Lesions in the posterior cranial fossa were visualized by single photon emission computed tomography (SPECT) with 123I-IMP (N-isopropyl-p-123I-iodoamphetamine) and 99mTc-HM-PAO (99mTc-hexametylpropyleneamine oxime). It is generally held that these radiopharmaceuticals penetrate the walls of cerebral blood vessels and that their accumulations in the brain tissue may reflect the cerebral blood flow.
Six patients with lesions in the central nervous system all showed wider areas of abnormality in SPECT than in X-ray CT, indicating a larger lesion of blood flow disturbance.
In the next series of 11 patients with vertigo or dizziness of unknown etiology, eight had abnormal findings in the scan with 123I-IMP as did four of the nine in the scan with 99mTc-HM-PAO. Thus, most patients with dizziness of unknown etiology may have some vertebral blood flow disorder, which in some cases is not clearly diagnosed by conventional vestibular examinations or even by X-ray CT scan.
The accuracy of these diagnostic measures for otoneurological problems awaits further studies of their sensitivity and specificity.
