Cranial Nerve Palsies — MCQs
Inability to abduct left eye with LMN fascial palsy on same side. The lesion is in
An 85-year-old man presents with a sudden onset of severe occipital headache, vomiting on two occasions, and double vision. He has a history of hypertension. His examination findings are a Glasgow Coma Scale of 15/15, mild neck stiffness, and normal power in both upper and lower limbs. Where is the likely site of pathology?
In head injury, unilateral dilatation of the pupil is seen due to?
Which of the following is the most common false localizing neurological sign in assessing brain tumors-
Most common neurological sign that can have non-neurological causes is:
Which of the following arteries is likely to be involved in a 3rd cranial nerve lesion?
True about Trotter's triad - a) Conductive deafness b) Involvement of CN VI c) Involvement of CN X d) Palatal paralysis e) Associated with nasopharyngeal angiofibroma
All of the following are seen in 3rd nerve palsy except
How can the degree of diplopia in maxillofacial trauma be accurately recorded?
A 65-year-old male with a history of hypertension and diabetes presents to the OPD with complaints of diplopia and squint. On examination, the secondary deviation is more than the primary deviation. Which of the following is the most likely diagnosis?
Cranial Nerve Palsies 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: An 85-year-old man presents with a sudden onset of severe occipital headache, vomiting on two occasions, and double vision. He has a history of hypertension. His examination findings are a Glasgow Coma Scale of 15/15, mild neck stiffness, and normal power in both upper and lower limbs. Where is the likely site of pathology?
- A. Posterior communicating artery (Correct Answer)
- B. Lenticulostriate artery
- C. P1 Segment of Posterior cerebral artery
- D. Anterior communicating artery
Explanation: ***Posterior communicating artery*** - Aneurysms in the **posterior communicating artery** are notorious for causing **oculomotor nerve (CN III) palsy**, leading to **double vision** due to impairment of eye movements. [2] - The sudden onset of severe **occipital headache** and **vomiting** suggests a subarachnoid hemorrhage, which is a common presentation of a ruptured cerebral aneurysm. [1] *Anterior communicating artery* - Aneurysms here typically present with **bifrontal headaches** and can cause **visual field defects** or **cranial nerve deficits** affecting the optic chiasm. - It usually does not specifically cause **double vision** due to oculomotor nerve involvement as a primary symptom. *Lenticulostriate artery* - These are small perforating arteries that supply the **basal ganglia** and **internal capsule**. - Rupture most commonly causes **intracerebral hemorrhage**, leading to motor or sensory deficits depending on the affected area, but less typically presents with isolated double vision or occipital headache. *P1 Segment of Posterior cerebral artery* - Aneurysms in the **P1 segment** are rare and typically involve structures around the **midbrain**, potentially causing specific neurological deficits like **contralateral hemiparesis** or **visual defects**. - While rupture can cause subarachnoid hemorrhage, presentation with isolated double vision from oculomotor nerve palsy is less characteristic than with a posterior communicating artery aneurysm.
Question 3: In head injury, unilateral dilatation of the pupil is seen due to?
- A. Ophthalmic N. compression
- B. Trigeminal N. compression
- C. Oculomotor nerve compression (Correct Answer)
- D. None of the options
Explanation: Oculomotor nerve compression - Unilateral pupillary dilation, often referred to as a **blown pupil**, is a classic sign of **oculomotor nerve (CN III) compression** due to increased intracranial pressure, typically from a **herniating uncus** [1]. - The parasympathetic fibers responsible for pupillary constriction run on the superficial aspect of the oculomotor nerve and are thus vulnerable to extrinsic compression [1], [2]. *Ophthalmic N. compression* - The **ophthalmic nerve (CN V1)** is a sensory nerve responsible for sensation to the forehead, scalp, upper eyelid, and cornea, not pupillary control. - Compression of this nerve would cause **sensory deficits** in its distribution and potentially abolish the **corneal reflex**, but not pupillary dilation. *Trigeminal N. compression* - The **trigeminal nerve (CN V)** is primarily responsible for sensation to the face and motor control of the muscles of mastication. - Compression would lead to **facial numbness or pain** and **weakness in chewing**, with no direct impact on pupillary size. *None of the options* - This option is incorrect because oculomotor nerve compression is a well-established cause of unilateral pupillary dilation in head injuries [1].
