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Biomedical subjects

P Tonali

Publications and source records attributed to P Tonali.

At least 55 records · Page 3Linked to original sources
PubMed2002

Occurrence of factor V Leiden mutation (Arg506Gln) and anticardiolipin antibodies in migraine patients.

The occurrences of factor V Leiden mutation (Arg506Gln) and antiphospholipid antibodies (APA) in migraine patients have been reported, but the findings are controversial. We investigated the presence of factor V Leiden and the serum level of anticardiolipin antibodies (aCL) in a consecutive series of 70 migraine patients (47 women; mean age, 34.1 years). Of these, 40 patients had migraine with aura. A matched sample of 70 healthy people was considered as the control group. Heterozygous genotype for factor V Leiden mutation was detected in 4 (5.7%) migraine patients (of which 2 had migraine with aura) and in 2 (2.8%) subjects of the control group. Although proportionally more migraine patients harbored the factor V Leiden mutation, this difference was not statistically significant, perhaps due to the small number of patients involved. We found normal serum levels of aCL in all migraine patients. Further studies and a long-term follow-up are warranted to determine the significance of this genetic abnormality in migraine.

Adult↗
PubMed2002

Myasthenia gravis outcome measure: development and validation of a disease-specific self-administered questionnaire.

We describe the development and validation of an outcome measure for patients with myasthenia gravis (MG) and show the correlation of the items with conventional MG measurements. In stage I, item generation, a group of methodologists, clinical experts generated a list of 56 items. The list was based on (1) a previous study on an MG sample, (2) clinical experience and (3) items proposed by MG patients. In stage 2, reduction of items, the list was reduced on the basis of results from field testing (41 patients completed the 56-item questionnaire). In stage 3, reliability and validity were assessed. A 25-item MG questionnaire (MGQ) was generated. Results were related to conventional measures of MG severity. Furthermore, the MGQ appeared reliable, sensitive and reproducible. The questionnaire was validated as an outcome measure.

Humans↗
PubMed2002

Peripheral neuropathy with hypomyelinating features in adult-onset Krabbe's disease.

We describe three brothers suffering from Krabbe's disease with onset in the fifth decade. The proband showed a complete deficiency of leukocyte enzyme galactocerebrosidase and was found to be heterozygous for two previously described mutations: G > A809 and 502T/del consisting of a 30 kb deletion. In all three brothers the neurological examination showed features of asymmetrical peripheral neuropathy associated with pyramidal signs and the electrophysiological examination showed a generalized slowing of nerve conduction velocities. Two patients died at 59 and 61 years of age due to respiratory failure. Both the proband and his brother underwent a sural nerve biopsy. In the former the most striking finding was the presence of uniformly thin myelin sheaths without evidence of demyelination; a complete absence of fibers was found in the latter. Our findings confirm that peripheral neuropathy may be the presenting feature of late-onset Krabbe's disease. Hypomyelination rather than demyelination may represent the distinguishing pathological finding of this condition.

Adult↗
PubMed2002

Hypermyelinating neuropathy, mental retardation and epilepsy in a case of merosin deficiency.

Children with a deficiency of laminin alpha 2 chain generally show an involvement of skeletal muscles, cerebral white matter and peripheral nerves. Among these patients, however, there is increasing evidence of molecular and phenotype heterogeneity. We report a 19-year-old girl with distal weakness, mental retardation and refractory epilepsy in whom elevated serum CK suggested a myopathy. Electrophysiological and neuroimaging examinations as well as studies of nerve and muscle biopsies were performed. Nerve conduction velocities were definitely reduced and brain MRI demonstrated a diffuse white matter involvement. The muscle biopsy showed both myopathic and neurogenic features. By immunohistochemistry laminin alpha 2 chain was mildly reduced in muscle and virtually absent in peripheral nerve. Teasing of sural nerve fibers showed a 'globular' hypermyelination characteristically located at the paranodal regions. A mild loss of myelinated fibers without any demyelination-remyelination changes was found. Haplotype analysis suggested linkage to the LAMA2 locus. Our case is peculiar as the putative mutation probably affects the expression of laminin alpha 2 chain is affected in a tissue specific manner: the protein is virtually absent in peripheral nerves but only mildly reduced in skeletal muscle. As to the disorder of nerve myelination, an absence or abnormal functioning of laminin alpha 2 chain can alter the feed-back control during myelinogenesis, leading to an over-ensheathment of axon. Alternatively, a compensatory up-regulation of other laminins can induce the hyperproduction of myelin sheaths. This case provides new evidence of the phenotypical heterogeneity of the LAMA2 gene and sheds light in understanding the role of laminin alpha 2 chain in myelination of peripheral nerve.

