Special Forms of Strabismus — MCQs
Inability to abduct left eye with LMN fascial palsy on same side. The lesion is in
Which of the following is NOT a feature of Moebius syndrome?
Most common ocular movement affected in thyroid ophthalmopathy:
Ataxia, nystagmus, and ophthalmoplegia are seen in which of the following conditions?
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
Which of the following is a hallmark feature of Duane retraction syndrome?
Obstacles in concomitant squint are:
Esotropia is commonly seen in which type of refractive error?
A patient presents with convergent squint in one eye. Vision in the squinting eye is 6/60, and vision in the non-squinting eye is also 6/60. What is the most appropriate next step in management?
A 10-year-old child presents with inward turning of the right eye, and examination shows limited abduction of the affected eye. What is the most likely diagnosis?
Special Forms of Strabismus Indian Medical PG Practice Questions and MCQs
Question 1: Inability to abduct left eye with LMN fascial palsy on same side. The lesion is in
- A. Left pons (Correct Answer)
- B. Cerebellar lesions
- C. CP angle tumor
- D. Right pons
Explanation: ***Left pons*** - A lesion in the **left pons** can affect both the **left abducens nucleus** (leading to inability to abduct the left eye) and the **left facial nucleus or nerve fibers** (causing left lower motor neuron facial palsy). [2] - This specific combination of ipsilateral (same-sided) symptoms is characteristic of a brainstem lesion, particularly within the pons where these cranial nerve nuclei are in close proximity. [1] *Cerebellar lesions* - **Cerebellar lesions** primarily cause symptoms like **ataxia**, dysmetria, and nystagmia, but typically do not cause isolated cranial nerve palsies of the abducens and facial nerves. [1] - While coordinating movements, the cerebellum does not house the nuclei for direct eye abduction or facial muscle control. *CP angle tumor* - A **cerebellopontine (CP) angle tumor** can affect cranial nerves VI and VII, but it typically presents with other symptoms like **vestibulocochlear nerve (VIII) dysfunction (hearing loss, vertigo)** early on due to its anatomical location. - While it can eventually compress the abducens and facial nerves, the combination of **isolated abducens and facial palsy** without VIII nerve involvement points more directly to an intraparenchymal pontine lesion. *Right pons* - A lesion in the **right pons** would cause **right-sided inability to abduct the eye** and **right-sided LMN facial palsy**, not left-sided as described in the case. - Brainstem lesions typically produce ipsilateral cranial nerve deficits due to the close proximity of the nuclei and fascicles before decussation of some pathways.
Question 2: Which of the following is NOT a feature of Moebius syndrome?
- A. Bilateral facial paralysis
- B. Impaired lateral eye movement
- C. Unilateral or bilateral abducens nerve involvement
- D. Decreased chest movements (Correct Answer)
Explanation: ***Decreased chest movements*** - **Decreased chest movements** are not a characteristic feature of **Moebius syndrome**, which primarily affects cranial nerves, particularly the **facial and abducens nerves**. - While other systemic issues can coexist, respiratory problems like decreased chest movements are not considered a direct or defining symptom of this condition. *Bilateral facial paralysis* - **Bilateral facial paralysis** is a hallmark of **Moebius syndrome**, resulting from congenital underdevelopment or absence of the **facial (VII) cranial nerves**. - This leads to a characteristic **mask-like facial expression**, difficulty with smiling, frowning, and other facial movements. *Impaired lateral eye movement* - **Impaired lateral eye movement** is a common feature due to involvement of the **abducens (VI) cranial nerves**, which control the **lateral rectus muscle**. - Patients often present with **esotropia** (crossed eyes) and are unable to move their eyes past the midline when looking to the side. *Unilateral or bilateral abducens nerve involvement* - **Unilateral or bilateral abducens (VI) nerve involvement** is a core diagnostic criterion for **Moebius syndrome**. - This leads to the characteristic deficit in **lateral gaze**, as the abducens nerve innervates the **lateral rectus muscle**.
