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Biomedical subjects

Bernard Dan

Publications and source records attributed to Bernard Dan.

At least 37 records · Page 2Linked to original sources
PubMed2005

Titus's tinnitus.

Historical approaches to tinnitus have depended highly on cultural factors. While ancient Oriental mysticism regarded it as sensitivity to the divine, Roman medicine associated it with depressive and seizure disorders on the basis of presumed common pathophysiology shared by the three conditions. In the Babylonian Talmud, tinnitus appears as Titus's curse: a gnat buzzing in the brain, responding to sound therapy, and then habituating. Various sources show varied emphases with common attention for contextual and emotional aspects that have become an important focus in modern management of tinnitus.

Ancient Lands↗
PubMed2004

Effect of simple spike firing mode on complex spike firing rate and waveform in cerebellar Purkinje cells in non-anesthetized mice.

Cerebellar Purkinje cells receive two different excitatory inputs from parallel and climbing fibers, causing simple and complex spikes, respectively. Purkinje cells present three modes of simple spike firing, namely tonic, silent and bursting. The influence of complex spike firing on simple spike firing has been extensively studied. However, it is unknown whether and how the simple spike firing mode may influence complex spike waveform and firing rate in vivo. We studied complex spike firing during tonic and silent mode periods in non-anesthetized mice. We found that complex spike firing rate is not influenced by simple spike firing modes, but that the complex spike waveform is altered following high frequency simple spike firing. This alteration is a specific decrement of the second depolarizing component of the complex spike. We demonstrate that the amplitude of the second depolarizing component is inversely proportional to the simple spike firing rate preceding the complex spike and that this amplitude is independent of previous complex spike firing. This waveform modulation is different from previously reported modulation in paired-pulse depression and refractoriness.

Action Potentials↗
PubMed2004

Inactivation of calcium-binding protein genes induces 160 Hz oscillations in the cerebellar cortex of alert mice.

Oscillations in neuronal populations may either be imposed by intrinsically oscillating pacemakers neurons or emerge from specific attributes of a distributed network of connected neurons. Calretinin and calbindin are two calcium-binding proteins involved in the shaping of intraneuronal Ca2+ fluxes. However, although their physiological function has been studied extensively at the level of a single neuron, little is known about their role at the network level. Here we found that null mutations of genes encoding calretinin or calbindin induce 160 Hz local field potential oscillations in the cerebellar cortex of alert mice. These oscillations reached maximum amplitude just beneath the Purkinje cell bodies and are reinforced in the cerebellum of mice deficient in both calretinin and calbindin. Purkinje cells fired simple spikes phase locked to the oscillations and synchronized along the parallel fiber axis. The oscillations reversibly disappeared when gap junctions or either GABA(A) or NMDA receptors were blocked. Cutaneous stimulation of the whisker region transiently suppressed the oscillations. However, the intrinsic somatic excitability of Purkinje cells recorded in slice preparation was not significantly altered in mutant mice. Functionally, these results suggest that 160 Hz oscillation emerges from a network mechanism combining synchronization of Purkinje cell assemblies through parallel fiber excitation and the network of coupled interneurons of the molecular layer. These findings demonstrate that subtle genetically induced modifications of Ca2+ homeostasis in specific neuron types can alter the observed dynamics of the global network.

Action Potentials↗
PubMed2004

Postural rhythmic muscle bursting activity in Angelman syndrome.

Postural impairment is one of the most consistent features of Angelman syndrome. Using multiple-channel electromyography, we studied a lower limb and an upper limb isometric postural task in 14 patients with Angelman syndrome and 18 unimpaired control subjects. Both tasks were associated with synchronous bursts of activity at frequencies of 6-8 s(-1) in all recorded muscles in all patients with Angelman syndrome and none of the control subjects. This pattern was not altered by extra-loading. Electroencephalogram recorded during the upper limb task showed no change in relation to the task. Burst-locked back-averaging of the electroencephalogram showed no spiking before or during the bursts. Various physiological and pathological rhythmic muscle activities have been proposed to be a manifestation of oscillations in the central nervous system and it has been suggested that such oscillations may have a role in the processing of motor commands. The mechanism of the rhythmic muscle bursting activity associated with maintaining posture in patients with Angelman syndrome is not clear, although it could be consistent with cerebellar Purkinje cell dysfunction, either as a pathological feature or as an adaptive process to overcome deficits in motor coordination.

