head tilt test) to minimize diplopia.

Question 15: A 63-year-old man is noticed to have asymmetric pupils. He is completely well and has no symptoms. On examination, the left pupil is small, round, and has a brisk response to light and near stimuli (accommodation). There is also ptosis of the left eyelid, but no other ocular movement abnormality or symptoms of double vision. For the above patient with a pupillary abnormality, select the most likely diagnosis.

A. Essential anisocoria
B. Horner syndrome (Correct Answer)
C. Tonic pupils (Holmes-Adie syndrome)
D. Argyll Robertson pupils

Explanation: ### Explanation **Correct Option: B. Horner Syndrome** The clinical triad of **miosis** (small pupil) and **ptosis** (drooping eyelid) on the same side is the hallmark of Horner Syndrome. It results from a lesion in the **oculosympathetic pathway**. * **Miosis:** Occurs due to paralysis of the *dilator pupillae* muscle, leaving the parasympathetic-innervated *sphincter pupillae* unopposed. Crucially, the light and near reflexes remain intact because they are mediated by the parasympathetic system. * **Ptosis:** This is a "partial" ptosis (1–2 mm) due to paralysis of **Müller’s muscle** (superior tarsal muscle), which is sympathetically innervated. Unlike a 3rd nerve palsy, there is no ophthalmoplegia (double vision). **Why Incorrect Options are Wrong:** * **A. Essential Anisocoria:** This is a physiological variation where the pupillary size difference remains constant in both light and dark, and there is **no associated ptosis**. * **C. Tonic Pupil (Adie’s):** Characteristically presents as a **large (dilated) pupil** that reacts poorly to light but slowly to accommodation (light-near dissociation). It is usually unilateral and lacks ptosis. * **D. Argyll Robertson Pupil:** Typically **bilateral**, small, and irregular. While it shows light-near dissociation, it is classically associated with neurosyphilis and does not present with ptosis. **NEET-PG High-Yield Pearls:** 1. **Cocaine Test:** Confirms Horner’s; the affected pupil **fails to dilate**. 2. **Apraclonidine Test:** The affected pupil shows **reversal of anisocoria** (dilates) due to denervation supersensitivity. 3. **Hydroxyamphetamine Test:** Differentiates pre-ganglionic (dilates) from post-ganglionic (no dilation) lesions. 4. **Pancoast Tumor:** A common cause of Horner syndrome involving the apex of the lung (pre-ganglionic fibers).

Question 16: Lateral rectus palsy is characterized by which type of diplopia?

A. Crossed diplopia
B. Uncrossed diplopia (Correct Answer)
C. Suppression of the eyeball
D. Upward rotated eyeball

Explanation: **Explanation:** The **Lateral Rectus (LR)** muscle is responsible for abduction (moving the eye outward) and is innervated by the **Abducens nerve (VI CN)**. **1. Why Uncrossed Diplopia is correct:** In Lateral Rectus palsy, the affected eye cannot abduct, leading to an **Esotropia** (inward deviation) due to the unopposed action of the medial rectus. When the patient looks at an object, the image in the deviated eye falls on the **nasal retina**. According to the laws of projection, the brain projects an image falling on the nasal retina to the **temporal visual field**. Therefore, the false image is seen on the same side as the paralyzed eye (e.g., right eye palsy leads to a false image on the right side). This is termed **Uncrossed (Homonymous) Diplopia**. **2. Why other options are incorrect:** * **Crossed Diplopia:** This occurs in **Exotropia** (outward deviation), typically seen in **3rd Nerve Palsy** or Medial Rectus weakness. The image falls on the temporal retina and is projected to the nasal visual field. * **Suppression:** This is a cortical phenomenon seen in childhood strabismus (Amblyopia) to avoid diplopia. It does not occur in acute adult-onset paralytic squint. * **Upward rotated eyeball:** This would suggest a vertical muscle imbalance or 4th nerve palsy (where the eye is hypertropic), not a pure horizontal muscle palsy like LR. **Clinical Pearls for NEET-PG:** * **Rule of Thumb:** **E**sotropia = **U**ncrossed diplopia (Mnemonic: **E-U**); **E**xotropia = **C**rossed diplopia. * Diplopia in LR palsy is **maximum on horizontal gaze** towards the side of the affected muscle. * The patient often adopts a **compensatory head turn** towards the side of the paralyzed muscle to minimize diplopia.

