Case 19 Questions 1-20

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Question 1

Newborn girl has been noticed to have a cleft lip. She is otherwise well. What is the most likely embryological abnormality?

  1. Failure of fusion of palatal shelves
  2. Failure of fusion of medial nasal prominence and maxillary prominence
  3. Breaking down of oropharyngeal membrane
  4. Persistence of pharyngeal clefts
  5. Failure of neural tube closure

The correct answer is option b, Failure of fusion of medial nasal prominence and maxillary prominence

Failure of fusion of palatal shelves causes cleft palate; Breaking down of oropharyngeal membrane leads to formation of oral cavity; Persistence of pharyngeal cleft leads to branchial cyst formation.

Question 2

Each pharyngeal arch is innervated by an arch-associated cranial nerve. Which cranial nerve is associated with the second arch?

  1. Trigeminal nerve
  2. Facial nerve
  3. Vestibulocochlear nerve
  4. Glossopharyngeal nerve
  5. Vagus nerve

The correct answer is option b, Facial nerve

The nerve associated with the second pharyngeal arch is the facial nerve (CN VII). It innervates all the muscular derivatives of the 2nd arch – the muscles of facial expression, stapedius, stylohyoid, platysma and the posterior belly of digastric. Trigeminal nerve is associated with first arch; glossopharyngeal with the third; vagus with the fourth.

Question 3

Which derivative is formed from the first pharyngeal pouch

  1. Eustachian tube and middle ear cavity
  2. Lining of the palatine tonsils
  3. Thymus
  4. Inferior parathyroid glands
  5. Superior parathyroid glands

The correct answer is option a, Eustachian tube and middle ear cavity

Lining of the palatine tonsils is derived from second pouch; thymus and inferior parathyroid gland from the third; superior parathyroid gland from the fourth.

Question 4

During neck surgery in the posterior triangle, there is a relatively high risk of an injury to one of the nerves due to its superficial location. What complication patient might experience due to the injury of this nerve?

  1. Inability to cough
  2. Loss of sensation to the elbow
  3. Weakness of the shoulder
  4. Absence of gag reflex
  5. Problems swallowing

The correct answer is option c, Weakness of the shoulder

Accessory nerve runs superficially in the posterior triangle of the neck. Damage to this nerve can lead to shoulder pain, weakness of trapezius muscle and winging of the scapular.

Question 5

A young woman presents with right-sided loss of fine-touch and vibration sensation. She also exhibits ipsilateral loss of proprioception. Which anatomical structure has likely been damaged?

  1. Left dorsal column
  2. Left spinothalamic tract
  3. Right dorsal column
  4. Right spinocerebellar tract
  5. Left spinothalamic tract

The correct answer is option c, Right dorsal column

This patient has a lesion to her dorsal column, as this part of the spinal cord is involved in fine-touch and vibration sensation, and proprioception. Dorsal column lesions are commonly caused by vitamin B12 deficiency (subacute combined degeneration of the cord) and trauma to the spinal cord, among other mechanisms.

The spinocerebellar tract and spinothalamic tract are not; they are involved in coordination and pain sensation, respectively. As this patient’s symptoms are on the right, the right dorsal column is the location of the lesion as each side of the spinal cord innervates the ipsilateral side of the body.

Question 6

A patient presents with sudden onset slurring of speech and left-sided weakness. On examination, you note left sided upper limb and facial weakness. On questioning, he understands your questions and is able to answer, but his speech is slurred. A lesion at which site of the following sites is most likely to cause dysarthria?

  1. Wernicke’s area
  2. Primary sensory cortex
  3. Broca’s area
  4. Corticobulbar tract
  5. Occipital lobe

The correct answer is option d, Corticobulbar tract

The correct answer is the corticobulbar tract. Dysarthria describes the failure to articulate speech. Articulation of speech is primarily a motor skill, involving the mouth and tongue. As the corticobulbar tract carries motor innervation to the cranial nerves (including the hypoglossal nerve which innervates the tongue), a lesion of the corticobulbar tract can cause problems with the articulation of speech. Lesions of the corticobulbar tract may also produce other cranial nerve signs, such as paralysis of the muscles of facial expression or problems swallowing.

