Differential Diagnosis for Bilateral Lower Extremity Weakness

Single Most Likely Diagnosis

• Lumbar Spinal Stenosis: This condition is a common cause of bilateral lower extremity weakness, especially in older adults. It occurs when the spinal canal narrows, putting pressure on the spinal cord and nerves, leading to symptoms such as weakness, numbness, and pain in the legs.

Other Likely Diagnoses

• Peripheral Neuropathy: Conditions like diabetic neuropathy can cause bilateral lower extremity weakness due to damage to the peripheral nerves.
• Myasthenia Gravis: An autoimmune disorder that affects the nerve-muscle connection, leading to muscle weakness that can be bilateral and affect the lower extremities.
• Guillain-Barré Syndrome: An autoimmune disorder where the body's immune system mistakenly attacks part of its peripheral nervous system, leading to muscle weakness and sometimes paralysis.
• Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): Similar to Guillain-Barré but chronic, it causes progressive weakness and loss of sensation in the legs.

Do Not Miss Diagnoses

• Spinal Cord Compression: Conditions such as tumors, abscesses, or fractures can compress the spinal cord, leading to rapid progression of weakness, which is a medical emergency.
• Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, leading to a wide range of neurological symptoms, including bilateral lower extremity weakness.
• Acute Transverse Myelitis: Inflammation of a segment of the spinal cord, which can cause bilateral lower extremity weakness, among other symptoms, and requires prompt treatment.

Rare Diagnoses

• Motor Neuron Disease (e.g., Amyotrophic Lateral Sclerosis - ALS): A progressive neurological disease that affects nerve cells in the brain and the spinal cord, causing loss of muscle control.
• Poliomyelitis: Although rare in areas with widespread vaccination, polio can cause acute flaccid paralysis, including bilateral lower extremity weakness.
• Toxic Neuropathies: Exposure to certain toxins (e.g., heavy metals, certain drugs) can lead to neuropathy and bilateral lower extremity weakness.
• Inherited Neuropathies (e.g., Charcot-Marie-Tooth Disease): A group of disorders that affect the peripheral nerves, leading to progressive muscle weakness and atrophy.