Causes of Leg Weakness

Diagnosis of Leg Weakness

A CT scan is valuable in determining if surgical removal of the clot can be considered. Most strokes will have sudden onset of unilateral symptoms like lower or upper extremity weakness, facial drooping, or blurred vision. 

Treatment for Leg Weakness

The mainstay of treatment is knowing the “last known well time” (e.g. when the patient last did not have symptoms). This could be difficult if the patient wakes up with symptoms. There is a goal time for various interventions from that start time to reduce side effects, which can be compounded by the distance EMS needs to travel. Once stable, acute rehab may be needed for the short term.

Leg Weakness Caused By Spinal Conditions

Spinal conditions can be from a traumatic injury or age-related arthritis. A common occurrence is herniation of the disk that sits in the middle of the vertebral body. This puts it in direct compression of the spinal cord (eg. central stenosis). In addition, facet joints between two vertebrae are the areas where nerve roots exit either side. 

Arthritis in the area can lead to thinning of the disk and thickening of the bone, which can result in compression of the nerve root as it exits either side of the vertebra (eg. foraminal stenosis). 

Both of these will lead to low back pain, but the extent to which it’s localized can be attributed to nerve pathology.

Diagnosis and Symptoms

A lumbar MRI is often used to confirm these conditions. Symptoms can include pain along a nerve root distribution in the leg, referred to as a dermatome.

Sciatica

Sciatica is typically considered a result of compression of the large sciatic nerve or its various composite roots in the spinal cord. In some patients, this could be due to a tight piriformis, a muscle in the gluteal region that compresses the nerve as it enters the leg. 

Sciatica Symptoms

Sciatica can either flare, causing increased leg weakness and numbness/tingling, or it can always be a baseline weakness. 

Treatments

Treatment for low back and sciatica pain includes NSAIDS, muscle relaxers, steroid injections, physical therapy, hot/cold application. Osteopathic manipulation can promote more natural alignment of the spine, resulting in relief as well. Other non-first-line treatments can be fusion surgeries, spinal cord stimulators, or nerve ablation.

Leg Weakness Caused By Diabetes

Diabetes is characterized by consistently high blood sugar. While blood sugar is supposed to be elevated after a meal, it should drop as insulin rises, prompting cells to start absorbing it. An A1c can act as an estimate of average blood sugar over three months. A1c above 6.4% is an indicator of diabetes. 

Blood sugar is toxic to peripheral nerve cell endings, leading to the eventual development of neuropathic pain if blood sugar is uncontrolled over time. The typical area sensation is lost in the sole of the feet, but symptoms higher in the leg are also possible.

From a surgical perspective, A1c less than 8.0% is typically preferred before surgical intervention due to glucose’s ability to impair wound healing and immune response. Once diabetes is diagnosed, practitioners will provide different classes of mediation to illicit glucose control.

Leg Weakness Caused By Neuromuscular Disorders

The neuromuscular junction between nerves and muscles is a site where the coordination between the two is impaired, resulting in weakness. Typically, the nerve cells release acetylcholine, which will bind to its receptor on muscle fibers to trigger contraction. Based on the pathology, this can be a sudden or gradual onset weakness with various symptoms.

Diagnosis

An EMG is a diagnostic test for various neuromuscular conditions. The practitioner can stimulate the nerve and quantify the contraction of the correlated muscle group. One example of this use is the diagnosis of carpal tunnel from presumed median nerve entrapment.

Three diverse disorders are listed below:

1. Myasthenia gravis is an autoimmune condition where the acetylcholine receptors are destroyed. It tends to manifest with central symptoms (eye weakness) and gradually goes to the limbs. Diagnosis can be done through identifying the antibody while treatment is stopping the breakdown of acetylcholine to maximize its effect.
2. Guillain Barre Syndrome is a more sudden bilateral onset starting with the extremities. This occurs due to nerves losing myelin, which helps it transmit signals. Viral disease can trigger this, and often, supportive therapy is all that’s done. At times, immune mediating medications can be used.
3. ALS (commonly known as Lou Gehrig’s disease) is another gradual nerve issue that breaks down the motor cells responsible for transmitting the signal to muscles (as compared to the myelin), leading to weakness. Patients can present with combined rigidity and flaccidity based on where the lesion is located.

Overall, while leg pain due to soreness may be a common explanation for weakness, this post highlights some of the other presentations that need a doctor’s evaluation.

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References

“Diabetic Neuropathy – NIDDK.” National Institute of Diabetes and Digestive and Kidney Diseases,

www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/nerve-damage-diabetic-neuropathies#:~:text=Diabetic%20neuropathy%20is%20nerve%20damage,nerve%20damage%20cause%20different%20symptoms. Accessed 7 Aug. 2023.

Kristen Gasnick, PT. “Types of Neuromuscular Disorders.” Verywell Health, 19 July 2021, www.verywellhealth.com/neuromuscular-disorders-5180051.

“Leg Weakness: Possible Causes and Related Symptoms.” Healthgrades, 16 Sept. 2022, www.healthgrades.com/right-care/bones-joints-and-muscles/leg-weakness.

“Lumbar Facet Syndrome (Spondylosis, Facet Arthropathy/Arthritis, Spondylitis, Facet Sprain).”Pain Management Specialist in Beverly Hills, www.orthopedicpaininstitute.com/services/lumbar-facet-syndrome/. Accessed 7 Aug. 2023.

Medically Reviewed by Scott Stephens, MD