Brain : a journal of neurology
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We examined ocular fixations during line bisection in five patients with left hemianopia, two patients with right hemianopia, nine patients with left hemi-neglect and nine normal control subjects. Compared with measures in control subjects, the median fixation, and left- and rightmost fixations were shifted contralaterally in patients with hemianopia alone and ipsilaterally in patients with hemi-neglect. The fixation with the longest duration and the bisection point were also shifted contralaterally with hemianopia and ipsilaterally with hemi-neglect. ⋯ Hemi-neglect patients had a broad distribution of fixation peaks in the ipsilateral hemispace. Of two hemi-neglect patients with many fixations, one clustered fixations at a position right of centre, as if a normal fixation pattern was shifted rightward, while the other had two fixation peaks: one to the far right and the other near the centre of the line, reminiscent of the dual peaks of activity seen in some recent hemi-neglect models. These data reveal a heterogeneity in the routes by which right-biased judgements of spatial centre are reached by hemi-neglect patients.
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Clinical Trial
Neural activation during acute capsaicin-evoked pain and allodynia assessed with PET.
The PET H2 15O-bolus method was used to image regional brain activity in normal human subjects during intense pain induced by intradermal injection of capsaicin and during post-capsaicin mechanical allodynia (the perception of pain from a normally non-painful stimulus). Images of regional cerebral blood flow were acquired during six conditions: (i) rest; (ii) light brushing of the forearm; (iii) forearm intradermal injection of capsaicin, (iv) and (v) the waning phases of capsaicin pain; and (vi) allodynia. Allodynia was produced by light brushing adjacent to the capsaicin injection site after ongoing pain from the capsaicin injection had completely subsided. ⋯ The cerebellar vermis was strongly activated by capsaicin, whereas light brush and experimental allodynia produced little or no activation, suggesting a selective association with C-fibre stimulation and nociceptive second-order spinal neurons. The experimental allodynia activated a network that partially overlapped those activated by both pain and light brush alone. Unlike capsaicin-induced pain, allodynia was characterized by bilateral activation of inferior prefrontal cortex, suggesting that prefrontal responses to pain are context dependent.
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We investigated various magnetic resonance MRI parameters for both brain and spinal cord to see if any improved the clinicoradiological correlation in multiple sclerosis. Ninety-one multiple sclerosis patients (28 relapsing-remitting, 32 secondary progressive and 31 primary progressive) were imaged using conventional T1, proton density- and T2-weighted MRI of the brain and spinal cord. Focal brain and spinal cord lesion load was scored, as were diffuse signal abnormalities, brain ventricular volume and spinal cord cross-sectional area. ⋯ In the primary progressive subgroup the clinicoradiological correlation was weak for brain parameters but was present between spinal cord symptoms and spinal cord MRI parameters. In conclusion, the different brain and spinal cord MRI parameters currently available revealed considerable heterogeneity between clinical subtypes of multiple sclerosis. In relapsing-remitting and secondary progressive multiple sclerosis both brain and spinal cord MRI may provide a tool for monitoring patients, while in primary progressive multiple sclerosis the clinicoradiological correlation is weak for brain imaging.
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The aim of this study was to compare, retrospectively, the value of chronic bilateral stimulation of the internal globus pallidus (GPi) and the subthalamic nucleus (STN) in patients with young onset Parkinson's disease. We selected 13 consecutive patients with similar characteristics at the time of surgery: age at onset < 40 years, disabling motor fluctuations (Hoehn and Yahr stage 4 or 5 in off-drug phases) and levodopa-induced dyskinesias (LID). Eight patients were operated on in the STN and five in the GPi. ⋯ In the on-drug phases there was a marked improvement in LID in the GPi group, as measured by the dyskinesias score during an acute levodopa test, whereas there was only a small decrease in the STN group (P < 0.05). However, in the long term, the reduction of levodopa dosage in the STN group led to an indirect reduction of LID similar to that in the GPi group during activities of everyday life. In conclusion, the overall results favour the neurosurgical treatment of Parkinson's disease by stimulating the STN rather than the GPi.
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We used PET to study regional cerebral blood flow (rCBF) changes in nine patients with unilateral central pain after a lateral medullary infarct (Wallenberg's syndrome). All patients presented, on the abnormal side, a combination of hypaesthesia to noxious and thermal stimuli and allodynia to rubbing of the skin with a cold object (i.e. abnormal pain to innocuous stimulation). The rCBF responses during allodynia were compared with those obtained during stimulation of the normal side using (i) a cold non-noxious stimulus identical to that applied to the painful side, and (ii) an electrical high-frequency stimulus at painful ranges. ⋯ The second abnormality associated with allodynic sensation was qualitative. It concerned exclusively the contralateral cingulate gyrus, which did not exhibit the usual pain-related rCBF increase reported in normal subjects. This abnormal cingulate response may account for the peculiar response of lateral medullary infarct patients to allodynic pain, which is not simply perceived as an exaggerated pain sensation, but as a new, strange and extremely unpleasant feeling, not previously experienced by the patients.