Management of Clonus in the Foot
Clonus in the foot should be treated primarily with baclofen as the first-line pharmacological agent, combined with cold application for immediate symptomatic relief, while addressing any underlying upper motor neuron pathology. 1, 2, 3
Understanding Clonus
Clonus represents involuntary, rhythmic muscle contractions caused by permanent lesions in descending motor neurons, typically occurring at 5-8 Hz frequency with ankle clonus periods of approximately 160-200 milliseconds. 2 This pathological motor pattern indicates corticospinal tract involvement and results from hyperactive stretch reflexes, though the exact mechanism remains debated between self-excitation of stretch reflexes versus central generator activity. 2
Primary Treatment Approach
Pharmacological Management
Baclofen is the FDA-approved and evidence-based first-line treatment for clonus, specifically indicated for alleviation of spasticity signs including flexor spasms, clonus, and muscular rigidity. 1, 2 The medication works by reducing hyperactive stretch reflexes that generate the rhythmic contractions. 1
- Baclofen tablets are particularly effective for patients with reversible spasticity from multiple sclerosis, spinal cord injuries, and other spinal cord diseases. 1
- The goal is restoring residual function by controlling the involuntary muscle contractions. 1
Tizanidine should NOT be used for clonus management as research demonstrates no significant effect on clonus despite its muscle relaxant properties. 3 This is a critical pitfall to avoid, as clinicians may mistakenly prescribe tizanidine expecting benefit similar to baclofen.
Physical Modality: Cold Application
Cold application provides statistically significant and clinically meaningful suppression of clonus, with both immediate and prolonged inhibitory effects. 2, 3
- Subsequent and long-term cold application induces prolonged inhibitory effects that persist beyond the application period. 3
- The suppression of clonus by cold highlights the importance of peripheral input mechanisms, suggesting that peripheral interventions can modulate central pathology. 3
- Cold should be applied to the affected extremity using standard cooling protocols. 2, 3
Alternative Interventions
For refractory cases not responding to baclofen and cold:
- Botulinum toxin injections can be considered for localized clonus management. 2
- Phenol injections represent another option for severe, treatment-resistant clonus. 2
Functional Management Strategies
For patients learning motor tasks (such as sit-to-stand transfers), physical constraint of the ankle by firmly placing the heel on the ground can reduce clonus occurrence. 4 This approach leverages the observation that clonus rarely occurs when the heel maintains ground contact with adequate ground reaction force. 4
- Orthotic devices that facilitate heel placement during functional activities may support motor learning while managing clonus. 4
- Progressive motor learning with clonus management can lead to improved function where patients eventually perform movements without clonus occurrence. 4
Critical Diagnostic Considerations
Distinguishing from Seizures
Clonus can mimic clonic epileptic seizures, particularly in children with encephalopathy, but video-EEG confirms the non-epileptic origin. 5 This is a crucial diagnostic pitfall, as misdiagnosis leads to inappropriate antiepileptic drug treatment that proves unsuccessful. 5
- Startle-induced clonic attacks with severe apnea may appear identical to epileptic seizures clinically. 5
- Myorelaxing drugs (like baclofen) produce dramatic improvement in these cases, whereas antiepileptic drugs fail. 5
Underlying Etiologies to Address
Common causes requiring evaluation include:
- Stroke and middle cerebral artery infarction 6
- Multiple sclerosis 2
- Spinal cord injuries and diseases 1
- Metabolic alterations including severe hepatic failure 6
- Serotonin syndrome 6
Common Pitfalls to Avoid
Do not prescribe tizanidine expecting clonus improvement - it lacks efficacy despite being a muscle relaxant. 3
Do not treat suspected clonus with antiepileptic drugs without EEG confirmation - clonus is non-epileptic and requires myorelaxing agents. 5
Do not overlook cold application as an adjunctive therapy - it provides significant benefit with minimal risk and should be incorporated into the treatment plan. 3
Do not use baclofen for rheumatic skeletal muscle spasm - it is not indicated for this condition and efficacy has not been established for stroke, cerebral palsy, or Parkinson's disease. 1