Question 17: Bilateral centrocaecal scotoma, more marked with red than white colour, is a feature of which condition?

A. Tobacco amblyopia (Correct Answer)
B. Leber's disease
C. Papilledema
D. Quinine amblyopia

Explanation: ### Explanation **Tobacco Amblyopia** (now often grouped under Tobacco-Alcohol Induced Toxic Optic Neuropathy) is characterized by a gradual, painless, bilateral decrease in vision. **Why Tobacco Amblyopia is the correct answer:** The hallmark visual field defect is a **bilateral centrocaecal scotoma** (a defect involving both the fixation point and the physiological blind spot). A key diagnostic feature is that the scotoma is **more marked with red targets** than white ones, indicating early dysfunction of the macular fibers which are highly sensitive to color perception. Pathologically, this is due to the toxic effects of cyanide (from tobacco) and a deficiency of Vitamin B12 (which normally detoxifies cyanide into thiocyanate). **Analysis of Incorrect Options:** * **Leber’s Hereditary Optic Neuropathy (LHON):** While it presents with bilateral centrocaecal scotomas, it typically affects young males and presents as a rapid, sequential (rather than simultaneous) loss of vision with a circumpapillary telangiectatic microangiopathy. * **Papilledema:** Early papilledema typically shows an **enlarged blind spot**. Centrocaecal scotomas only occur in the late, atrophic stages, but are not the primary diagnostic feature. * **Quinine Amblyopia:** This presents with sudden vision loss followed by **marked peripheral field contraction (tubular vision)** and "cherry red spot" in the acute phase, rather than centrocaecal scotomas. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment:** Tobacco amblyopia is treated with **Hydroxycobalamin** (injectable B12), which acts as a cyanide scavenger. * **Centrocaecal scotoma differential:** Toxic (Tobacco/Alcohol), Nutritional (B12/Folate deficiency), and Hereditary (Leber’s, Kjer’s) optic neuropathies. * **Red-Green Color Defect:** This is often the earliest sign of toxic optic neuropathy, preceding significant visual acuity loss.

Question 18: Which tumours are most common to cause early papilledema?

A. Cerebellum
B. Midbrain
C. Parieto-occipital region
D. All of the above (Correct Answer)

Explanation: **Explanation:** Papilledema is defined as passive swelling of the optic disc due to increased intracranial pressure (ICP). The timing of its onset depends primarily on the tumor's location relative to the **ventricular system** and its ability to obstruct the flow of Cerebrospinal Fluid (CSF). **Why "All of the Above" is Correct:** Tumors in these specific regions cause early papilledema because they lead to rapid obstructive hydrocephalus: 1. **Cerebellum (Posterior Fossa):** These tumors (e.g., Medulloblastoma) compress the **Fourth Ventricle**, causing a quick rise in ICP. 2. **Midbrain (Pineal Region):** Tumors here (e.g., Pinealoma) compress the **Aqueduct of Sylvius**, which is the narrowest part of the ventricular system, leading to early internal hydrocephalus. 3. **Parieto-occipital Region:** Large tumors in these lobes can compress the **posterior horns of the lateral ventricles** or the vein of Galen, obstructing drainage and elevating ICP rapidly. **Comparison with "Late" Papilledema:** In contrast, tumors in the **frontal lobe** or slow-growing supratentorial masses often present with papilledema much later, as the brain has more space to compensate before CSF flow is compromised. **High-Yield Clinical Pearls for NEET-PG:** * **Foster-Kennedy Syndrome:** Seen in frontal lobe/olfactory groove tumors (e.g., Meningioma). It presents with ipsilateral optic atrophy (due to direct compression) and contralateral papilledema (due to raised ICP). * **Pseudo-papilledema:** Often caused by **Optic Disc Drusen**; distinguished from true papilledema by the absence of venous congestion and hemorrhages. * **Earliest Sign of Papilledema:** Loss of normal spontaneous venous pulsations (SVP) and blurring of the nasal disc margin. * **Paton’s Lines:** Circumferential retinal folds seen in chronic papilledema.

Question 19: A patient presented with complaints of diplopia. On examination, pupils were dilated and both direct and consensual light reflexes were lost. What is the most likely diagnosis?

