A new nystagmographic test for the elicitation of sub-clinical vertebro-basilar insufficiency and poor cochleo-vestibular vascularization.

The nystagmus due to vertebro-basilar artery insufficiency is that nystagmus which is induced by torsion and extension of the neck, continued for more than 3 minutes, after nystagmus of other types has been excluded. It is of vascular origin, in contra-distinction to nystagmus of cervical origin, which is proprioceptive. It permits the detection of sub-clinical vertebro-basilar insufficiency, and it should be elicited before any operation which requires prolonged cervical rotation. It is a very simple method which can be performed at the end of the classical torsion swing test, and we have found the results very informative.