Adult↗
PubMed2002

Contribution of GABAergic cortical circuitry in shaping somatosensory evoked scalp responses: specific changes after single-dose administration of tiagabine.

OBJECTIVES: To determine whether conventional as well as high-frequency somatosensory evoked potentials (SEPs) to upper limb stimulation are influenced by GABAergic intracortical circuitry. METHODS: We recorded SEPs from 6 healthy volunteers before and after a single-oral administration of tiagabine. Conventional low-frequency SEPs have been obtained after stimulation of the median nerve, as well as after stimulation of the first phalanx of the thumb, which selectively involves cutaneous finger inputs. Median nerve SEPs have been further analyzed after digital narrow-bandpass filtering, to selectively examine high-frequency responses. Lastly, in order to explain scalp SEP distribution before and after tiagabine administration, we performed the brain electrical source analysis (BESA) of raw data. RESULTS: After tiagabine administration, conventional scalp SEPs showed a significant amplitude increase of parietal P24, frontal N24 and central P22 components. Similarly, BESA showed a significant strength increase of the second peak of activation of the first two perirolandic dipoles, which are likely to correspond to the N24/P24 and P22 generators. By contrast, no significant changes of high-frequency SEPs were induced by drug intake. CONCLUSIONS: Our findings support the view that both N24/P24 and P22 SEP components are probably generated by deep spiny cell hyperpolarization, which is strongly increased by inhibitory inputs from GABAergic interneurons. By considering the clear influence of inhibitory circuitry in shaping these SEP components, conventional scalp SEP recording could be useful in the functional assessment of the somatosensory cortex in different physiological and pathological conditions. By contrast, intrinsic firing properties of the cell population generating high-frequency SEP responses are unaffected by the increase of recurrent GABAergic inhibition.

Adult↗
PubMed2002

Distinct fronto-central N60 and supra-sylvian N70 middle-latency components of the median nerve SEPs as assessed by scalp topographic analysis, dipolar source modelling and depth recordings.

OBJECTIVES: To investigate the possible contribution of the second somatosensory (SII) area in the generation of the N60 somatosensory evoked potential (SEP). METHODS: In 7 epileptic patients and in 6 healthy subjects scalp SEPs were recorded by 19 electrodes placed according to the 10-20 system. All epileptic patients but one were also investigated using depth electrodes chronically implanted in the parieto-rolandic opercular cortex. Scalp SEPs underwent brain electrical source analysis. RESULTS: In both epileptic patients and healthy subjects, scalp recordings showed two middle-latency components clearly distinguishable on the basis of latency and scalp distribution: a fronto-central N60 potential contralateral to stimulation and a later bilateral temporal N70 response. SEP dipolar source modelling showed that a contralateral perisylvian dipole was activated in the scalp N70 latency range whereas separate perirolandic and frontal sources were activated at the scalp N60 latency. Depth electrodes recorded a biphasic N60/P90 response in the parieto-rolandic opercular regions contra- and ipsilateral to stimulation. CONCLUSIONS: Two different middle-latency SEP components N60 and N70 can be distinguished by topographic analysis and source modelling of scalp recordings, the sources of which are located in the fronto-central cortex contralateral to stimulation and in the supra-sylvian cortex on both sides, respectively. The source location of the scalp N70 in the SII area is strongly supported by its spatio-temporal similarities with SEPs directly recorded in the supra-sylvian opercular cortex.

