This article reviews the causes, diagnosis, and treatment of clonus.
Causes of Clonus
Clonus is a type of stretch reflex, meaning that when a muscle group is stretched or stimulated, neurons perceive that stretch and cause contraction of the same muscle group. This type of reflex is meant to protect against strains and muscle tears. With clonus, however, the normal contraction occurs not once but several times before subsiding.
While the exact cause of clonus remains unclear, clonus can be seen in a number of different diseases affecting the nervous system.
Common Causes of Clonus
Multiple sclerosis Cerebral palsy Stroke Spinal cord injury Traumatic brain injury Orthopedic trauma Serotonin syndrome
Clonic movements can also be observed in the context of seizures, side effects of certain medications, and chemical imbalances.
Clonus and MS
Multiple sclerosis (MS) is a chronic autoimmune inflammatory disease in which the immune system destroys the protective sheath covering nerve cells, known as myelin. This damage leads to miscommunications between the brain and other areas of the body, as well as a lower trigger threshold for stretch reflexes.
Given the nature of the disease, people with MS often experience clonus, as well as other symptoms like involuntary muscle spasms, tremors, muscle weakness, and spasticity. Other symptoms include sensory loss, coordination issues, and cognitive impairment.
Clonus and Spasticity
Spasticity is often seen in people with neurological diseases. It refers to abnormal muscle tightness or contraction.
In addition to painful muscle spasms, spasticity can also lead to clonus, pain, permanent muscle contractures, joint deformities, and even decreased ability to perform activities of daily living.
How Clonus Is Diagnosed
Clonus can be observed during the physical examination portion of a medical appointment. Depending on the area affected, a healthcare provider can apply stress or “stretch” a muscle or tendon and observe the subsequent response or reflex. With clonus, the healthcare provider can then measure or count the number of involuntary contractions which occur.
Once clonus is observed, it becomes incredibly important to try and determine the cause of the neurologic issue. To get to the root cause of clonus, a healthcare provider may order:
Specific blood tests MRI scan of the brain and/or spinal cord Nerve conduction studies Lumbar puncture (spinal tap)
Treatment for Clonus
When it comes to managing clonus, there are several oral medications and alternative therapies that can be beneficial.
While there is no “one-size-fits-all” therapy, a tailored treatment regimen managing both the symptoms and the underlying disease can increase a person’s quality of life.
The treatment of clonus due to chemical imbalances, seizure, or medication side effects is to correct these acute medical problems.
Medications
The goal of oral medications used to manage clonus due to spasticity is to relax the affected muscles and decrease rigidity. Some of these medications include:
Muscle relaxants, such as baclofen and tizanidineBenzodiazepines, such as diazepam and clonazepam
These medications should be used with caution, as they come with side effects. These include, but are not limited to, drowsiness, dizziness, and fatigue.
Other Therapies
Targeted injections of either botulinum toxin A/B or phenol may provide relief for clonus.
Botulinum toxin is typically injected within the affected muscle, weakening or temporarily paralyzing specific muscles so they can not involuntarily contract. It can take up to 10 days before results are noticeable and increased range of motion and function may be observed. If successful, these injections could provide relief for several months.
Unlike botulinum toxin injections, phenol injections are administered close to the affected nerve roots and immediately block nerve conduction, causing the muscle to relax. If effective, phenol injections may also provide several months worth of relief.
Surgery
If all other treatment options fail, a healthcare provider may recommend surgery to alleviate clonus. Surgery can either be done to release a tendon which has become inflamed and caused a contracture of the underlying muscle, or it can be done to sever the affected neuron-muscle pathway.
While these surgeries may relieve clonus, they can also lead to permanent and disabling limited mobility and muscle functionality.
Outlook
While there are several treatment options to help alleviate clonus, the severity and prognosis really depends on the underlying cause. Clonus can range from a mild annoyance to a disabling reflex.
Adequate management of the underlying disease or cause, if possible, can result in minimization of clonus.
Summary
Clonus can refer to the involuntary and repetitive muscle contractions that occur after stimulating a muscle. Common causes of clonus include multiple sclerosis, cerebral palsy, spinal cord or traumatic brain injuries, and more. It is also seen in the context of certain seizures, medication side effects, or chemical imbalances.
Through a thorough history and physical examination, a healthcare provider will be able to diagnose clonus and offer treatment options such as physical therapy, medications, targeted injections, and surgery. The prognosis for clonus depends on the underlying cause and how effectively it can be managed.
A Word From Verywell
Clonus can range from inconvenient to disabling. If you are suffering from clonus, it’s important to speak with your healthcare provider about your symptoms. Management of clonus requires multi-disciplinary collaboration between neurologists, orthopedists, physical therapists, and others. Thankfully, there are several treatment options available which can help manage clonus.
