Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society
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J Clin Neurophysiol · Jan 1997
ReviewStimulation of the central and peripheral nervous system for the control of pain.
After suffering some setbacks since its introduction in 1967, stimulation of the spinal and peripheral nervous systems has undergone rapid development in the last ten years. Based on principles enunciated in the Gate Control Hypothesis that was published in 1968, stimulation-produced analgesia [SPA] has been subjected to intensive laboratory and clinical investigation. Historically, most new clinical ideas in medicine have tended to follow a three-tiered course. ⋯ Modern development of SCS with outcome studies, particularly in relation to failed back surgery syndrome [FBSS] and the outcome of peripheral nerve surgery for chronic regional pain syndromes, has earned both modalities a place in the ongoing management of patients with intractable neuropathic pain. The last section, dealing with pain of peripheral vascular and myocardial ischemia, is perhaps one of the more exciting developments in stimulation produced analgesia and as the papers discussed demonstrate, can provide a level of analgesia and efficacy that is unattainable by other treatment modalities. SCS and PNS has an important role to play in the management of conditions that are otherwise refractory to conservative or other conventional management.
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J Clin Neurophysiol · Jul 1996
Case ReportsRecovery from brain-stem lesions involving the nociceptive pathways: comparison of clinical findings with laser-evoked potentials.
Dissociated sensory impairment in brain-stem disorders suggests a lateral lesion involving the spinothalamic tract. Evoked potential studies of the somatosensory system with standard electrical stimulation (SEP) generally fail to establish objective correlates of such sensory deficits, because electrical stimuli predominantly activate large myelinated fibers that project into the medial lemniscal system. In contrast, laser-evoked potentials (LEPs), in response to brief radiant heat pulses, stimulate nociceptive afferents of the superficial skin and allow evaluation of thin fiber and spinothalamic tract function. ⋯ The peak-to-peak amplitude of the main LEP component (N250-P400) correlated significantly with clinical pain sensitivity scored by standardized sensory testing (r = 0.76, p < 0.01). In contrast, early and late SEPs, after standard electrical median or tibial nerve stimulation, were normal in all patients, consistent with their intact mechanosensitivity. In conclusion, LEP studies allow the status of nociceptive function to be objectively and reliably documented on repeated examinations and therefore provide a useful supplement to multimodal sensory assessment in brain-stem disorders.
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J Clin Neurophysiol · Mar 1996
Comparative StudyPolysomnographic analysis of arousal responses in obstructive sleep apnea syndrome by means of the cyclic alternating pattern.
Obstructive sleep apnea syndrome (OSAS) is characterized by multiple interruptions of airflow between periods of arousals. A key feature of OSAS is the 20- to 40-s cyclic pattern of electrophysiologic parameters. The periodicity of the OSAS-related phenomena is reminiscent of the natural electroencephalographic (EEG) arousal rhythm of non-rapid eye movement (NREM) sleep known as the cyclic alternating pattern (CAP). ⋯ The great majority of respiratory pauses (96% in NREM and 80% in REM sleep) were coupled with CAP. All CAP-related respiratory events rose in close temporal connection with a phase B, while effective breathing was always recovered during phase A (especially A2 and A3 subtypes). These data suggest that (a) phase B of CAP offers a vulnerable background for upper airway collapse and for attenuation of biochemical and neural mechanisms in the control of the ventilatory drive and (b) survival in OSAS patients is effected by the enhancement of the strongest components of the natural arousal rhythm at sleep quality's expense.
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J Clin Neurophysiol · Jan 1996
Case ReportsMonitoring of median nerve somatosensory evoked potentials during cervical spinal cord decompression.
We evaluated the intraoperative utility of monitoring median nerve somatosensory evoked potentials (SEPs) in 31 consecutively hospitalized neurosurgical patients (mean age 55.3 +/- 2.1 years) who underwent spinal cord decompression for cervical herniated disc, spondylosis, or tumor. Pre- and postoperative standard neurological examinations included evaluation of motor function, sensory responses, gait, tone, and reflexes. Evoked potentials were recorded from clavicular Erb's (N9) and contralateral cortical (N20) points. ⋯ The SEP waveform disappeared in two of the group II and in none of the group I subjects. In the two group II subjects exhibiting increases of N9-N20 latencies, increments were > 20%. These findings indicate that in patients undergoing cervical spinal cord decompression, disappearance of SEPs or increases > 20% in the N9-N20 interpeak latency are suggestive of operative conditions that place patients at risk for poor neurological outcome.
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J Clin Neurophysiol · Sep 1995
ReviewComparative assessment of sensorimotor function using functional magnetic resonance imaging and electrophysiological methods.
Accurate assessment of the location of the sensorimotor cortex is important in presurgical investigation of and planning for patients with lesions impinging on this region. In this review, the relationship between the assessment of sensorimotor cortex by invasive electrophysiological mapping and functional magnetic resonance imaging (fMRI) is discussed. A number of areas are covered: (a) brief backgrounds of MRI and fMRI are provided, (b) existing fMRI literature of sensorimotor cortex activation is surveyed, (c) results of fMRI sensorimotor studies and intracranial somatosensory evoked potential (SEP) recordings and cortical stimulation in neurosurgical patients are compared, and (d) the locus of fMRI activation is discussed in the light of cortical generators of SEP components.