Isolated hypoglossal nerve palsy due to internal carotid artery dissection.

A case of an isolated hypoglossal nerve palsy is reported. The differential diagnosis is discussed, in the context of the requirement for careful scrutiny of the entire course of the hypoglossal nerve on imaging, to detect underlying pathology remote from the tongue, and to avoid unnecessary invasive diagnostic procedures prompted by the appearance of a 'pseudomass' of the weak tongue both clinically and radiologically.