Action Potentials↗
PubMed2004

Gait control in spinal palsy.

Developmental motor impairment with lower limb spasticity most commonly corresponds to cerebral palsy of the spastic diplegia type. Here we describe a 4-year-old girl whose locomotor phenotype reflects early cortico-spinal lesion at the spinal level. This child has developmental spastic paraparesis secondary to D4-D8 cord compression. We analysed her gait using the ELITE optoelectronic system and compared it to that of six normal age-matched controls and six age-matched children with leucomalacic spastic diplegia. Gait characteristics of the patient included preservation of head orientation and arm swing similar to findings in normal controls and contrasting with children with spastic diplegia. She also had truncal instability and displayed lack of selectivity in lower limb movement as in spastic diplegia and in contrast with normal controls. This may reflect differences in locomotor control between developmental spasticity of cerebral and spinal origin. The latter might correspond to spinal palsy defined as abnormal movement and posture secondary to non-progressive pathological processes affecting the immature spinal cord.

Arm↗
PubMed2004

Electrophysiological assessment of the effect of intrathecal baclofen in dystonic children.

OBJECTIVE: To evaluate the effect of intrathecal baclofen in a group of dystonic children using electrophysiological procedures previously validated in spastic children. METHODS: Seven children (aged 2-16 years) with dystonia of various aetiologies (dyskinetic cerebral palsy, pantothenate kinase-associated neurodegeneration and Aicardi-Goutières syndrome) underwent transcranial magnetic stimulation, H-reflex and flexor reflex studies before and after intrathecal injection of baclofen. The Barry-Albright Dystonia Scale (BADS) was used for clinical evaluation of dystonia. RESULTS: Motor-evoked potentials, present in 2 of 5 patients before baclofen, were preserved after injection. Before baclofen, H reflex was present in 6 of 7 patients (mean H(max)/M(max:) 0.45+/-0.21). It was markedly reduced after the injection (mean H(max)/M(max:) 0.09+/-0.11) (P<0.001). Area of flexor reflex significantly decreased after baclofen (P=0.047), while threshold significantly increased (P=0.01). No significant clinical improvement of the BADS scores was observed (P=0.058). CONCLUSIONS: These electrophysiological procedures, previously demonstrated to quantify the action of intrathecal baclofen in spastic adults and children, also appear sensitive in dystonic children. The electrophysiological changes are consistent with primarily spinal sites of action of baclofen. They appear more sensitive than clinical evaluation.

Adult↗
PubMed2004

Motor strategies in standing up in children with hemiplegia.

In spastic hemiplegia, the organization of whole body movements is impaired by deficient postural control. We studied segmental motor patterns involved in standing up from supine position in 15 children with spastic hemiplegic cerebral palsy and 14 unimpaired children using a visual analysis scale previously validated for developmental research. This approach examines specific movement patterns in upper limbs, axis, and lower limbs. We found that children with hemiplegia use movement patterns described in normal children but with reduced interindividual variability and a significant preponderance of asymmetric patterns. One previously undescribed stereotyped lower limb pattern was observed in two children with spastic hemiplegia. Emergence of these patterns is consistent with the referent body image theory. This approach can systematically characterize the limited repertoire of movement in patients with disorders of movement and posture and therefore contribute to a better understanding of motor control. The approach may guide management proposals with particular reference to variability and symmetry and might be used as a follow-up tool.

Cerebral Palsy↗
PubMed2004

Cervical myelitis from herpes simplex virus type 1.

