Anatomy
4 questionsWhich muscles are responsible for the elevation of the eye?
Yoke muscle for the right superior rectus is:
Downward and outward movement of eye is affected in injury of?
What is the distance of the medial rectus from the limbus?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 1071: Which muscles are responsible for the elevation of the eye?
- A. SR and IO (Correct Answer)
- B. IO and SO
- C. IR and SR
- D. SO and IR
Explanation: ***SR and IO*** - The **superior rectus (SR)** muscle primarily elevates the eye, especially when the eye is **abducted** [1]. - The **inferior oblique (IO)** muscle also contributes to elevation, particularly when the eye is **adducted** [1]. *IO and SO* - While the **inferior oblique (IO)** elevates the eye, the **superior oblique (SO)** muscle is responsible for **depression** and **intorsion**, not elevation [1]. - Therefore, this combination does not exclusively perform elevation. *IR and SR* - The **superior rectus (SR)** muscle elevates the eye, but the **inferior rectus (IR)** muscle is responsible for **depression** of the eye, not elevation [1]. - This pair has opposing primary actions in vertical movement. *SO and IR* - Both the **superior oblique (SO)** and **inferior rectus (IR)** muscles are primarily involved in **depression** of the eye [1]. - The superior oblique also causes **intorsion**, and the inferior rectus causes **extorsion** [1].
Question 1072: Yoke muscle for the right superior rectus is:
- A. Left Inferior Oblique (Correct Answer)
- B. Left Lateral Rectus
- C. Left Superior rectus
- D. Left Inferior rectus
Explanation: ***Left Inferior Oblique*** - Yoke muscles are pairs of synergistic muscles, one in each eye, that act together to produce conjugate eye movements in the same direction of gaze. - The **right superior rectus** and **left inferior oblique** are yoke muscles that work together during **upward and rightward gaze** (dextro-elevation) [1]. - Right SR elevates the **adducted** right eye, while left IO elevates the **abducted** left eye, producing coordinated upward-right movement [1]. - This follows **Hering's Law of Equal Innervation**, where yoke muscles receive equal and simultaneous innervation. *Left Superior rectus* - The left superior rectus is the **contralateral homologous muscle**, not a yoke muscle for the right superior rectus. - Both superior recti work together for **upward gaze in primary position**, but they are versional muscles, not yoke pairs. - Yoke muscles produce conjugate movements in oblique directions, not straight up. *Left Inferior rectus* - The left inferior rectus depresses the left eye and is an antagonist to elevation. - It would pair with the **right superior oblique** for downward-left gaze (levo-depression), not with the right superior rectus. *Left Lateral Rectus* - The left lateral rectus is responsible for **abduction** of the left eye (leftward gaze). - Its yoke muscle is the **right medial rectus** for leftward horizontal gaze (levoversion), not for upward-right gaze.
Question 1073: Downward and outward movement of eye is affected in injury of?
- A. 3rd nerve (Correct Answer)
- B. 4th nerve
- C. 5th nerve
- D. 6th nerve
Explanation: The 3rd cranial nerve (oculomotor nerve) controls most extraocular muscles including the superior rectus, inferior rectus, medial rectus, and inferior oblique, as well as the levator palpebrae superioris. Injury to the 3rd nerve results in paralysis of these muscles, leaving only the lateral rectus (6th nerve) and superior oblique (4th nerve) functioning. This causes the classic "down and out" position of the eye at rest due to the unopposed action of these two muscles [1]. The eye is pulled downward by the superior oblique and outward by the lateral rectus [1]. Additional features include ptosis (drooping eyelid), dilated pupil, and diplopia (double vision) [1][2]. The patient loses the ability to move the eye upward, downward (via inferior rectus), and medially. Incorrect Option: 4th nerve - The 4th cranial nerve (trochlear nerve) innervates the superior oblique muscle. The superior oblique primarily causes depression (downward), intorsion, and abduction of the eye [1]. However, its action is most effective for downward and INWARD movement when the eye is adducted. - 4th nerve palsy results in vertical diplopia (especially when looking down and inward, like reading or descending stairs), hypertropia (upward deviation), and head tilt to the opposite side. This does NOT produce a "down and out" position. Incorrect Option: 5th nerve - The 5th cranial nerve (trigeminal nerve) provides sensory innervation to the face and motor innervation to the muscles of mastication. It has no role in eye movements. Incorrect Option: 6th nerve - The 6th cranial nerve (abducens nerve) innervates the lateral rectus muscle, responsible for abduction (outward movement) of the eye [1]. 6th nerve palsy causes inability to abduct the eye, resulting in esotropia (inward deviation) and horizontal diplopia.
