Absence of hemispheric dominance for mental rotation ability: a transcranial Doppler study.

Mean blood flow velocity (MFV) of the middle cerebral arteries was monitored in 19 healthy, adult, right-handed subjects during the resting phase and the execution of a series of neuropsychological tests: two right/left discrimination tasks, two mental rotation paradigms (the Ratcliff's test and a cube comparison test) and a phonemic fluency task, which was utilised as an internal control. In the group as a whole, the Ratcliff's test was associated with a significant bilateral increase in MFV versus both the resting state (right: p < .000001, left: p < .000001) and right/left discrimination tasks (task 1: right: p = .003, left: p = .005; task 2: right: p = .001, left: p = .001). The cube comparison in turn produced a significant increase in MFV versus both the baseline conditions (right: p < .000001, left: p < .000001) and the Ratcliff's test (right: p = .01, left: p = .002). As expected, the fluency task was associated with a significant asymmetric increase in cerebral perfusion (left > right: p = .0001). Increasing task difficulty (right/left discrimination < Ratcliffs test < cube comparison) was paralleled by a roughly proportional rise in MFV values (right: r = .424, p < .01; left: r = .331, p = .01). In conclusion, we were able to demonstrate that (1) in addition to the amount of MFV variation due to right/left discrimination (when required), mental rotation per se causes a bihemispheric activation irrespective of the experimental paradigm; (2) the MFV variation is proportional to the difficulty of the tasks.

Migraine with aura and right-to-left shunt on transcranial Doppler: a case-control study.

Right-to-left shunt (RLS), usually due to patent foramen ovale, is a well-established risk factor for ischemic stroke in young patients, while the role of migraine as an independent factor is still debated. We evaluated 44 patients suffering from migraine with aura, and compared them with 73 patients younger than 50 with focal cerebral ischemia, and 50 controls, asymptomatic for cerebrovascular disease, and without a history of migraine. All the subjects underwent bilateral transcranial Doppler with injection of contrast medium in an antecubital vein. The test was performed during normal ventilation and during Valsalva maneuver, recording both the middle cerebral arteries and the basilar artery. Criteria for diagnosing RLS was the presence of at least 3 microbubbles within 15 s from injection. Eighteen out of 44 migraine patients (41%) showed RLS, as opposed to 8 of 50 controls (16%) (p < 0.005). Twenty-six out of 73 patients with cerebral ischemia had RLS (35%). We conclude that the prevalence of RLS in patients with migraine with aura is significantly higher than in normal controls, and is similar to the prevalence of RLS in young patients with stroke. These findings could be helpful in understanding the relationship between migraine and stroke.