The sign that suggests bilateral fourth nerve involvement is the alternating hypertropia. 오른쪽 시선에는 왼쪽 비대가 있고 왼쪽 시선에는 오른쪽 비대가 있습니다. The Bielschowsky headtilt test also changes from side to side if one looks to the right or to the left when performing the test.