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Biomedical subjects

L Bertolasi

Publications and source records attributed to L Bertolasi.

35 records · Page 2Linked to original sources
PubMed1998

Antisulfatide polyneuropathy: antibody-mediated complement attack on peripheral myelin.

Increased titers of circulating antisulfatide antibodies are consistently associated with a variety of chronic axonal and demyelinating polyneuropathy syndromes. Previous studies have shown that the pattern of antisulfatide binding to neural tissues correlates with the type of neuropathy. This suggests a possible role for antisulfatide antibodies in inducing peripheral nerve dysfunction, although their exact contribution to the pathogenesis of neuropathy is still unknown. We examined sural nerve biopsy specimens from two patients with sensorimotor and small fiber sensory neuropathy associated with high titers of IgM monoclonal antibodies to sulfatide. Electrophysiological and pathological findings were consistent with predominant demyelination in the patient with sensorimotor involvement, whereas evidence of demyelination was obtained only by teased fiber examination in the other patient. The ultrastructural study disclosed in both cases the presence of myelinated fibers with widely spaced myelin, due to a separation of leaflets of the intraperiod lines. Immunocytochemistry, performed on frozen sections, demonstrated the presence of IgM and complement product C3d bound to myelin sheaths of almost all fibers. Few fibers were immunoreactive for complement components C1q and C5. In addition, the terminal complement complex neoantigen C5b-C9, not associated with S protein, was detected on some myelinated fibers. The results suggest that, at the least in some forms of demyelinating neuropathy associated with antisulfatide antibodies, pathological changes are complement mediated. Our data further confirm previous clinical and experimental observations that complement activation initiates separation of myelin intraperiod lines.

Aged↗
PubMed1998

Possible risk factors for primary adult onset dystonia: a case-control investigation by the Italian Movement Disorders Study Group.

OBJECTIVES: Little is known about the aetiology of idiopathic adult onset dystonia. The Italian Movement Disorders Study Group promoted a case-control study on some hypothetical risk factors including past medical events, life events, life habits, occupational hazards, and family history of dystonia, parkinsonism, and tremor. METHODS: Cases affected by idiopathic adult onset dystonia (age at symptom onset >20 years, duration of disease >one year and <five years) were selected among consecutive outpatients attending 14 Italian centres. Control outpatients matched for age (+/-5 years), sex, and referral centre were identified among diagnostic categories thought to be unassociated with study exposures. Information was obtained by a standardised questionnaire administered by medical interviewers. Conditional logistic univariate and multivariate regression analyses were performed by a standard statistical package. RESULTS: Multivariate analysis on 202 cases and 202 age and sex matched control outpatients indicated that head or facial trauma with loss of consciousness, family history of dystonia, and family history of postural tremor independently increased the risk of developing adult onset dystonia, whereas hypertension and cigarette smoking exerted a protective effect. The findings also suggested a positive association between local body injury-for example, previous ocular diseases and neck or trunk trauma-and dystonia of the same body part. CONCLUSIONS: The results support the idea that environmental and genetic factors may both be important in the aetiology of adult onset dystonia, and suggest aetiological clues worthy of further analytical investigation.

Adult↗
PubMed1997

Botulinum toxin treatment of muscle cramps: a clinical and neurophysiological study.

