Central somatosensory conduction time in comatose patients

Hume, Ann L.; Cant, B.R; Shaw, N.A.

doi:10.1002/ana.410050412

Cited by 128 publications

(20 citation statements)

References 19 publications

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“…In contrast to the N20 component of the SEP, which is rather resistant to state parameters such as waking and sleep [Lü ders et al, 1986], or barbiturate-induced coma [Hume et al, 1979], the high frequency oscillations superimposing the N20 component of the SEP show a strong state dependency and disappear during sleep [Emerson et al, 1988;Yamada et al, 1988;Hashimoto et al, 1996]. In humans, Antognini et al [1997] have shown, that isoflurane anaesthesia blunts the fMRI response to noxious and innocuous stimuli.…”

Section: Discussionmentioning

confidence: 96%

Frequency dependence of the functional MRI response after electrical median nerve stimulation

2000

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Localizing sensorimotor areas with high resolution functional MRI is of considerable interest for a wide range of medical applications from the preoperative planning of neurosurgical interventions to determining the course of neuroplastic reorganisation after brain lesions. We examined the effect of the stimulation frequency on the blood oxygen level dependent (BOLD) fMRI response and on perfusion weighted fMRI using electrical median nerve stimulation at 5, 15, 40, and 100 Hz. BOLD fMRI was performed using a single shot gradient echo EPI sequence to acquire 15 contiguous slices. For the qualitative flow sensitive studies, a single slice inversion recovery prepared spin echo echoplanar sequence (IR-SE EPI) was used. In the primary sensorimotor cortex, a linear increase of the fMRI-BOLD response, affecting both the number of activated pixels and the amplitude of the signal changes, was seen with increasing stimulation frequencies. The qualitative in-flow sensitive studies, using the IR-SE EPI sequence, indicate that the tissue perfusion also increases over the same range of frequencies. This implicates that larger fMRI responses can be obtained if electrical median nerve stimulation is performed at higher frequencies. The results are compared with electrophysiological data, which show a decrease of the early somatosensory evoked potentials at higher frequencies.

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Section: Discussionmentioning

confidence: 96%

Frequency dependence of the functional MRI response after electrical median nerve stimulation

2000

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“…17 N13-N20 IPLs were measured to evaluate the central conduction time. 18 Peaks after N20 were generated after entering the primary sensory cortex. N20-N65 IPLs were measured for cortical responses.…”

Section: Subjectsmentioning

confidence: 99%

Somatosensory evoked potentials in subclinical portosystemic encephalopathy: A comparison with psychometric tests

Yang

Chiang

et al. 1998

Hepatology

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We prospectively studied the role of somatosensory evoked potentials (SEPs) and psychometric tests in the assessment of subclinical portosystemic encephalopathy (PSE) Evoked potentials are noninvasive, objective electrical manifestations of the nervous system function in response to stimulation. 3,4 Somatosensory evoked potentials (SEPs) can detect the integrity of somatosensory pathways from the peripheral to the central nervous system. 3,4 SEPs are useful in the objective assessment and monitoring of HE in a variety of liver diseases. 5,6 In HE, median nerve-stimulated SEPs showed a progressive prolongation of N20-N65 interpeak latencies (IPLs) correlating with the severity of HE. 6 N20-N65 IPLs have been used in the clinical monitoring of HE, evaluation of the treatment for HE, and prediction of prognosis. [7][8][9][10] In acute and chronic liver disease, approximately one half of the patients with decompensated liver function with grade 0 HE had abnormal prolongation of N20-N65 interpeak latencies. 6,11,12 It is likely that SEP can be of value in the detection of subclinical HE. 13 Therefore, we studied and compared the roles of SEPs and psychometric tests in detection of subclinical HE in cirrhotic patients. PATIENTS AND METHODS Subjects.One hundred consecutive documented cases of cirrhotic patients without clinical HE were studied prospectively at the Cathay General Hospital between 1994 and 1996. Twenty healthy volunteers served as controls. An additional 6 uneducated healthy volunteers underwent only psychometric tests. Sixty-five cirrhotic patients (hepatitis B virus, 30; hepatitis C virus, 28; hepatis B virus and hepatitis C virus, 2; hepatitis B virus and hepatitis D virus, 2; cryptogenic, 3) were included in the present study. Thirty-five cirrhotic patients were excluded because of serious complications and incomplete study. Cirrhosis was diagnosed when patients developed chronic hepatitis with serum alanine transamine (ALT) levels higher than 1.5 times the upper normal limit (normal ALT activity, Ͻ35 IU/L) over a period of more than 6 months, sonographic findings of small liver as well as splenomegaly, and moderate or severe degrees of esophageal varices proven by upper endoscopy.Cirrhotic patients with grade 0 HE were included in the present study. Patients with other neurological diseases and metabolic disorders such as alcoholism, diabetes mellitus, or end-stage renal disease were excluded to avoid coexistent neuropathy or other brain dysfunction. Patients with fever, sepsis, or shock were also excluded to avoid variations caused by body temperature. All cirrhotic patients underwent blood tests, tests for grading of HE and degree of asterixis, psychometric tests, electroencephalography (EEG), and SEPs.Hepatic Encephalopathy. The degree of HE was semiquantified as grade 1 to 4, based on the mental changes proposed by Conn et al. 2 immediately before SEP testing.Blood Tests. Peripheral blood was collected after overnight fasting and within 12 hours of SEP testing for biochemistry at a central lab...

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“…1973;Ommaya and Gennarelli, 1974). More recently, evoked piitentials have been used to study the later stages of head injuries, and in some of these Shaw, 1979: Hume andCant. 1981) evidence of delayed transmission of somatosensory information to the primary sensory cortex has been found.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Experimental Concussion on Somatosensory Evoked Potentials

1984

Aust J Exp Biol Med

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Summary, Cortical somatosensory evoked potentials (SEPs) were recorded following experimental acceleralion concussion in the rat. Immediately after head injury there was a general reduction in Ihe amplitude of Ihe SEP, and all ils components were either temporarily abolished or increased in latency. The early components of the SEP recovered much more rapidly than did the amplitude and latencies of the later potentials. The purpose of the study was to investigate the relative cITccts of concussion on the lemniscal system (whose activity is reflected by the discrete early components of the SEP) and the reticular activating system (whose activity is reflected hy the ditfuse high amplitude late component of the SEP). Conlrary to a widely accepted theory, there was a delay in transmission of somatosensory information through the lemniscal pathways as well as through the reticular system following head injury. Such an observation is consistenl with recent studies of SEPs recorded from humans comatose after head trauma. As the changes in the morphology of the waveform of the SEP following concussion can be simulated by simply recording evoked potentials at high rales of stimulation, this suggests that the delays are caused by a failure or malfunction of .synaptic transmission, but the level at which this i.s occurring remains to be determined.

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Central somatosensory conduction time in comatose patients

Cited by 128 publications

References 19 publications

Frequency dependence of the functional MRI response after electrical median nerve stimulation

Frequency dependence of the functional MRI response after electrical median nerve stimulation

Somatosensory evoked potentials in subclinical portosystemic encephalopathy: A comparison with psychometric tests

The Effect of Experimental Concussion on Somatosensory Evoked Potentials

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