A. 2nd nerve palsy
B. 3rd nerve palsy (Correct Answer)
C. 5th nerve palsy
D. 7th nerve palsy

Explanation: **Explanation:** The clinical presentation of **diplopia** combined with a **dilated pupil** and loss of both direct and consensual light reflexes is a classic sign of **3rd Nerve (Oculomotor) Palsy**. **1. Why 3rd Nerve Palsy is Correct:** The Oculomotor nerve carries parasympathetic fibers (originating from the Edinger-Westphal nucleus) that supply the **sphincter pupillae** muscle. Damage to these fibers leads to an unopposed dilator pupillae, resulting in a **dilated (mydriatic) pupil**. Since the efferent limb of the pupillary light reflex is mediated by the 3rd nerve, both direct and consensual responses are lost in the affected eye. Diplopia occurs due to the paralysis of the extraocular muscles (Superior, Inferior, and Medial Recti, and Inferior Oblique). **2. Why Other Options are Incorrect:** * **2nd Nerve (Optic) Palsy:** This would cause a loss of the **direct** light reflex in the affected eye but the **consensual** reflex would remain intact (when the normal eye is stimulated). It does not cause diplopia or a fixed dilated pupil. * **5th Nerve (Trigeminal) Palsy:** This nerve provides sensory innervation to the face and motor innervation to muscles of mastication. It is involved in the **afferent** limb of the corneal reflex, not the light reflex. * **7th Nerve (Facial) Palsy:** This nerve is responsible for facial expression and the **efferent** limb of the corneal reflex (orbicularis oculi). It does not affect pupillary size or ocular motility. **3. High-Yield Clinical Pearls for NEET-PG:** * **Rule of Pupil:** In 3rd nerve palsy, a **dilated pupil** suggests external compression (e.g., **PCOM artery aneurysm**), while a **pupil-sparing** palsy suggests medical causes like **Diabetes Mellitus** (due to microvascular ischemia of central fibers). * **Clinical Triad:** Complete 3rd nerve palsy presents with **Ptosis**, a **"Down and Out"** eye position, and **Mydriasis**. * **Light Reflex Pathway:** Afferent = 2nd Nerve; Efferent = 3rd Nerve.

Question 20: Which of the following is NOT true regarding the optic chiasma?

A. It lies superior to the tuberculum sellae.
B. A tumor compressing the chiasma can cause visual field defects.
C. Decussation of fibers from the medial half of each retina occurs at the chiasma.
D. Inferonasal fibers of the optic nerve are related to the posterior portion of the chiasma. (Correct Answer)

Explanation: ### Explanation The optic chiasma is a vital structure in the visual pathway where partial decussation occurs. Understanding its anatomical relationships and fiber orientation is high-yield for NEET-PG. **Why Option D is the Correct (False) Statement:** The **inferonasal fibers** (which carry information from the superotemporal visual field) do not relate to the posterior portion. Instead, they decussate in the **anterior** part of the chiasma. Specifically, they loop forward into the contralateral optic nerve before proceeding to the optic tract; this loop is known as **Wilbrand’s Knee**. It is the **superonasal fibers** that are related to the posterior portion of the chiasma. **Analysis of Other Options:** * **Option A:** The chiasma typically lies above the **tuberculum sellae** and the diaphragma sellae. In most individuals (approx. 80%), it is "centrally posited" over the pituitary gland. * **Option B:** Because the chiasma contains crossing nasal fibers, compression (most commonly by a Pituitary Adenoma) leads to classic **Bitemporal Hemianopia**. * **Option C:** The chiasma is defined by the decussation of fibers from the **nasal (medial) retina**. These fibers represent the temporal visual fields. **Clinical Pearls for NEET-PG:** 1. **Wilbrand’s Knee:** Lesion at the junction of the optic nerve and chiasma causes **Junctional Scotoma** (ipsilateral central scotoma + contralateral superotemporal field defect). 2. **Blood Supply:** Primarily from the Circle of Willis (Internal Carotid and Anterior Communicating arteries). 3. **Anatomical Variations:** * **Prefixed chiasma (15%):** Overlies the tuberculum sellae. * **Postfixed chiasma (5%):** Overlies the dorsum sellae.

Practice by Chapter

Anatomy of Visual Pathways

Practice Questions

Pupillary Disorders

Practice Questions

Optic Neuritis

Practice Questions

Ischemic Optic Neuropathies

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Other Optic Neuropathies

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Papilledema

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Cranial Nerve Palsies

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Nystagmus

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Visual Field Defects

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Neuro-ophthalmic Manifestations of Intracranial Lesions

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Functional Visual Disorders

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Migraine and the Eye

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