TESTING THE VALIDITY OF THE LACUNAR HYPOTHESIS - THE NORTHERN MANHATTAN STROKE STUDY EXPERIENCE

Background/Objective: Few studies have attempted to validate the ''lac unar hypothesis.'' The accuracy of identifying lacunar and other nonla cunar mechanisms of infarction will be increasingly important in evalu ating potential stroke treatments. The aim of this study was to determ ine the value of lacunar syndromes in predicting radiologic lacunes an d the value of clinicoradiologic lacunes in predicting ''lacunar infar ction'' as final stroke mechanism. Methods: From 1990 to 1994, 591 pat ients with cerebral infarction, who were from northern Manhattan and o ver the age of 39, were prospectively examined. Data were collected on the admitting clinical syndrome (lacunar or nonlacunar) and brain ima ging findings. Lacunar syndromes were categorized as pure motor hemipa resis (PMH), pure sensory syndrome (PSS), sensorimotor syndrome (SMS), ataxic-hemiparesis (A-H), and other lacunar syndromes. Brain imaging findings were classified as radiologic lacune or nonlacune. Positive p redictive values, sensitivities, and specificities of lacunar syndrome s for identifying radiologic lacunes were calculated. The final mechan ism of infarction was determined after review of all the diagnostic te sts and compared among the lacunar groups. Results: Lacunar syndromes occurred in 225 cases. PMH was the most common lacunar syndrome, accou nting for 45%, SMS 20%, A-Pi 18%, and PSS 7%. Lacunar syndromes had an overall positive predictive value (PPV) of 87% for detecting radiolog ic lacune: PSS 100%, A-H 95%, SMS 87%, and PMH 79%. Among the 195 pati ents who presented with a lacunar syndrome and had this condition conf irmed radiologically, 147 were classified as having a final diagnosis of lacunar mechanism of infarction (PPV = 75%). Atherosclerosis accoun ted for 17 (9%), cardioembolism 10 (5%), cryptogenic 17 (9%), and othe r unusual causes 4 (2%). Conclusion: While lacunar syndromes, especial ly PSS and A-H, are highly predictive of lacune, in about one in four patients presenting with lacunar syndromes confirmed radiologically th e condition is associated with nonlacunar mechanisms of infarction. No ninvasive neurovascular and cardiac evaluations are still warranted ev en among patients with lacunes.