Neural Pathways and Tracts — MCQs

10 questions

Which tract is responsible for the loss of proprioception and fine touch?

A woman with right-sided loss of sensations of both the upper and lower limb complains of shooting pain from her fingers to the right shoulder and a burning sensation when touching cold water. Motor functions are normal. Which of the following structures is likely to be involved?

Which structure carries axons from the nucleus gracilis to the thalamus?

Pain and temperature are carried by:

Spinal pathway mainly regulating fine motor activity?

Which thalamic nuclei can produce basal ganglia symptoms?

What is the cause of loss of pain and temperature sensation on the ipsilateral face and contralateral body due to thrombosis?

Wernicke's hemianopic pupillary response is seen in lesion of-

Which of the following is true about multiple sclerosis except

Q10

Which of the following sensations is NOT perceived by spinal nucleus of trigeminal nerve?

Neural Pathways and Tracts Indian Medical PG Practice Questions and MCQs

Question 1: Which tract is responsible for the loss of proprioception and fine touch?

A. Anterior spinothalamic tract
B. Lateral spinothalamic tract
C. Dorsal column (Correct Answer)
D. Corticospinal tract

Explanation: ***Dorsal column*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting **fine touch**, **vibration**, and **proprioception** from the body to the cerebral cortex. - Damage to this tract (e.g., in **tabes dorsalis** or **vitamin B12 deficiency**) leads to a loss of these sensations. *Anterior spinothalamic tract* - This tract primarily conveys crude touch and pressure sensations. - While it carries tactile information, it does not transmit the fine discriminative touch or proprioception associated with the dorsal columns. *Lateral spinothalamic tract* - This pathway is responsible for transmitting **pain** and **temperature** sensations. - It does not play a role in proprioception or fine touch. *Corticospinal tract* - The **corticospinal tract** is a **motor pathway** responsible for voluntary movement. - It has no role in transmitting sensory information such as proprioception or fine touch.

Question 2: A woman with right-sided loss of sensations of both the upper and lower limb complains of shooting pain from her fingers to the right shoulder and a burning sensation when touching cold water. Motor functions are normal. Which of the following structures is likely to be involved?

A. Anterior spinothalamic tract
B. Spinocerebellar tract
C. Lateral spinothalamic tract (Correct Answer)
D. Posterior column

Explanation: ***Lateral spinothalamic tract*** - The symptoms described, such as **loss of sensations**, **shooting pain** (neuropathic pain), and **burning sensation** with cold water (dysesthesia/allodynia), are characteristic of damage to the **spinothalamic tract**, which carries **pain and temperature** sensations. - Involvement of the **right-sided upper and lower limb** indicates a lesion affecting sensory pathways on the ipsilateral side of the body before decussation, or more commonly a contralateral lesion above the level of decussation for the specific tract. Given the symptoms affecting pain and temperature, the lateral spinothalamic tract is the primary candidate. *Anterior spinothalamic tract* - This tract primarily transmits **crude touch** and **pressure** sensations. - While loss of sensation is present, the prominent **shooting pain** and **burning sensation with cold water** are not typically associated with isolated anterior spinothalamic tract lesions. *Spinocerebellar tract* - This tract is responsible for transmitting **proprioceptive information** to the cerebellum for motor coordination. - Damage to the spinocerebellar tracts would manifest as **ataxia** and **incoordination**, not pain or loss of touch/temperature sensation, and motor functions are stated as normal in the patient. *Posterior column* - The posterior column (dorsal column-medial lemniscus pathway) transmits **fine touch**, **vibration**, and **proprioception**. - While a loss of sensation is present, the specific complaints of **shooting pain** and **burning sensation to cold water** are not characteristic of posterior column damage, which would typically present with deficits in discriminative touch, vibratory sense, and position sense.

Question 3: Which structure carries axons from the nucleus gracilis to the thalamus?

