Magnetic stimulation of the hand area of the motor cortex in both hemispheres was performed at rest and during reading aloud to observe modulated facilitation of hand muscle motor potentials in 6 right-handed patients, with supratentorial lesions but no motor impairment or aphasia, who had undergone the Wada test to determine speech dominance, showing that 5 were left hemisphere dominant and one was bilateral hemisphere dominant. Motor potentials were facilitated during reading aloud in only the right hand in 3 patients, all left hemisphere dominant, greater in the right hand in one, left hemisphere dominant, and greater in the left hand in one patient, bilateral hemisphere dominant. Based on these results we defined a laterality index which was consistent with the Wada test results. Magnetic stimulation may prove useful for determining cerebral dominance, as our method correlates well with the Wada test, and is safe, convenient, and inexpensive.
Hemispheric dominance was investigated in left-handed subjects using single transcranial magnetic stimulation to assess the possible effect of forced change in the dominant hand. Single transcranial magnetic stimuli were delivered randomly over the hand area of the left or right motor cortex of 8 Japanese self-declared left-handed adult volunteers. Electromyographic responses were recorded in the relaxed first dorsal interosseous muscle while the subjects read aloud. Laterality quotient calculated by the Edinburgh Inventory ranged from −100 to −5.26 and laterality index calculated from motor evoked potentials ranged from −86.2 to 38.8. There was no significant correlation between laterality quotient and laterality index. Mean data values across all 8 subjects indicated significant increases only in the left hand. Our ratio analysis of facilitation of the hand motor potentials showed that 2 each of the 8 self-declared left-handers were right- and left-hand dominant and the other 4 were bilateral-hand dominant. Speech dominancy was localized primarily in the right cerebral hemisphere in left-handed subjects, but some individuals exhibited bilateral or left dominance, possibly attributable to the forced change of hand preference for writing in childhood. Our findings suggest changes in the connections between the speech and hand motor areas.
Objective and subjective assessments of postoperative improvement and impairment in cognition were prospectively compared in patients who underwent carotid endarterectomy (CEA). Each patient underwent subjective cognitive assessment by a neurosurgeon and the patient's next of kin, and neuropsychological testing consisting of five test scores within 7 days before surgery and between 1 and 2 months after surgery. Of 213 patients studied, 24 (11%), 166 (78%), and 23 (11%) patients were defined as having subjectively improved, unchanged, and impaired cognition, respectively, following surgery. In all neuropsychological tests, differences in test scores between the two tests (postoperative test score − preoperative test score) significantly differentiated patients with subjectively improved, unchanged, and impaired cognition after surgery. Receiver operating characteristic analysis showed that the cut-off point for the differences in neuropsychological test scores in detecting subjective improvement and impairment in cognition after surgery was identical to mean +2 standard deviations (SDs) and mean −2 SDs, respectively, of the control value obtained from normal subjects. Of 27 patients with differences in neuropsychological test scores more than the upper cut-off point and 26 patients with differences in neuropsychological test scores less than the lower cut-off point in one or more neuropsychological tests, 24 (89%) and 23 (88%) exhibited subjectively improved and impaired cognition, respectively, after surgery. The present study indicates that neuropsychological test scores reflect the subjective assessment of postoperative change in cognition, and can detect subjective improvement and impairment in cognition after CEA using the optimal cut-off points for the test scores.
A 74-year-old man with a history of asymptomatic right internal carotid artery (ICA) occlusion experienced amaurosis fugax in the left eye. Angiography showed left cervical ICA stenosis in addition to right cervical ICA occlusion. The right anterior and middle cerebral artery (MCA) territories were perfused from the left ICA via the anterior communicating artery. Brain perfusion single-photon emission computed tomography revealed reduced cerebral blood flow and reduced cerebrovascular reactivity to acetazolamide only in the right cerebral hemisphere. The patient underwent left carotid endarterectomy (CEA). Transcranial Doppler monitoring showed microembolic signals in the left MCA during dissection of the left ICA, but intraoperative monitoring suggested absence of global hypoperfusion or ischemia in the bilateral cerebral hemispheres during left ICA clamping. Transient and slight motor weakness of the left upper extremity was noted on recovery from anesthesia. Diffusion-weighted magnetic resonance imaging demonstrated the development of new spotty ischemic lesions only in the right cerebral hemisphere. The present case suggests that intraoperative cerebral embolism causing postoperative neurological deficits can develop exclusively in the cerebral hemisphere contralateral to CEA if the hemisphere has preoperative hemodynamic impairment and collateral circulation via the anterior communicating artery from the ICA ipsilateral to CEA.
Ultrasonography has become a common method for evaluation of the central nervous system. We present our experience with ultrasonography monitoring with a burr-hole transducer for investigation of intracranial lesions. Common indications for this technique included guidance for placement of catheters, localization of masses, aspiration of cystic lesion, and confirmation of removal. Postoperative computed tomography (CT) was obtained to corroborate the appropriate procedures performed under ultrasonography guidance. Intraoperative ultrasonography provided immediate real-time information about the anatomy and pathological location of lesions. Postoperative CT findings were consistent with intraoperative ultrasonography findings. No procedure-related complication was noted and problems were minimal. Intraoperative ultrasonography using a burr-hole transducer has proved to be useful in burr-hole surgery.
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