With regard to the differential evaluation for cervicogenic dizziness, it is important to note that this patient's symptoms of dizziness remained consistent in that they occurred only during cervical movement and that they did not increase as end-range cervical positions were maintained. Dizziness that occurs with cervical movement is called positioning-type dizziness, whereas dizziness that increases with maintained position is called positional-type dizziness). If cervical positioning contributed to a reduction in arterial lumen diameter and a change in flow rate, it seems logical that this symptom would increase while test positions were maintained (i.e., delayed onset or latency of symptoms). At this point in the clinical examination, differential evaluation testing did not suggest the vertebrobasilar, visual, or vestibular system as the source of the patient's report of dizziness during cervical motion. Although the tests used for this differentiation process have been reported by several authors the reliability, validity, and responsiveness of this process have not been determined.