Botulinum toxin is now widely used in the treatment of several hyperkinetic movement disorders. To evaluate its efficacy in treating muscle cramping syndromes, we studied clinical and neurophysiological variables before and after botulinum toxin injections into calf muscles and small flexor muscles of the foot in patients with an inherited benign cramp-fasciculation syndrome. At each assessment the clinical severity of cramp was scored and the cramp threshold frequency was measured with repetitive electrical peripheral nerve stimulation. Botulinum toxin injection significantly lowered our patients' clinical cramp severity scores (mean +/- SD: before, 3.80 +/- 0.44; after, 1.40 +/- 0.54), left muscle strength unchanged and significantly increased their cramp threshold frequencies (before, 4.22 +/- 2.26 Hz; after, 10.0 +/- 3.74 Hz). The clinical benefit induced by botulinum toxin lasted about 3 months. Botulinum toxin injections also significantly reduced fasciculation potentials in relaxed muscles (before, 0.86 +/- 0.19 fasciculations/sec; after, 0.45 +/- 0.11 fasciculations/sec). These findings show that local intramuscular injections of botulinum toxin provide effective, safe, and long-lasting relief of cramps possibly by reducing presynaptic cholinergic stimulation of motor nerve terminals and by impairing the input/output function of intrafusal and extrafusal motor end plates.

Adult↗
PubMed1997

Binocular interaction in normal vision studied by pattern-reversal visual evoked potential (PR-VEPS).

Monocular and binocular visual evoked potentials (VEPs) in response to different check size (15-21-38-84 minutes or arc) were studied in 14 subjects with normal visual acuity and stereopsis. The binocular VEP amplitude is slightly higher than the VEP amplitude on stimulation of the "better eye" and significantly higher than the VEP amplitude on stimulation of the "worse eye"; this effect is observed using small checks and almost exclusively involved N75-P100. Both the N75 and P100 peaks occur earlier after binocular than monocular stimulation. The shortening of the N75 mean latency is significantly greater than that of the P100 mean latency when larger check sizes are used. The mean latency of the N145 potential is not significantly different in monocular and binocular stimulus conditions. The slight summation effect and latency shortening in the binocular VEPs are not consistent with the hypothesis that it is the sum of separate monocular signals originating from the visual cortex that gives rise to the response. The early components of both monocular and binocular VEPs are thought to be of post-synaptic origin (outside layer 4c of area 17), where the inputs become mixed so that most cells receive information from both eyes. The amplitude enhancement of binocular VEPs, which mainly occurs when using small checks, may be related to the increase in the total amount of cortical activity representing the macular region; this may account for binocular superiority in fine spatial resolution. The latency shortening in binocular conditions can be explained by considering that the critical determinant of the latency is the fundamental spatial frequency of the pattern. When coarse patterns are used, their effectiveness in parafoveal stimulation may affect the VEPs, with a significant contribution coming from the more peripheral retina. The enlargement of the visual field when the eyes see simultaneously may therefore further reduce the latency of the response when using the larger checks suitable for eccentric stimulation.

Adult↗
PubMed1997

Guidelines for the therapeutic use of botulinum toxin in movement disorders. Italian Study Group for Movement Disorders, Italian Society of Neurology.

Since its introduction in the early '80s the use of botulinum toxin has improved the quality of life of the patients affected by movement disorders. Toxin's neuromuscular blocking action allows a symptomatic treatment of those clinical conditions characterised by excessive muscular activity. Although the dosages used are safe and the side-effects are reversible, a correct use of botulinum toxin depends on the knowledge of its clinical pharmacology and of the anatomy of the body segments to be injected. In addition, the treatment of more complex conditions, i.e. laringeal dystonia, imposes an inter-disciplinary approach and specialised injection techniques. In this review, the Italian Study Group on Movement Disorders presents the consensus guidelines for the therapeutic use of botulinum toxin in movement disorders. The main toxin types, their use and administration modalities, and the training guidelines will be presented.

Botulinum Toxins↗
PubMed1995

Role of HIV in the pathogenesis of distal symmetrical peripheral neuropathy.

