47. Tongue Protrusion

What is Being Tested?

Fasciculations and atrophy are signs of lower motor neuron lesions (see Table 3.3 in Neuroanatomy through Clinical Cases 3e). Unilateral tongue weakness causes the tongue to deviate toward the weak side. Tongue weakness can result from lesions of the tongue muscles, the neuromuscular junction, the lower motor neurons of the hypoglossal nerve (CN XII), or the upper motor neurons originating in the motor cortex. Lesions of the motor cortex cause contralateral tongue weakness.