From the Research
The specific localization for the pouting sign is the corner of the mouth on the affected side of the face, which is observed in patients with facial nerve palsy due to weakness or paralysis of the orbicularis oris muscle, innervated by the facial nerve (cranial nerve VII) 1. This sign is characterized by the corner of the mouth on the paralyzed side drooping downward and outward, and when the patient attempts to pucker their lips or pout, the affected corner of the mouth remains immobile and does not move upward and inward as it should. The pouting sign helps clinicians localize the lesion to the facial nerve and differentiate facial nerve palsy from other conditions affecting facial muscles or central nervous system disorders. Some studies have reported that the corticobulbar tract fibers descend near the corticospinal tract, mostly to the upper medulla, where they decussate and ascend in the dorsolateral medulla to connect with the contralateral facial nucleus 2. However, the most relevant study to this question is the one that describes pure motor hemiplegia including the face induced by an infarct of the medullary pyramid, which suggests that the lesion responsible for an upper motor neuron facial palsy affects the corticobulbar tract at the level of the midpons or more rostrally 1. Other studies have discussed the clinical features that distinguish primary lateral sclerosis, upper motor neuron-dominant amyotrophic lateral sclerosis, and typical amyotrophic lateral sclerosis, but these are not directly relevant to the specific localization of the pouting sign 3. Similarly, studies on the use of botulinum toxin in the treatment of upper motor neuron lesions have discussed the pathophysiological aspects of this condition, but do not provide information on the specific localization of the pouting sign 4. In summary, the pouting sign is a clinical feature that helps localize the lesion to the facial nerve, and its specific localization is the corner of the mouth on the affected side of the face, as described in the study by 1.