We report the results of a clinical, electrophysiological and pathological study conducted in 18 AIDS patients presenting a distal symmetrical predominantly sensory polyneuropathy (DSPN) characterized by painful dysesthesias as main complaint. Onset of the neuropathy was at CDC (Center for Disease Control) stage II in 2 patients, at CDC stage III in 5 patients and at CDC stage IV in the remainder. Electrophysiological investigation confirmed the presence of an axonal alteration in the sensory nerves, but also revealed motor involvement in all cases. The neuropathological features of sensory nerves were fiber loss and axonal degeneration with macrophagic activation. The expression of monocyte-macrophage markers and of major histocompatibility complex class II antigens appeared up-regulated in endoneurial ramified cells, while expression of CR3, a complement receptor involved in the process of phagocytosis, was down-regulated. In six nerve biopsy samples and in two out of five DSPN dorsal root ganglia we found HIV-related mRNA and protein located in scattered cells of the endoneurium which we presume to be macrophages. These data suggest that: (a) DSPN may occur early in the course of the disease and is not limited to later stages; (b) DSPN is not a ganglionitis but is actually a sensory-motor neuropathy; (c) the virus enters the peripheral nervous system and induces changes in the immunocompetent cell population with activation of macrophages. Storage of the virus inside macrophages may act both as a reservoir for the virus and as a putative cause of nerve damage, probably through release of cytotoxins and/or interaction with trophic factors.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Spinal somatosensory evoked potentials in patients with tethered cord syndrome.

We studied the electrophysiological changes occurring in six patients with tethered cord syndrome. Evidence of spinal malformations was provided by magnetic resonance imaging. The functional assessment of the spinal cord was performed by analysing both spinal and cortical somatosensory evoked potentials. The evoked electrospinogram was recorded from the thoracic and lumbosacral spinous processes. The N22 lumbosacral potential was selectively affected, being rostrocaudally displaced and reduced in amplitude or even absent in patients with neurological signs indicating a segmental lower cord lesion. Inter-peak somatosensory evoked potentials latency was normal in all cases, suggesting that ascending axonal potentials in the dorsal column fibres may be synchronized. Segmental potentials of the lumbosacral response, originating from the post-synaptic activity of dorsal horn interneurons, are selectively affected in this syndrome resulting from the rostrocaudal displacement of the spinal cord due to tethering. Our findings in the clinical field are consistent with previous experimental evidence indicating a different sensitivity of the gray vs. white matter to progressive stretching.

Adult↗
PubMed1994

Hemiparkinsonism-hemiatrophy syndrome: neuroradiological and neurophysiological findings.

A rare form of secondary parkinsonism has been recently described as 'hemiparkinsonism-hemiatrophy syndrome'. We report a case with such clinical features. A neurophysiological study of the evoked potentials, somatosensory and motor, has been conducted. We stress the neuroradiological findings at nuclear magnetic resonance, which documented the presence of an area of altered signal in the mesencephalon, between the cerebral pedunculus and the red nucleus on the right side. The etiopathogenetic considerations and diagnostic criteria are discussed. Moreover we evaluate the efficacy of levodopa therapy.

Adult↗
PubMed1994

Variability of tibial nerve early cortical potentials in normal subjects.

The aim of the study was to calculate and test the variability of several tibial nerve SEP parameters, particularly scalp amplitude distribution, with a view to obtaining more reliable clinico-electrophysiological correlations. The parameters were evaluated in 20 healthy subjects using a simple, easily reproducible recording method. The absolute latency of the P40 wave was greater than that of the N37 wave, except in two cases. Paradoxical lateralization was present in all subjects. On the basis of the scalp amplitude distribution of the ipsi- and contralateral potentials, three distinct groups were identified: a) dominance of ipsilateral P40, 29 sides; b) dominance of P37, 15 sides; and c) equivalent amplitude of P37 and ipsilateral P40, 5 sides. The individual amplitude values of these potentials were plotted on a normogram. The results suggest that (i) the absence of one or more early cortical SEPs may be considered abnormal; (ii) when SEP scalp lateralization is present, it may be useful to compare the amplitude distribution of the individual components in normal and pathological populations; and (iii) for this purpose, lateralized potentials are more reliable owing to their lower degree of amplitude dispersion.

