Changes of Neural Activity Correlate With the Severity of Cortical Ischemia in Patients With Unilateral Major Cerebral Artery Occlusion

Abstract

Background and Purpose-In major cerebral arterial steno-occlusive diseases, there can be remarkably decreased hemodynamic reserve without marked neurological impairments. In such settings, it is not known whether the neural activity is well maintained or disturbed according to the severity of cerebral ischemia. The present study was therefore undertaken to examine the neural activity under mild cerebral ischemia resulting from major cerebral arterial occlusion. Methods-Seven patients with minor neurological impairment as well as either unilateral internal carotid artery or middle cerebral artery occlusion were studied. The severity of the cortical ischemia was assessed by measuring regional cerebral blood flow (rCBF) with positron emission tomography. The change in neural activity in the ischemic brain was then evaluated by means of somatosensory evoked magnetic field with magnetoencephalography. Results-The

Hypoperfusion without stroke alters motor activation in the opposite hemisphere

“…The ROI analysis did not, however, show a significant difference (t [10] ϭ 0.96, two-tailed p ϭ 0.36; see Fig 2B). Thus, unlike previous reports, we did not see a significant reduction in the BOLD response in the hypoperfused hemisphere compared with controls.…”

“…The lack of significant interaction between task and group suggests that hypoperfusion causes changes in ipsilateral recruitment in motor tasks through a mechanism that is separate from mechanisms sensitive to task complexity. There was no significant difference in ipsilateral activation across the same five ROIs when controls and patients used their right hand (t [10] ϭ 0.19, two-tailed p ϭ 0.85; see 3C). Thus, the difference in ipsilateral activation between patients and controls was specific to the hemisphere opposite the stenosis/occlusion.…”

“…8,9 A correlation has also been found between degree of neural activity and cerebral blood flow (CBF) in patients with unilateral major cerebral artery occlusion. 10 In healthy subjects, ipsilateral activation during the performance of finger/hand movement tasks is dependent on task complexity/difficulty. [11][12][13][14] Our secondary hypothesis was that the mechanism that leads to ipsilateral activation from exhausted VMR is separate from that caused by variations in difficulty/complexity of the task.…”

Impaired hemodynamics and neural activation?

“…Previous research provided evidence for changes of neural activity, which correlated with the severity of hemodynamic impairment in the somatosensory system: a graded reduction of the initial somatosensory evoked field component (N20) and an augmentation of the second field component (N30) as a compensatory mechanism were described. 3 The existence of a neuronal reserve mechanism, supplementing hemodynamic reserve strategies in an attempt to maintain neuronal function, thus appears probable. The current study assessed the influence of impaired hemodynamics on the fMRI blood oxygenation level dependent (BOLD) signal changes and their relation to neural activation of the involved functional network in both hemispheres.…”

“…Surgical treatments like denervation of the parotid gland, 3 salivary duct ligation, 4 or bilateral excision of the sublingual salivary glands 5 may risk irreversible adverse effects. Botulinum toxin A (BTX-A; Dysport, Ipsen Pharma, Germany) is a known inhibitor of acetylcholine release in cholinergic nerve terminals and is well known to effectively alleviate dystonic and spastic symptoms.…”