Question 4: Which of the following is the most common false localizing neurological sign in assessing brain tumors-
- A. Seizures
- B. Diplopia (due to sixth nerve palsy) (Correct Answer)
- C. Unilateral papilloedema
- D. Abnormal unilateral pupil
Explanation: ***Diplopia (due to sixth nerve palsy)*** - **Diplopia** resulting from **sixth nerve (abducens) palsy** is the most common false localizing sign in patients with brain tumors, often due to elevated intracranial pressure [1]. - The sixth cranial nerve has a **long intracranial course**, making it particularly susceptible to compression or stretching from generalized intracranial hypertension, regardless of the tumor's specific location [1]. *Seizures* - Seizures are a common symptom of brain tumors, but they are typically **localizing or lateralizing**, pointing towards the region of cortical irritation [1]. - While a seizure can be the initial presentation, it doesn't usually cause a false localization of the primary tumor site, but rather reflects the tumor's irritative effect on the brain region. *Abnormal unilateral pupil* - An abnormal unilateral pupil, such as a dilated pupil, is usually a **true localizing sign** indicating compression of the **oculomotor nerve (CN III)** due to uncal herniation, a specific and grave sign of mass effect [1]. - This symptom strongly suggests a lesion in the ipsilateral temporal lobe compressing the CN III, rather than general raised intracranial pressure. *Unilateral papilloedema* - **Papilloedema** is typically a **bilateral sign** of raised intracranial pressure, as both optic nerves are affected by increased CSF pressure. - While asymmetric or rarely unilateral papilloedema can occur, the classic presentation of a brain tumor with raised ICP is bilateral, making unilateral presentation a less common false localizing sign compared to sixth nerve palsy.
Question 5: Most common neurological sign that can have non-neurological causes is:
- A. Unilateral papilledema
- B. Diplopia (Correct Answer)
- C. Wasting of hands
- D. Abnormal unilateral pupil
Explanation: **Diplopia** - **Diplopia** (double vision) can stem from various non-neurological issues, such as **refractive errors** (e.g., astigmatism), **cataracts**, or **dry eyes**, which interfere with clear image formation [1]. - Ocular misalignment due to **strabismus** (a non-neurological ophthalmological condition) can also cause diplopia by preventing the eyes from focusing together [1]. *Unilateral papilledema* - **Unilateral papilledema** is almost exclusively a neurological sign, indicating an **increase in intracranial pressure** or a **localized optic nerve sheath tumor** [1]. - It results from the transmission of elevated intracranial pressure to the subarachnoid space surrounding the optic nerve. *Wasting of hands* - **Wasting of hands** typically points to a neurological problem affecting the **peripheral nerves** or **anterior horn cells**, such as neuropathies or motor neuron disease. - While disuse atrophy can occur, significant, unexplained wasting normally merits a neurological investigation. *Abnormal unilateral pupil* - An **abnormal unilateral pupil** (e.g., anisocoria that is not physiological) often signifies a neurological pathology, such as a **third nerve palsy**, **Horner's syndrome**, or an **oculomotor nerve lesion** [1]. - These conditions affect the innervation of the pupillary muscles by either the parasympathetic or sympathetic nervous systems [1].
Question 6: Which of the following arteries is likely to be involved in a 3rd cranial nerve lesion?
