Differential Diagnosis for Left Leg Weakness in an 87-Year-Old Male
Given the patient's presentation of left leg weakness with full perfusion, no history of falls, no tenderness, no changes in sensation, and a normal neuro exam, the following differential diagnoses are considered:
- Single Most Likely Diagnosis
- Peripheral Artery Disease (PAD): Although the patient has full perfusion, intermittent claudication or PAD could still be a consideration, especially in an elderly patient with potential risk factors for atherosclerosis. The normal neuro exam and lack of sensory changes might suggest a vascular rather than a neurological cause.
- Other Likely Diagnoses
- Musculoskeletal Issues (e.g., Muscle Strain, Tendinitis): These could cause weakness without sensory changes, especially if the patient has been active or experienced minor, unreported trauma.
- Electrolyte Imbalance: Conditions like hypokalemia or hyperkalemia can cause muscle weakness. Given the patient's age, electrolyte imbalances could occur due to various reasons, including medication side effects or underlying renal issues.
- Medication Side Effects: Certain medications, such as statins, can cause muscle weakness as a side effect.
- Do Not Miss Diagnoses
- Spinal Cord Compression: Although the patient has a normal neuro exam and no changes in sensation, spinal cord compression (e.g., due to metastatic cancer, osteoporotic compression fracture) can present subtly and would be catastrophic if missed.
- Abdominal Aortic Aneurysm (AAA): While less likely given the lack of abdominal symptoms, an expanding AAA could potentially cause leg weakness due to emboli or compression effects.
- Stroke or Transient Ischemic Attack (TIA): Despite the normal neuro exam, it's crucial to consider cerebral vascular events, especially in an elderly patient, as the presentation can sometimes be atypical.
- Rare Diagnoses
- Inflammatory Myopathies (e.g., Polymyalgia Rheumatica, Dermatomyositis): These conditions can cause muscle weakness but are less common and might not initially present with the typical systemic symptoms or skin findings.
- Neuromuscular Junction Disorders (e.g., Myasthenia Gravis): These are rare but could cause fluctuating weakness without sensory changes, although they are less likely given the patient's age and presentation.