Adult↗
PubMed2002

Natural history of ulnar entrapment at elbow.

OBJECTIVE: No clinical-neurophysiological data on natural history of ulnar neuropathy at elbow (UNE) are reported. The aim of the current study is to assess the course of untreated UNE. METHODS: We performed a follow-up at 1 year of 30 neurophysiologically positive UNE, 24 were untreated and 6 were operated on. The evaluation was based on a phone interview and sometimes on neurophysiological investigation. With regard to management of UNE, at initial evaluation we explained to the patients what UNE is and how to avoid posture that can worsen nerve compression. RESULTS: Around half of the untreated patients reported improvement of symptoms at follow-up. Comparison between baseline and follow-up neurophysiological measurements showed a significant spontaneous improvement. Most patients reported changing of arm posture after UNE diagnosis. CONCLUSIONS: Some UNE cases improve spontaneously without surgical treatment. A part of the improvements could be due to the changing of arm postures. We hypothesize that a good diagnosis that includes an explanation of the anatomical condition of the nerve during postures and movements represents the first therapy for the entrapments.

Adult↗
PubMed2002

Lower limb nerve impairment in diabetic patients: multiperspective assessment.

To assess the relationship between patient's perception of his own inferior limbs symptom and function and the clinical-neurophysiological assessment in patients affected by insulin-dependent diabetes mellitus (IDDM). We studied 50 consecutive outpatients affected by IDDM (23 men, 27 women). We used validated measurements clinical [Semmes-Weinstein (SW), vibration perception threshold (VPT), muscle strength, osteotendineous reflexes, etc.], neurophysiological (sural, peroneal nerves), metabolic and patient-oriented [North American Spine Society (NASS) questionnaire]. Patient-oriented scores were significantly related with neurophysiological findings of the inferior limbs. Our data suggest that electrodiagnostic tests are useful to assess the severity of the diabetic polyneuropathy not only because they provide a biological measurement of the nerve function but also because they appeared related to the patient's quality of life related to the peripheral nerve involvement.

Adult↗
PubMed2001

Descending spinal cord volleys evoked by transcranial magnetic and electrical stimulation of the motor cortex leg area in conscious humans.

1. Descending corticospinal volleys evoked after transcranial magnetic or electrical stimulation of the leg area of the motor cortex were recorded from an electrode in the spinal epidural space of six conscious patients who had electrodes implanted for treatment of chronic pain, and from one anaesthetised patient undergoing surgery for a spinal tumour. 2. At threshold, the shortest-latency volley (L1 volley) was evoked by stimulation with an anode 2 cm lateral to the vertex. Anodal stimulation at the vertex also elicited a volley at this latency in two patients, but in the other patients the first volley evoked appeared 1-1.3 ms later (L2 volley), at the same latency as the initial volley evoked by magnetic stimulation. High-intensity stimulation of any type could evoke both the L1 and L2 waves as well as later ones (L3, L4, etc.) that had a periodicity of about 1.5 ms. 3. Voluntary contraction increased the amplitude of the L2 and later volleys, but had no effect on the L1 volley. 4. Intracortical inhibition between pairs of magnetic stimuli resulted in clear suppression of the L4 and later waves. The L2 and L3 waves were unaffected. 5. In the anaesthetised patient the L1 volley occurred 1.7 ms later than the volley produced by transmastoid stimulation of the corticospinal pathways in the brainstem. 6. The L1 volley is likely to be a D wave produced by the direct activation of pyramidal axons in the subcortical white matter; the L2 and later volleys are likely to be I waves produced by the trans-synaptic activation of corticospinal neurones. The implication is that electrical stimulation with an anode at the vertex is more likely to evoke I waves preferentially than stimulation over the hand area. A more secure way to ensure D wave activation of corticospinal fibres from the leg area is to place the anode 2 cm lateral to the vertex.

Adult↗
PubMed2001

Coenzyme Q10 reverses pathological phenotype and reduces apoptosis in familial CoQ10 deficiency.

