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Biomedical subjects

G Curio

Publications and source records attributed to G Curio.

67 records · Page 4Linked to original sources
PubMed1989

Biomagnetic functional localization of a peripheral nerve in man.

The first detection of the magnetic field of a stimulated peripheral nerve in man is presented. The measurement was performed noninvasively and in vivo on a healthy subject. The spatio-temporal field distribution is utilized to calculate the location of bioelectric activity on the basis of the equivalent current dipole model. The localization of the active nerve tissue is confirmed by a computer tomography image of the upper arm cross-section. Furthermore, a calculation of the total current distribution in the nerve explains the observed morphology of the signal.

Electric Stimulation↗
PubMed1988

Intraparenchymatous ponto-mesencephalic field distribution of brain-stem auditory evoked potentials in man.

Brain-stem auditory evoked potentials (BAEPs) were recorded simultaneously from scalp electrodes and intraparenchymatous sites along a ponto-mesencephalic stereotactic penetration path in a patient with the unique condition of a brain-stem tumour which therapeutically necessitated radionuclide implantation but did not grossly affect scalp BAEPs. The data suggest major contributions to scalp peak III from the pons ipsilateral to the stimulated ear, to peak IV from both ipsi- and contralateral sources, and to peak V mainly from contralateral, more rostral sites. Some local activities evidently did not project to the scalp.

Adult↗
PubMed1987

Peripheral origin of BAEP wave II in a case with unilateral pontine pathology: a comparison of intracranial and scalp records.

In a patient with unilateral hearing impairment due to a predominantly ipsilateral pontine pathology, BAEP peak II in a vertex to ipsilateral mastoid derivation (BAEP-II) was preserved on stimulation of the affected ear. All later activity was lost. Intracranial recording from electrodes intraoperatively placed over both cochlear nuclei on the floor of the IVth ventricle showed potentials with size and wave form comparable to the scalp records. Thus only peripheral sources, distant from the ventricular electrode, seem to contribute to scalp BAEP-II. Upon stimulation of the unaffected ear considerably larger intracranial activity was seen with peak 2-4 wave shapes obviously different from the scalp BAEP II-IV. It is concluded that intracranial electrodes sense a complex field distribution predominantly originating in structures to which they are in close electrical connection. This activity, however, need not necessarily project to the scalp.

Brain Neoplasms↗
PubMed1985

Visual-vestibular interaction studied with stroboscopically illuminated visual patterns.

Horizontal DC-electrooculograms were recorded in subjects rotating on a horizontal turntable sinusoidally at 0.1 Hz and 35 to 40 degrees amplitude. The subjects either fixated a stroboscopically illuminated vertically striped pattern (1.15 to 3.45 degrees period) rotating with the turntable or initiated Sigma-OKN before the rotation began and tried to maintain Sigma-OKN during rotation. In a third paradigm, interaction of vestibulo-ocular reflex (VOR) and Phi-OKN was studied. VOR-suppression by fixation was complete within the limits of EOG-recording precision (+/- 1 degree X s-1) for flash frequencies fs greater than 10 flashes X s-1. VOR-suppression decreased monotonically with fs between 10 and 1 flashes X s-1. A similar dependency on fs was found for VOR-suppression during Sigma- or Phi-OKN. Above 10 flashes X s-1 VOR-suppression remained incomplete; below 5 flashes X s-1 VOR-suppression was stronger with the Sigma-OKN paradigm than during fixation and depended on spatial frequency of the pattern. During sinewave rotation of the subject the perceived speed Vp of Sigma-movement correlated to the movement of gaze in space and not to the movement of the eye in head. In a control experiment with normal optokinetic stimulation, OKN-suppression by fixating a small flashing target was found to depend on fs in a similar way as VOR-suppression in the experiments described above.

Adult↗
PubMed1984

Severe local tissue lesions after chemonucleolysis with collagenase.

The authors report the case of a young female patient submitted to chemonucleolysis at L4-5 with collagenase, in whom severe tissue lesions affecting the cartilaginous end-plate, the vertebral bone, the posterior intervertebral ligament, the epidural fat, and the dura mater were verified at laminectomy, which had become necessary due to functional motor deterioration.

Adult↗
PubMed1984

Morphological alterations of the degenerated lumbar disc following chemonucleolysis with chymopapain.

Lumbar disc tissue from 10 patients who had previously undergone chemonucleolysis without success was studied by light and scanning electron microscopy. Seven patients had a sequestrated disc; three had large protrusions. As a control, material from 10 patients subjected to disc surgery without previous chemonucleolysis was studied in the same way. The control discs revealed the characteristic signs of degeneration: alteration of the collagen, microcystic areas, and giant chondromas. Changes following chemonucleolysis were restricted exclusively to the ground substance and characterized by a marked loss of basophilia in the cartilage matrix. There was no involvement of the anulus fibrosus, cartilage plate, or bone. Following chymopapain administration, scanning electron microscopy showed a naked collagen network devoid of ground substance.

Adult↗
PubMed1984

Intradiscal pressure-volume response: a methodological contribution to chemonucleolysis. Preliminary results.

A new method is presented to verify whether a lumbar disc is degenerated prior to chemonucleolysis. This consists in rapid injection of a 0.3-ml bolus of saline into the center of the disc (through the needle employed for chemonucleolysis), under continuous recording of the intradiscal pressure changes caused by this volume load. If the intradiscal pressure falls below 600 mm Hg within 2 minutes after the injection, there is a high probability (p less than 0.001) that the disc is degenerated. This method has many advantages: it obviates additional injection of contrast medium prior to chemonucleolysis, it prevents inhibition of chymopapain by the contrast medium, it saves time, and it reduces the total amount of fluid injected during chemonucleolysis.

Adult↗
PubMedDate not supplied

Intra-ponto-mesencephalic recording of binaural interaction in human brain-stem auditory evoked potentials.

Brain-stem auditory evoked potentials (BAEPs) were recorded at intraparenchymatous sites along a ponto-mesencephalic stereotactic penetration path in a patient with the rare condition of a ponto-medullary lesion which required biopsy but did not grossly alter scalp BAEPs. Click stimuli were applied either monaurally (with contralateral masking noise against acoustic cross-talk; conditions 'R,' 'L') or binaurally (condition 'RL'). A binaural interaction trace ('BI') was derived by subtracting the sum of the monaural from the binaural responses: BI = (RL)-(R + L). Despite failure to obtain significant BI components above noise level for scalp BAEPs, at the lower pons clearly discernible, multiphasic BI activity could be recorded beginning at the peak latency of scalp wave III and extending over approximately the next 4 msec. Its amplitude rapidly fell off with distance toward more rostral, mesencephalic recording sites. In relation to this positive finding, the equivocality among some of the previous studies on the detection of BI components in human scalp BAEPs is tentatively rephrased in terms mainly of a low signal-to-noise ratio and of functional peculiarities introduced by the respective stimulation protocols.

Adult↗