Unilateral atrophy of the tongue is the most important radiologic feature of hypoglossal nerve paralysis. When it is identified, thorough assessment of the hypoglossal nerve from brainstem to the tongue should be performed.

In acute hypoglossal nerve palsy:

• tongue deviation toward the weak side
• edematous change (T1WI hypointense, T2WI hyperintense)

In chronic hypoglossal nerve palsy:

• tongue deviation toward the weak side
• tongue atrophy (volume loss)
• fatty infiltration (both T1WI and T2WI hyperintense)