Point 7 Intro Pathway Deficit Note Summary Overview Problems Contents Anatomy

Following a lesion of the hypoglossal nucleus or nerve, there is ATROPHY of the muscles of the IPSILATERAL one-half of the tongue. This is a lower motor neuron lesion (the damaged neuron or axon directly innervates skeletal muscle). Upon closer examination, FASCICULATIONS (tiny, spontaneous contractions) can be seen. Both fasciculations and atrophy result from the loss of the normal innervation of the muscle by the lower motor neurons in the hypoglossal nucleus. Upon protrusion, the tongue will deviate TOWARD the side of the lesion (i.e., same side). This is due to the unopposed action of the genioglossus muscle on the normally innervated side of the tongue (the genioglossus pulls the tongue forward).