Although subacute ascending paralysis without sensory involvement is typically evocative of Guillain-Barré syndrome, it can alternatively be due to infection or inflammation of the spinal cord. We describe a 16-month-old female who presented with ascending flaccid paresis after an upper respiratory tract infection. She then developed signs of upper motor neuron involvement of the lower limbs associated with upper motor neuron involvement of the upper limbs. Motor nerve conduction and electromyographic studies of upper limbs demonstrated anterior horn cell involvement. Neuroimaging was consistent with cervical myelitis, and cerebrospinal fluid polymerase chain reaction was positive for herpesvirus-1. Although association with the primary infection of the respiratory tract may be fortuitous, possible neurotropic or hematogenous spread of herpesvirus-1 to the cervical spinal cord cannot be excluded. She then developed signs of upper motor neuron involvement of the lower limbs associatred with lower motor neuron involvement of the upper limbs [corrected].

Cervical Vertebrae↗
PubMed2004

From electrophysiology to chromatin: a bottom-up approach to Angelman syndrome.

Angelman syndrome is one of the most studied human diseases related to a gene that is expressed on the maternal chromosome only in at least some brain cells. It is caused by inactivation of the UBE3A gene in the brain due to various abnormalities of the 15q11-q13 chromosome inherited from the mother. It is characterized by severe developmental delay, seizures, virtual absence of speech, motor impairment, and a particular behavioral phenotype. Studies of cortical, electromyographic and cerebellar electrophysiology in patients with Angelman syndrome and a mouse model revealed unique rhythmic neurophysiological activities in the cerebral cortex, cerebellar cortex, and muscles. The oscillatory patterns may be linked to molecular pathophysiology of the syndrome involving dysregulation of synaptic neurotransmission through UBE3A-related modulation of functional GABAA receptor complexes.

Angelman Syndrome↗
PubMed2004

Development of pendulum mechanism and kinematic coordination from the first unsupported steps in toddlers.

The inverted pendulum model in which the centre of mass of the body vaults over the stance leg in an arc represents a basic mechanism of bipedal walking. Is the pendulum mechanism innate, or is it learnt through walking experience? We studied eight toddlers (about 1 year old) at their first unsupported steps, 18 older children (1.3-13 years old), and ten adults. Two infants were also tested repeatedly over a period of 4 months before the onset of independent walking. Pendulum mechanism was quantified from the kinematics of the greater trochanter, correlation between kinetic and gravitational potential energy of the centre of body mass obtained from the force plate recordings, and percentage of recovery of mechanical energy. In toddlers, these parameters deviated significantly (P<10(-5)) from those of older children and adults, indicating that the pendulum mechanism is not implemented at the onset of unsupported locomotion. Normalising the speed with the Froude number showed that the percentage of recovery of mechanical energy in children older than 2 years was roughly similar to that of the adults (less than 5% difference), in agreement with previous results. By contrast, the percentage of recovery in toddlers was much lower (by about 50%). Pendulum-like behaviour and fixed coupling of the angular motion of the lower limb segments rapidly co-evolved toward mature values within a few months of independent walking experience. Independent walking experience acts as a functional trigger of the developmental changes, as shown by the observation that gait parameters remained unchanged until the age of the first unsupported steps, and then rapidly matured after that age. The findings suggest that the pendulum mechanism is not an inevitable mechanical consequence of a system of linked segments, but requires active neural control and an appropriate pattern of inter-segmental coordination.

Adult↗
PubMed2003

Impaired emotional facial expression recognition in alcoholics, opiate dependence subjects, methadone maintained subjects and mixed alcohol-opiate antecedents subjects compared with normal controls.