Question 7

The thalamus acts as a relay for sensory information entering the cortex from the peripheries. Which of the following nucleus of the thalamus is responsible for conveying auditory input from the vestibulocochlear nerve (cranial nerve VIII) to the primary auditory cortex?

  1. Ventro-posterior medial nucleus
  2. Ventro-posterior lateral nucleus
  3. Ventral anterior nucleus
  4. Medial geniculate nucleus
  5. Lateral geniculate nucleus

The correct answer is option d, Medial geniculate nucleus

The two geniculate nuclei are responsible for carrying auditory and visual sensory information. The medial geniculate sits above the tegmentum and takes input from the inferior colliculus which in turn takes input from the contralateral vestibulocochlear nerve via the inferior olive. The lateral geniculate sits at the end of the optic tracts and conveys visual information.

The ventral anterior nucleus receives input regarding unconscious proprioception from the cerebellum. The medial and lateral ventro-posterior nuclei carry somatosensory information from the face and body respectively.

Question 8

Neurones in brain cortex have a laminar alignment, with different layers containing different types of neurones and performing different functions. Which layer consists mainly of Stellate cells and performs a function of the main input cortical station?

  1. Molecular (plexiform) layer
  2. External granular layer
  3. External pyramidal layer
  4. Internal granular layer
  5. Internal pyramidal layer

The correct answer is option d, Internal granular layer

Internal granular layer is the main input cortical station (meaning that most of the stimuli from the periphery, arrive here), and for that reason, it is specially developed within the sensory areas.

Question 9

Which of the following is most indicative of pathology affecting the sciatic nerve?

  1. Decreased power when flexing the knee
  2. Increased tone in the muscles of the leg
  3. Increased knee jerk reflex
  4. Fasciculations in affected muscles
  5. Spastic paralysis in affected muscles

The correct answer is option

option d is the only LMN sign. The sciatic nerve is a LMN.
option a is common to both UMN and LMN pathologies.
Options 2, 3, and 5 are UMN signs.

Question 10

Which of the following is the best description of the motor pathway which controls head movement in response to visual stimuli, for example tracking a moving object?

  1. Located in the posterior spinal column
  2. Decussates at the level of the pyramids of the medulla
  3. Originates at the superior colliculus
  4. Originates in the reticular formation
  5. The primary neurones pass through the internal capsule

The correct answer is option c, Originates at the superior colliculus

option a, tectospinal pathway is located in the anterior (ventral) spinal column. The dorsal column is located in the posterior spinal column
Options 2, tectospinal pathway decussates at the level of the red nucleus and superior colliculus.
option d, the reticulospinal tract originates in the reticular formation.
option e, the internal capsule contains the corticospinal and corticobulbar tracts as well as some sensory neurons.

Question 11

Where do tertiary neurones communicating fine touch information whose primary neurones originate in the feet terminate?

  1. Post-central gyrus, medial portion
  2. Post-central gyrus, lateral portion
  3. Pre-central gyrus, medial portion
  4. Pre-central gyrus, lateral portion
  5. Pre-central gyrus, anterior portion

The correct answer is option a, Post-central gyrus, medial portion

Post-central gyrus contains the primary somatosensory cortex which is where the fine touch pathway terminates. The medial portion receives the fibers from the gracilis fasciculus. As according to the cortical homunculus.

Question 12

Which of the following best describes the course of a secondary neurone in the anterolateral tract?

  1. Cell body located in the ventral horn of a spinal segment ascending ipsilaterally decussating in the medulla and synapsing in the thalamus
  2. Cell body located in the ventral horn of a spinal segment crossing contralaterally at the same level and ascending and synapsing in the cortex
  3. Cell body located in the ventral horn of a spinal segment crossing contralaterally at the same level and ascending and synapsing in the thalamus
  4. Cell body located in the dorsal horn of a spinal segment ascending ipsilaterally, decussating in the medulla and synapsing in the thalamus
  5. Cell body located in the dorsal horn of a spinal segment crossing contralaterally at the same level and ascending and synapsing in the thalamus

The correct answer is option e

Cell body located in the dorsal horn of a spinal segment crossing contralaterally at the same level and ascending and synapsing in the thalamus
option a-3 are not true of any sensory nerve fibre as all sensory fibres pass through the dorsal horn.
option d describes fibres in the dorsal column.
option e describes fibres in the anterolateral or spinothalamic tract.

