Understanding skew deviation and a new clinical test to differentiate it from trochlear nerve palsy.
Skew deviation is a vertical strabismus caused by a supranuclear lesion in the posterior fossa. Because skew deviation may clinically mimic trochlear nerve palsy, it is sometimes difficult to differentiate the 2 conditions. In this review we compare the clinical presentations of skew deviation and trochlear nerve palsy and examine the pathophysiology that underlies skew deviation. We then describe a novel clinical test-the upright-supine test-to differentiate skew deviation from trochlear nerve palsy: a vertical deviation that decreases by > or =50% from the upright to supine position suggests skew deviation and warrants investigation for a lesion in the posterior fossa as the cause of vertical diplopia.
Wong
Agnes M F
AM
Department of Ophthalmology and Vision Science, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada. agnes.wong@utoronto.ca
D002648:Child; D003937:Diagnosis, Differential; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D013285:Strabismus / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D020432:Trochlear Nerve Diseases / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*