Clonus refers to the involuntary, periodic, and recurring muscular contractions, which could occur in the ankles, knees, or the wrists. However, the ankles are the commonest areas to be affected. This can be explained as a deep tendon reflex which is caused due to an anomaly in the neuromuscular activity.
A clonus occurs when the muscles are stretched, and can be observed in the ankles when the foot is jerked upwards at the ankle, or whilst trying to hold the muscles still.
What Causes Clonus In The Ankle?
An abnormality in neuromuscular activity is the causative factor. The following etiological factors have been commonly seen to trigger a clonus:
- Multiple Sclerosis: A chronic progressive autoimmune nervous disorder which is typified by the loss of the myelin sheath around the nerve fibers; this disturbs the messages sent between the brain and the spinal cord and afflicts movement, sensation, and bodily functions.
- Meningitis: Meningitis is a bacterial infection which results in the inflammation of the meninges which envelope the brain and the spinal cord, and manifests as severe headache, vomiting, fever, stiffness in the neck, and muscle contractions.
- Huntington’s disease: It is a rare hereditary neuro-degenerative condition, which results in progressive jerky muscle movements which afflict normal muscle coordination, and also causes mental decline.
- Spinal Cord Injury: Trauma to the spinal cord damages the myelinated fiber tracts which carry messages to and fro from the brain. This leads to a loss of sensation and motor control.
- Pre-eclampsia: Seen during pregnancy, pre-eclampsia is characterized by high blood pressure, retension of fluid and proteinuria.
- Cerebral Palsy: It is a non-progressive movement and posture disorder occurring due to an abnormal development of the motor control centers of the brain.
- Upper Motor Neuron Lesion: Upper motor neurons are motor neurons which originate from the motor region of the cerebral cortex. They are concerned with carrying signals from the brain and spinal cord. Damage to the nerve tract, especially between the brain and the level at which the peripheral nerves come out of the spinal cord, can cause clonus.
- Stroke: A sudden and quick loss of brain function because of a breach or closure of a blood vessel in the brain, results in necrosis of the brain tissue and this causes loss of muscle control.
- Spastic Paraparesis: It results in a mild loss of motor function, along with spasms and weakness in various parts of the body. An injury to the motor cortex or descending motor pathways triggers this condition.
- Subacute Sclerosing Pan-encephalitis: An abnormal immune reaction to the measles virus is the cause for this fatal brain disorder. It is common in children, and becomes apparent as myoclonic seizures, progressive impairment of mental and motor functioning, and behavioral changes.
Symptoms: An ankle clonus manifests as a recurring, rhythmic and involuntary contraction of the muscles of the ankle joint.
Diagnostic Tests For Ankle Clonus
The first step is to identify the exact cause of the condition; and then start prompt treatment to manage the case successfully. Your health care provider will order to the following tests to establish the cause of the clonus in the ankle:
- Computerized Tomography
- Magnetic Resonance Imaging
- Cerebrospinal Fluid assessment
- Radiography using X-ray of the spinal cord to identify any lesions.
The treatment regimen depends upon the results of the investigations and understanding the precise cause. Thus, early diagnosis plays a critical part in identifying the underlying neurological problem and starting appropriate treatment.