Question 1

Lesions rostral to the red nucleus result in which of the following?&#10;A) Lower extremity weakness&#10;B) Upper limb flexion and lower limb extension&#10;C) Loss of pain and temperature sensation&#10;D) Deviation of the tongue on protrusion&#10;E) Weakness of the masticatory muscles

Accepted Answer

Lesions rostral to the red nucleus, such as in the midbrain, can affect the rubrospinal tract, which is involved in motor control. The red nucleus has a role in facilitating flexor tone in the upper limbs and inhibiting it in the lower limbs. Therefore, damage above this level can result in increased flexor tone in the upper limbs and increased extensor tone in the lower limbs, leading to the posture described in option B.

Question 2

A 58-year-old woman complains of left hand weakness that she noticed while planting flowers in her garden. Neurological examination indicates weak wrist and finger flexion and extension. She also has weakness when abducting, adducting, and opposing her thumb. All other motor and sensory tests are normal. The combined deficits in this patient can most accurately be attributed to a lesion in which of the following?

A) Left precentral gyrus
B) Left postcentral gyrus
C) Right postcentral gyrus
D) Right precentral gyrus
E) Superior frontal gyrus

D

Accepted Answer

The right precentral gyrus is responsible for motor control of the left side of the body. The weakness in wrist and finger movements, as well as thumb movements, suggests a motor deficit, indicating a lesion in the right precentral gyrus.

Question 3

A 24-year-old woman is brought to the emergency department from the scene of a motor vehicle collision. A neurological examination reveals that her tongue deviates to the left on protrusion and that she is unable to raise the right corner of her mouth when asked to smile. In addition, she is unable to move the entire right side of her body. Which of the following represents the most likely location of a lesion?

A) Right anterior limb of the internal capsule
B) Pontine tegmentum
C) Left posterior limb of the internal capsule
D) Right precentral gyrus
E) Pyramidal decussation

C

Accepted Answer

The symptoms described indicate a lesion that affects both the cranial nerves and the motor pathways controlling the body's right side. The tongue deviation to the left suggests a lower motor neuron lesion of the hypoglossal nerve (CN XII), which innervates the tongue muscles. The inability to raise the right corner of the mouth indicates facial nerve (CN VII) involvement, and the inability to move the entire right side of the body suggests a lesion in the motor pathway above the decussation (crossing) in the medulla. Since motor fibers decussate (cross over) to the opposite side, a lesion in the left posterior limb of the internal capsule would affect the right side of the body and could also impact the cranial nerve nuclei or fibers due to its proximity to those pathways as they travel to the brainstem.

Question 4

A 32-year-old woman visits her dermatologist several days before her wedding for botulinum toxin injections around her eyes. What effect does this toxin have on the neuromuscular junction?&#10;A) Blocks release of acetylcholine&#10;B) Stimulates muscarinic cholinergic receptors&#10;C) Depletes norepinephrine&#10;D) Enhances release of acetylcholine esterase&#10;E) Stimulates nicotinic cholinergic receptors

Accepted Answer

Botulinum toxin blocks the release of acetylcholine at the neuromuscular junction, leading to muscle relaxation. This is why it is used cosmetically to reduce wrinkles.

Question 5

A 53-year-old man complains to his family physician of cramping, twitching, and weakness in his lower limbs. The man states that the weakness in his lower limbs has progressively worsened over the past 4 months, making it difficult for him to climb stairs and stand from a seated position. He has also begun to notice that his upper limbs have become weak. What is the most likely cause of this patient's weakness?

A) Myasthenia gravis
B) Syringomyelia
C) Charcot-Marie Tooth disease
D) Spinocerebellar ataxia
E) Amyotrophic lateral sclerosis

Accepted Answer

Amyotrophic lateral sclerosis (ALS) is characterized by progressive weakness due to the degeneration of both upper and lower motor neurons, which matches the symptoms described.

Question 6

A 35-year-old roofer is examined in the emergency department after falling two stories and landing abdomen first on a barrel. Examination reveals weakness and loss of pain and temperature sensation in the left and right lower limbs. A magnetic resonance image indicates thrombosis of an artery in the abdomen. Which of the following arteries is most likely involved?

A) Anterior spinal
B) Abdominal aorta
C) Anterior radicular
D) Posterior spinal
E) Posterior radicular

Accepted Answer

The anterior spinal artery supplies the anterior two-thirds of the spinal cord, including areas responsible for motor function and pain and temperature sensation. Thrombosis of this artery can lead to weakness (due to motor pathway involvement) and loss of pain and temperature sensation in the lower limbs, as described in the scenario.

Question 7

A 52-year-old woman unable to move her left leg visits your office. Sensory modalities in all of her limbs are retained and there appears to be no sign of weakness in any of her other limbs. In which of the following structures are the cell bodies of lower motor neurons innervating the lower limb located?

A) Lamina I-VI
B) Lamina VIII, IX
C) Lamina X
D) Lamina I, II
E) Lamina III, IV

Accepted Answer

The cell bodies of lower motor neurons innervating the lower limb are located in Lamina VIII and IX of the spinal cord. These laminae are part of the ventral horn, where motor neurons that project to skeletal muscles are found.

Deck 9: Sensory Receptors and the Peripheral Nervous System