[Use of SPECT in the diagnosis of vertigo syndromes of vascular nature].

Dizziness is doubtlessly one of the most common symptoms to arise in ischemia of the brainstem. In such cases the circulatory deficit can not only cause a direct lesion of the vestibular structures but it may also block the compensatory process. There are, however, significant difficulties in establishing whether such dizziness can be attributed to a brainstem insufficiency (BI). In fact, both CAT and NMR provide data only in the case of permanent CNS tissue lesions and tests such as the Doppler examination of neck blood vessels are unable to establish the true state of cerebral blood flow. In order to obtain semi-quantitative data regarding cerebral blood flow 99mTc-HMPAO-S.P.E.T. (Single Photon Emission Tomography) was used in 18 patients suffering from dizziness and for whom there was strong indication that the underlying cause could be vascular. There was a discrepancy between the Doppler and S.P.E.T. findings in 50% of the cases. CAT, however, proved negative in all but one of the cases. These data indicate that Doppler testing of the neck blood vessels can provide useful information regarding the status of the cerebral-afferent vessels but that these cannot be correlated to the level of cerebral blood flow. On the other hand, with S.P.E.T., in 15 of the 18 patients, it proved possible to identify significant alterations in cerebral blood flow in the absence of any permanent tissue lesions as those revealed by CAT and NMR. In the light of the present results cerebral S.P.E.T. appears to be a highly valid tool when, faced with dizziness for which a vascular origin is suspected, one must evaluate cerebral prognosis and therapy.