Neurologic and visual symptoms in essential thrombocythemia: efficacy of low-dose aspirin.

Neurologic and visual symptoms frequently occurred in 56 reported patients with essential thrombocythemia (ET). They may either precede or follow the well-known microcirculatory complications of ET of acroparesthesias, erythromelalgia, and acrocyanosis or ischemia of one or more toes. In comparison with transient ischemic attacks in patients with vascular risk factors, the usual neurologic presentation of ET consists of brief attacks of sudden cerebral or visual dysfunction, which can be either well localized or diffuse and entirely nonspecific. A dull and throbby headache usually lasting for several hours frequently accompanies the neurologic symptoms. Visual symptoms are less frequent and include transient monocular blindness and global symptoms such as scintillating scotomas and attacks of blurred vision. Neurologic and visual symptoms may leave minor sequelae but are generally nondisabling. The striking similarity to migraine, together with the absence of vascular risk factors and the striking efficacy of aspirin treatment supports the hypothesis that the ischemic neurologic and visual symptoms in ET are caused by shear rate-induced intravascular activation and aggregation of platelets with subsequent transient sludging or occlusion of the cerebral arterial microvasculature. Available data show that both the erythromelalgic distress and the ischemic neurologic attacks in ET are completely abolished by control of platelet function with low dose aspirin alone or reduction of platelet counts to normal as well as by the combination of platelet reducing therapy and low-dose aspirin. Early recognition and appropriate treatment of neurologic symptoms in patients with ET is therefore of great clinical relevance.