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Biomedical subjects

P Boulu

Publications and source records attributed to P Boulu.

16 recordsLinked to original sources
PubMed1996

Recent data on the pathophysiology of nerve root compression and pain.

Both mechanical and biochemical factors are involved in the pathophysiology of nerve root compression. Chronic compression produces severe demyelination and fibrosis of the nerve root. Similar lesions can result from exposure to irritant substances released from the nucleus pulposus. Pain sensations arise from the peripheral nervous system as a result of structural radicular damage and sensitization. Structural nerve root changes (deafferentation, formation of ephapses or microneuromas) increase the sensitivity of the spinal nociceptive neurones. Algogenic substances are released that lower the activation threshold of nociceptors, producing peripheral sensitization. In the central nervous system, neuroplasticity and increased transmission of nociceptive signals in the spinal cord result in permanent excitation and sensitization of the spinal convergent neurones. The practical implications of these data are discussed.

Biomechanical Phenomena↗
PubMed1993

[Motor evoked potentials].

Due to the motor evoked potentials recorded in limb muscles after transcranial and spinal magnetic stimulation, conduction in the central motor pathways can now be evaluated safely and painlessly in man. The central motor conduction time obtained includes the time required for transmission, along the fast pyramidal fibres, from the cortex to the spinal motoneurons, the synaptic transmission to motoneurons and the conduction on a short segment of the motor nerve root. Lengthening of this time almost always reflects dysfunction of the central motor pathways. The abnormalities observed are not specific of any particular cause, and they must be interpreted in relation to the context. The usefulness of this new electrophysiological technique is being tested by radiological and anatomico-clinical correlations in various diseases of the central nervous system (e.g. disseminated sclerosis, cerebral infarction, spinal cord injury) and the locomotor apparatus (e.g. cervical myelopathy, radiculopathy).

Cerebral Infarction↗
PubMed1988

[Writer's cramp and left frontal meningioma].

A 55 year-old, right-handed, man developed a progressive writer's cramp spreading to a right hemidystonia. He had a left paramedian frontal meningioma. The association of an hemidystonia with contralateral lesions in the basal ganglia has been often reported. Its occurrence with a frontal lesion appear to be much less frequent. This association suggests a possible disorder of frontostriatal connections.

Dystonia↗
PubMed1986

[Idiopathic diffuse polyalgia syndrome].

The term "idiopathic diffuse polyalgia syndrome" is suggested to designate an entity well known to neurologists, rheumatologists and all physicians interested in pain. In this syndrome pain is diffuse but often predominates in a given region. Physical examination shows excessive tenderness in well-defined areas. Radiological and laboratory examinations are negative. Psychological factors are not always obvious. Several arguments are in favour of dysfunction of the pain control mechanisms. The effectiveness of the various treatments prescribed is related to the quality of the doctor-patient relation.

Humans↗
PubMed1985

[Somatosensory evoked potential and pain. I. Late cortical responses obtained at different levels of stimulation].

The characteristics of the late components of the somatosensory evoked potential (SEP) as a function of stimulation intensity have been studied in 10 normal volunteers following electrical stimulation of the distal cutaneous branches of the median nerve. The stimulus intensity (either single shock or train) was adapted in order to produce the following 4 types of sensation: liminal tactile (ST); frankly tactile but never painful (4 times ST); pain threshold (SD); and 1.5 time SD. A significant relationship was observed between the amplitude of the late component (N150-P220-N400), of the SEP and the stimulus intensity for a low rate of stimulation (below 0.25 Hz). In contrast this relationship is not verified for higher stimulation rates. These data are discussed with respect to their implication in pain research.

Adult↗
PubMed1985

[Evoked potentials and pain. II. Comparative study of subjective sensations, late components of the cortical potentials and afferent volleys].

The subjective sensations and late components of the cortical somatosensory evoked potential (SEP) have been correlatively studied when elicited by stimulation parameters which were selected in order to activate selectively, either the largest afferent fibers (train of shocks of 10 mA, with a 0.05-0.2 msec duration for each shock) or the several groups of fibers (A alpha beta; A delta and C) of the cutaneous branches of the median nerve (single shock, 1 msec duration; 20 mA). In both cases, a good correlation was found between the quality and intensity of sensations and the amplitude of the late component N150-P220-N400 of the SEP. However, it was also found that this relationship was not linear and suggested that it is possible to saturate the cortical integrative system responsible for the SEP. A selective blockage of the largest fibers (compression) or of the finest ones (lidocaine) have shown that there is no specific involvement of a particular type of peripheral fiber in the genesis of the N150-P220-N400 components. Moreover, these late components could also be recorded with similar latencies when cutaneous stimulations were applied in any part of the body.

Adult↗
PubMed1984

Electrophysiological evidence for crossed oligosynaptic trigemino-facial connections in normal man.

