Clonus and spasticity are two motor abnormalities that indicate an underlying neural dysfunction. They have very different characteristics, causes, and management strategies. Both originating from injuries to the higher motor neurons, clonus and spasticity can coexist, particularly in conditions involving severe upper motor neuron lesions. In such cases, patients may experience both rhythmic muscle contractions and sustained increased muscle tone, which are the symptoms of clonus and spasticity, respectively.
Comparative Table: Clonus vs Spasticity
Explore below the differences between Clonus vs Spasticity in tabular format.
| Feature | Clonus | Spasticity |
| Definition | Rhythmic, involuntary muscle contractions | Increased muscle tone and stiffness |
| Occurrence | Intermittent, triggered by stretch | Continuous, with variable intensity |
| Rhythmicity | Yes, rhythmic oscillations | No, sustained resistance |
| Velocity Dependence | Not dependent on stretch velocity | Resistance increases with speed |
| Common Sites | Ankles, knees, wrists, jaw | Limbs, especially flexors and extensors |
| Pathophysiology | Hyperactive reflex arc, ion channel issues | Enhanced gamma neuron activity, synaptic changes |
| Triggering Factors | Sudden stretch, maintained stretch | Movement, external stimuli |
| Management Strategies | Medications (e.g., antispasmodics), physical therapy | Medications (e.g., muscle relaxants), physical therapy, surgical interventions |
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What is Clonus?
Clonus is a sequence of involuntary, rhythmic, muscular contractions and relaxations. It is often triggered by a sudden stretch of the muscle. It is usually observed in ankles (ankle clonus) but it can also occur in the knees, wrists, and jaw. Depending on the severity of the cause it can last for a few seconds to minutes.
Causes
Usually, clonus results from damage or disturbances to the central nervous system, especially to the higher motor neurons. The main reasons are as follows:
- Multiple Sclerosis (MS): Demyelination of nerve fibers hinders signal transmission, leading to hyperactive reflexes.
- Spinal Cord Injury (SCI):spinal cord damage that severs pathways that typically prevent reflex action causing clonus.
- Cerebral Palsy (CP): Brain damage during development affects motor control pathways, often resulting in clonus.
- Stroke: strokes can damage areas of the brain responsible for controlling muscle tone and reflexes, leading to clonus.
- Brain Injuries: Traumatic brain injuries (TBI) can disrupt neural circuits and pathways, leading to abnormal reflex activity and clonus.
Symptoms
- Rhythmic Contractions that are Involuntary, rapid, and repetitive muscle contractions and relaxations.
- Clonus is often triggered by sudden stretching of the muscle or maintaining a muscle in a stretched position.
- Frequently occurs in the ankles (ankle clonus), but can also be seen in the knees, wrists, and jaw.
- The episodes can last from a few seconds to several minutes, depending on the severity and underlying cause.
- Patients may also experience muscle stiffness, weakness, and in some cases, pain due to repeated muscle contractions.
Treatment
Treatment for clonus focuses on reducing muscle contractions and improving function
- Medications:Drugs like diazepam, baclofen are given to reduce muscle hyperactivity and can help relax muscles.
- Physical Therapy: Regular stretching can help to gain flexibility,Weight-Bearing Activities or Standing or walking can help reduce clonus frequency.
- Botulinum Toxin Injections:Used in severe cases to temporarily paralyze overactive muscles.
- Assistive Devices:Braces or splints can help manage muscle positioning and reduce clonus.
- Surgical Options: surgeries such as selective dorsal rhizotomy might be considered to reduce nerve root activity in some cases
What is Spasticity?
An abnormally high level of muscle tone or stiffness is known as spasticity, and it can impair speech, mobility, and cause pain and discomfort. It is frequently linked to disorders of the central nervous system (CNS).
Causes of Spasticity
- Neurological Disorders: Damage to the CNS, including the brain and spinal cord.
- Multiple Sclerosis (MS): Demyelination of nerve fibers affects muscle control.
- Cerebral Palsy: Damage to the developing brain affects movement and muscle tone.
- Stroke: Brain injury resulting in impaired movement control.
- Spinal Cord Injury: Disruption of nerve signals between the brain and muscles.
Symptoms
The Main symptoms of spasticity are as follows,
- Stiffness and Tightness: Difficulty in moving limbs.
- Increased Muscle Tone: Muscles remain contracted.
- Pain and Discomfort: Persistent contraction can cause pain.
- Clonus: Rapid muscle contractions in response to stretching.
- Exaggerated Reflexes: Hyperactive reflex responses.
Treatment procedures
- Physical Therapy: Exercises to improve range of motion and muscle strength.
- Medications: Medicines that help in Muscle relaxants like baclofen, tizanidine, and diazepam.
- Botox Injections: Botulinum toxin to reduce muscle stiffness.
- Surgery : In severe cases, surgery may be necessary to release tendons or cut nerves.
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Key Difference Between Clonus and Spasticity
Involuntary, repetitive muscular contractions and relaxations, usually brought on by an abrupt muscle stretch, are the hallmark of clonus. On the other hand, spasticity is characterized by a continuous rise in muscle tone that causes stiffness and movement resistance that is frequently velocity-dependent (that is, resistance increases as the stretch speed does).
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