A. Medial lemniscus (Correct Answer)
B. Fasciculus gracilis
C. Fasciculus lemniscus
D. Lateral spinothalamic tract

Explanation: ***Medial lemniscus*** - The **medial lemniscus** is formed by the decussation of internal arcuate fibers, which originate from the **nucleus gracilis** and nucleus cuneatus [1]. - These fibers carry **fine touch**, **vibration**, and **proprioception** from the body to the thalamus [1]. *Fasciculus gracilis* - The **fasciculus gracilis** is part of the **dorsal column** in the spinal cord, ascending ipsilaterally [1]. - It carries sensory information from the **lower body** to the nucleus gracilis in the medulla, not directly to the thalamus [1]. *Fasciculus lemniscus* - This is an **incorrect anatomical term**; there is no recognized neurological structure called the fasciculus lemniscus. - The term "lemniscus" refers to ascending sensory tracts, but it does not combine with "fasciculus" in this manner. *Lateral spinothalamic tract* - The **lateral spinothalamic tract** carries information about **pain** and **temperature** from the body to the thalamus [1]. - It originates from the dorsal horn of the spinal cord and decussates at the spinal cord level, distinct from the dorsal column-medial lemniscus pathway [1].

Question 4: Pain and temperature are carried by:

A. Lateral spinothalamic tract (Correct Answer)
B. Dorsal column pathway
C. Anterior spinothalamic tract
D. Ventral column pathway

Explanation: ***Lateral spinothalamic tract*** - The **lateral spinothalamic tract** is primarily responsible for transmitting **pain** and **temperature** sensations from the body to the brain. - This pathway decussates (crosses) at the level of the spinal cord segment where the sensory neuron enters, then ascends contralaterally. *Dorsal column pathway* - The **dorsal column pathway** (also known as the posterior column-medial lemniscus pathway) is responsible for **fine touch, vibration, and proprioception**. - It ascends ipsilaterally in the spinal cord and decussates in the medulla oblongata. *Anterior spinothalamic tract* - The **anterior spinothalamic tract** primarily carries information related to **crude touch** and **pressure**. - While part of the spinothalamic system, it does not carry pain and temperature as its primary function. *Ventral column pathway* - The term **ventral column pathway** is not a standard, precise neuroanatomical classification for a specific sensory tract. - While parts of the spinothalamic tracts (anterior and lateral) are located in the ventral/anterior funiculus of the spinal cord, "ventral column pathway" itself is not a primary sensory pathway.

Question 5: Spinal pathway mainly regulating fine motor activity?

A. Lateral corticospinal tract (Correct Answer)
B. Vestibulospinal tract
C. Anterior corticospinal tract
D. Reticulospinal tract

Explanation: ***Lateral corticospinal tract*** - This pathway contains **85-90% of corticospinal fibers** that cross at the medullary pyramids and descend in the **lateral funiculus** of the spinal cord - It is the **primary pathway for fine, precise, voluntary movements** of **distal extremities**, particularly the hands, fingers, feet, and toes - Enables intricate skilled movements like writing, buttoning, and fine manipulation due to direct monosynaptic connections to motor neurons - Damage results in loss of fine motor control and skilled movements *Anterior corticospinal tract* - Contains only **10-15% of corticospinal fibers** that descend uncrossed in the anterior spinal cord - Controls **bilateral movements of axial and proximal muscles** (neck, trunk, shoulders) - Not specialized for fine motor control of distal limbs *Vestibulospinal tract* - Regulates **posture and balance** by modulating extensor muscle tone - Coordinates head position and maintains upright posture - Does not control fine voluntary movements *Reticulospinal tract* - Modulates **muscle tone, posture, and locomotion** - Provides general motor control and autonomic regulation - Not specialized for precise, intricate fine motor movements

Question 6: Which thalamic nuclei can produce basal ganglia symptoms?

