Characterized by a series of rhythmic, involuntary muscular contractions, clonus is often indicative of neurological conditions that are associated with upper motor neuron lesions. The following HealthHearty write-up provides information on its contributing factors.
Clonus refers to repetitive, rhythmic contraction and relaxation of muscles that occurs due to abnormal neuromuscular activity in the motor neurons originating from the motor region in the cerebral cortex. These neurons transmit motor information to the nerve cells in the brain stem and spinal cord. The rapid muscular contractions occur when these nerves are injured or damaged due to lesions or diseases.
The contributing factors include spinal cord injury, stroke, hepatic encephalopathy, multiple sclerosis, etc. When the myelin sheath around the nerve fibers is lost, it causes disruption of impulses sent by the brain and spinal cord. Thus, leading to rapid contraction and relaxation of muscles.
Other contributing factors include epilepsy, spastic paraparesis, Huntington’s disease, meningitis, Creutzfeldt-Jakob Disease, Brown-Séquard syndrome, etc. Serotonin syndrome, which could occur due to an adverse reaction to serotonergic drugs, could also lead to this condition.
The most common way to detect this condition is to undergo the ankle clonus test. In this test, the doctor gently pushes the foot backwards into a dorsiflexion position. When the foot is released, it should quickly come back to its normal position. However, in people who are affected, the foot tends to repeat the contraction and relaxation motion. Doctors may also check for abnormal reflex movements by pushing down the patella (kneecap) towards the toes. If the rapid flexion and extension of the foot that is set in motion by reflex testing shows more than 5 beats, it may indicate an underlying neurological problem.
If the reflex testing shows 5 beats or more, the doctor would analyze the patient’s medical history and try to ascertain the underlying cause. The symptoms might resolve once the underlying medical condition is treated. For instance, if a spinal injury is the underlying cause, then surgery is advised to treat the damaged or injured nerve. Drugs such as immunosuppressants, anticonvulsants, tranquilizers, etc., might be prescribed. Physical therapy might be recommended. The administration of botox injections might prove to be beneficial in controlling involuntary muscle contractions.
If the beat frequency is less than five in reflex testing, it is not a cause of concern. However, proper diagnosis and treatment is required if a frequency of more than 5 beats is observed.
Disclaimer: The information provided in this article is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.