Characteristics and utility of combined duplex color-coded ultrasonography in the cervical rotational position with head MRI and MRA in the differential diagnosis of apogeotropic direction-changing positional nystagmus

OBJECTIVE: To determine whether cervical ultrasonography, magnetic resonance imaging (MRI), and magnetic resonance angiography (MRA) are useful in the differential diagnosis of etiology and understanding the pathophysiology in cases of apogeotropic direction-changing positional nystagmus (DCPN). METHODS: Thirty patients with apogeotropic DCPN were classified into 11 cases of central disease, seven cases of mixed central and peripheral disease, and 12 cases of peripheral disease by differential diagnosis based on various balance function, neuro-otological, and imaging tests. Cervical ultrasonography using the cervical rotation method and MRI and MRA of the head and neck were performed in most patients with apogeotropic DCPN. We reviewed the presence of abnormal imaging findings according to the disease etiology. RESULTS: Of the 30 patients with apogeotropic DCPN, 23 showed vascular abnormalities or central lesions on imaging. Vascular lesions were found in six of the 12 patients with peripheral disease. Cervical ultrasonography with cervical rotation detected blood flow disturbance in the vertebral artery in eight patients in whom the disturbance could not be detected by MRI or MRA of the head and neck. DISCUSSION: We hypothesize that the causative disease of apogeotropic DCPN may be strongly associated with circulatory insufficiency of the vertebrobasilar and carotid arteries, and that impaired blood flow in these vessels may affect peripheral vestibular and central function. In patients with apogeotropic DCPN, examinations of vestibular function, central nervous system symptoms, and brain hemodynamics are valuable for differential diagnosis.