- A. Anterior communicating
- B. Posterior communicating (Correct Answer)
- C. Posterior cerebral
- D. Anterior cerebral
Explanation: ***Posterior communicating*** - The **posterior communicating artery (PCoA)** is anatomically juxtaposed to the **oculomotor nerve (CN III)** as it exits the midbrain. - An **aneurysm** of the PCoA can compress the CN III, leading to findings such as **ptosis**, **mydriasis**, and **"down and out" deviation** of the eye [1]. *Anterior communicating* - The **anterior communicating artery (AComA)** is located more anteriorly and inferiorly, primarily associated with the **optic chiasm** and **olfactory tracts**. - While aneurysms here can cause visual field defects or frontal lobe dysfunction, they are less likely to directly compress the **oculomotor nerve**. *Posterior cerebral* - The **posterior cerebral artery (PCA)** supplies regions like the **visual cortex** and midbrain. - PCA aneurysms or infarctions typically result in deficits such as **hemianopia**, **alexia**, or specific midbrain syndromes, not isolated CN III compression. *Anterior cerebral* - The **anterior cerebral artery (ACA)** supplies the medial aspects of the frontal and parietal lobes. - Aneurysms or strokes in the ACA territory commonly lead to **contralateral leg weakness** or behavioral changes, not cranial nerve palsies due to its anatomical location.
Question 7: True about Trotter's triad - a) Conductive deafness b) Involvement of CN VI c) Involvement of CN X d) Palatal paralysis e) Associated with nasopharyngeal angiofibroma
- A. bde
- B. bc
- C. acd (Correct Answer)
- D. ad
Explanation: ***acd*** - Trotter's triad consists of **conductive deafness** (option a) due to Eustachian tube obstruction, **ipsilateral trigeminal neuralgia** (CN V involvement), and **soft palate paralysis** (option d) caused by tumor infiltration. - Option c refers to **CN X (vagus nerve) involvement**, which can contribute to palatal paralysis, making it part of the clinical presentation. - The combination of **conductive deafness**, **CN X involvement** causing palatal issues, and **palatal paralysis** are correct components of Trotter's triad. - This triad is classically associated with **nasopharyngeal carcinoma**. *Incorrect Option: bde* - This option incorrectly includes CN VI involvement (abducens nerve), which is **not part of Trotter's triad**. - It also incorrectly associates the triad with **nasopharyngeal angiofibroma** rather than carcinoma. - While option d (palatal paralysis) is correct, the combination is incorrect due to options b and e. *Incorrect Option: bc* - Option b refers to **CN VI (abducens nerve) involvement**, which is **not part of the classic Trotter's triad**. - The triad involves **CN V (trigeminal)** for neuralgia, not CN VI. - While CN X involvement (option c) can be present, this combination misses the essential conductive deafness and includes the wrong cranial nerve. *Incorrect Option: ad* - This option correctly includes **conductive deafness** (a) and **palatal paralysis** (d). - However, it **misses option c (CN X involvement)**, which is important for explaining the mechanism of palatal paralysis. - While partially correct, it's incomplete compared to option acd.
Question 8: All of the following are seen in 3rd nerve palsy except
- A. Ptosis
- B. Pupillary dilatation
- C. Loss of abduction (Correct Answer)
- D. Exotropia and hypotropia
Explanation: ***Correct Answer: Loss of abduction*** - **Abduction** (moving the eye laterally/outward) is controlled by the **lateral rectus muscle**, which is innervated by the **abducens nerve (CN VI)**, not the oculomotor nerve (CN III) - Therefore, **loss of abduction is NOT seen in 3rd nerve palsy** - it is characteristic of **6th nerve palsy** - This is the correct answer for this "EXCEPT" question *Incorrect: Ptosis* - **Ptosis** (drooping of the upper eyelid) is a **hallmark feature** of 3rd nerve palsy - Caused by paralysis of the **levator palpebrae superioris muscle** (innervated by CN III) - This IS seen in 3rd nerve palsy, so it's not the exception *Incorrect: Pupillary dilatation* - **Pupillary dilatation** (mydriasis) is a classic sign of **compressive 3rd nerve palsy** - The parasympathetic fibers running with CN III control pupillary constriction via the sphincter pupillae - When these fibers are damaged, unopposed sympathetic tone causes pupil dilation - This IS seen in 3rd nerve palsy (especially with compressive lesions), so it's not the exception *Incorrect: Exotropia and hypotropia* - **Exotropia** (eye deviated laterally) and **hypotropia** (eye deviated downward) occur in complete 3rd nerve palsy - Results from paralysis of muscles innervated by CN III: medial rectus, superior rectus, inferior rectus, and inferior oblique - With these muscles paralyzed, the **lateral rectus (CN VI)** and **superior oblique (CN IV)** act unopposed, causing the eye to be "down and out" - This IS seen in 3rd nerve palsy, so it's not the exception
Question 9: How can the degree of diplopia in maxillofacial trauma be accurately recorded?
