Chaddock’s sign is a neurological reflex indicative of pyramidal tract dysfunction, commonly used in the assessment of upper motor neuron lesions. It encompasses two distinct manifestations: the Chaddock toe sign, characterized by dorsiflexion of the great toe and fanning of the other toes upon stimulation of the lateral foot, and the Chaddock wrist sign, defined by flexion of the wrist and extension of the fingers when the ulnar forearm is stimulated. This sign helps identify corticospinal tract lesions in adults and children beyond the age of seven months.

Pathophysiology

Chaddock’s sign arises from disruption of inhibitory corticospinal pathways that normally regulate spinal reflexes. Key mechanisms include:

• Loss of pyramidal inhibition leading to hyperactive cutaneous reflexes.

• Disinhibition of spinal motor neurons, producing extensor plantar responses or abnormal hand reflexes.

• Neuronal plasticity in infants, accounting for physiologic positivity up to 7 months of age.

Upper motor neuron lesions, including stroke, traumatic brain injury, demyelinating disorders, or cerebral palsy, result in these abnormal reflex responses.

Examination technique

Patient Observation

• Inspect spontaneous movements and posture of the lower limbs and upper limbs.

• Assess for accompanying signs of pyramidal tract involvement (e.g., spasticity, hyperreflexia, clonus).

Structured Assessment

Chaddock Toe Sign

1. Position the patient supine with legs relaxed.

2. Stroke the lateral aspect of the foot distal to the lateral malleolus from heel to little toe.

3. Observe the great toe for dorsiflexion and other toes for fanning.

Chaddock Wrist Sign

1. Position the patient’s forearm relaxed in supine or seated posture.

2. Stroke the ulnar surface near the wrist.

3. Observe for flexion of the wrist and extension of the fingers.

Clinical features

Differential Diagnosis

Diagnostic approach

• Clinical assessment remains primary; positive sign indicates upper motor neuron involvement.

• Neuroimaging: MRI or CT to localize lesions.

• Electrophysiology: EMG or nerve conduction studies if needed.

• Developmental history in children to distinguish physiologic positivity from pathology.

Management

Underlying Cause Treatment

• Stroke: supportive care, rehabilitation, and secondary prevention.

• Multiple sclerosis: disease-modifying therapy, symptomatic management.

• Traumatic brain injury: neurorehabilitation and supportive care.

Supportive Care

• Physical therapy to manage spasticity.

• Occupational therapy for limb function and dexterity.

• Patient and caregiver education on safe mobility and fall prevention.

Pediatric considerations

• Chaddock sign is normal in infants up to 7 months due to immature corticospinal pathways.

• After 7 months, positivity warrants neurologic evaluation.

Geriatric considerations

• Common in older adults with stroke, neurodegenerative disorders, or post-traumatic lesions.

• Interpretation should consider comorbidities and polypharmacy.

Patient counseling

• Explain that the sign is a neurological reflex used to detect upper motor neuron injury.

• Reassure that the test is safe, noninvasive, and part of a standard neurologic examination.

• Emphasize the importance of follow-up and rehabilitation if an underlying lesion is identified.

Conclusion

Chaddock’s sign is a valuable clinical indicator of pyramidal tract dysfunction in adults and children beyond infancy. It complements other reflex assessments, aiding in the diagnosis and localization of upper motor neuron lesions. Proper technique, interpretation, and correlation with the clinical context optimize patient evaluation and management.

References

1. Chaddock C. The reaction of the toes and ankle in hemiplegia. J Nerv Ment Dis. 1911;38:714–720.

2. Ropper AH, Samuels MA, Klein JP. Adams and Victor’s Principles of Neurology. 11th ed. New York: McGraw-Hill; 2021.

3. Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science. 5th ed. New York: McGraw-Hill; 2013.

4. Frowein RA, Mumenthaler M. Clinical examination of pyramidal signs. Neurol Clin. 2000;18:595–610.

5. American Academy of Neurology. Neurological Examination Guidelines. 2022.