Adult↗
PubMed1993

The influence of muscular lengthening on cramps.

Muscle cramps induced by voluntary contraction and by electrical stimulation of the peripheral nerve were studied electrophysiologically in 10 healthy subjects. The aim was to verify that cramps can be evoked by electrical stimulation of peripheral nerve and to clarify the physiological mechanism responsible by analyzing the effect of muscular stretching on cramps. Our results showed: (1) Cramps can be induced even after peripheral nerve block by electrical stimulation distal to the block. (2) No cramps were recorded during or following maximal voluntary contraction without muscular shortening, while 7 of 10 subjects showed a true cramp following maximal effort with shortening of the muscle. (3) Muscle stretching caused a sudden interruption of cramps induced by either voluntary contraction or electrical stimulation of the peripheral nerve, even after the induction of nerve block. (4) The lengthening state of the muscle can strongly influence the possibility of evoking cramps by electrical stimulation of nerve. Our study verifies the experimental model proposed by Lambert in 1969, emphasizing the relevance of frequency of stimulation and confirming the hypothesis that cramps are of peripheral origin. The effects of muscle stretch and lengthening on cramp interruption and development also have a peripheral mechanism.

Adult↗
PubMed1993

Transcranial electric and magnetic stimulation of the leg area of the human motor cortex: single motor unit and surface EMG responses in the tibialis anterior muscle.

We compared single motor unit and surface EMG responses in the active right tibialis anterior following anodal electrical or magnetic stimulation of the motor cortex over the vertex. Magnetic stimulation used a monophasic current pulse through a circular coil centred 3 cm anterior to the vertex. Lowest threshold magnetic stimulation occurred when the current in the coil flowed from the left to the right side at the posterior rim of the coil. Such stimulation produced single unit and surface EMG responses which had the same latency as those produced by anodal electric stimulation. If the direction of the magnetic stimulating current was reversed, response latencies became more variable from unit to unit, and on average they occurred 1.0 +/- 0.5 msec later. In single motor units anodal and magnetic post-stimulus time histogram (PSTH) peaks had the same duration. This was similar to the duration of the PSTH peaks produced by a single low intensity stimulus given to the common peroneal nerve. We conclude that magnetic stimulation can produce direct activation of corticospinal neurones to the tibialis anterior if the direction of induced current flow is optimal. This projection is likely to be either monosynaptic or oligosynaptic.

Adult↗
PubMed1993

Some saccadic eye movements can be delayed by transcranial magnetic stimulation of the cerebral cortex in man.

In 15 normal subjects we investigated the effect on visually guided saccadic eye movements of giving a single transcranial magnetic stimulus through a circular coil centered at the vertex. In the normal paradigm, subjects fixated a target which moved randomly to the left or right by 11 degrees. The mean saccadic reaction time of 189 ms was increased by 40-50 ms if a magnetic stimulus was given in random trials some 60 ms prior to the expected onset time of control saccades. The duration and amplitude of the saccades was unchanged. The delay was smaller if the stimulus was given earlier in the reaction period, or if the coil was moved anterior or posterior to the vertex. Larger stimulus intensities produced longer delays. Three subjects were trained to produce express saccades (mean saccadic reaction times of 107-141 ms) in a 'gap' paradigm. The latency of these saccades, which are thought to be mediated by collicular mechanisms without involvement of the cortex, was not affected by magnetic stimulation. This suggests that magnetic stimulation delays normal visually guided saccades by an action on the cerebral cortex, rather than on the oculomotor centres of the brainstem. Five subjects made non-targeted saccades in darkness in response to an auditory stimulus. These saccades, like visually guided saccades, could be delayed by magnetic brain stimulation. We conclude that saccadic delay is produced by interference with cortical areas involved in the execution of saccades rather than by interfering with the perception of the visual or auditory 'go' stimulus. These probably include supplementary and frontal eye field and posterior parietal cortex. The fact that visually guided saccades emerged intact after the delay indicates that the instructions for amplitude and direction were stored separately from those involved in timing when the movement was to occur.