A. Lateral dorsal
B. Pulvinar
C. Ventral anterior (Correct Answer)
D. Intralaminar

Explanation: ***Ventral anterior*** - The **ventral anterior (VA)** and **ventral lateral (VL)** nuclei of the thalamus receive significant input from the **basal ganglia** and project to the motor cortex [1]. - Dysfunction in these nuclei can disrupt the basal ganglia's influence on motor control, leading to symptoms like **dyskinesia** or **rigidity** [1]. *Lateral dorsal* - The **lateral dorsal nucleus** is primarily involved in **limbic system** functions and episodic memory. - It does not have direct nor significant connections with the basal ganglia motor circuits that would produce typical basal ganglia symptoms. *Pulvinar* - The **pulvinar** is the largest thalamic nucleus, primarily involved in **visual processing**, attention, and eye movements. - While it has extensive cortical connections, it is not directly involved in the motor circuits of the basal ganglia. *Intralaminar* - The **intralaminar nuclei** (e.g., centromedian and parafascicular) receive input from the basal ganglia but primarily project diffusely to the cerebral cortex and are involved in **arousal** and consciousness [2]. - While they modulate cortical activity, their dysfunction typically wouldn't produce the classic motor symptoms associated with basal ganglia disorders.

Question 7: What is the cause of loss of pain and temperature sensation on the ipsilateral face and contralateral body due to thrombosis?

A. Thrombosis of the superior cerebellar artery
B. Thrombosis of the anterior inferior cerebellar artery (AICA)
C. Thrombosis of the posterior inferior cerebellar artery (PICA) (Correct Answer)
D. Thrombosis of the posterior cerebral artery

Explanation: ***Thrombosis of the posterior inferior cerebellar artery (PICA)*** - This pattern of **ipsilateral facial** and **contralateral body** pain and temperature loss is characteristic of **lateral medullary syndrome (Wallenberg syndrome)**, which is most often caused by PICA occlusion [1]. - The PICA supplies the **lateral medulla**, affecting the **spinal trigeminal nucleus and tract** (ipsilateral face) and the **spinothalamic tract** (contralateral body) [1]. *Thrombosis of the superior cerebellar artery* - Occlusion of the superior cerebellar artery typically causes **ipsilateral limb ataxia**, **dysarthria**, and **contralateral hemianesthesia**, primarily affecting the **cerebellum** and **midbrain**. - It does not involve the lateral medulla where the decussating pain and temperature fibers for the body and the trigeminal pathways for the face are located. *Thrombosis of the anterior inferior cerebellar artery (AICA)* - AICA occlusion typically leads to **ipsilateral deafness**, **vestibular symptoms**, **facial weakness**, and **cerebellar ataxia**, along with **contralateral loss of pain and temperature sensation** in the body, primarily due to involvement of the lower pons [2]. - While it can cause contralateral body sensory loss, it usually causes **ipsilateral facial sensory loss in a different pattern** (often involving touch and proprioception as well) or **facial paralysis**, and is less commonly associated with the classic lateral medullary syndrome sensory pattern [2]. *Thrombosis of the posterior cerebral artery* - PCA occlusion primarily affects the **occipital lobe** and parts of the **temporal lobe and thalamus**, leading to symptoms like **contralateral homonymous hemianopia**, and potentially **thalamic pain syndrome** or memory deficits. - It does not explain the combined ipsilateral facial and contralateral body pain and temperature loss pattern as seen in Wallenberg syndrome.

