Mechanisms of early aphasia recovery

Background: The course of recovery of aphasia after stroke is highly variable. Some patients, even with severe aphasia, recover rapidly over the first days after onset. The mechanism of this early recovery (and later recovery) is unclear. Plausible accounts include reperfusion of ischaemic tissue surrounding the stroke, and rapid reorganisation of structure/function relationships. Aims: Based on a recent study showing that the severity of word comprehension impairment in acute stroke patients is strongly correlated with the severity of hypoperfusion (low blood flow) in Wernicke's area, we hypothesised that early recovery of spoken word comprehension is due to reperfusion (restored blood flow) to Wernicke's area. Our objective was to evluate this hypothesis using advanced magnetic resonance imaging techniques of perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI). Methods and Procedures: A series of 100 patients with acute, left hemisphere ischaemic stroke were evaluated within 24 hours of onset or worsening of symptoms, and 3 days later, using PWI, DWI, and a battery of lexical tasks, including spoken word/picture verification. A subset of 18 patients with impaired spoken word comprehension at Day 1 were included in the study. Chi square analysis was used to identify the association between early recovery of spoken word comprehension and reperfusion of each of 10 Brodmann's areas (BA). Outcomes & Results: Early recovery of spoken word comprehension was significantly associated with reperfusion of BA 22 (Wernicke's area), but not with reperfusion of other BAs. All patients who showed early recovery of word comprehension also showed reperfusion of Wernicke's area, due to carotid endarterectomy, carotid stenting, induced blood pressure elevation, or spontaneous reperfusion. Conclusions: Tissue recovery, brought about by restored blood pressure elevation, likely accounts for cases of rapid resolution of aphasia in the first few days of stroke. Other mechanisms of recovery, including reorganisation of structure/function relationships, and learning of compensatory strategies, are likely important in later stages of recovery.

[1]  T. Olsen,et al.  Blood flow and vascular reactivity in collaterally perfused brain tissue. Evidence of an ischemic penumbra in patients with acute stroke. , 1983, Stroke.

[2]  J. Ulatowski,et al.  Reperfusion of Specific Brain Regions by Raising Blood Pressure Restores Selective Language Functions in Subacute Stroke , 2001, Brain and Language.

[3]  B. Rosen,et al.  A functional MRI study of subjects recovered from hemiparetic stroke. , 1997, Stroke.

[4]  G. Sette,et al.  Acute ischemic strokes improving during the first 48 hours of onset: predictability, outcome, and possible mechanisms. A comparison with early deteriorating strokes. , 1997, Stroke.

[5]  Richard S. J. Frackowiak,et al.  The functional anatomy of motor recovery after stroke in humans: A study with positron emission tomography , 1991, Annals of neurology.

[6]  D. Walker-Batson,et al.  A Double-Blind, Placebo-Controlled Study of the Use of Amphetamine in the Treatment of Aphasia , 2001, Stroke.

[7]  R. Nudo,et al.  Neural Substrates for the Effects of Rehabilitative Training on Motor Recovery After Ischemic Infarct , 1996, Science.

[8]  L H Schwamm,et al.  Time course of lesion development in patients with acute stroke: serial diffusion- and hemodynamic-weighted magnetic resonance imaging. , 1998, Stroke.

[9]  N. Lassen,et al.  Original Contributions Blood Flow and Vascular Reactivity in Collaterally Perfused Brain Tissue Evidence of an Ischemic Penumbra in Patients with Acute Stroke , 1983 .

[10]  R. J. Seitz,et al.  Thalamic metabolism and corticospinal tract integrity determine motor recovery in stroke , 1996, Annals of neurology.

[11]  William M. Jenkins,et al.  Neocortical representational dynamics in adult primates: Implications for neuropsychology , 1990, Neuropsychologia.

[12]  A. Hillis,et al.  Hypoperfusion of Wernicke's area predicts severity of semantic deficit in acute stroke , 2001, Annals of neurology.

[13]  D. J. Felleman,et al.  Topographic reorganization of somatosensory cortical areas 3b and 1 in adult monkeys following restricted deafferentation , 1983, Neuroscience.

[14]  M. Merzenich,et al.  Reorganization of neocortical representations after brain injury: a neurophysiological model of the bases of recovery from stroke. , 1987, Progress in brain research.

[15]  H. Freund,et al.  The role of diaschisis in stroke recovery. , 1999, Stroke.

[16]  C. Xerri,et al.  Acute reorganization of the forepaw representation in the rat SI cortex after focal cortical injury: neuroprotective effects of piracetam treatment , 1999, The European journal of neuroscience.

[17]  Fausto Viader,et al.  Spontaneous neurological recovery after stroke and the fate of the ischemic penumbra , 1996, Annals of neurology.

[18]  Argye E. Hillis,et al.  Neural substrates of the cognitive processes underlying reading: Evidence from magnetic resonance perfusion imaging in hyperacute stroke , 2001 .