Name the center shown as $X$ in the cut section of medulla which is responsible for control of respiration.
Q2
Identify the structure shown below. (Recent NEET Pattern 2019)
Q3
Identify the nerve marked with an arrow in the given section of cranial cavity.
Q4
A child is brought with fever and ear pain. On examination following findings are noted. The cranial nerve involved for ear pain is:
Q5
A 4-day-old neonate under phototherapy in NICU. The child has shrill cry. All are true about the acute presentation of the disease except:
Q6
At what age does maximum brain growth occur?
Q7
Arrange in sequence the structures involved in the direct pathway (1=Striatum, 2=GPi, 3=Thalamus, 4=Cortex output, 5=Cortex input):-
Q8
A 12-year-old boy is brought to his primary care physician because he has been tripping and falling frequently over the past 2 months. He says that he feels like he loses his balance easily and finds it difficult to walk in tight spaces such as his school hallways. Furthermore, he says that he has been experiencing insomnia over the same time period. His past medical history is significant for some mild allergies, but otherwise he has been healthy. Physical exam reveals that his eyes are fixed downwards with nystagmus bilaterally. Which of the following structures is most likely affected by this patient's condition?
Q9
One week after being involved in a bicycling accident, a 32-year-old woman comes to the physician because of intermittent double vision. She reports worsening of symptoms when she tries to type on her computer or while buttoning her shirts. Physical examination shows a slight right-sided head tilt. Her left eye is deviated laterally and upwards, which becomes even more prominent when she attempts left eye adduction. This patient's symptoms are most likely due to impaired innervation to which of the following muscles?
Q10
A 28-year-old man presented with gradually progressive gait disturbances since 10 years of age. His gait was clumsy and slow, and it was very difficult for him to perform brisk walking and running. After a few years, he developed tremors involving both upper limbs along with progressively increasing fatigability. Over the last several months, his friends have noticed that his speech has become slow, slurred, and sometimes incomprehensible. He has also developed difficulty in swallowing recently. On physical examination, he is vitally stable with normal sensorium and normal higher mental functions. The neurological examination reveals absent deep tendon reflexes in the lower extremities and the extensor plantar response bilaterally. Muscle tone is normal in different muscle groups with significant distal muscle wasting in the extremities. There is a marked loss of vibration and position senses. His gait is ataxic and nystagmus is present. His speech is explosive and dysarthric. The neurologist suspected a specific condition and asked for genetic testing, which identified 2 GAA trinucleotide repeat expansions. Which of the following is a correct statement related to the diagnosis of this patient?
Neuroanatomy US Medical PG Practice Questions and MCQs
Question 1: Name the center shown as $X$ in the cut section of medulla which is responsible for control of respiration.
A. Pneumotaxic centre
B. Pre-Botzinger Complex (Correct Answer)
C. Nucleus Para-brachialis
D. Dorsal group of respiratory neurons
E. Ventral group of respiratory neurons
Explanation: ***Pre-Botzinger Complex***
- The **pre-Bötzinger complex** in the medulla is crucial for generating the **respiratory rhythm** and is the primary site of inspiratory rhythmogenesis.
- It is located ventral to the nucleus ambiguus and contains **pacemaker neurons** that fire spontaneously.
*Pneumotaxic centre*
- The **pneumotaxic center** is located in the **pons**, specifically the upper pons, and primarily regulates respiratory rate and depth.
- It works by sending inhibitory signals to the inspiratory center, thereby **limiting inspiration**.
*Nucleus Para-brachialis*
- The **nucleus parabrachialis** is located in the pons and includes the pneumotaxic center, affecting the **transition between inspiration and expiration**.
- It helps in fine-tuning respiratory patterns rather than initiating the basic rhythm.
*Dorsal group of respiratory neurons*
- The **dorsal respiratory group (DRG)**, located in the medulla, primarily controls **inspiration** and receives sensory input from chemoreceptors and mechanoreceptors.
- While it initiates the basic inspiratory muscle activity, the pre-Bötzinger complex is considered the rhythm generator.
*Ventral group of respiratory neurons*
- The **ventral respiratory group (VRG)**, located in the ventrolateral medulla, contains neurons responsible for both **inspiration and expiration**.
- The pre-Bötzinger complex is actually part of the VRG and serves as the **rhythm-generating center** within this larger group.
