Differential Diagnosis for the 86-year-old Patient

The patient's symptoms suggest a complex clinical picture that could be indicative of several conditions. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Multi-System Atrophy (MSA): This condition is characterized by a combination of symptoms including orthostatic hypotension, incontinence, and motor symptoms such as rigidity and tremors. The patient's flailing of legs during sleep could be indicative of REM sleep behavior disorder, which is often associated with MSA. Hot flashes, particularly with a temperature discrepancy between the face and the rest of the body, can also occur. The constellation of these symptoms makes MSA a strong consideration.

• Other Likely Diagnoses

  • Parkinson's Disease (PD): While PD primarily presents with motor symptoms like tremors, rigidity, and bradykinesia, some patients can experience autonomic dysfunction (like orthostatic hypotension) and REM sleep behavior disorder. However, the presence of significant autonomic symptoms early in the disease course is more suggestive of MSA.
  • Dementia with Lewy Bodies (DLB): This condition can present with cognitive decline, visual hallucinations, and fluctuations in alertness and attention. Some patients with DLB may also experience REM sleep behavior disorder and autonomic dysfunction, but the primary presentation is usually cognitive.
  • Autonomic Dysfunction: This can be a standalone condition or part of other neurodegenerative diseases, presenting with orthostatic hypotension, urinary incontinence, and other autonomic symptoms.

• Do Not Miss Diagnoses

  • Neurosyphilis: Although rare, neurosyphilis can present with a wide range of neurological symptoms, including autonomic dysfunction, and can mimic other neurodegenerative diseases. It's crucial to consider and rule out due to its treatable nature.
  • Pernicious Anemia: Vitamin B12 deficiency can cause a range of neurological symptoms, including gait disturbances that could lead to falls, and autonomic dysfunction. It's easily treatable and thus important not to miss.
  • Spinal Cord Lesions: Lesions in the spinal cord, whether due to trauma, infection, or tumors, can cause a variety of symptoms including autonomic dysfunction, incontinence, and motor symptoms.

• Rare Diagnoses

  • Pure Autonomic Failure (PAF): A rare condition characterized by progressive autonomic dysfunction without other significant neurological symptoms. It could be considered if the patient's primary symptoms are autonomic without significant motor or cognitive findings.
  • Familial Dysautonomia (Riley-Day Syndrome): A rare genetic disorder that affects the development of the autonomic nervous system, presenting with a variety of autonomic symptoms. However, it typically presents in infancy, making it unlikely in an 86-year-old patient unless the diagnosis was missed or the patient has a very mild or atypical form.