Bielschowsky’s sign is head tilt toward the shoulder, typically toward
the side contralateral to a trochlear (IV) nerve palsy. The intorsion of
the unaffected eye brought about by the head tilt compensates for the
double vision caused by the unopposed extorsion of the affected eye.
Very occasionally, head tilt is paradoxical (i.e., toward the involved
side: presumably the greater separation of images thus produced
allows one of them to be ignored).
Bielschowsky’s (head tilt) test consists of the examiner tipping the
patient’s head from shoulder to shoulder to see if this improves or
exacerbates double vision, as will be the case when the head is respec-
tively tilted away from or toward the affected side in a unilateral
trochlear (IV) nerve lesion. The test is usually negative in a skew devi-
ation causing vertical divergence of the eyes. This test may also be used
as part of the assessment of vertical diplopia to see whether hyper-
tropia changes with head tilt to left or right; increased hypertropia on
left head tilt suggests a weak intortor of the left eye (superior rectus);
increased hypertropia on right head tilt suggests a weak intortor of the
right eye (superior oblique).
Diplopia; Hypertropia; Skew deviation