Two brothers with myopathic coenzyme Q10 (CoQ10) deficiency responded dramatically to CoQ10 supplementation. Muscle biopsies before therapy showed ragged-red fibers, lipid storage, and complex I + III and II + III deficiency. Approximately 30% of myofibers had multiple features of apoptosis. After 8 months of treatment, excessive lipid storage resolved, CoQ10 level normalized, mitochondrial enzymes increased, and proportion of fibers with TUNEL-positive nuclei decreased to 10%. The authors conclude that muscle CoQ10 deficiency can be corrected by supplementation of CoQ10, which appears to stimulate mitochondrial proliferation and to prevent apoptosis.

Adolescent↗
PubMed2001

Multiperspective follow-up of untreated carpal tunnel syndrome: a multicenter study.

OBJECTIVE: To assess the course of untreated carpal tunnel syndrome (CTS). METHODS: The Italian CTS Study Group prospectively followed up (10 to 15 months) 196 untreated patients (274 hands) with idiopathic CTS with multiple measurements of CTS. Baseline factors were used to predict the evolution of untreated CTS in multiple regression analysis. RESULTS: Comparison of baseline and follow-up data showed a significant spontaneous improvement of patient-oriented and neurophysiologic measurements. A significant correlation between evolution and initial severity of CTS was observed. CTS measurements improved in patients with more severe initial impairment whereas they worsened in patients with milder initial impairment. The main positive prognostic factor was short duration of symptoms. Similarly, spontaneous improvement was more frequently associated with young age. Conversely, baseline bilateral symptoms and positive Phalen predicted a poor prognosis. CONCLUSIONS: Some patients with CTS improve spontaneously without surgical treatment.

Adult↗
PubMed2001

Dopamine dependency of oscillations between subthalamic nucleus and pallidum in Parkinson's disease.

The extent of synchronization within and between the nuclei of the basal ganglia is unknown in Parkinson's disease. The question is an important one because synchronization will increase postsynaptic efficacy at subsequent projection targets. We simultaneously recorded local potentials (LPs) from the globus pallidus interna (GPi) and subthalamic nucleus (STN) in four awake patients after neurosurgery for Parkinson's disease. Nuclei from both sides were recorded in two patients so that a total of six ipsilateral GPi-STN LP recordings were made. Without medication, the power within and the coherence between the GPi and STN was dominated by activity with a frequency <30 Hz. Treatment with the dopamine precursor levodopa reduced the low-frequency activity and resulted in a new peak at approximately 70 Hz. This was evident in the power spectrum from STN and GPi and in the coherence between these nuclei. The phase relationship between the nuclei varied in a complex manner according to frequency band and the presence of exogenous dopaminergic stimulation. Synchronization of activity does occur between pallidum and STN, and its pattern is critically dependent on the level of dopaminergic activity.

Biological Clocks↗
PubMed2001

Characterizing somatosensory evoked potential sources with dipole models: advantages and limitations.

Several methods have been developed to investigate the cerebral generators of scalp somatosensory evoked potentials (SEPs), because simple visual inspection of the electroencephalographic signal does not allow for immediate identification of the active brain regions. When the neurons fired by the afferent inputs are closely grouped, as usually occurs in SEP generation, they can be represented as a dipole, that is, as a linear source with two opposite poles. Several techniques for dipolar source modeling, which use different algorithms, have been employed to build source models of early, middle-latency, and late cognitive SEPs. Modifications of SEP dipolar activities after experimental maneuvers or in pathological conditions have also been observed. Although the effectiveness of dipolar source analysis should not be overestimated due to the intrinsic limitations of the approach, dipole modeling provides a means to assess SEPs in terms of cerebral sources and voltage fields that they produce over the head.

Evoked Potentials, Somatosensory↗
PubMed2001

The effect on corticospinal volleys of reversing the direction of current induced in the motor cortex by transcranial magnetic stimulation.

