Understanding Fasciculations and Cramps: Causes and What They Mean

What are fasciculations and cramps?
Fasciculations are involuntary, small, localized muscle contractions that occur spontaneously in a group of muscle fibers innervated by the same motor neuron. A fasciculation is when a small group of these fibers activates on its own, without your conscious decision. These contractions are usually subtle enough to be seen only as a slight tremor or vibration just under the skin, and they generally do not cause any movement in the limb. Many people experience fasciculations at some point in their lives, and in the vast majority of cases, they are completely benign.

Cramps, on the other hand, are involuntary, sudden, and often painful muscle contractions that affect an entire muscle or group of muscles. During a cramp, the muscle tenses and resists, and the sensation can range from mild discomfort to very severe pain. Cramps can last from a few seconds to several minutes. Like fasciculations, cramps are a common experience, and although they can be very annoying, in most situations they are not indicative of a serious health problem.

What can cause fasciculations and cramps?
The causes of fasciculations are diverse. In many cases, they occur in healthy people and can be related to factors such as stress, anxiety, fatigue, intense exercise, or caffeine consumption. They can also be a side effect of some medications. While fasciculations can be a symptom of certain neurological diseases affecting motor neurons (such as ALS) or peripheral nerves, it is crucial to understand that the vast majority of people who experience fasciculations do not have these diseases.

Cramps also have a wide range of possible causes. Exercise-associated muscle cramps are common and are often related to muscle fatigue, dehydration, and electrolyte imbalances such as sodium, potassium, calcium, and magnesium. Other common causes include pregnancy, prolonged inactivity, certain medical conditions such as chronic kidney failure, diabetes, circulatory problems, and some medications (diuretics, statins, etc.). As with fasciculations, although cramps can occur in the context of neurological diseases, most cramps have benign causes.

Among the most common syndromes associated with these symptoms, especially when they are more noticeable, are benign fasciculation syndrome (only fasciculations without other problems) and idiopathic fasciculation-cramp syndrome (coexistence of both without a clear cause).

What do they feel and look like?
Fasciculations are often perceived as a small tremor, vibration, or throbbing just under the skin. Sometimes, the person experiencing them can see the muscle moving slightly.

Cramps feel like a sharp, intense pain in the affected muscle, which feels hard to the touch. Once the cramp passes, a feeling of pain or tenderness may remain in the muscle.

When should you consider seeing a specialist?

Although most fasciculations and cramps are benign, there are situations in which it is advisable to seek medical attention, especially if these symptoms are accompanied by:

• Muscle weakness.
• Loss of sensation.
• Changes in muscle size (atrophy).
• Symptoms that progressively worsen.
• Persistent pain that interferes with your daily activities.

In these cases, it is advisable to see a neurology specialist for a more detailed evaluation. The specialist will be able to determine if additional studies are needed to rule out neurological causes or other medical conditions.

What tests may be performed?
The evaluation may include a detailed physical examination and a review of your medical history. If your doctor suspects an underlying cause, they may order blood tests to assess electrolyte levels, thyroid, kidney, and liver function, among others. In some cases, electromyography (EMG), which measures the electrical activity of muscles and nerves, and nerve conduction velocity (NCV) studies may be performed to assess peripheral nerve function.

How is it typically addressed?
Management of fasciculations and cramps depends on the cause. In many benign cases, no specific treatment is required beyond reassuring the patient and advising about possible triggers (such as reducing caffeine consumption or improving hydration). For cramps, preventative measures such as regular stretching, maintaining good hydration, and ensuring adequate electrolyte intake may be helpful. During a cramp, gently stretching the affected muscle often provides relief. In cases where symptoms are severe or related to an underlying medical condition, drug treatment may be considered under the supervision of a physician.

Remember that while it is important to be informed about the possible causes of fasciculations and cramps, most of the time they are not a cause for concern. However, if you have any concerns or experience other associated symptoms, it is always best to consult a healthcare professional.