Internal carotid artery dissection is a frequent cause of stroke in young people. The artery dissection and the formation of an intramural hematoma could also cause mass effect on surrounding structures, causing disorders such as cranial nerve palsies (about 12% of the cases), including XII cranial nerve. In the setting of an ischemic stroke, lower cranial nerve palsy could also be due to infratentorial ischemic lesions; however, there have been also rare reports of lower cranial nerve palsy due to supratentorial cerebral ischemic lesions. We describe a case of a 55-year-old man who presented with right internal carotid artery dissection and deviation to the left of the protruded tongue. The direction of the deviation of the protruded tongue was unexpected in this patient, because if the XII nerve palsy was due to mass effect related to the intramural hematoma of the dissected artery, a deviation to the right should have happened. Anyway, a subsequent magnetic resonance revealed also an acute ischemic lesion in the right tongue area in the primary motor cortex of the patient, providing a rare, but a fitting neuroanatomical explanation of the deviation and also providing clinical evidence of functional dominance of the crossed projections of the cortico-lingual tracts.
Keywords: Cerebrovascular diseases; Hypoglossal nerve palsy; Internal carotid artery dissection; Neuroanatomy; Tongue.