Differential Diagnosis for Sudden Lower Extremity Weakness
The patient's presentation of sudden lower extremity weakness leading to falls warrants a thorough differential diagnosis. The following categories outline potential causes, ranging from the most likely to rare conditions.
- Single most likely diagnosis
- Stroke: The sudden onset of lower extremity weakness is a classic presentation of a stroke, particularly if it involves the motor cortex or corticospinal tract. The weakness is often unilateral but can be bilateral in the case of brainstem or spinal cord involvement.
- Other Likely diagnoses
- Spinal Cord Injury or Compression: Trauma, herniated discs, or spinal stenosis can cause sudden weakness in the lower extremities by compressing or damaging the spinal cord.
- Peripheral Neuropathy: Conditions like Guillain-Barré Syndrome can lead to rapid onset of muscle weakness, often starting in the lower extremities.
- Electrolyte Imbalance: Severe imbalances in potassium, sodium, or calcium can affect muscle function, leading to weakness.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Spinal Epidural Hematoma: A medical emergency that requires immediate intervention. It can cause sudden spinal cord compression leading to weakness, pain, and potentially permanent paralysis if not promptly treated.
- Aortic Dissection: Although more commonly associated with chest or back pain, an aortic dissection can lead to spinal cord ischemia, presenting as sudden lower extremity weakness.
- Cauda Equina Syndrome: A condition where the nerves in the spinal canal are compressed, leading to loss of function of the lumbar plexus. It's a surgical emergency.
- Rare diagnoses
- Multiple Sclerosis: An autoimmune disease that can cause a wide range of neurological symptoms, including sudden weakness, due to demyelination in the central nervous system.
- Acute Demyelinating Neuropathy: Similar to Guillain-Barré Syndrome but can have a more varied presentation.
- Vasculitis affecting the nervous system: Conditions like giant cell arteritis or primary central nervous system vasculitis can lead to stroke-like symptoms, including sudden weakness, although they are less common.
Each of these diagnoses requires careful consideration of the patient's history, physical examination, and diagnostic tests to determine the underlying cause of the sudden lower extremity weakness.