Question 8: Wernicke's hemianopic pupillary response is seen in lesion of-

A. Optic chiasm
B. Lateral geniculate body
C. Optic radiation
D. Optic tract (Correct Answer)

Explanation: ***Optic tract*** - Wernicke's hemianopic pupillary response describes the phenomenon where the pupil does not constrict when light is shone on the **blind (hemianopic) side of the retina** in patients with a lesion of the **optic tract**. - This response is due to the interruption of the afferent visual pathway from the affected retinal ganglion cells before they reach the **pretectal nucleus**, which mediates the pupillary light reflex. *Optic chiasm* - Lesions of the optic chiasm typically cause **bitemporal hemianopia**, affecting the temporal visual fields of both eyes. - While visual fields are affected, the pupillary light reflex pathways from the nasal retinas (which cross at the chiasm) are often spared sufficiently to maintain a light reflex. *Lateral geniculate body* - The lateral geniculate body (LGB) is a **relay station for visual information** on its way to the visual cortex. - Lesions here cause **contralateral homonymous hemianopia**, but the pupillary light reflex, which bypasses the LGB to reach the pretectal nucleus, remains intact. *Optic radiation* - The optic radiations carry visual information from the **LGB to the primary visual cortex**. - Lesions of the optic radiation result in **contralateral homonymous hemianopia or quadrantanopia**, but the pupillary reflex arc is preserved because the fibers mediating this reflex have already diverged from the visual pathway before the LGB.

Question 9: Which of the following is true about multiple sclerosis except

A. Nystagmus on adducting eye
B. One and half syndrome
C. Pendular nystagmus (Correct Answer)
D. Nystagmus on abducting eye

Explanation: ***Pendular nystagmus*** - **Pendular nystagmus** is a rhythmic oscillation of the eyes that is not typically described as a classic finding in **multiple sclerosis (MS)**. While nystagmus (involuntary eye movements) is common in MS due to demyelination in the brainstem or cerebellum, the specific pattern usually observed is **jerk nystagmus**. - **Pendular nystagmus** is characterized by equal velocity in both directions of movement, lacking a fast and slow phase, and is more commonly associated with conditions like congenital nystagmus or severe visual impairment. *Nystagmus on adducting eye* - **Nystagmus on adducting eye** is a component of **internuclear ophthalmoplegia (INO)**, which is a classic brainstem syndrome caused by demyelination in the **medial longitudinal fasciculus (MLF)** in MS [1]. - In INO, the adducting eye exhibits nystagmus, while the abducting eye shows normal movement or mild nystagmus. *One and half syndrome* - **One and a half syndrome** is a severe form of INO, indicating a more extensive lesion in the **paramedian pontine reticular formation (PPRF)** and the adjacent **medial longitudinal fasciculus (MLF)**. - This syndrome results in the inability to move one eye horizontally past the midline (half a gaze paralysis) and the other eye only in abduction (one gaze paralysis), with nystagmus in the abducting eye. It is a highly characteristic finding in MS. *Nystagmus on abducting eye* - The **abducting eye** in **internuclear ophthalmoplegia (INO)**, a common manifestation of MS, often exhibits **nystagmus**. - This is due to the compensatory increase in neural impulse to the abducting eye to overcome the weak adduction of the contralateral eye, further indicating a lesion in the **medial longitudinal fasciculus (MLF)**.

Question 10: Which of the following sensations is NOT perceived by spinal nucleus of trigeminal nerve?

A. Pain
B. Temperature
C. Proprioception (Correct Answer)
D. Crude touch

Explanation: ***Proprioception*** - **Proprioception** from the face (joints and muscles of mastication) is primarily processed by the **mesencephalic nucleus of the trigeminal nerve**, not the spinal nucleus. [3] - This nucleus is unique as it contains the primary afferent neurons for proprioception within the central nervous system. *Pain* - The **spinal nucleus of the trigeminal nerve** is the primary processing center for **pain sensation** from the face and oral cavity. [1] - It receives noxious stimuli transmitted via the trigeminal nerve and projects to higher centers for pain perception. *Temperature* - Similar to pain, the **spinal nucleus of the trigeminal nerve** processes **temperature sensation** (both warm and cold) from the face. [2] - Fibers carrying temperature information synapse here before ascending to the thalamus. *Crude touch* - **Crude touch** (non-discriminative touch) from the face is also relayed through the **spinal nucleus of the trigeminal nerve**. [2] - This contrasts with fine touch, which is mainly processed by the chief (principal) sensory nucleus of the trigeminal nerve.

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