Vestibular disorders in primary thrombocytosis

Objective: Balance disturbances are some of the most common symptoms among the clinical manifestations of chronic myeloproliferative disorders (MPDs) with a high platelet count, such as essential thrombocythaemia (ET) and pol ycythaemia vera (PV). In this study, we evaluated the vestibulo-oculomotor and vestibulospinal reflexes in a group of patients suffering from these di seases. Design: Evaluation of balance disturbances. Setting: Department of Neurosciences, ENT Unit, University of Pisa, Italy. Method: In this study, we evaluated 43 patients suffering from ET and PV wh o underwent otoneurologic examination, based on a study of the vestibulo-oc ulomotor and vestibulospinal reflexes. Results: There was exclusive central vestibular involvement in 26 cases (60 .4%), peripheral and central signs were associated in 8 cases (18.6%), and the involvement was purely peripheral in 1 patient. In six patients (14%), the otoneurologic examination revealed no alterations. Conclusions: The high percentage of balance disorders in cases of ET and PV probably depends upon disorders of the microcirculation due to platelet dy sfunction. We also postulate a full explanation of the involvement of the c entral vestibular system on the basis of a greater availability of central activated serotonin acting as neuromediator.