Explanation: ***Fornix***
- The arrow points to a C-shaped bundle of **nerve fibers** in the brain that acts as the primary efferent (output) pathway of the **hippocampus**, a crucial structure for memory.
- It is located inferior to the corpus callosum and its position in the image is consistent with the anatomical location of the fornix.
*Corpus callosum*
- The corpus callosum is a large, **C-shaped nerve fiber bundle** located beneath the cerebral cortex in the longitudinal fissure, connecting the left and right cerebral hemispheres.
- While visible in the image, the arrow specifically indicates the structure immediately beneath it, which is the fornix, not the corpus callosum itself.
*Pineal gland*
- The **pineal gland** is a small endocrine gland located in the epithalamus, near the center of the brain, behind the thalamus.
- Its position is medial and inferior to the structure indicated by the arrow.
*Splenium*
- The **splenium** is the posterior, thicker part of the **corpus callosum**, forming its most caudal end.
- The arrow points to a more anterior and inferior structure than the splenium.
*Septum pellucidum*
- The **septum pellucidum** is a thin, vertical membrane separating the anterior horns of the left and right lateral ventricles.
- It is located superior and anterior to the fornix, positioned between the corpus callosum above and the fornix below, which is different from the structure indicated by the arrow.
Question 3: Identify the nerve marked with an arrow in the given section of cranial cavity.
A. Trochlear
B. Trigeminal
C. Oculomotor
D. Abducens (Correct Answer)
E. Facial
Explanation: ***Abducens***
- The image shows the abducens nerve passing through **Dorello's canal** on its way to the **cavernous sinus**.
- Its unique path makes it susceptible to injury in cases of increased intracranial pressure, leading to **lateral rectus palsy**.
*Trochlear*
- The trochlear nerve is the **smallest cranial nerve** and exits the brainstem dorsally, then wraps around to the ventral side.
- It innervates the **superior oblique muscle** of the eye.
*Trigeminal*
- The trigeminal nerve is a large cranial nerve with **three main divisions** and is responsible for sensations in the face and motor functions like chewing.
- It arises more laterally from the pons and is typically seen entering the **Meckel's cave**.
*Oculomotor*
- The oculomotor nerve emerges from the **midbrain** and controls most of the extrinsic eye muscles and pupillary constriction.
- It is usually visible superior to the abducens nerve in the **cavernous sinus**.
*Facial*
- The facial nerve exits the brainstem at the **cerebellopontine angle** and enters the **internal acoustic meatus** with the vestibulocochlear nerve.
- It controls muscles of **facial expression** and carries taste sensation from the anterior two-thirds of the tongue.
Question 4: A child is brought with fever and ear pain. On examination following findings are noted. The cranial nerve involved for ear pain is:
A. 5th nerve
B. 7th nerve
C. 9th nerve (Correct Answer)
D. 10th nerve
E. 12th nerve
Explanation: ***9th nerve***
- The **glossopharyngeal nerve (CN IX)** innervates the **nasopharynx, tonsils, soft palate, and Eustachian tube**, areas that can refer pain to the ear.
- Infection or inflammation in these structures, such as a **pharyngitis** or **tonsillitis** (as suggested by the image showing exudative tonsils), can cause **referred otalgia** via CN IX.
*5th nerve*
- The **trigeminal nerve (CN V)** primarily supplies sensory innervation to the face, teeth, and anterior two-thirds of the tongue.
- While it has a small branch (auriculotemporal) to the external ear, it is less commonly involved in referred ear pain associated with a pharyngeal infection compared to the glossopharyngeal nerve.
*7th nerve*
- The **facial nerve (CN VII)** is primarily a motor nerve for facial expression and taste sensation.
- It carries some sensory fibers from the external auditory canal, but it is not a major pathway for referred ear pain from the pharynx.
*10th nerve*
- The **vagus nerve (CN X)** innervates a wide range of structures, including parts of the pharynx, larynx, and external ear canal (Arnold's nerve).
- While it can be involved in referred otalgia, the **glossopharyngeal nerve (CN IX)** is more frequently associated with ear pain originating from the tonsillar and pharyngeal regions, especially in cases of infection.
*12th nerve*
- The **hypoglossal nerve (CN XII)** is a purely motor nerve that innervates the intrinsic and extrinsic muscles of the tongue.
