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  • 1
    Electronic Resource
    Electronic Resource
    Impairment of callosal and corticospinal system function in adolescents with early-treated phenylketonuria: a transcranial magnetic stimulation study (1999)
    Springer
    Journal of neurology 246 (1999), S. 21-30 
    Details
    ISSN: 1432-1459
    Keywords: Key words Corpus callosum ; Corticospinal tract ; Phenylketonuria ; Focal transcranial magnetic brain ; stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The transcranial activation and the conduction properties of corticospinal and callosal neurons were investigated in 12 early-treated adolescents (aged 17.3, SD 3.5 years; range 14–27 years) with phenylketonuria (PKU) by focal transcranial magnetic stimulation (fTMS) of the motor cortex. The patients had no functionally relevant motor disturbances in daily life or on clinical testing. Corticospinally mediated excitatory (response thresholds, amplitudes, central motor latencies) and inhibitory [duration of postexcitatory inhibition (PI)] effects of fTMS were investigated in contralateral hand muscles. Transcallosal inhibition (TI) (onset latency, duration, transcallosal latency) of tonic electromyographic (EMG) activity was tested in ipsilateral muscles. Peripheral motor latencies were determined for responses elicited by magnetic stimulation over cervical nerve roots. Ten normal subjects served as controls. Since in all PKU patients, central and peripheral motor latencies were normal, no neurophysiological indication of a demyelination of corticospinal or peripheral motor fibres was found. However, cortical thresholds of corticospinally mediated responses were increased (52.1, SD 11.6% versus 35.0, SD 7.4% of maximum stimulator output; P 〈 0.05; n = 24 hands) and their amplitudes reduced (2.9, SD 1.4 mV versus 6.1, SD 1.5 mV, P 〈 0.05). The duration of PI was shortened (132, SD 53 ms versus 178, SD 57 ms; P 〈 0.05). TI was absent in 37.5% of the investigated hands or tended to be weak. When TI was present, its onset latencies (38.0, SD 3.6 ms versus 34.7, SD 3.3 ms) and transcallosal latencies were prolonged (18.5, SD 3.8 ms versus 14.8, SD 3.2 ms), while its duration was normal. These abnormal excitatory and inhibitory effects of fTMS suggest a reduced susceptibility of cortical excitatory and inhibitory neuronal structures compatible with a loss of neurons or a rarefication of their dendrites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050301
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  • 2
    Electronic Resource
    Electronic Resource
    Callosal and corticospinal tract function in patients with hydrocephalus: a morphometric and transcranial magnetic stimulation study (1998)
    Springer
    Journal of neurology 245 (1998), S. 280-288 
    Details
    ISSN: 1432-1459
    Keywords: Key words Corpus callosum ; Corticospinal tract ; Hydrocephalus ; Brain morphometry ; Transcranial magnetic brain stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In 15 patients with symptomatic hydrocephalus, pressure-induced morphological changes of the brain and the function of callosal and corticospinal fibres were studied. Morphometry of the corpus callosum (CC) was performed on midsagittal MR images. Focal transcranial magnetic stimulation of the motor cortex was used to assess simultaneously excitatory motor responses in contralateral hand muscle (corticospinally mediated effect) and inhibition of tonic EMG activity in ipsilateral hand muscles (transcallosal inhibition (TI) of the contralateral motor cortex). Before a shunt operation, the midsagittal area of the CC was reduced by 34% on average. The height and, to a lesser degree the length, of the CC were increased before the shunt operation. Thresholds and central motor latencies of corticospinally mediated responses were normal, response amplitudes were smaller than in normal subjects. Motor thresholds increased from 38, SD 5 to 52, SD 8% (P〈0.01) within 7 days after ventricular drainage, reflecting the increase in the distance between stimulation coil and brain. The threshold increase paralleled a restoration of normal anatomical conditions within 7 days after shunt operation and the improvement of motor symptoms and might be a predictor of successful decompression. Transcallosal inhibition could be elicited in all patients. The measurements of TI lay within the normal range except the duration, which was prolonged in 73% of 15 patients before shunt operation as a probable indicator of an increased dispersion of callosal conduction. The normalization of the area and shape of the CC after shunt operation and the normal corticospinal and callosal conduction times exclude degeneration, demyelination or functional block of a large proportion of callosal or corticospinal tract fibres or a substantial loss of nerve cells in motor cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004150050219
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Reorganisation of descending motor pathways in patients after hemispherectomy and severe hemispheric lesions demonstrated by magnetic brain stimulation (1991)
    Springer
    Experimental brain research 83 (1991), S. 419-426 
    Details
    ISSN: 1432-1106
    Keywords: Magnetic brain stimulation ; Hemispherectomy ; Corticospinal tract ; Cortico-reticulospinal pathways ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Numerous clinical studies on patients after hemispherectomy (HS) have provided clear evidence that two distinct groups can be recognized on the basis of the quality of their motor functions after operation. One of these consists of cases where HS was performed after normal brain maturation, the other of patients where the removed hemisphere was damaged early in life. The post-operative motor function has been found to be much better in the latter group. In the present paper it is demonstrated that in contrast to normal subjects ipsilateral compound muscle action potentials (CMAPs) induced by magnetic stimulation of the one intact motor cortex are present in patients after HS. The amplitudes of ipsilateral CMAPs in the muscles roughly correlate with their individual residual motor capacities and show a proximo-distal gradient. In patients with early brain damage prior to HS, CMAPs had short latencies and large amplitudes, whereas in patients with later acquired brain damage prior to HS, CMAPs had long latencies and small amplitudes. It is suggested that reinforcement of the ipsilateral corticospinal pathway may be responsible for residual motor functions in patients with early brain damage, whereas in patients with later acquired brain damage cortico-reticulospinal pathways may play a dominant role in ipsilateral motor control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231167
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    Paper (German National Licenses)
    Fulltext
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