Differential Diagnosis for Bilateral Lower Limb Weakness

Single Most Likely Diagnosis

• Peripheral neuropathy: This is a common cause of bilateral lower limb weakness, often due to diabetes, vitamin deficiencies, or alcohol abuse. The gradual onset of symptoms and the presence of other neurological deficits such as numbness or tingling support this diagnosis.

Other Likely Diagnoses

• Spinal stenosis: This condition, often related to aging, can cause bilateral lower limb weakness due to compression of the spinal cord or nerve roots. Symptoms typically worsen with standing or walking and improve with sitting or leaning forward.
• Multiple sclerosis: An autoimmune disease that can cause a wide range of neurological symptoms, including bilateral lower limb weakness. The presence of other symptoms such as vision changes, balance issues, or cognitive difficulties may suggest this diagnosis.
• Stroke or spinal cord infarction: Although less common, a stroke or spinal cord infarction can cause sudden onset of bilateral lower limb weakness. The presence of other symptoms such as upper limb weakness, facial weakness, or bladder/bowel dysfunction may indicate a vascular cause.

Do Not Miss Diagnoses

• Guillain-Barré Syndrome: An autoimmune disorder that can cause rapid onset of bilateral lower limb weakness, potentially leading to respiratory failure if not promptly treated. Recent infection or vaccination may precede the onset of symptoms.
• Spinal epidural abscess: A serious infection that can cause bilateral lower limb weakness due to compression of the spinal cord. Fever, back pain, and recent history of infection or instrumentation are red flags for this condition.
• Cauda equina syndrome: A condition caused by compression of the nerve roots in the lower spine, leading to bilateral lower limb weakness, as well as bladder and bowel dysfunction. Prompt recognition and surgical intervention are crucial to prevent permanent damage.

Rare Diagnoses

• Inherited neuropathies (e.g., Charcot-Marie-Tooth disease): These are genetic disorders that can cause progressive bilateral lower limb weakness, often with a family history of similar symptoms.
• Toxic neuropathies: Exposure to certain toxins (e.g., heavy metals, certain medications) can cause bilateral lower limb weakness. A detailed history of exposure is essential for diagnosis.
• Inflammatory myopathies (e.g., polymyositis, dermatomyositis): These are autoimmune conditions that can cause muscle weakness, including bilateral lower limb weakness, often accompanied by skin changes or other systemic symptoms.