Question 3: Most common ocular movement affected in thyroid ophthalmopathy:
- A. Elevation (Correct Answer)
- B. Adduction
- C. Abduction
- D. Depression
Explanation: ***Elevation*** - **Restrictive myopathy** of the **inferior rectus muscle** is the most common cause of impaired eye elevation in thyroid ophthalmopathy. - This typically leads to **diplopia** on upward gaze, known as **Graves' ophthalmopathy**. - The inferior rectus is the **most frequently affected** muscle, followed by medial rectus, superior rectus, and lateral rectus (mnemonic: "I'M SLow"). *Adduction* - Impaired adduction (inward movement) is less common and usually associated with **medial rectus restriction**. - While it can occur (second most common muscle involvement), it is not the most frequent manifestation of thyroid ophthalmopathy. *Abduction* - Impaired abduction (outward movement) suggests **lateral rectus involvement**, which is the least common in thyroid ophthalmopathy. - **Sixth nerve palsy** would also cause impaired abduction but is not typically directly caused by thyroid ophthalmopathy. *Depression* - Impaired depression (downward movement) is uncommon in thyroid ophthalmopathy. - Depression is primarily controlled by the **inferior rectus** (which is commonly affected but causes elevation problems, not depression problems) and inferior oblique. - Superior rectus involvement would cause impaired elevation, not depression.
Question 4: Ataxia, nystagmus, and ophthalmoplegia are seen in which of the following conditions?
- A. 3rd nerve palsy
- B. Wernicke encephalopathy (Correct Answer)
- C. Myasthenia gravis
- D. Chronic progressive external ophthalmoplegia
Explanation: ***Wernicke encephalopathy*** - This condition is characterized by the classic triad of **ataxia**, **nystagmus**, and **ophthalmoplegia** (often presenting as external ophthalmoplegia), alongside confusion [2]. - It results from a **thiamine (vitamin B1) deficiency** [2], [3], commonly seen in chronic alcoholics or individuals with severe malnutrition. *Myasthenia gravis* - This is an **autoimmune disorder** affecting the neuromuscular junction, leading to fluctuating muscle weakness that worsens with activity [1]. - While it can cause **ophthalmoplegia** (especially ptosis and diplopia), it does not typically present with ataxia or nystagmus. *3rd nerve palsy* - A **third nerve palsy** specifically affects the oculomotor nerve, causing a constellation of symptoms including ptosis, pupillary dilation, and inability to move the eye up, down, or medially. - While it causes **ophthalmoplegia** affecting one eye, it does not typically cause nystagmus or ataxia. *Chronic progressive external ophthalmoplegia* - This is a mitochondrial disorder characterized by **slowly progressive weakness** of the extraocular muscles, leading to bilateral ptosis and limitation of eye movements. - It causes a specific type of **ophthalmoplegia** but is not typically associated with nystagmus or prominent ataxia.
Question 5: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 6: Which of the following is a hallmark feature of Duane retraction syndrome?
- A. Hyperopia
- B. Retraction of globe (Correct Answer)
- C. Head tilt
- D. None of the options
Explanation: ***Retraction of globe*** - **Globe retraction** upon attempted adduction and/or abduction is a classic sign due to co-contraction of the antagonistic rectus muscles. - This abnormal innervation causes the eye to pull back into the orbit and narrow the palpebral fissure. *Hyperopia* - **Hyperopia** (farsightedness) is a refractive error and not a primary diagnostic feature of Duane retraction syndrome. - While it can co-occur, it is not a hallmark of the syndrome's motor abnormalities. *Head tilt* - A **head tilt** can be adopted by patients with Duane syndrome to compensate for the limited eye movements and maintain binocular vision, but it is a compensatory mechanism, not a hallmark feature itself. - It's a secondary sign that helps manage the primary problem of ocular motility impairment. *None of the options* - This option is incorrect because **globe retraction** is indeed a hallmark feature of Duane retraction syndrome.
Question 7: Obstacles in concomitant squint are:
- A. Sensory obstacles
- B. Motor obstacles
- C. Central obstacles
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Concomitant squint** involves **sensory obstacles** (e.g., amblyopia, eccentric fixation), **motor obstacles** (e.g., muscle imbalance, inadequate fusional vergence), and **central obstacles** (e.g., defective brain processing of visual information). - All these factors interact to cause and maintain the misalignment of the eyes. *Sensory obstacles* - These include conditions like **amblyopia** (lazy eye) due to suppression of the deviated eye's image, and **eccentric fixation**, where the fovea is not used for central vision. - While significant, sensory obstacles alone do not fully explain concomitant squint, as motor and central components are also crucial. *Motor obstacles* - These involve issues with the **extraocular muscles**, such as imbalance in muscle tone, or problems with the **neural control** of eye movements, leading to a deviation that is relatively constant in all gaze positions. - Motor obstacles are a key component but are often influenced by central and sensory factors. *Central obstacles* - These refer to problems within the brain's visual pathways and centers responsible for **fusion**, **vergence**, and maintaining **ocular alignment**. - Defective processing of visual input or an inability to maintain binocular vision can directly contribute to squint, highlighting the brain's role in coordinating eye movements.
