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Objective:To compare the diffusion and perfusion MRI metrics of normal-appearing white matter (NAWM) with and without impaired cerebrovascular reactivity (CVR).Methods:Seventy-five participants with moderate to severe leukoaraiosis underwent blood oxygen level–dependent CVR mapping using a 3T MRI system with precise carbon dioxide stimulus manipulation. Several MRI metrics were statistically compared between areas of NAWM with positive and negative CVR using one-way analysis of variance with Bonferroni correction for multiple comparisons.Results:Areas of NAWM with negative CVR showed a significant reduction in fractional anisotropy by a mean (SD) of 3.7% (2.4), cerebral blood flow by 22.1% (8.2), regional cerebral blood volume by 22.2% (7.0), and a significant increase in mean diffusivity by 3.9% (3.1) and time to maximum by 10.9% (13.2) (p < 0.01), compared to areas with positive CVR.Conclusions:Impaired CVR is associated with subtle changes in the tissue integrity of NAWM, as evaluated using several quantitative diffusion and perfusion MRI metrics. These findings suggest that impaired CVR may contribute to the progression of white matter disease.

Objective: To characterize the relationship between cerebrovascular reactivity (CVR) and white matter (WM) diffusion in patients with internal carotid artery (ICA) occlusive disease.Methods: In this exploratory observational study, 41 patients with severe stenosis or occlusion of the extracranial ICA and 12 healthy control subjects underwent CVR mapping using the fMRI response to hypercapnia. Conventional anatomic and diffusion-weighted MRI sequences were used to calculate maps of the apparent diffusion coefficient (ADC) and to exclude areas of previous ischemic injury. In all subjects, ADC was compared between WM with positive and negative CVR. In 27 patients with unilateral ICA involvement, ADC and CVR were compared between ipsilateral and contralateral WM while covarying for relevant clinical risk factors.Results: In patients with bilateral disease and in the ipsilateral hemisphere of patients with unilateral disease, negative CVR was associated with increased WM ADC (p Conclusions: CVR impairment is associated with ADC elevation in normal-appearing WM of patients with severe stenosis or occlusion of the extracranial ICA. This finding is consistent with the presence of early, low-grade ischemic injury. Neurology (R) 2011;77:431-438

Serial fMRI was performed in a patient who underwent transfer of the left great toe to the hand following amputation of the right thumb. Motor activation within the primary sensorimotor cortex (SMC) of both hemispheres was quantified over 2 years, showing a transient increase in contralateral but not ipsilateral primary SMC. The temporal pattern of motor cortical activation observed in this patient may represent a "signature" of good functional recovery.

The nature of the adaptive changes that occur in the cerebral cortex following injury to the cervical spinal cord are largely unknown.To investigate these adaptive changes by examining the relationship between the motor cortical representation of the paretic right upper extremity compared with that of the tongue. The tongue was selected because the spinal cord injury (SCI) does not affect its movement and the cortical representation of the tongue is adjacent to that of the paretic upper extremity.FMRI was used to map cortical representations associated with simple motor tasks of the right upper extremity and tongue in 14 control subjects and 9 patients with remote (5.5 months) cervical SCI.The mean value for the site of maximum cortical activation during upper limb movement was identical between the two groups. The site of maximum left hemispheric cortical activation during tongue movement was 12.8 mm (p0.01) medial and superior to that of control subjects, indicating the presence of a shift in cortical activation.The findings indicate that the adult motor cortex does indeed adapt following cervical SCI. The nature of the adaptation and the underlying biological mechanisms responsible for this change require further investigation.

Chronic pain may be accompanied by abnormal functioning in pain, attention, or homeostatic systems. We recently identified abnormal rectal-evoked functional MRI responses in patients with irritable bowel syndrome (IBS) in brain regions associated with such systems, including the insula and anterior cingulate cortex (ACC).1 However, it is not known whether structural brain abnormalities contribute to these responses. We tested the hypothesis that abnormal cortical responses in IBS are at least partly due to structural differences within the insula and ACC. ### Methods. Right-handed healthy control subjects (n = 11, 7 women, 4 men; 24 to 50 years old) and patients with IBS (n = 9, 6 women, 3 men; 30 to 58 years old) provided written consent to procedures approved by the University Health Network Research Ethics Board. Control subjects were excluded if they had a history of bowel disorders, chronic pain, fibromyalgia, diabetes, or psychiatric illness. Patients were recruited from the Toronto Western Hospital Gastrointestinal Unit, met Rome III criteria2 for diagnosis of IBS, and had mild to moderate symptoms and pain for more than 2 years. Exclusion criteria were a history of …

The authors used voxel-based morphometry to compare sensorimotor cortical gray and white matter volume on structural MR images of a group of 17 individuals with cervical spinal cord injury (SCI) and a group of 17 healthy subjects. SCI subjects had reduced gray matter volume bilaterally in primary somatosensory cortex (p < 0.001). These findings suggest that the somatosensory cortex of the human brain atrophies after SCI.

Objective: The authors hypothesized that central factors may underlie sensory deficits in patients with nondermatomal somatosensory deficits (NDSD) and that functional brain imaging would reveal altered responses in supraspinal nuclei. Background: Patients with chronic pain frequently present with NDSD, ranging from hypoesthesia to complete anesthesia in the absence of substantial pathology and often in association with motor weakness and occasional paralysis. Patients with pain and such pseudoneurologic symptoms can be classified as having both a pain disorder and a conversion disorder (Diagnostic and Statistical Manual of Mental Disorders–IV classification). Methods: The authors tested their hypothesis with functional MRI (fMRI) of brush and noxious stimulation-evoked brain responses in four patients with chronic pain and NDSD. Results: The fMRI findings revealed altered somatosensory-evoked responses in specific forebrain areas. Unperceived stimuli failed to activate areas that were activated with perceived touch and pain: notably, the thalamus, posterior region of the anterior cingulate cortex (ACC), and Brodmann area 44/45. Furthermore, unperceived stimuli were associated with deactivations in primary and secondary somatosensory cortex (S1, S2), posterior parietal cortex, and prefrontal cortex. Finally, unperceived (but not perceived) stimuli activated the rostral ACC. Conclusions: Diminished perception of innocuous and noxious stimuli is associated with altered activity in many parts of the somatosensory pathway or other supraspinal areas. The cortical findings indicate a neurobiological component for at least part of the symptoms in patients presenting with nondermatomal somatosensory deficits.