Differential Diagnosis for Unilateral Leg Weakness
Single Most Likely Diagnosis
- Peripheral neuropathy: This is often the most common cause of unilateral leg weakness, resulting from damage to the nerves supplying the muscles of the leg. Conditions such as diabetic neuropathy, compression neuropathy (e.g., peroneal neuropathy), or radiculopathy can lead to this symptom.
Other Likely Diagnoses
- Stroke or transient ischemic attack (TIA): Although more commonly associated with unilateral weakness of the face and arm, stroke or TIA can also cause leg weakness, especially if the lesion is located in the motor cortex or corticospinal tract.
- Lumbar disc herniation or spinal stenosis: These conditions can compress nerve roots, leading to unilateral leg weakness, pain, and sensory changes.
- Multiple sclerosis: This demyelinating disease can cause a wide range of neurological symptoms, including unilateral leg weakness, especially in younger patients.
Do Not Miss Diagnoses
- Spinal cord compression: Conditions such as metastatic cancer, epidural abscess, or hematoma can compress the spinal cord, leading to rapid progression of neurological deficits, including leg weakness. Early recognition and treatment are crucial to prevent permanent damage.
- Guillain-Barré syndrome: An autoimmune disorder that can cause ascending paralysis, starting with leg weakness, which can progress to respiratory failure if not promptly recognized and treated.
- Vascular malformations or arteriovenous fistulas: These can cause leg weakness due to spinal cord ischemia or compression and require urgent intervention to prevent further damage.
Rare Diagnoses
- Inflammatory myopathies: Conditions such as polymyositis or dermatomyositis can cause progressive muscle weakness, including unilateral leg weakness, although this is less common.
- Neurodegenerative diseases: Such as amyotrophic lateral sclerosis (ALS), which can present with unilateral leg weakness, although this is often accompanied by other symptoms like fasciculations or upper motor neuron signs.
- Infections: Such as neurosyphilis or Lyme disease, which can cause a range of neurological symptoms, including unilateral leg weakness, although these are relatively rare causes.