- It has no sensory function and does not contribute to ear pain or referred otalgia.
Question 5: A 4-day-old neonate under phototherapy in NICU. The child has shrill cry. All are true about the acute presentation of the disease except:
A. Seizures
B. Opisthotonus
C. Retrocollis
D. Athetosis (Correct Answer)
E. Hypotonia
Explanation: ***Athetosis***
- **Athetosis** refers to slow, writhing involuntary movements, which are typically a **chronic manifestation** of severe neurological damage, such as that caused by **kernicterus**, rather than an acute presentation.
- Acute bilirubin encephalopathy primarily presents with signs of severe neurological distress but not typically with athetosis.
- This is a **late sequela** of kernicterus, appearing weeks to months after the acute injury.
*Seizures*
- **Seizures** are a common acute manifestation of **acute bilirubin encephalopathy (kernicterus)** due to bilirubin toxicity in the brain, especially in the basal ganglia.
- The **shrill cry** mentioned in the patient's presentation can be a precursor or an accompanying symptom of neurological irritation that can lead to seizures.
*Opisthotonus*
- **Opisthotonus** is a severe neurological sign characterized by **arching of the back and neck**, often due to severe spasm of the extensor muscles.
- It is a classic **acute manifestation of kernicterus**, indicating significant bilirubin-induced damage to the central nervous system.
*Retrocollis*
- **Retrocollis** is a specific type of **dystonia** characterized by involuntary **backward deviation of the head and neck**.
- This is an **acute neurological symptom** that can occur in severe cases of kernicterus as part of the overall extrapyramidal involvement.
*Hypotonia*
- **Hypotonia** (decreased muscle tone) is an **acute manifestation** of bilirubin encephalopathy.
- It occurs during the early phase of acute kernicterus along with lethargy, poor feeding, and loss of the Moro reflex.
Question 6: At what age does maximum brain growth occur?
A. 6 months (Correct Answer)
B. 1 year
C. 2 years
D. 3 years
E. 5 years
Explanation: ***6 months***
- **Brain growth** is most rapid during the early postnatal period, with the brain reaching almost **50% of its adult size by 6 months of age**.
- This period involves rapid **synaptogenesis** and myelination, crucial for early cognitive and motor development.
*1 year*
- While significant **brain growth** continues, the peak rate of increase in brain volume has typically passed by 1 year.
- At this age, the brain has reached approximately **75% of its adult size**.
*2 years*
- By 2 years, the brain is about **80% of its adult size**, indicating ongoing but slower growth compared to the first year.
- This period is more characterized by refinement of neural circuits rather than rapid volumetric expansion.
*3 years*
- At 3 years, the brain has attained around **90% of its adult size**, though important developmental changes continue.
- The rate of **neural development** at this stage largely focuses on strengthening existing connections and pruning less used ones.
*5 years*
- By 5 years, the brain has reached approximately **90-95% of its adult size**, with growth significantly slower than in earlier years.
- Development at this age focuses primarily on **synaptic pruning** and refinement of neural networks rather than volumetric growth.
Question 7: Arrange in sequence the structures involved in the direct pathway (1=Striatum, 2=GPi, 3=Thalamus, 4=Cortex output, 5=Cortex input):-
A. 1,3,4,2,5
B. 5,1,2,3,4 (Correct Answer)
C. 1,2,3,4,5
D. 5,4,2,3,1
E. 5,1,3,2,4
Explanation: ***5,1,2,3,4***
- The direct pathway of the basal ganglia begins with the **cortex** (5) sending excitatory signals to the **striatum** (1).
- The striatum then inhibits the **internal globus pallidus (GPi)** (2), which disinhibits the **thalamus** (3), leading to excitation of the **cortex** (4).
- This is the correct sequence: **Cortex input → Striatum → GPi → Thalamus → Cortex output**.
*1,3,4,2,5*
- This sequence is incorrect as it starts with the striatum instead of cortical input.
- The direct pathway does not begin with striatal activity; the cortex must first activate the striatum.
*1,2,3,4,5*
- This order is incorrect because it implies the pathway starts at the striatum rather than the cortex.
- The cortex should be the starting point (5) and the ending point (4) of the motor loop.
*5,4,2,3,1*
- This sequence is incorrect as it places cortex output (4) before the striatum receives input.