Question 13

The skin contains many receptors for different types of stimulus. Which of the following best describes the mechanism for stimulating an action potential in a nociceptor?

  1. Mechanoreceptor contains friable cells that release Na+ when burst in response to a high threshold pressure
  2. Mechanoreceptor responds to low threshold pressure by deforming and opening pressure-sensitive K+ channels
  3. Mechanoreceptor responds to low threshold pressure by deforming and opening pressure-sensitive Na+ channels
  4. Free nerve ending that responds to stimuli greater than a high threshold by opening Na+ channels
  5. Free nerve ending that responds to stimuli greater than a low threshold by opening Na+ channels

The correct answer is option d, Free nerve ending that responds to stimuli greater than a high threshold by opening Na+ channels

option d describes a nociceptor as it is in response to a high threshold. All other skin receptors respond at a low threshold.
option a-2 do not describe any skin receptor
option c describes a Pacinian corpuscle.

Question 14

Which of the following is true with regards to the initiation of movement?

  1. The cerebellum receives input from fibres of the dorsal column to adjust the intended movement
  2. The cerebellum plays an active role in deciding the movement
  3. The decision to move originates in the pre-central gyrus
  4. The amygdala is responsible for excitation, causing movement due to its role in learned movement
  5. The body of the descending motor neurone originates in the basal ganglia

The correct answer is option a, The cerebellum receives input from fibres of the dorsal column to adjust the intended movement

option a is correct; cerebellum receives input from proprioceptive fibres and adjust movement accordingly.
option b, cerebellum plays a passive role and adjusts the pre-determined movement
option c, the decision to move originates in the posterior parietal cortex, not in the primary motor cortex
option d, amygdala does not have a major role in learned movement and the basal ganglia as a whole are responsible for inhibition, not excitation of movement
option e, the body of the descending motor neuron originates in the pre-central gyrus (1° motor cortex)

Question 15

Which receptor is found on the cell membrane of a muscle fibre as part of the neuromuscular junction?

  1. Glutamate receptor
  2. Alpha adrenergic receptor
  3. Nicotinic receptor
  4. Muscarinic receptor
  5. 5-HT3 receptor

The correct answer is option c, Nicotinic receptor

option a and 5 are incorrect, not present in LMN synapses.
option b is found at the pre-ganglionic synapse in sympathetic nerves
option d is found at the pre-ganglionic synapse in parasympathetic nerves.

Question 16

Which of the following is the best description of a motor unit?

  1. A single motor neurone synapses with a single muscle fibre to form a single neuromuscular junction
  2. A single motor neurone synapses with multiple muscle fibres to form a single neuromuscular junction
  3. A single motor neurone synapses with multiple muscle fibres to form multiple neuromuscular junctions
  4. Multiple motor neurones synapse with a single muscle fibre to form a single neuromuscular junction
  5. Multiple motor neurones synapse with all the muscle fibres of a muscle to form multiple neuromuscular junctions

The correct answer is option c, A single motor neurone synapses with multiple muscle fibres to form multiple neuromuscular junctions

Question 17

Which of the following is the best description of a dermatome?

  1. Area where muscles are innervated by a pair of spinal nerves
  2. Area where muscles are innervated by a single spinal nerve
  3. Area of skin which is innervated by a pair of spinal nerves
  4. Area of skin which is innervated by a single spinal nerve
  5. Area of skin which is innervated by all spinal nerves from a vertebra

The correct answer is option d, Area of skin which is innervated by a single spinal nerve

Question 18

A patient present to the ED with a left hemisection of their T12 vertebrae. Which of the following patterns of presentation best fits this pathology?