The present study aims to explore whether an impairment in emotional facial expressions (EFE) decoding is specific to alcoholism compared with opiate dependence. An EFE decoding test consisting of 16 photographs of EFE portraying happiness, anger, sadness and disgust was administered to five different groups of 30 subjects each: recently detoxified alcoholics (RA); opiate addicts under methadone maintenance treatment (OM); detoxified opiate addicts (OA); detoxified subjects with both alcohol and opiate dependence antecedents (DAO); and normal controls (NC). Repeated measures analysis of variance using a multivariate approach was conducted on EFE decoding accuracy scores with group as the between-subjects factor. Accuracy scores were significantly lower in RA and DAO than in OM and OA, which had significantly lower scores than NC. Low accuracy scores in RA and DAO confirm previous results indicating that alcoholism is associated with impaired EFE recognition. Results in OM and OA indicate that opiate dependence is also associated with an impaired EFE decoding but less than in alcoholism. Alcohol and opiate chronic consumption could both exercise a deleterious effect on EFE-decoding brain function, alcohol having the most severe impact. Alternatively, EFE-decoding problems could be present before the development of alcohol and opiate dependence, with an additional effect of chronic alcohol consumption on EFE decoding. In this context, EFE-decoding impairment could reflect a more general emotional intelligence deficit in addicted populations.

Adult↗
PubMed2003

Unilateral cortical necrosis following status epilepticus with hypoglycemia.

Isolated status epilepticus or severe hypoglycemia rarely causes irreversible focal neurologic deficits in children. We describe three children who presented with status epilepticus and prolonged hypoglycemia resulting in hemiplegia due to unilateral hemispheric damage. The non-vascular cortical topography of the lesions is consistent with selective neuronal necrosis, confirmed by histopathology in one patient. This suggests increased neuronal vulnerability to necrosis secondary to energy failure resulting from combination of hypoglycemia and status epilepticus.

Brain Damage, Chronic↗
PubMed2003

Nonsurgical cerebellar mutism (anarthria) in two children.

Cerebellar mutism (anarthria) is a well-described complication of posterior fossa tumor resection. It is accompanied by a characteristic behavior including irritability and autistic features. This syndrome is typically reversible within days to months. Underlying pathophysiology is unknown. We describe two children who presented with a similar clinical finding after nonsurgical cerebellar involvement, hemolytic-uremic syndrome in one and cerebellitis in the other. Postmortem pathologic findings in the first patient indicated cerebellar ischemic necrosis. Single-photon emission computed tomography in the second patient revealed diffuse cerebellar hypoperfusion with no supratentorial abnormalities, refuting a phenomenon of diaschisis between cerebellar and frontal connections. These findings confirm that this clinical syndrome may occur in a nonsurgical, nontraumatic context. They are consistent with recent integrative hypotheses explaining cerebellar anarthria.

Cerebellar Diseases↗
PubMed2003

Predictive value of electrophysiology in children with hypoxic coma.

Assessment of prognosis of children in hypoxic coma is difficult. The value of clinical evaluation is often limited. The usefulness of electrophysiologic tests has been documented mostly in adults and neonates and in cases of traumatic coma. We reviewed retrospectively 39 consecutive children with nontraumatic hypoxic coma to assess the prognostic value of EEG, visual, and auditory evoked potentials. Correlation between electrophysiology and neurologic outcome after mean follow-up period of 30 months was significant (r(s) = 0.6, P < 0.001). In contrast there was no correlation between Pediatric Risk of Mortality score (PRISM) and outcome (r(s) = -0.42, P = 0.8). Combining magnetic resonance imaging with electrophysiology further enhanced their prognostic value (r(s) = 0.69, P < 0.001). Neuroimaging was highly sensitive but less specific, and electrophysiologic tests were highly specific but less sensitive. We conclude that early electrophysiology can contribute to predicting outcome in pediatric hypoxic coma.

Adolescent↗
PubMed2002

Motor strategies in standing up in leukomalacic spastic diplegia.

In spastic diplegia impaired postural control jeopardizes the organization of whole-body movements. We studied segmental motor patterns involved in standing up from a supine position in ten children with spastic diplegia associated with periventricular leukomalacia and 14 unimpaired children using a visual analysis scale previously devised for developmental research. This approach examines specific movement patterns in upper limbs, axis and lower limbs. We found that children with spastic diplegia use movement patterns described in normal children but with markedly reduced intra- and interindividual variability. One previously undescribed stereotyped lower limb pattern was observed in four patients. This approach can systematically characterize the limited repertoire of movement in patients with spastic diplegia and therefore contribute to a better understanding of motor control.

Biomechanical Phenomena↗