Acoustic Stimulation↗
PubMed1992

Cortical projection to erector spinae muscles in man as assessed by focal transcranial magnetic stimulation.

We stimulated the motor cortex in 9 subjects using focal transcranial magnetic stimulation with a figure of 8 coil in order to examine the cortical representation of the erector spinae muscles. Recordings were made from the erector spinae 3.5 cm lateral to the third lumbar vertebra. In 5 subjects clearly reproducible responses could be obtained which had a latency compatible with transmission via fast conducting fibers in a mono- or oligosynaptic pathway. In the remaining 4 subjects responses were poorly defined. Latencies in surface recordings varied between 13 and 24 msec but were longer when needle recordings were used. Mapping of the motor cortex was performed by moving the coil in 2 cm steps on either side of Cz. Different patterns of hemispheric representation were found ranging from a contralateral projection in either hemisphere to a representation of both back muscles in one hemisphere (2 subjects). Responses were followed by a silent period. The latter was interrupted or terminated by a response between 52 and 85 msec post stimulus which was found predominantly in the muscle ipsilateral to the side of stimulation.

Adult↗
PubMed1990

Far-field and cortical somatosensory evoked potentials in motor neuron disease.

We examined median somatosensory evoked potentials (SEPs) in 26 patients with sporadic motor neuron disease (MND). SEPs were recorded with multiple scalp derivations, using both the midfront and the earlobe as references for each subject. Central conduction time (CCT) was abnormal in three patients, but only when using the midfront reference. Moreover, an exclusive alteration of the early prerolandic potentials (absent or delayed P20 and/or P22) was noted using the earlobe reference in amyotrophic lateral sclerosis and in progressive bulbar palsy (54% and 50% of patients, respectively) but not in progressive muscular atrophy. These findings correlated with clinical evidence of upper motor neuron signs and with the severity of the disease. In agreement with recent views regarding the sources of the early anterior cortical responses, neuronal loss in the motor cortex may be considered as affecting the generator sites of these potentials.

Adult↗
PubMed1988

[Continuous muscular activity. Clinical aspects and neurophysiological differences from Isaacs' syndrome].

We report a case of continuous muscle activity, unusual from both the clinical and neurophysiological point of views. The neurological examination revealed a continuous rippling of muscles, but limited to the lower part of the face, to the forearm and to the muscles of the thenar eminence. All deep reflexes were normal. Hyperperspiration, spasms and stiffness of abnormal postures were absent. Electromyography displayed continuous motor unit discharges. An abnormal F wave was elicited only from the affected territories. The disappearances of the spontaneous activity and of the F wave occurred not only after the motor nerve block, but also after the block of the afferent sensitive fibres. Therapy with carbamazepine, hydantoin, diazepam and baclofen did not bring improvement.

Action Potentials↗
PubMedDate not supplied

[Peripheral neuropathy caused by incongruous posture in shoe manufacture workers].

Nine cases of local neuropathy are described in shoe-manufacture workers. Clinical and electrophysiological examination excluded diseases such as toxic polyneuropathies due to n-hexane. Specific lesions of the ulnar nerve were located near the elbow where the forced and uncomfortable posture facilitated the compression of the nerve in the cubital tunnel. The severity of the neuropathies ranged from relatively slight, with paresthesia of some of the fingers, to evident hypotrophy of the inter-osseous muscles of the hand. All the 9 cases sewed shoe uppers using sewing machines operating 25 cm above the arm support, thus obliging the operator to work with one or both elbows resting on the support, with the arms and shoe-upper held up. Five cases presented a neuropathy of the right arm, 3 of the left arm, and in one case the lesions were bilateral. The features of the work station are described and the possible promoting factors and the ergonomic pathogenesis of these neuropathies are discussed.

Adolescent↗