The tibialis anterior response revisited

Area of Science:

• Neurology
• Clinical Neurophysiology
• Peripheral Neuropathy

Background:

• The idiomuscular response to direct percussion is an underutilized diagnostic tool due to unclear mechanisms and significance.
• Previous observations suggested distinct responses in specific neurological conditions during routine examinations.

Purpose of the Study:

• To investigate the diagnostic utility of the idiomuscular response of the tibialis anterior muscle in patients with bilateral lower limb weakness.
• To differentiate between acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and upper motor neuron (UMN) lesions using this reflex.

Main Methods:

• Assessed 73 consecutive patients presenting with bilateral lower limb weakness.
• Evaluated the idiomuscular response to direct percussion of the tibialis anterior muscle.
• Correlated the observed responses (dorsiflexion, inversion) with confirmed diagnoses of AIDP and UMN involvement.

Main Results:

• A strong dorsiflexion response was observed in 78.6% of AIDP patients, with 100% specificity.
• An inversion response showed a sensitivity of 92.3% in patients with UMN involvement and 96.7% specificity.
• The idiomuscular response proved highly sensitive and specific for differentiating these conditions.

Conclusions:

• Percussion of the tibialis anterior muscle elicits a valuable idiomuscular response for diagnosing neurological disorders.
• This simple clinical test can aid in assessing patients with unexplained bilateral lower limb weakness, distinguishing AIDP from UMN lesions.