Traumatic trochlear nerve palsy following minor occipital impact--four case reports.

Four patients presented with transient trochlear nerve palsy following occipital impact. The impact was slight in all patients, and neuroimaging found no lesions of the nerve. Three patients had delayed onset. Two patients did not complain of diplopia, but were only aware of blurred vision. In such patients, the head tilting test was useful for diagnosis. Minor occipital impact can cause trochlear nerve palsy, which requires careful neurological examinations to identify.