Lower facial weakness can produce the appearance of tongue deviation when none is present because of distortion of the normal facial appearance. Manually pulling up the weak side of the face eliminates the “deviation.” It may help to gauge tongue position in relation to the tip of the nose or the notch between the upper incisor teeth. Tongue weakness may result from a supranuclear, nuclear, or infranuclear lesions. Supranuclear lesions cause weakness but no atrophy, and the weakness is rarely severe. Since the genioglossus—the principal tongue protractor—has mainly crossed supranuclear innervation, the tongue protrudes toward the side opposite a supranuclear lesion. In a large series of patients with acute unilateral ischemic strokes above the lower brainstem, tongue deviation occurred in 29%, always toward the side of limb weakness.(3) In addition to weakness, nuclear and infranuclear lesions cause atrophy of the involved side. The tongue protrudes toward the weak side, which is also the side of the lesion. Progressive nuclear lesions, such as motor neuron disease, often cause fasciculations in addition to weakness.
In hemiparesis due to a carotid dissection, the tongue may deviate to the side opposite the hemiparesis because the dissection injures the hypoglossal nerve as it curves around the carotid sheath. Carotid dissection may also present as an isolated hypoglossal nerve palsy.(4) Keane reported four cases of “wrong way” tongue deviation — toward the normal side rather than the hemiparetic side — in functional hemiparesis.(5) This should not be confused with a medial medullary lesion.
Video used by permission of Paul D. Larsen, M.D., University of Nebraska Medical Center and Suzanne S. Stensaas, Ph.D., University of Utah School of Medicine. Additional materials were drawn from resources provided by Alejandro Stern, Stern Foundation, Buenos Aires, Argentina; Kathleen Digre, M.D., University of Utah; and Daniel Jacobson, M.D., Marshfield Clinic, Wisconsin. The movies are licensed under a Creative Commons Attribution-NonCommerical-ShareAlike 2.5 License. Available at http://library.med.utah.edu/neurologicexam/html/gait_abnormal.html#13.
1. Campbell WW. DeJong's the neurologic examination, 7th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2013.
2. Campbell WW. Clinical signs in neurology: a compendium. Philadelphia: Wolters Kluwer Health, 2016.
3. Umapathi T, Venketasubramanian N, Leck KJ, et al. Tongue deviation in acute ischaemic stroke: a study of supranuclear twelfth cranial nerve palsy in 300 stroke patients. Cerebrovasc Dis 2000;10:462–465.
4. Fujii H, Ohtsuki T, Takeda I, et al. Isolated unilateral hypoglossal nerve paralysis caused by internal carotid artery dissection. J Stroke Cerebrovasc Dis. 2014;23:e405-e406.
5. Keane JR. Wrong-way deviation of the tongue with hysterical hemiparesis. Neurology 1986;36:1406-7.