Question 8: Esotropia is commonly seen in which type of refractive error?
- A. Myopia
- B. Hypermetropia (Correct Answer)
- C. Astigmatism
- D. Presbyopia
Explanation: ***Hypermetropia*** - **Esotropia**, or convergent strabismus, is commonly associated with **uncorrected hypermetropia**, especially in children. - The constant effort to **accommodate** to see clearly for hypermetropic individuals can lead to excessive convergence, causing the eye to turn inward. *Myopia* - Myopia, or **nearsightedness**, rarely causes esotropia. - In some cases, high myopia can be associated with **exotropia** (divergent strabismus) due to reduced accommodative effort. *Astigmatism* - **Astigmatism** causes blurry vision at all distances due to an irregularly shaped cornea or lens, but it is not directly linked to specific forms of strabismus like esotropia or exotropia. - While it can contribute to **amblyopia** if severe and uncorrected, it does not typically cause the eyes to turn inward. *Presbyopia* - **Presbyopia** is an age-related loss of the eye's ability to focus on nearby objects due to stiffening of the lens. - It affects accommodation but does not cause strabismus such as esotropia; it typically begins around age 40.
Question 9: A patient presents with convergent squint in one eye. Vision in the squinting eye is 6/60, and vision in the non-squinting eye is also 6/60. What is the most appropriate next step in management?
- A. Glasses
- B. Refraction and treat underlying cause of poor vision (Correct Answer)
- C. Squint surgery
- D. Botulinum toxin
Explanation: ***Refraction and treat underlying cause of poor vision*** - When **both eyes have equally poor vision (6/60)** with a convergent squint, this suggests a **bilateral pathology** affecting visual acuity, not simply a refractive accommodative esotropia. - The **first step** is comprehensive **cycloplegic refraction** to determine if refractive error contributes to the poor vision. - **Equally important** is identifying the **underlying cause** of bilateral vision loss (6/60 in both eyes), which could be: - **Bilateral amblyopia** (though unusual to have equal severity) - **Uncorrected high refractive error** (hypermetropia causing accommodative esotropia) - **Cataracts** (congenital or developmental) - **Retinal pathology** or **optic nerve disorders** - Only after identifying and treating the underlying cause can definitive management of the squint be planned. *Glasses* - While **glasses** may be part of the treatment if refractive error is found, **prescribing glasses alone** without first performing refraction and investigating why both eyes have 6/60 vision is incomplete management. - This option is too narrow and doesn't address the need to identify the underlying pathology causing bilateral poor vision. *Squint surgery* - **Squint surgery** addresses ocular misalignment but does **not improve vision**. - Surgery should only be considered **after** refractive correction, treatment of amblyopia (if present), and management of any underlying pathology. - Operating without addressing the cause of poor vision would be premature. *Botulinum toxin* - **Botulinum toxin** is used for certain types of strabismus as a temporary or alternative to surgery. - Like surgery, it addresses alignment but **not visual acuity**. - The priority is to improve vision and identify the underlying cause before considering alignment procedures.
Question 10: A 10-year-old child presents with inward turning of the right eye, and examination shows limited abduction of the affected eye. What is the most likely diagnosis?
- A. Concomitant strabismus
- B. Paralytic squint (Correct Answer)
- C. Exotropia
- D. Hypertropia
Explanation: ***Paralytic squint*** - The key finding is an **inward turning of the right eye** (**esotropia**) combined with **limited abduction** of that eye, strongly suggesting paralysis or weakness of the **lateral rectus muscle**. - A paralytic squint is characterized by an **underacting extraocular muscle**, leading to a deviation that varies with the direction of gaze and often results in **diplopia** (double vision) and a compensatory head turn. *Concomitant strabismus* - In concomitant strabismus, the **degree of ocular deviation is constant** in all directions of gaze, and there is no limitation of eye movement. - It typically results from an **imbalance in the binocular visual system** rather than a muscle paralysis. *Exotropia* - **Exotropia** refers to an **outward turning of the eye**, which is the opposite of the inward turning (**esotropia**) described in the clinical presentation. - While it is a type of strabismus, its direction of deviation does not match the patient's symptoms. *Hypertropia* - **Hypertropia** is an **upward deviation of one eye**, meaning the affected eye is higher than the other. - This condition is also not consistent with the reported inward turning of the eye.
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