Question 1074: What is the distance of the medial rectus from the limbus?
- A. 4.5 mm
- B. 5.5 mm (Correct Answer)
- C. 7.0 mm
- D. 10 mm
Explanation: ***5.5 mm*** - The **medial rectus muscle** inserts into the sclera at an average distance of **5.5 mm** from the limbus [1]. - This distance is an important anatomical landmark in **ophthalmic surgery** and ocular motility studies. - The insertion distances follow the **Spiral of Tillaux** pattern. *4.5 mm* - This distance does **not correspond** to any of the standard rectus muscle insertion points. - The closest insertion is the **medial rectus at 5.5 mm**, followed by the **inferior rectus at 6.5 mm** [1]. *7.0 mm* - This distance corresponds to the insertion point of the **lateral rectus muscle** from the limbus [1]. - It is the **second farthest insertion point** among the recti muscles. *10 mm* - This distance is incorrect for any of the **rectus muscle insertions** from the limbus. - The rectus muscles insert at varying distances following the **Spiral of Tillaux**: medial (5.5 mm), inferior (6.5 mm), lateral (7.0 mm), and superior (7.7 mm).
Internal Medicine
3 questionsWhat is the primary brain region associated with ocular bobbing?
Down-beat nystagmus is seen in lesion of ?
Down beat nystagmus is seen in?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 1071: What is the primary brain region associated with ocular bobbing?
- A. Midbrain
- B. Pons (Correct Answer)
- C. Medulla
- D. Cerebral cortex
Explanation: Pons - **Ocular bobbing** is a characteristic eye movement disorder strongly associated with **pontine lesions**, particularly infarctions or hemorrhages affecting the tegmentum. - The pons contains critical connections for vertical gaze control within the **brainstem**, and damage here disrupts these pathways [1]. *Midbrain* - While important for eye movements, particularly **vertical gaze centers**, injuries to the midbrain typically cause disorders like Parinaud syndrome (upgaze palsy), not classic ocular bobbing. - Midbrain lesions might cause other types of nystagmus or gaze palsies but not generally the rapid downward and slow upward movement seen in bobbing. *Medulla* - The medulla primarily controls vital functions like breathing and heart rate, as well as some ocular reflexes, but is less directly involved in the generation of sustained vertical eye movements. - Damage to the medulla is more likely to cause effects like **nystagmus** (e.g., downbeat nystagmus in some cases) or other brainstem signs, rather than ocular bobbing. *Cerebral cortex* - The cerebral cortex is responsible for voluntary eye movements and integration of visual information, but it does not directly generate or control the brainstem reflexes associated with ocular bobbing [1]. - Lesions in the cortex would typically manifest as **gaze preference**, apraxia, or other higher-level visual processing deficits, not involuntary brainstem driven eye movements like bobbing.
Question 1072: Down-beat nystagmus is seen in lesion of ?
