AANP Family Nurse Practitioner (FNP) Certification ExamAssessmentMedium
A 45-year-old female presents with a 6-month history of progressive fatigue, generalized weakness, and occasional double vision, especially at the end of the day. She also reports difficulty chewing and swallowing after prolonged meals. On physical examination, ptosis is noted, which worsens with sustained upward gaze. Which diagnostic test is most appropriate for initial evaluation?
- AThyroid stimulating hormone (TSH) and free T4
- BBrain MRI with and without contrast
- CElectromyography (EMG) with nerve conduction studies (NCS)
- DAcetylcholine receptor (AChR) antibody test
Show answer & explanationAnswer & explanation
Correct answer: D. Acetylcholine receptor (AChR) antibody test
The patient's symptoms of fluctuating muscle weakness that worsens with activity and improves with rest, ptosis, diplopia, and bulbar symptoms (difficulty chewing/swallowing) are highly characteristic of Myasthenia Gravis. The acetylcholine receptor (AChR) antibody test is the most specific and commonly used initial diagnostic test for this condition.
Why the other options are wrong
- A. While fatigue can be a symptom of thyroid dysfunction, the specific pattern of fluctuating muscle weakness, ptosis, and bulbar symptoms is not typical of hypothyroidism.
- B. Brain MRI would be considered if central nervous system pathology were suspected (e.g., stroke, MS), but the clinical presentation points to a neuromuscular junction disorder, not a brain lesion.
- C. EMG with NCS may show decremental response with repetitive nerve stimulation, which supports a diagnosis of Myasthenia Gravis, but the AChR antibody test is often the first-line and most specific serological test.
Myasthenia Gravis Diagnosis
An autoimmune disorder characterized by fluctuating muscle weakness that worsens with activity and improves with rest, due to antibodies against acetylcholine receptors at the neuromuscular junction.
- Cardinal symptoms include ptosis, diplopia, dysphagia, and generalized fatigable weakness.
- Acetylcholine receptor (AChR) antibody test is the primary diagnostic assay.
- Ice pack test and edrophonium test (Tensilon test) can also be used for diagnosis.
Memory trick: MG: Muscles Get Weak, Getting Worse with Work.