How does Multiple Sclerosis (MS) cause muscle cramping?

From the Guidelines

Multiple sclerosis causes muscle cramping primarily through nerve damage and disruption of nerve signals, leading to muscle spasticity and weakness, which can be managed with a multidisciplinary approach, including medical nutrition therapy and lifestyle modifications. In MS, the immune system attacks the protective myelin sheath covering nerve fibers, disrupting nerve signals between the brain and muscles, as noted in the context of managing malnutrition and nutrient deficiencies in patients with MS 1. This disruption leads to muscle spasticity, where muscles remain in a state of continuous contraction, resulting in cramping and stiffness. Additionally, MS-related fatigue, which can be addressed through adequate nutrition and medical nutrition therapy 1, causes muscles to tire more easily, making them prone to cramping. Muscle weakness from nerve damage forces other muscles to compensate, leading to overuse and cramping. Deconditioning from reduced physical activity and altered calcium regulation in damaged nerves further contribute to cramping. Some key factors to consider in managing muscle cramping in MS patients include:

• Preventing malnutrition and nutrient deficiencies through medical nutrition therapy and dietary advice 1
• Maintaining flexibility and strength through physical therapy and regular gentle stretching
• Proper hydration and maintaining electrolyte balance
• Considering muscle relaxants or other medications as needed, under the guidance of a neurologist and a multidisciplinary team 1. Overall, managing MS-related cramping requires a comprehensive approach that addresses the underlying causes of muscle dysfunction and spasticity, and incorporates lifestyle modifications and medical interventions tailored to individual symptoms and needs.

From the FDA Drug Label

Tizanidine’s capacity to reduce increased muscle tone associated with spasticity was demonstrated in two adequate and well controlled studies in patients with multiple sclerosis or spinal cord injury. In one study, patients with multiple sclerosis were randomized to receive single oral doses of drug or placebo A statistically significant reduction of the Ashworth score for tizanidine compared to placebo was detected at 1,2 and 3 hours after treatment.

The FDA drug label does not directly answer how multiple sclerosis causes muscle cramping, but it does show that tizanidine can reduce increased muscle tone associated with spasticity in patients with multiple sclerosis 2.

• Muscle tone was rated on a 5 point scale (Ashworth score)
• A statistically significant reduction of the Ashworth score for tizanidine compared to placebo was detected at 1,2 and 3 hours after treatment
• Spasm counts were also collected, but there were no differences in the number of spasms occurring in each group.

From the Research

Muscle Cramping in Multiple Sclerosis

• Muscle cramping in multiple sclerosis is often associated with spasticity, a common symptom of the disease 3, 4, 5.
• Spasticity is characterized by an abnormal increase in muscle tone, leading to stiffness, spasms, and cramping 4, 5.
• The exact mechanism of muscle cramping in multiple sclerosis is not fully understood, but it is thought to be related to the damage to the central nervous system (CNS) and the resulting disruption of neuromotor transmission 6.
• Skeletal muscle dysfunction, including reduced muscle mass and contractility, may also contribute to muscle cramping in people with multiple sclerosis 6.
• Treatment options for muscle cramping and spasticity in multiple sclerosis include medications such as tizanidine and baclofen, as well as botulinum toxin injections 3, 4, 7, 5.
• These treatments can help to reduce muscle tone, relieve spasms and cramping, and improve mobility and quality of life for people with multiple sclerosis 4, 7, 5.

Treatment Options

• Tizanidine and baclofen are two commonly used medications for the treatment of spasticity in multiple sclerosis 3, 4, 5.
• Botulinum toxin injections have also been shown to be effective in reducing muscle spasms and cramping in people with multiple sclerosis 7.
• The choice of treatment depends on the individual's specific symptoms and needs, as well as the potential side effects of each medication 4, 5.

Underlying Mechanisms

• The underlying mechanisms of muscle cramping in multiple sclerosis are complex and multifactorial 6.
• Damage to the CNS and disruption of neuromotor transmission can lead to abnormal muscle activation patterns and reduced muscle function 6.
• Skeletal muscle dysfunction, including reduced muscle mass and contractility, may also contribute to muscle cramping and spasticity in people with multiple sclerosis 6.