Neuro-Ophthalmology Practice Questions

Q: 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?

Superior oblique. **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.

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

Bitemporal hemianopia. **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**).

Q: 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?

Inferior colliculus. **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.

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

It is the thickest cranial nerve.. **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.

Q: 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.

Horner syndrome. ### 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).

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

Uncrossed diplopia. **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.

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

Tobacco amblyopia. ### 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.

Q: Which tumours are most common to cause early papilledema?

All of the above. **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 1

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?

Accepted Answer

Superior oblique

Answer

Inferior rectus

Answer

Inferior oblique

Answer

Lateral rectus

Question 2

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

Accepted Answer

Bitemporal hemianopia

Answer

Binasal hemianopia

Answer

Quadrantanopia

Answer

Superior quadrantanopia ('Pie in the sky' defect)

Question 3

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?

Accepted Answer

Inferior colliculus

Answer

Optic chiasm

Answer

Superior colliculus

Answer

Edinger Westphal nucleus

Question 4

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

Accepted Answer

It is the thickest cranial nerve.

Answer

It is the only cranial nerve to emerge from the dorsal aspect of the brainstem.

Answer

It is the only cranial nerve that completely crosses to the opposite side before emerging from the brainstem.

Answer

It has the fewest axons of any cranial nerve.

Question 5

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.

Accepted Answer

Horner syndrome

Answer

Essential anisocoria

Answer

Tonic pupils (Holmes-Adie syndrome)

Answer

Argyll Robertson pupils

Question 6

Lateral rectus palsy is characterized by which type of diplopia?

Accepted Answer

Uncrossed diplopia

Answer

Crossed diplopia

Answer

Suppression of the eyeball

Answer

Upward rotated eyeball

Question 7

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

Accepted Answer

Tobacco amblyopia

Answer

Leber's disease

Answer

Papilledema

Answer

Quinine amblyopia

Question 8

Which tumours are most common to cause early papilledema?

Accepted Answer

All of the above

Answer

Cerebellum

Answer

Midbrain

Answer

Parieto-occipital region

Question 9

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?

Accepted Answer

3rd nerve palsy

Answer

2nd nerve palsy

Answer

5th nerve palsy

Answer

7th nerve palsy

Question 10

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

Accepted Answer

Inferonasal fibers of the optic nerve are related to the posterior portion of the chiasma.

Answer

It lies superior to the tuberculum sellae.

Answer

A tumor compressing the chiasma can cause visual field defects.

Answer

Decussation of fibers from the medial half of each retina occurs at the chiasma.

Neuro-Ophthalmology — MCQs

Neuro-Ophthalmology — MCQs

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