Intermittent Numbness and Weakness in Feet: Causes and Solutions

Intermittent numbness in both feet?

Hello Doctor: I am 24 years old and have been working for some time.
I have hyperthyroidism, which I have been treating for six months.
I have been going to the hospital for follow-ups, and my condition is currently stable and normal.
However, recently, I have been experiencing intermittent numbness and weakness in the soles of my feet, possibly due to work-related stress or other factors.
At times, I also experience tremors in my hands and feet.
After resting for a few hours, I gradually feel better, but the symptoms keep recurring.
I have undergone MRI scans and evaluations of my central nervous system and spinal cord, all of which came back normal.
Therefore, I would like to ask the doctor what might be causing these symptoms.

Xiao Ru, 20~29 year old female. Ask Date: 2018/08/23

Dr. Chen Shunfu reply Internal Medicine

Based on the brief medical history you provided, it is recommended that hyperthyroidism be managed according to medical advice and that regular follow-ups are conducted.
You should first rule out the possibility of having Thyrotoxic Periodic Paralysis (TPP).
Statistics indicate that approximately 2% of patients with hyperthyroidism in China and Japan have TPP, with a male-to-female ratio of about 20:1.
The pathogenic mechanism remains unclear but is fundamentally related to hyperthyroidism and genetic abnormalities.
In TPP, genetic anomalies lead to an excessive influx of extracellular potassium ions into the cells, resulting in low extracellular potassium ion concentration, which prevents muscle cells from depolarizing, thereby causing muscle weakness.
The initial onset typically occurs between the ages of 20 and 40, with TPP episodes often occurring late at night or early in the morning.
Most patients experience prodromal symptoms, including muscle pain, cramps, and stiffness, followed by muscle weakness that progresses symmetrically, usually starting in the proximal lower limbs and potentially advancing to all four limbs, leading to quadriplegia in severe cases.
Clinically, the symptoms and signs of hyperthyroidism may be quite subtle, including palpitations, weight loss, heat intolerance, increased appetite, goiter, tachycardia, warm and moist skin, fever, exophthalmos, and tremors.
Approximately 50% of patients may not exhibit obvious hyperthyroid symptoms during a TPP episode.
Additionally, TPP does not occur during exercise but rather after resting post-exercise.
Muscle weakness typically lasts about 3 to 96 hours and may resolve spontaneously without potassium supplementation.
It is advisable for you to follow up on thyroid function tests (TSH, T3, and FT4), serum potassium and phosphate levels, as well as urinary potassium/creatinine ratios to facilitate further diagnosis and treatment.

Reply Date: 2018/08/23

More Info

Intermittent numbness and weakness in the feet can be concerning, especially when accompanied by symptoms such as tremors in the hands and feet. Given your age and medical history, it’s essential to consider various potential causes for these symptoms.

Firstly, it’s worth noting that you have a history of hyperthyroidism, which can lead to a range of neurological symptoms, including peripheral neuropathy. Although your thyroid levels are currently stable, fluctuations in thyroid hormone levels can still affect nerve function, leading to sensations of numbness or weakness. Hyperthyroidism can also cause muscle weakness, particularly in the proximal muscles, which may contribute to the feelings of instability or weakness you are experiencing.

Another potential cause of your symptoms could be related to anxiety or stress, particularly given your mention of work-related pressure. Stress can lead to physical symptoms, including muscle tension, tremors, and even changes in sensation. The body's stress response can cause hyperventilation, which may lead to temporary numbness or tingling in the extremities. If you find that your symptoms worsen during stressful periods, this could be a contributing factor.

Additionally, intermittent numbness and weakness can be indicative of peripheral nerve issues, such as neuropathy or entrapment syndromes. Conditions like carpal tunnel syndrome or tarsal tunnel syndrome can lead to symptoms in the feet and hands, respectively. However, since you mentioned that MRI and other neurological evaluations have returned normal results, these specific conditions may be less likely.

It’s also important to consider the possibility of vitamin deficiencies, particularly B vitamins, which are crucial for nerve health. A deficiency in vitamin B12, for instance, can lead to neurological symptoms, including numbness and weakness. If you haven’t already, it may be beneficial to have your vitamin levels checked.

Given that your symptoms are intermittent and improve with rest, it may also be worthwhile to evaluate your daily activities and ergonomics. Poor posture, prolonged sitting, or repetitive movements can lead to nerve compression or muscle fatigue, contributing to your symptoms. Incorporating regular breaks, stretching, and strengthening exercises into your routine may help alleviate some of the discomfort.

In conclusion, while your symptoms could stem from a variety of causes, including residual effects of hyperthyroidism, stress-related responses, or peripheral nerve issues, it is crucial to continue working closely with your healthcare provider. They may recommend further evaluations or referrals to specialists, such as a neurologist or an endocrinologist, to explore these symptoms in greater depth. Additionally, lifestyle modifications, stress management techniques, and possibly nutritional supplementation could be beneficial in managing your symptoms. Always remember to prioritize your health and seek medical advice when symptoms persist or worsen.

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