Which pathophysiologic change is found in the brain tissue of people who have Alzheimer's disease?

A. Carbidopa itself does not cross the blood-brain barrier. Its primary role in Sinemet is to inhibit the peripheral breakdown of levodopa (the precursor of dopamine) into dopamine before it reaches the brain.
B. It is true that it may take a few weeks to see the full effects of this medication, as the body needs time to adjust to it.
C. Parkinson's disease is progressive, and as the disease advances, the dosage and frequency of levodopa with carbidopa may need to be adjusted to maintain symptom control. Over time, higher doses or additional medications may be required to manage symptoms effectively.
D. Levodopa does not protect Carbidopa; rather, Carbidopa protects Levodopa from early conversion to dopamine outside the brain, which would make it less effective.

A. MS is a chronic autoimmune disorder affecting the central nervous system (CNS), specifically the brain and spinal cord. It typically presents with a wide range of neurological symptoms such as blurred vision, sensory disturbances, weakness, and difficulties with coordination and balance. However, MS does not typically present with a sudden onset of ascending numbness and weakness starting in the feet and moving upwards.
B. GBS is an acute autoimmune disorder where the immune system attacks the peripheral nervous system. It often starts with numbness, tingling, and weakness in the feet and legs, which then

progresses symmetrically upwards to involve the upper limbs and potentially affect respiratory muscles. This ascending pattern of weakness is characteristic of GBS, making it the most likely diagnosis in this scenario.
C. Myasthenia gravis is a chronic autoimmune disorder affecting neuromuscular junctions, leading to muscle weakness and fatigue, especially with repetitive use. It typically presents with fluctuating muscle weakness that worsens with activity and improves with rest. The pattern of ascending numbness and weakness seen in the scenario does not align with the typical presentation of myasthenia gravis.
D. Parkinson's disease is a progressive neurological disorder primarily affecting movement. It presents with symptoms such as tremors, bradykinesia (slowness of movement), rigidity, and postural instability. It does not typically cause numbness or a symmetrical ascending pattern of weakness as described in the scenario.