- A. Cerebellum (Correct Answer)
- B. Basal ganglia
- C. Hippocampus
- D. Brainstem
Explanation: ***Cerebellum*** * **Down-beat nystagmus (DBN)** is most commonly associated with lesions in the **craniocervical junction** and **posterior fossa**, particularly affecting the **flocculonodular lobe** of the cerebellum. * The cerebellum plays a crucial role in maintaining **gaze stability** and coordinating eye movements; damage to specific cerebellar pathways can disrupt the vestibulo-ocular reflex, leading to DBN [1]. *Brainstem* * While the **brainstem** contains critical circuits for eye movements, lesions here typically result in other forms of nystagmus, such as **up-beat nystagmus** or **gaze-evoked nystagmus**, depending on the specific structures involved [1]. * Damage to brainstem nuclei or pathways controlling vertical gaze is usually indicated by different patterns of oculomotor dysfunction. *Basal ganglia* * Lesions in the **basal ganglia** are primarily associated with **movement disorders** like Parkinson's disease or Huntington's disease. * They do not typically cause primary nystagmus; any ocular abnormalities would generally be secondary to global motor control issues rather than direct involvement in oculomotor pathways. *Hippocampus* * The **hippocampus** is a key structure involved in **memory formation** and spatial navigation. * Lesions in the hippocampus cause **amnesia** and navigational deficits, but they are not directly involved in eye movement control or the generation of nystagmus.
Question 1073: Down beat nystagmus is seen in?
- A. Brain stem lesions
- B. Pontine hemorrhage and other conditions
- C. Labyrinthine damage and other conditions
- D. Arnold Chiari malformation and other conditions (Correct Answer)
Explanation: ***Arnold Chiari malformation and other conditions*** - Downbeat nystagmus is a characteristic finding in Arnold-Chiari malformations, especially **Chiari type 1**, due to compression of cerebellar structures. - Other conditions associated with downbeat nystagmus include **medullary lesions**, **magnesium deficiency**, and **lithium toxicity** [1]. *Brain stem lesions* - While brainstem lesions can cause various nystagmus types, **pure downbeat nystagmus** is less commonly the primary or most specific finding compared to cerebellar involvement [1]. - **Upbeat nystagmus** and other complex nystagmus patterns are more often associated with brainstem lesions like those in the tegmentum. *Pontine hemorrhage and other conditions* - Pontine hemorrhages are more commonly associated with **ocular bobbing**, **blink reflex abnormalities**, or **horizontal gaze palsies**, rather than downbeat nystagmus. - A pontine hemorrhage would typically present with more severe neurological deficits such as **coma** or **quadriparesis**, which are not directly associated with isolated nystagmus. *Labyrinthine damage and other conditions* - **Peripheral vestibular abnormalities** from labyrinthine damage typically cause **horizontal or torsional nystagmus**, often suppressed by visual fixation. - Downbeat nystagmus is a **central vestibular sign**, indicating a problem with central vestibular processing rather than the peripheral labyrinth [1].
Ophthalmology
3 questionsFoster Kennedy syndrome is
Forced duction test is to find out?
In which condition is a positive forced duction test observed?
NEET-PG 2013 - Ophthalmology NEET-PG Practice Questions and MCQs
Question 1071: Foster Kennedy syndrome is
- A. I/L Optic atrophy C/L papilloedema (Correct Answer)
- B. I/L Optic atrophy with papilloedema
- C. I/L Papilloedema with C/L optic atrophy
- D. I/L Papilloedema C/L papilitis
Explanation: ***I/L Optic atrophy C/L papilloedema*** - **Foster Kennedy syndrome** is characterized by the combination of **ipsilateral optic atrophy** and **contralateral papilledema**. - This constellation of signs is typically caused by a **frontal lobe mass** (e.g., meningioma or glioma) that directly compresses the ipsilateral optic nerve, leading to atrophy, while also causing increased **intracranial pressure** that manifests as papilledema in the contralateral eye. *I/L Papilloedema with C/L optic atrophy* - This describes the reverse of Foster Kennedy syndrome and is not a recognized clinical entity associated with a specific pathological process. - Papilledema is due to **increased intracranial pressure**, and optic atrophy is due to nerve damage; these would typically manifest in specific patterns related to the location and timing of the insult. *I/L Optic atrophy with papilloedema* - This option describes both conditions occurring in the **same (ipsilateral) eye**, which contradicts the characteristic presentation of Foster Kennedy syndrome. - While an eye can have both optic atrophy and papilledema (e.g., resolving papilledema or an underlying condition), it is not the defining feature of Foster Kennedy syndrome. *UL Papilloedema C/L papilitis* - This option mentions **papilledema** in one eye (unilateral or ipsilateral is implied) and **papillitis** in the other. - **Papillitis** is an inflammatory condition of the optic nerve head, while papilledema is due to increased intracranial pressure. This combination is not characteristic of Foster Kennedy syndrome, which specifically involves atrophy and papilledema due to a mass lesion.