- This reverses the functional flow and does not follow the **disinhibitory mechanism** of the direct pathway.
*5,1,3,2,4*
- This sequence incorrectly places the thalamus (3) before the GPi (2).
- In the direct pathway, the striatum must first inhibit the GPi before the thalamus can be disinhibited.
Question 8: A 12-year-old boy is brought to his primary care physician because he has been tripping and falling frequently over the past 2 months. He says that he feels like he loses his balance easily and finds it difficult to walk in tight spaces such as his school hallways. Furthermore, he says that he has been experiencing insomnia over the same time period. His past medical history is significant for some mild allergies, but otherwise he has been healthy. Physical exam reveals that his eyes are fixed downwards with nystagmus bilaterally. Which of the following structures is most likely affected by this patient's condition?
A. Pineal gland (Correct Answer)
B. Cerebellum
C. Pituitary gland
D. Thalamus
E. 4th ventricle
Explanation: ***Pineal gland***
- This patient presents with the classic triad of **Parinaud syndrome** (dorsal midbrain syndrome): **downward gaze palsy** (eyes fixed downward), **bilateral nystagmus** (convergence-retraction type), and **ataxia**.
- Pineal region tumors (e.g., **germinoma**, **pineoblastoma**) compress the **tectal plate/superior colliculus** causing vertical gaze paralysis and pupillary light-near dissociation.
- **Insomnia** results from disruption of **melatonin production** by the pineal gland, which regulates circadian rhythms.
- **Ataxia** occurs secondary to **obstructive hydrocephalus** from compression of the **cerebral aqueduct** by the tumor.
- This is a **classic USMLE presentation** of a pineal region mass in a pediatric patient.
*Cerebellum*
- While cerebellar lesions cause **ataxia** and **nystagmus** (typically horizontal or rotatory), they do **NOT** cause **vertical gaze palsy** or downward fixation of eyes.
- Posterior fossa tumors like **medulloblastoma** present with coordination deficits but lack the characteristic **setting sun sign** (downward gaze) seen here.
- The combination of **downward gaze palsy + insomnia** specifically points away from isolated cerebellar pathology.
*Pituitary gland*
- Pituitary lesions primarily cause **endocrine abnormalities** (growth hormone deficiency, precocious puberty, diabetes insipidus) or **bitemporal hemianopsia** from optic chiasm compression.
- They do not typically cause **vertical gaze palsies** or the motor coordination deficits described.
*Thalamus*
- Thalamic lesions can cause **sensory deficits**, **movement disorders** (e.g., thalamic tremor), or **altered consciousness**.
- They do not cause the specific combination of **downward gaze palsy** and **insomnia** seen in this patient.
*4th ventricle*
- While **hydrocephalus** from 4th ventricle obstruction can cause headache, nausea, and papilledema, the ventricle itself is a **CSF-filled space** without neural tissue.
- The **specific downward gaze palsy** indicates tectal plate compression, which occurs with **pineal region masses**, not primary 4th ventricle pathology.
Question 9: One week after being involved in a bicycling accident, a 32-year-old woman comes to the physician because of intermittent double vision. She reports worsening of symptoms when she tries to type on her computer or while buttoning her shirts. Physical examination shows a slight right-sided head tilt. Her left eye is deviated laterally and upwards, which becomes even more prominent when she attempts left eye adduction. This patient's symptoms are most likely due to impaired innervation to which of the following muscles?
A. Superior rectus
B. Inferior oblique
C. Lateral rectus
D. Inferior rectus
E. Superior oblique (Correct Answer)
Explanation: ***Superior oblique***
- The patient's symptoms, including **intermittent double vision**, worsening with specific tasks (typing, buttoning), a **right-sided head tilt**, and a **left eye deviation (lateral and upward)** that becomes more prominent on adduction, are classic signs of **trochlear nerve (CN IV) palsy** affected the superior oblique muscle.
- The **superior oblique muscle** is responsible for **intorsion**, depression, and abduction of the eye; its paralysis leads to **extorsion** (manifested as head tilt to compensate), and vertical diplopia that worsens when looking down and in. The eye will be deviated upwards and outwards due to the unopposed action of the inferior oblique and other extraocular muscles.
*Superior rectus*
- Innervated by the **oculomotor nerve (CN III)**, this muscle primarily elevates and intorts the eye.
