A patient has symptoms that are characteristic of multiple sclerosis (MS). Which diagnostic tests are likely to be ordered to aid in the diagnosis of this patient?

Choice A rationale

Myasthenia gravis primarily affects voluntary muscles, especially those involved in breathing and facial movements. Gastrointestinal (GI) and lower extremity muscles are generally not the main muscles affected by this condition. It is an autoimmune disorder that impacts the neuromuscular junction, where nerves communicate with muscles, leading to muscle weakness and fatigue.

Choice B rationale

The central nervous system (CNS), memory, and cognition are not typically impacted by myasthenia gravis. This disorder primarily involves peripheral nervous system issues that affect voluntary muscle control rather than cognitive functions. Myasthenia gravis does not cause alterations in memory or cognition as seen with central nervous system disorders like Alzheimer's disease.

Choice C rationale

Myasthenia gravis notably affects respiratory and facial muscles. The autoimmune attack on acetylcholine receptors leads to muscle weakness, particularly in muscles controlling eye movements, facial expressions, and breathing. Patients may experience difficulty breathing, swallowing, and maintaining an open airway due to this muscle weakness.

Choice D rationale

The cardiovascular system and postural muscles are not commonly affected by myasthenia gravis. This condition involves the neuromuscular junction and leads to fatigue in voluntary muscles, primarily those involved in eye movement, facial expressions, and respiration. Cardiovascular symptoms are not a direct consequence of myasthenia gravis.

Choice A rationale

Parkinson's disease is characterized by an imbalance of dopamine and acetylcholine, primarily due to the degeneration of dopamine-producing neurons in the substantia nigra. This imbalance results in the characteristic motor symptoms of Parkinson's disease, such as tremors, rigidity, and bradykinesia.

Choice B rationale

Parkinson's disease involves decreased dopamine production, not increased. The disease is caused by the progressive loss of dopamine-producing neurons in the brain, leading to reduced dopamine levels and an imbalance with acetylcholine.

Choice C rationale

Alzheimer's disease is not primarily characterized by a decrease in dopamine. Instead, it involves the degeneration of cholinergic neurons and a deficiency in acetylcholine, which is crucial for memory and cognitive functions.

Choice D rationale

Alzheimer's disease is associated with a deficiency of acetylcholine rather than an excess. The disease is also characterized by the presence of neuritic plaques and neurofibrillary tangles in the brain, which contribute to cognitive decline.