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Biomedical subjects

E Berthier

Publications and source records attributed to E Berthier.

6 recordsLinked to original sources
PubMed2001

Nonlocal thermodynamic equilibrium self-consistent average-atom model for plasma physics.

A time-dependent collisional-radiative average-atom model is presented to study statistical properties of highly charged ion plasmas in off-equilibrium conditions. The time evolution of electron populations and the electron covariance matrix is obtained as approximate solutions of a master equation. Atomic structure is described either with a screened-hydrogenic model including l splitting, or by calculating one-electron states in a self-consistent average-atom potential. Collisional and radiative excitation/deexcitation and ionization/recombination rates, as well as autoionization and dielectronic recombination rates, are formulated within the average-configuration framework. Local thermodynamic equilibrium is obtained as a specific steady-state solution. The influence of atomic structure and the role of autoionization and dielectronic recombination processes are studied by calculating steady-state average ionization and ionization variance of hot plasmas with or without radiation field.

Journal Article↗
PubMed1996

Diagnostic utility of somatosensory evoked potentials (SEPs) in presurgical assessment of cervical spondylotic myelopathy.

Median and tibial nerve SEPs were recorded in 27 patients with spondylotic myelopathy. SEP data were compared with clinical and MRI data. SEPs were abnormal in all but five patients. Segmental dysfuction of the cervical cord was observed in 12 patients (45%), whereas abnormality of dorsal column conduction was observed in 10 (37%) and 16 (59.3%) patients after median and tibial nerve stimulation, respectively. No clear correlation was found between the severity of MRI abnormalities and that of clinical presentation or SEP abnormalities. However, there was no patient with normal SEPs and severe MRI abnormalities, including narrowing of cervical cord diameter or impingement of the cervical cord or intramedullary T2 signal hyper intensity. Conversely, 8 of the 13 patients with no evidence of cord narrowing or T2 signal abnormality showed abnormal SEPs. This divergence between SEP and MRI data suggests that SEP recording should be included in presurgical assessment of these patients, especially those without clear MRI evidence of cervical cord compression.

Evaluation Studies as Topic↗
PubMed1994

Facial motor responses evoked by direct electrical stimulation of the trigeminal root. Localizing value for radiofrequency thermorhizotomy.

In Sweet's description of RF-thermocoagulation for trigeminal neuralgia, the trigeminal nerve was stimulated at 50 c/s to evoke paraesthesias, in order to check the electrode location before the thermolesion is made. In 1979, we changed the frequency to 5 c/s, so as to produce in addition twitches in the masticatory muscles (in stead of the less detectable tetanization produced by 50 c/s stimulation). Since then, we started to observe, also, twitches in the muscles innervated by the facial nerve. These twitches were not always in the Orbicularis oculi (which corresponds to the classical blink reflex), but also in the lower facial muscles. Such clinically observable evoked motor responses (EMR)-which had not been reported before--were noticed in 44% of the 459 procedures performed from 1979 to 1988. When EMR were present, the threshold to evoke paraesthesias before thermolesion, and the duration of the thermolesion for obtaining a marked hypoaesthesia covering the entire painful territory, were significantly lower, respectively p < 0.01 and p < 0.001, than when EMR were absent. This indicates that the electrode was closer to the nerve when EMR were present. As a probable consequence, recurrence of pain was significantly lower in the EMR (+) group: 1.4%, than in the EMR (-) group: 5.8% (p < 0.05). The twitches corresponded to the territory of the evoked paraesthesias in 95%, and to the hypoaesthetic area created by the thermolesion in 96%. So, getting EMR in the territory of the pain can be a helpful indicator for an accurate location of the electrode in the trigeminal root, according to its somatotopic organization. These EMR are hypothesized to be due to a trigemino-facial reflex. A preliminary intra-operative EMG study clearly shows that for EMR in the upper part of the face we are dealing with blink-like reflexes, whilst for EMR in the lower face, mechanisms still remain unclear and need further study to be understood.

Adult↗
PubMed1992

[Idiopathic cranial polyneuropathies].

A series of 43 cases with multiple cranial nerve deficits was collected between 1972 and 1990. No diagnosis was established in 15 cases. The facial and the trigeminal nerves were most frequently affected. In 10 cases, a monophasic course was observed usually with recovery. Recurrence was present in 5 cases. An inflammatory mechanism was likely in 10 cases. Nosological relations between these cases and either Bell's palsy (idiopathic facial paralysis) or Tolosa-Hunt's syndrome are discussed.

Adult↗
PubMed1992

[Juvenile arteriosclerotic leukoencephalopathy: anatomoclinical study of a case].

A 34-year old right-handed man was suffering from recurrent cerebro-vascular insults. CT-scans revealed several subcortical lacunar infarcts, and leukoaraïosis. Arteriography of the left and the right carotid arteries was performed respectively on the 4th and the 9th year of the disease, and did not elicit significant extracranial and intracranial vascular lesions. There were no arguments in favor of infectious, inflammatory, or auto-immune vascular diseases. The patient had tardive hypertension and dementia, and died at the age of 44. Pathological findings, limited to the brain and cervical spinal cord, revealed numerous ischemic lacunar infarcts. Histological lesions were consistent with the diagnosis of arteriosclerotic leukoencephalopathy. There were oedema, palor, and loss of myelin in the white matter, and nonspecific diffuse arteriosclerotic lesions that were particularly pronounced in the intimal part of the arterial wall. No inflammatory process nor amyloid deposits were found. Despite the onset of the disease in a young adult and the late occurrence of hypertension, our case report shares most of the pathological features of the Binswanger's type of arteriosclerotic encephalopathy.

Adult↗