A crossed short latency component (R1) of the human blink reflex could be elicited in orbicularis oculi muscles to stimulation of the contralateral supraorbital nerve, when infraliminal conditioning stimuli were applied to various cutaneous afferents of the body (facial, upper and lower limbs). The crossed R1 responses appeared when the time interval between the conditioning and the test stimuli was of 30 to 40 ms, 50 to 65 ms and 95 to 110 ms for facial, upper and lower limbs afferents respectively. For the same time intervals, these conditioning volleys also exerted a facilitatory effect on the ipsilateral R1 responses. Furthermore, crossed R1 responses were also obtained during supraspinal facilitation induced by a voluntary contraction of the eyelids. These data show that crossed oligosynaptic trigemino-facial reflex connections exist in normal subjects, which become functional when adequate conditioning stimuli are available.

Adult↗
PubMed1984

Sympathetic skin response--a method of assessing unmyelinated axon dysfunction in peripheral neuropathies.

The sympathetic skin response (SSR) was measured in 33 patients with peripheral neuropathies and in 30 normal control subjects. Abnormalities of the response were correlated with clinical, pathologic, and EMG observations. The response was usually absent in axonal neuropathies, but present in demyelinating disorders. Abnormalities of the sympathetic skin response did not correlate well with clinical evidence of dysautonomia, but were a reliable indicator of disorders affecting unmyelinated axons.

Adolescent↗
PubMed1982

Depressive effect of high frequency peripheral conditioning stimulation upon the nociceptive component of the human blink reflex. Lack of naloxone effect.

High frequency (100 Hz) low intensity (2 mA) peripheral conditioning stimulation of either segmental or heterosegmental cutaneous nerves induced non-naloxone-reversible depression of the nociceptive component of the human blink reflex. Electrophysiological studies suggest that this depression is due to a local synaptic inhibitory mechanism involving convergence interactions between several cutaneous afferents onto a same internuncial pool in the trigemino-facial path.

Acoustic Stimulation↗
PubMed1981

[Electrophysiological study of blink reflex in man: segmental, intersegmental, auditory and visual interactions (author's transl)].

The effects of conditioning facial (trigeminal and facial nerves, second cervical roots), peripheral (radial and sural nerves), auditory and visual stimuli on the blink reflex components have been studied in normal subjects. In all the RI response was facilitated and the R2 one was inhibited. By electrophysiological techniques it has been shown that this inhibition is due to a synaptic phenomenon and that the conditioning afferents converge on the same neuronal pool. An unspecific mechanism is proposed to account for these data.

Acoustic Stimulation↗
PubMedDate not supplied

[Iatrogenic neuropathies].

During the last few years the list of drugs capable of inducing a iatrogenic neuropathy has been considerably lengthened. Drug toxicity to peripheral nerves may be discovered at the experimental stage, but it is usually recognized after the drug has been launched on the market, hence the importance of pharmacovigilance. The responsibility of a drug for the occurrence of neuropathy may be difficult to prove, particularly when the drug is used in the treatment of a disease which, by itself, may be responsible for a lesion of the peripheral nervous system. Iatrogenic neuropathies are usually axonal, but some drugs produce a primary disorder in the myelin-Schwann cell couple. Schwann cell diseases may be induced by drugs, such as perhexiline maleate, amiodarone or chloroquine, which inhibit lysosomal enzyme activity. In such cases inclusions representing fat-loaded lysosomes can be detected in various tissues, and particularly in Schwann cells. In certain patients, notably those treated with gold salts, an immune mechanism might be responsible for neuropathy. Most drug-induced neuropathies are due to a primary lesion of the neuron which is more often an axonopathy than a neuronopathy. It is usually a retrograde distal axonopathy the occurrence of which is attributed to a disorder of the fast retrograde axonal flow. In a few cases, the finding of a biochemical mechanism perturbing the axonal flow may help in preventing the occurrence of a iatrogenic neuropathy.

Amiodarone↗
PubMedDate not supplied

[Physiological and clinical recall on equilibrium disorders].

Static and dynamic equilibrium (posture and gait) is indispensable for a normal behavior in human. Its mechanisms are nearly the same in superior species and in man, but humans are the only ones to have acquired exclusively biped upright position and gait. Equilibrium is a sensory function involving 3 sub systems: visual, vestibular and sensori-motor (proprioceptive), controlled by cerebellum and cerebral structures. Information coming from those 3 sub systems must be concordant. In case of discordance, the patient is in a state of sensory conflict. This conflict can induce disequilibrium or true vertigo. After a recall on equilibrium, the authors report the results of an epidemiologic study upon 5298 patients suffering of balance disorders and treated by an alpha-blocker: nicergoline (30 mg/day during 6 months).

Humans↗