Clinical neuroscience with illustrative cases Flashcards
What are the main components of the motor axis?
The motor axis includes the upper motor neurons (UMN), lower motor neurons (LMN), neuromuscular junction (NMJ), and muscles
What role do the basal ganglia and cerebellum play in motor function?
The basal ganglia and cerebellum are involved in the quality and quantity of movement, but lesions in these areas do not typically result in weakness
What is the reflex arc, and why is it important?
The reflex arc consists of an afferent sensory neuron and an efferent LMN. It prevents overstretching of muscles, maintains posture, and generates tone. UMN input modulates and regulates this arc
What changes occur in the reflex arc in UMN and LMN lesions?
In UMN lesions, reflexes become brisk due to loss of higher-level modulation. In LMN lesions, the reflex arc is broken, resulting in absent reflexes and muscle wasting(
What is a common sign of an LMN lesion?
LMN lesions commonly result in hypotonia, absent reflexes, and denervative changes like muscle wasting and fasciculations
Describe the presentation of a spinal cord lesion affecting the thoracic level.
A thoracic spinal cord lesion may present with full power in the arms, no power in the legs, hyperreflexic leg reflexes, and sensory loss to pinprick up to the umbilicus
What does the “Owl’s Eye” sign on an MRI of the spinal cord indicate?
The “Owl’s Eye” sign is typically seen with a cord infarct in the thoracic spine
In which type of nerve lesion are reflexes usually not affected?
Reflexes are typically not affected in ulnar nerve lesions, as they do not contribute to the reflexes tested in the arm
What could cause dermatomal weakness and numbness in a single limb?
This could be due to a peripheral nervous system issue, potentially involving a nerve root, plexus, or distal nerve
