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A Journal on Otorhinolaryngology, Head and Neck Surgery,
Plastic Reconstructive Surgery, Otoneurosurgery
Indexed/Abstracted in: EMBASE, Scopus
Otorinolaringologia 1999 March;49(1):39-45
The use of transcranial Doppler in subjects with instability and possible alterations of the autonomous nervous system function
Magnano M., Orione M., Canale G., Tondolo E., Bona-Galvagno M., Lerda W.*, Poli L.**, Monge L.***
Università degli Studi - Torino Ospedale Mauriziano - Torino
* UO ORL
** Istituto di Geriatria Ospedale «S. Giovanni Battista e della Città di Torino» - Torino
*** Divisione di Diabetologia
Background and aim. The onset of vertigo symptoms or the feeling of instability is often hard to evaluate and earlier authors have identified alterations of the autonomous nervous system (ANS) which may lead to a dysautoregulation of cerebral blood flow and the onset of vertigo. This hypothesis has been verified by the use of transcranial Doppler in subjects suffering from instability and it has been hypothesised that the cause of disequilibrium is cerebral vasoconstriction.
Methods. The authors examined ANS function in a group of 24 subjects (14 females, 10 males) suffering from vertigo and instability of undefined etiology using a computerized system to evaluate cardiovascular reflex responses, in particular the cardiovascular responses to ANS activation tests: measurement of alteration in heart frequency during transition from clino- to orthostatism (LS1) and vice versa (SL1-SL2), making the patient cough (CT), during Valsalva’s manoeuvre (VR), during deep breathing 4DB) and measurement of arterial pressure while standing. In this way, it was possible to identify two groups of subjects: 9 patients with normal tests and 15 with altered tests. All 24 subjects underwent transcranial Doppler on the middle cerebral artery to evaluate changes in systolic, diastolic and mid flow and the pulse index in basal conditions, orthostatism, apnea and after hyperventilation.
Results. The comparison between the two groups showed a reduced cerebral vascular response in dysautonomic subjects after hyperventilation affecting diastolic spped. Moreover, a statistically significant correlation was observed between LS1 and the mean rate of flow in apnea (p=0.030), between CT and the systo-diastolic index (p=0.051) and between VR and systolic rate of flow. During hyperventilation, there was a significant correlation between rate of flow in diastole, mean speed and the systo-diastolic index.
Conclusions. A careful analysis of the results of the cardiovascular tests and their correlation with the results of transcranial Doppler confirms the findings of other authors during dysautonomia, namely the presence of an altered cerebral autoregulation which takes the form of increased intracranial vascular resistance. The symptoms of vertigo or instability might be the expression of an insufficient posterior circulation responsible for the vascularisation of those structures which preserve balance and are sensitive to ischemia caused by dysregulation and fostered by arterial hypertension.