What are the Babinski sign and the Hoffmann sign?

Babinski and Hoffmann Signs: Neurological Examination Findings

The Babinski sign and Hoffmann sign are clinical examination findings that indicate upper motor neuron (pyramidal tract) dysfunction, with the Babinski sign being more specific for corticospinal tract lesions while the Hoffmann sign serves as a sensitive screening tool for cervical myelopathy and cord compression.

Babinski Sign

The Babinski sign is elicited by stroking the lateral plantar surface of the foot from heel to toe. A positive response consists of dorsiflexion (upward movement) of the great toe with or without fanning of the other toes 1, 2.

Clinical Significance:

• Indicates pyramidal tract dysfunction when the lesion involves fibers projecting to foot muscle motoneurons 1
• Mediated by the extensor hallucis longus muscle 1
• Normal in infants but pathological after approximately 2 years of age 1
• Can appear transiently in epilepsy, strychnine poisoning, or during acute illness 1

Important Caveats:

• May be absent acutely after transverse spinal cord lesions or acute brain lesions due to temporary spinal motoneuron inexcitability 1
• Can be absent despite other clear pyramidal signs ("formes frustes") 1
• Found in 33% of patients with mild cervical myelopathy (mJOA scores 14-16) but in 83% with severe myelopathy (mJOA ≤10) 3

Associated Conditions:

The Babinski sign appears in multiple neurological conditions including hepatic encephalopathy 4, upper motor neuron lesions 5, and various forms of myelopathy 6.

Hoffmann Sign

The Hoffmann sign is elicited by flicking the distal phalanx of the middle finger downward and observing for flexion of the thumb and index finger 3.

Clinical Significance:

• More sensitive than Babinski sign for detecting cervical myelopathy, particularly in early disease 3
• Present in 68% of surgically-treated cervical myelopathy patients overall 3
• In mild myelopathy (mJOA 14-16): present in 46% of cases compared to only 10% with Babinski sign 3
• In severe myelopathy (mJOA ≤10): present in 81% of cases 3

Screening Value:

Among patients presenting with lumbar spine complaints only 3:

• Bilateral positive Hoffmann sign: 91% had cervical cord compression on MRI
• Unilateral positive Hoffmann sign: 50% had cervical cord compression on MRI
• Overall prevalence of positive Hoffmann sign: 12% in this population

This makes the bilateral Hoffmann sign a highly sensitive screening tool for occult cervical pathology 3.

Examination Technique Considerations

When assessing these signs 5:

• Test for hyperreflexia (present in 60% of cervical myelopathy cases) 3
• Assess muscle tone, strength, and bulk through functional observation
• Check for asymmetry in reflexes or responses
• Document the quality and intensity of responses

Pathophysiological Note

While both signs indicate upper motor neuron dysfunction, hyper-reflexia with positive Hoffmann and Babinski signs can occasionally occur in lower motor neuron disorders like acute motor axonal neuropathy (AMAN) due to immune-mediated damage to spinal inhibitory interneuronal networks 7. In such cases, MRI and transcranial magnetic stimulation would show no corticospinal tract involvement, distinguishing this from true pyramidal lesions.

Clinical Application Algorithm

1. If Hoffmann sign is positive bilaterally → Obtain cervical spine MRI (91% likelihood of cord compression) 3
2. If Hoffmann sign is positive unilaterally → Consider cervical MRI based on clinical context (50% likelihood) 3
3. If Babinski sign is positive → Indicates more advanced pyramidal dysfunction; investigate for structural CNS lesions 1, 3
4. If both signs are absent → Does not exclude early myelopathy, especially in acute presentations 1