Refers to a series of involuntary, rhythmic, muscular contractions and relaxations.
Explained as a deep tendon reflex, arising from an abnormality in neuromuscular activity.
Occurs when the muscles are stretched.
Generally associated with neurological problems originating in the spinal cord, especially if both the legs are affected.
May be associated with epilepsy.
Rare causes include Huntington’s disease, meningitis, Brown-Sequard Syndrome and Creutzfeldt-Jakob disease.
A sign of a neurological condition, particularly associated with upper motor neuron lesions involving descending motor pathways.
Lesions in the upper motor neurons are the most common cause of this finding, and they arise from the motor region of the cerebral cortex.
Motor neurons carry impulses from the brain and spinal cord.
Any damage to the nerve tract, particularly between the brain and the level at which the peripheral nerves come out of the spinal cord can cause this condition.
Many cases associated with spasticity .
Has large motions that are usually initiated by a reflex.
Clonus beat frequency ranges from 3- 8 Hz.
Clonus may last a few seconds to several minutes depending on the underlying clinical process.
Seen in patients with stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy which are associated with upper motor neuron lesions.
Multiple sclerosis disrupts the communication between the brain and the spinal cord and can lead to clonus.
Stenosis of the spinal cord, which is the case with disc diseases, can lead to clonus.
May be associated with exposure to serotonergic drugs.
Proposed mechanisms of clonus include self-re-excitation of hyperactive stretch reflexes, or the presence of a central oscillator.
Clonus is due to an increased motor neuron excitation and is common in muscles with long conduction delays.
Commonly seen in the ankle but may exist in the patella, triceps, or biceps, finger and toes.
Clonus is most commonly found at the ankle with a dorsiflexion/plantarflexion inducing a stretch to the gastrocnemius muscle.
Sustained clonus of 5 beats or more is an abnormal finding.
Rapidly pushing the patella towards the toes can elicit a patella clonus.
Evaluation of clonus includes CT scan or MRI of the spinal cord, brain and brain stem.
Spinal fluid analysis and myelography may be helpful to determine if a spinal cause is the site of an abnormality.