  1. Moderate weakness and paraesthesia on their left side, increased pain and temperature sensation on their right side
  2. Moderate weakness and paraesthesia on their left side, decreased pain and temperature sensation on their right side
  3. Paralysis and loss of fine touch and proprioception on their left side, increased pain and temperature sensation on their right side
  4. Paralysis and loss of fine touch and proprioception on their left side, decreased pain and temperature sensation on their right side
  5. Paralysis, loss of fine touch, proprioception, pain, and temperature sensation on both sides

The correct answer is option d, Paralysis and loss of fine touch and proprioception on their left side, decreased pain and temperature sensation on their right side

Motor, fine touch, and proprioceptive fibres decussate at the level of the medulla. Pain and temperature fibres decussate at the level they leave the spinal cord. So motor, fine touch, and proprioceptive is lost on the ipsilateral side of damage and pain and temperature is lost on the contralateral side.

It is worth noting that 10% of corticospinal fibres descend ipsilateral to the side of origin and decussate at the level in a similar layout to spinothalamic tracts. However, these fibres tend to innervate axial muscles like the trunk so any motor loss is harder to notice and the literature suggests is not always present.

Question 19

A person with loss of balance may have damage to which structure?

  1. The spinocerebellum
  2. The neocerebellum
  3. The flocculonodular lobe
  4. The basal ganglia
  5. The thalamus

The correct answer is option c, The flocculonodular lobe

The flocculonodular lobe,I.e. the vestibulocerebellum. This is involved in posture and balance as it receives and sends information from and to the vestibular nucleus (the nucleus which contains cell bodies of the vestibular nerve, which originates from the inner ear). Damage to this area results in balance loss and subsequent falls.
The spinocerebellum. This part of the cerebellum contains the vermis, the fastigial nucleus and the intermediate cerebellum. It receives information from the spinal cord, hence its name, and uses this information to modify descending motor commands as the movement is happening. It then feeds back up to the red nucleus. Signs of damage may include ataxia (lack of voluntary coordination of movement) and hypotonia (due to loss of activity of pontoreticulospinal fibres).
The neocerebellum. This is the lateral part of the hemisphere of the cerebellum but also consists of the dentate nucleus. It is involved in the initiation and planning of movement, and motor learning. It receives input from the cerebral cortex and outputs to the premotor cortex via the thalamus. Signs of damage include bradykinesia, speech impairment, dysdiadochokinesis, rebound phenomena, and intention tremor.
The basal ganglia. The basal ganglia are a group of nuclei situated at the top of the midbrain, with strong connections to the cortex, thalamus and brainstem (but not the spinal cord). They receive input from the cortex (areas involved in planning and execution of movement) and feedback to the thalamus. They are important in the initiation and control of movement. Damage to the basal ganglia may result in conditions such as Parkinson’s (loss of dopaminergic neurones in the substantia nigra leading to difficulty initiating movement, i.e. bradykinesia), or Huntington’s.
The thalamus. This is the ‘relay centre’ which receives input from the basal ganglia and cerebellum, and feeds back to the cerebral cortex. Every sensory system (except the olfactory) has a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area for interpretation.

Question 20

Which sensory receptor is responsible for sensation of light touch?

  1. Merkel cell
  2. Hair follicle receptor
  3. Pacinian corpuscle
  4. Ruffini corpuscle
  5. Meissner corpuscle

The correct answer is option a, Merkel cell

Merkel cell. Mechanoreceptor which detects touch – is an on/off receptor. Has a small receptive field and is a type II fibre.
Hair follicle receptor.Mechanoreceptor which detects motion of the hair follicle e.g. wind blowing, and is only present where we have hair follicles. Type II fibre.
Pacinian corpuscle. Mechanoreceptor which detects pressure and vibration at a higher frequency (60-300Hz) and has a large receptive field. Type II fibre.
Ruffini corpuscle. Mechanoreceptor to do with skin stretch/slippage. As you are holding on to something and it starts to slip, these receptors detect this and there is a reflex to grip whatever you are holding on to. Large receptive field, type II fibre.
Meissner corpuscle. A mechanoreceptor which detects tap or flutter from 5-40Hz, has a small receptive field and is a type II fibre. Is more to do with pressure and vibration.

Credits

  • 1-10 (Mariia Akulich, 5th year)
  • 11-19 (Theo Randall, 3rd year)
  • 20 (Molly Mercurio, 3rd year)