Differential Diagnosis

The patient's complex presentation of progressive neuropathy, cognitive decline, and cardiac symptoms requires a thorough evaluation of potential diagnoses. The following categories outline the differential diagnosis:

• Single most likely diagnosis
  • Multifocal motor neuropathy with conduction block: This diagnosis is considered due to the patient's progressive neuropathy, weakness, and muscle atrophy, particularly in the legs. The presence of conduction block on EMG studies would support this diagnosis. However, the patient's EMG results are reported as normal, which may argue against this diagnosis.
• Other Likely diagnoses
  • Amyotrophic lateral sclerosis (ALS): The patient's progressive weakness, muscle atrophy, and difficulty with gait, combined with the presence of cognitive decline, make ALS a possible diagnosis. However, the absence of clear upper motor neuron signs and the normal EMG results may argue against this diagnosis.
  • Lewy body dementia: The patient's cognitive decline, visual hallucinations (geometric design), and fluctuating symptoms, such as sudden fatigue and dizziness, are consistent with Lewy body dementia.
  • Autonomic dysfunction: The patient's symptoms of orthostatic intolerance, tachycardia, and syncopal episodes suggest autonomic dysfunction, which could be related to various underlying conditions, including autoimmune disorders or neurodegenerative diseases.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Multiple sclerosis: Although the patient's brain MRI showed T2 hyperintensities, the clinical presentation is not typical for multiple sclerosis. However, it is essential to consider this diagnosis due to the potential for severe disability and the availability of disease-modifying treatments.
  • Vasculitis: The patient's symptoms of neuropathy, cognitive decline, and cardiac involvement could be related to a vasculitic process, such as giant cell arteritis or primary central nervous system vasculitis.
  • Cardiac arrhythmia: The patient's history of atrial fibrillation and the presence of heart rate spikes over 200 bpm on the loop recorder highlight the importance of considering cardiac arrhythmias as a potential cause of syncope and other symptoms.
• Rare diagnoses
  • Tangier disease: This rare genetic disorder is characterized by neuropathy, cognitive decline, and cardiac symptoms, which are similar to the patient's presentation.
  • Sjögren's syndrome: Although the patient does not have a clear history of dry eyes or mouth, Sjögren's syndrome can cause neuropathy, cognitive decline, and cardiac symptoms, making it a rare but possible diagnosis to consider.