The Chaddock sign is a neurological reflex test named after Charles Gilbert Chaddock (1861–1936), an American neurologist, psychiatrist, translator, and poet. It is one of several “Babinski-like” reflexes used to evaluate upper motor neuron (UMN) lesions, particularly in the corticospinal (pyramidal) tract.
1. Historical Background and Biography
Dr. Charles G. Chaddock was born in Jonesville, Michigan, in 1861. He earned his MD from the University of Michigan in 1885 and later studied in Munich and Paris. While in Paris, he became a student of Joseph Babinski, one of the most influential neurologists of his time.
Chaddock was more than a clinician. He was also a linguistic pioneer in medical translation. Notably, he introduced terms such as “homosexuality,” “heterosexuality,” and “bisexuality” into the English medical lexicon through his 1892 translation of Richard von Krafft-Ebing’s Psychopathia Sexualis. His work helped shape psychiatric and neurological discourse in English-speaking medicine.
2. Origin and Description of the Chaddock Sign
In 1911, Chaddock presented the reflex that bears his name to the St. Louis Neurological Society. His aim was to develop a more sensitive and reliable way to elicit abnormal plantar responses, especially when the Babinski reflex was difficult to provoke.
Elicitation Method:
The Chaddock sign is elicited by stroking the skin around the lateral malleolus (the outer ankle).
A positive response is dorsiflexion of the great toe, sometimes accompanied by fanning of the other toes — identical to the Babinski response.
He proposed that stimulating the ankle region would reduce withdrawal artifacts, which sometimes confound Babinski testing due to plantar hypersensitivity.
3. Clinical Significance
A positive Chaddock sign is indicative of upper motor neuron (UMN) lesions, and may be seen in:
Stroke
Multiple sclerosis
Spinal cord injury
Amyotrophic lateral sclerosis (ALS)
It is particularly useful when the Babinski sign is absent, equivocal, or hard to interpret, making it a valuable supplementary tool in neurological exams.
4. Chaddock’s Other Contributions
In 1912, Chaddock also described the Chaddock wrist sign, a lesser-known reflex associated with pyramidal tract lesions of the upper limb. While it never gained the same prominence as the lower limb sign, it illustrates Chaddock’s commitment to refining bedside neurology.
Chaddock remained active in academic neurology until his death on July 20, 1936, at the age of 74.
5. Related Reflexes
Chaddock’s sign belongs to a group of pathological reflexes used to detect corticospinal tract dysfunction. Others include:
Babinski sign – the prototype
Oppenheim sign
Gordon sign
Schaefer sign
All these elicit dorsiflexion of the great toe but differ in stimulation site and technique.
6. Use in Modern Medicine
While neuroimaging has revolutionized neurological diagnostics, bedside signs like the Chaddock reflex remain essential, especially in:
Resource-limited settings
Early neurologic assessments
Medical education (teaching reflex physiology and clinical reasoning)
They also encourage clinicians to maintain a hands-on, observation-based approach to neurological diagnosis.
7. Summary Table: Babinski vs Chaddock
8. Conclusion
The Chaddock sign is a classic example of eponymous neurology — a physical exam finding named after a clinician who sought to refine diagnostic precision. Charles G. Chaddock’s broader legacy as a physician-scholar, translator, and neurologist highlights the interdisciplinary richness of early neurology.
Though over a century old, the Chaddock sign continues to reflect the enduring value of the careful physical examination in modern clinical practice.