- A. Hess chart. (Correct Answer)
- B. Force duction test.
- C. None.
- D. Glasgow scale.
Explanation: ***Hess chart*** - The **Hess chart** is a valuable tool for objectively assessing and quantifying the extent of **diplopia** by mapping the fields of gaze and identifying specific muscle palsies. - It helps in documenting the size and direction of the *deviation of the eye*, crucial for monitoring improvement or deterioration over time in **maxillofacial trauma**. *Glasgow scale* - The **Glasgow Coma Scale (GCS)** is used to assess the level of **consciousness** in patients with head injuries, not specifically for diplopia. - It evaluates eye opening, verbal response, and motor response, providing a general measure of *neurological impairment*. *Force duction test* - The **forced duction test** is a diagnostic procedure performed by the clinician to differentiate between *restrictive extraocular muscle entrapment* and *paretic muscles*. - It assesses the mechanical restriction of globe movement but does not quantify the patient's perception of **diplopia**. *None* - This option is incorrect as the **Hess chart** is a recognized and effective method for accurately recording the degree of **diplopia**.
Question 10: A 65-year-old male with a history of hypertension and diabetes presents to the OPD with complaints of diplopia and squint. On examination, the secondary deviation is more than the primary deviation. Which of the following is the most likely diagnosis?
- A. paralytic squint (Correct Answer)
- B. concomitant strabismus
- C. restrictive strabismus
- D. pseudo strabismus
Explanation: ***Paralytic squint*** The key finding of **secondary deviation being greater than primary deviation** is a classic sign of **paralytic strabismus**. This occurs because the paretic eye (due to neurological deficit) has to work harder to fixate, leading to an exaggerated innervation to the yoked muscle in the healthy eye, causing a larger deviation (Hering's law of equal innervation). The patient's age and history of **hypertension and diabetes** increase the risk of **cranial nerve palsies** (e.g., oculomotor, trochlear, abducens), which are common causes of paralytic squint due to microvascular ischemia. *Concomitant strabismus* In **concomitant strabismus**, the degree of deviation remains constant in all directions of gaze, meaning **primary and secondary deviations are equal**. This contradicts the clinical finding in the patient. Concomitant strabismus often presents in childhood and is typically non-paralytic, with no underlying neurological deficit affecting muscle action. *Restrictive strabismus* **Restrictive strabismus** is characterized by physical limitation of eye movement due to mechanical restriction of an extraocular muscle, often seen in conditions like **thyroid eye disease** or **orbital trauma**. While restrictive strabismus can cause diplopia and reduced eye movement, it typically involves a **limited range of motion** and usually does not present with secondary deviation being greater than primary deviation in the same manner as a paralytic squint. *Pseudo strabismus* **Pseudo strabismus** is an apparent misalignment of the eyes where the eyes are actually straight. This can be due to features like a **wide epicanthal fold** or a **small interpupillary distance**. In pseudo strabismus, there is **no true deviation** on cover-uncover testing, and therefore, the concepts of primary and secondary deviation do not apply, nor would there be actual diplopia.
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