Descending corticospinal volleys were recorded from a bipolar electrode inserted into the cervical epidural space of four conscious human subjects after monophasic transcranial magnetic stimulation over the motor cortex with a figure-of-eight coil. We examined the effect of reversing the direction of the induced current in the brain from the usual posterior-anterior (PA) direction to an anterior-posterior (AP) direction. The volleys were compared with D waves evoked by anodal electrical stimulation (two subjects) or medio-lateral magnetic stimulation (two subjects). As reported previously, PA stimulation preferentially recruited I1 waves, with later I waves appearing at higher stimulus intensities. AP stimulation tended to recruit later I waves (I3 waves) in one of the subjects, but, in the other three, I1 or D waves were seen. Unexpectedly, the descending volleys evoked by AP stimulation often had slightly different peak latencies and/or longer duration than those seen after PA stimulation. In addition the relationship between the size of the descending volleys and the subsequent EMG response was often different for AP and PA stimulation. These findings suggest that AP stimulation does not simply activate a subset of the sites activated by PA stimulation. Some sites or neurones that are relatively inaccessible to PA stimulation may be the low-threshold targets of AP stimulation.

Adult↗
PubMed2001

Inhibition of biceps brachii muscle motor area by painful heat stimulation of the skin.

ract This study aimed to evaluate whether painful cutaneous stimuli can affect specifically the excitability of the arm proximal muscle motor area. The motor evoked potentials (MEPs), recorded from the right biceps brachii muscle after either transcranial magnetic or electrical anodal stimulation of the left primary motor (MI) cortex, were conditioned by painful CO2 laser stimuli delivered either on the right hand dorsum or on the lateral surface of the right arm. Painful CO2 laser stimuli delivered on the hand skin reduced significantly the amplitude of MEPs evoked by the transcranial magnetic stimulation of the contralateral MI area, while the MEP amplitude was not significantly modified by CO2 laser pulses delivered on the arm skin. The inhibitory effect followed the arrival of the nociceptive inputs to the cerebral cortex. The amplitude of MEPs evoked by anodal electrical stimulation of the motor cortex was not decreased by conditioning painful stimuli delivered on the hand dorsum. Since the magnetic stimulation led to transynaptic activation of pyramidal neurons, while the anodal stimulation activated directly corticospinal axons, our findings suggest that CO2 laser pulses delivered on the hand are able to inhibit the arm proximal muscle motor area.

Adult↗
PubMed2001

Comparison of descending volleys evoked by monophasic and biphasic magnetic stimulation of the motor cortex in conscious humans.

The descending spinal volleys evoked by monophasic and biphasic magnetic stimulation of the motor cortex were recorded from a bipolar electrode inserted into the cervical epidural space of four conscious human subjects. The results suggest that both phases of the biphasic pulse are capable of activating descending motor output. The pattern of recruitment of descending activity depends on the intensity of the stimulus and the relative threshold of each volley to each direction of current flow.

Adult↗
PubMed2001

Pure motor chronic inflammatory demyelinating polyneuropathy.

We describe four patients affected by chronic inflammatory demyelinating polyneuropathy (CIDP) in a pure motor form. Selective involvement of motor fibers was suggested by the absence of sensory symptoms, normal sensation at neurological examination and normal findings on electrophysiological testing of sensory fibres and sural nerve biopsy. The onset of the disease occurred at a young age (3-29 years) and the clinical course was relapsing-remitting. Over a follow-up period of 1.5-14 years, periodical clinical and electrophysiological examinations showed that selective involvement of motor fibers remained a constant feature. Electromyography and nerve conduction studies continued to show a purely demyelinating neuropathy without signs of axonal impairment. All patients were steroid-unresponsive, whereas they considerably improved after being treated with immunoglobulins. Two patients were treated with interferon alpha and showed a good response. In conclusion, the occurrence in our four patients of pure motor involvement over a long period of time during which several relapses occurred, suggests that pure motor CIDP may represent the result of a specific immunological process rather than of a random distribution of inflammation throughout peripheral nerves.

Adult↗