Brain : a journal of neurology
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Spinal cord injury (SCI) frequently results in neuropathic pain. However, the pathophysiology underlying this pain is unclear. In this study, we compared clinical examination, quantitative sensory testing (QST) and somatosensory evoked potentials (SEPs) in SCI patients with and without pain below spinal lesion level, with a control group of 20 subjects without injury. ⋯ There was no difference in intensity of pain evoked by repetitive pinprick at lesion level between patient groups. There was a significant correlation between intensity of brush-evoked dysaesthesia at lesion level and spontaneous pain below lesion level of SCI. These data suggest that lesion of the spinothalamic pathway alone cannot account for central pain in SCI patients, and that neuronal hyperexcitability at injury or higher level may be an important mechanism for pain below injury level.
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We recorded laser-evoked cortical potentials (LEPs) in 54 consecutive patients presenting with unilateral neuropathic central pain (n = 42) or with lateralized pain of non-organic origin (n = 12). A number of cases in each group had superimposed hyperalgesia or allodynia. In patients with central pain, LEPs were significantly attenuated after stimulation over the painful territory, relative to stimulation of the homologous normal territory. ⋯ In neuropathic cases, partial LEP preservation might increase the probability of developing provoked pain (allodynia/hyperalgesia). The possible predictive value of this phenomenon, when observed before the development of pain, remains to be demonstrated. In selected contexts (pain sine materia, non-organic anaesthesia), normal or enhanced LEPs may support a psychogenic participation in the syndrome.
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Clinical Trial
Response to levodopa in parkinsonian patients with bilateral subthalamic nucleus stimulation.
The response to levodopa changes over time in Parkinson's disease, probably due to alterations in the dopaminergic system, progression of the disease and pulsatile oral intake of the drug. Bilateral high-frequency stimulation of the subthalamic nucleus (STN) allows a large reduction or the complete cessation of levodopa intake in patients with advanced Parkinson's disease. We studied variation in the motor short-duration response (SDR) during a levodopa challenge in bilaterally STN-stimulated patients. ⋯ On the whole, chronic bilateral STN stimulation tended to decrease the magnitude of the levodopa SDR without changing the duration and latency of the response. These results suggest that continuous STN stimulation induces long-term plastic changes of the dopaminergic system, with slow and partial desensitization. In addition, the persistence of levodopa intake after surgery might hinder this beneficial process.
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This paper reviews disorders of memory. After a brief survey of the clinical varieties of the amnesic syndrome, transient and persistent, selected theoretical issues will be considered by posing a series of questions. (i) What is impaired and what is spared in anterograde amnesia? (ii) Do temporal lobe, diencephalic and frontal lobe amnesias differ? (iii) How independently semantic is semantic memory? (iv) What determines the pattern and extent of retrograde memory loss? (v) Can retrograde amnesia ever be "isolated"? (vi) Does psychogenic amnesia involve the same mechanisms as organic amnesia? (vii) How and when do false memories arise? Commonalities as well as differences across separate literatures will be emphasized, and the case for a more "dynamic" (interactionist) approach to the investigation of amnesia will be advocated.
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With the growth in antiepileptic drug treatment, the question arises as to what extent we are merely treating the symptom (i.e. the seizures) rather than the underlying disease process (i.e. epileptogenesis). Epileptogenicity can be considered as the process whereby structural and functional changes occur following an insult that in some cases result in epilepsy. Epileptogenicity also describes some of the changes and processes that contribute to the progression observed in some epilepsies. ⋯ This highlights the importance of medical care at the time of an insult, and of prevention of the insults. This review discusses the data that support the concepts underlying epileptogenesis and the model systems that are presumed to reflect the human condition. Particular attention is paid to the potential for interrupting the processes underlying epileptogenesis.