Question 1072: Forced duction test is to find out?
- A. Ocular muscle palsy
- B. Ocular muscle spasm
- C. Angle of deviation
- D. Mechanical restriction of eye movement (Correct Answer)
Explanation: ***Mechanical restriction of eye movement*** - The forced duction test is specifically designed to **detect mechanical restriction** that prevents free passive movement of the globe. - Performed under **topical anesthesia**, the examiner grasps the eye at the limbus with forceps and attempts to passively rotate it in the direction of limited motility. - A **positive test** (resistance to passive movement) indicates mechanical restriction from causes like **thyroid-associated orbitopathy, orbital floor fracture, entrapment, or fibrosis**. - This is the **primary clinical indication** for performing the test - to differentiate restrictive from paretic causes of strabismus. *Ocular muscle palsy* - In muscle palsy (paretic strabismus), the forced duction test is **negative** - the eye moves freely with passive movement. - The test helps **differentiate paretic from restrictive causes** of limited motility, but the test itself detects restriction, not palsy. - Free passive movement confirms that the limitation is due to muscle weakness rather than mechanical factors. *Ocular muscle spasm* - Active muscle spasm would not be detected by this test because it is performed **under topical or general anesthesia**, which eliminates active muscle contraction. - The test assesses **passive mechanical restriction**, not active muscle activity or spasm. - Spasm would be a neurogenic rather than mechanical cause and would show free passive movement on testing. *Angle of deviation* - The forced duction test does not measure the **degree or angle of deviation** in strabismus. - Tests like the **prism cover test** or **Hirschberg test** are used to quantify deviation. - The forced duction test provides qualitative information about the cause of limitation, not quantitative measurement of misalignment.
Question 1073: In which condition is a positive forced duction test observed?
- A. Mechanical restriction of ocular movement (Correct Answer)
- B. Non-concomitant strabismus
- C. No condition
- D. Extraocular muscle paralysis
Explanation: ***Mechanical restriction of ocular movement*** - A **positive forced duction test** indicates a physical impediment to eye movement, meaning the eye cannot be passively moved beyond a certain point. - This test is crucial for differentiating between **muscle restriction** (e.g., thyroid eye disease, orbital floor fracture with muscle entrapment, post-surgical adhesions) and muscle weakness or paralysis. - When the examiner attempts to passively rotate the globe, there is **resistance** indicating mechanical tethering or restriction of the extraocular muscles. *Non-concomitant strabismus* - This refers to a squint where the magnitude of deviation varies with the direction of gaze. - While it can be caused by muscle restriction, non-concomitant strabismus itself is a **type of ocular misalignment**, not the specific finding of a forced duction test. - The forced duction test helps determine the **cause** of non-concomitant strabismus (mechanical vs. paralytic). *No condition* - This option is incorrect because a positive forced duction test specifically indicates mechanical obstruction or restriction in eye movement. - A positive result always points to an underlying pathological condition affecting ocular motility, not a normal finding. *Extraocular muscle paralysis* - In cases of **muscle paralysis**, the eye cannot move actively in the direction of the paralyzed muscle's action. - However, the **forced duction test would be negative** as the globe can be passively moved in all directions because there is no mechanical restriction. - This differentiates paralytic strabismus (negative test) from restrictive strabismus (positive test).