- Palsy would typically result in difficulty looking up, and an eye that is deviated downwards and slightly outwards, rather than the described lateral and upward deviation that worsens on adduction.
*Inferior oblique*
- Also innervated by the **oculomotor nerve (CN III)**, the inferior oblique muscle elevates, extorts, and abducts the eye.
- Palsy would lead to difficulty looking up and out, with the eye deviating downwards and inwards, which does not match the patient's presentation.
*Lateral rectus*
- Innervated by the **abducens nerve (CN VI)**, this muscle is responsible for abducting the eye.
- Palsy would cause the eye to be deviated medially (esotropia) and the inability to abduct it, resulting in horizontal diplopia, which is not the primary presentation here.
*Inferior rectus*
- Innervated by the **oculomotor nerve (CN III)**, this muscle primarily depresses and extorts the eye.
- Palsy would result in difficulty looking down, with the eye elevated and slightly intorted, which is inconsistent with the patient's specific presentation of deviation worsening on adduction.
Question 10: A 28-year-old man presented with gradually progressive gait disturbances since 10 years of age. His gait was clumsy and slow, and it was very difficult for him to perform brisk walking and running. After a few years, he developed tremors involving both upper limbs along with progressively increasing fatigability. Over the last several months, his friends have noticed that his speech has become slow, slurred, and sometimes incomprehensible. He has also developed difficulty in swallowing recently. On physical examination, he is vitally stable with normal sensorium and normal higher mental functions. The neurological examination reveals absent deep tendon reflexes in the lower extremities and the extensor plantar response bilaterally. Muscle tone is normal in different muscle groups with significant distal muscle wasting in the extremities. There is a marked loss of vibration and position senses. His gait is ataxic and nystagmus is present. His speech is explosive and dysarthric. The neurologist suspected a specific condition and asked for genetic testing, which identified 2 GAA trinucleotide repeat expansions. Which of the following is a correct statement related to the diagnosis of this patient?
A. Gait ataxia in this condition is a pure sensory ataxia
B. Restrictive cardiomyopathy is seen in approximately 50% of the patients
C. The gene locus which is mutated in this condition is on chromosome 9 (Correct Answer)
D. The condition is inherited as autosomal dominant condition
E. Vertical nystagmus is characteristically seen in patients with this condition
Explanation: ***The gene locus which is mutated in this condition is on chromosome 9***
- The patient's presentation with gradually progressive gait disturbances, tremors, dysarthria, dysphagia, absent lower extremity deep tendon reflexes, extensor plantar responses, distal muscle wasting, loss of vibration/position senses, ataxic gait, and nystagmus, along with **GAA trinucleotide repeat expansions**, is classic for **Friedreich's ataxia**.
- The genetic defect in Friedreich's ataxia involves a **GAA trinucleotide repeat expansion** in the **FXN gene** located on **chromosome 9q13**, leading to reduced frataxin protein levels.
*Gait ataxia in this condition is a pure sensory ataxia*
- While **sensory ataxia** due to dorsal column dysfunction (loss of vibration and position sense) is a prominent feature, the ataxia in Friedreich's ataxia also has a significant **cerebellar component** as evidenced by dysarthria and nystagmus.
- Therefore, it is a **mixed sensory and cerebellar ataxia**, not a pure sensory ataxia.
*Restrictive cardiomyopathy is seen in approximately 50% of the patients*
- **Hypertrophic cardiomyopathy** is a common cardiac manifestation in Friedreich's ataxia, affecting approximately 60-90% of patients, and is a significant cause of morbidity and mortality.
- **Restrictive cardiomyopathy** is not a characteristic feature of Friedreich's ataxia.
*The condition is inherited as autosomal dominant condition*
- Friedreich's ataxia is inherited in an **autosomal recessive** pattern, meaning an individual must inherit two copies of the mutated gene (one from each parent) to develop the condition.
- The presence of the disease in only one parent would not lead to the child having the condition in an autosomal recessive inheritance pattern.
*Vertical nystagmus is characteristically seen in patients with this condition*
- Although nystagmus is common in Friedreich's ataxia, it is typically **horizontal nystagmus** or gaze-evoked nystagmus.
- **Vertical nystagmus** is more characteristic of other neurological conditions and is not a hallmark of Friedreich's ataxia.
