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Biomedical subjects

G Comi

Publications and source records attributed to G Comi.

At least 397 records · Page 22Linked to original sources

Peripheral nerve abnormalities in newly-diagnosed diabetic children.

The prevalence of clinical and subclinical peripheral neuropathy was evaluated in 51 unselected children at the time of onset of type I diabetes. Twenty-eight patients were followed for one year in order to establish the influence of metabolic control on peripheral nerve function. Twenty-two % of the diabetic children showed nerve conduction abnormalities at the onset and 11.7% had clinical features of peripheral neuropathy. After one year of disease, these figures had changed to 14.3% and 7.1%. Five of 7 children with altered electrophysiological tests in the baseline assessment had had normalization of all parameters one year later. No correlations between insulin requirement and nerve conduction were found. The M value was significantly correlated only with median sensory conduction velocity (p less than 0.005). Significant correlations were demonstrated between HbA1 concentration and both peroneal motor conduction velocity (p less than 0.025) and median sensory conduction velocity (p less than 0.005); these correlations were still present after one year of disease. In the first period of diabetic disease there is functional rather than structural damage of the nerves. The pathogenetic role of hyperglycemia is confirmed; however individual susceptibility to nerve dysfunction may play an important role in the nerve impairment in diabetes.

Adolescent↗

Clinical and pharmacological characterization of anomalous metoclopramide-induced growth hormone secretion in insulin-dependent diabetes mellitus.

An abnormal growth hormone (GH) increase after non-specific stimuli (such as TRH, LHRH and, in a few cases, metoclopramide), has been described in insulin-dependent diabetes. Sixty-nine non-hypogonadic male insulin-dependent diabetic patients (mean age 38.6 years, range 18-54; mean duration of diabetes 11.1 years, range 1.3-28, in different degree of metabolic control, some of them with retinopathy, nephropathy and peripheral and/or autonomic neuropathy) were tested twice with 10 mg i.v. metoclopramide (MCP), an antidopaminergic agent with weak serotoninergic activity. Anomalous GH response (i.e. GH increment equal to or higher than 5 ng/ml from basal level) occurred in 33 patients (47.8%). Mean (+/- SE) MCP-induced GH release in these 'responder' patients peaked up to 17.2 +/- 1.7 ng/ml in comparison with no variation found in 'non-responders' and in 25 healthy control men. Abnormal GH secretion appeared to be unrelated to age, metabolic control, basal GH values and duration of diabetes. Moreover, it remained unmodified by pretreatments with placebo, cimetidine, meclastine, propranolol, acetylsalicylic acid and naloxone, while it was enhanced by metergoline, significantly reduced by bromocriptine and almost completely blunted by pirenzepine, a cholinergic muscarinic receptor antagonist. Neuropathy and nephropathy were equally distributed in the two groups, while retinopathy was more frequent in 'responders'. In conclusion, the exact mechanism(s) by which MCP may induce a paradoxical GH release in many insulin-dependent diabetic patients, is still unclear; it might be dependent, at least in part, on the activation of cholinergic pathways. Indeed, it seems to indicate the presence, in diabetes, of a rather complex derangement in the regulatory mechanisms of GH secretion.

Adult↗

Reproducibility of cardiovascular autonomic tests in diabetics with and without autonomic dysfunction and in normal controls.

The present study evaluates the reproducibility of five cardiovascular reflex tests, deep breathing (DB), Valsalva maneuver (VM), sustained hand-grip (SHG), postural hypotension (PH) and lying to standing (LS) in normal subjects and in insulin dependent (type I) diabetic patients. The study was carried out in 10 normal subjects, in 10 diabetics with autonomic neuropathy and in 10 diabetics without autonomic neuropathy. The five cardiovascular reflex tests were performed five times on five consecutive days by the same investigator and in identical basal conditions. The intraindividual variability of DB, LS and VM was significantly reduced in diabetics with autonomic neuropathy compared with normal controls, but there was no difference between diabetics without neuropathy and normal controls. The intraindividual variability of PH was significantly increased in diabetics with autonomic neuropathy compared with diabetics without autonomic neuropathy and with normal controls. There was no difference among the three groups in the reproducibility of SHG. In normal subjects the intraindividual variability only exceptionally produced a shift from normal to abnormal values or vice versa; in diabetics with autonomic neuropathy this shift was more frequent.

Adult↗

Presence of carpal tunnel syndrome in diabetics: effect of age, sex, diabetes duration and polyneuropathy.

Common thought is that diabetic neuropathy is a predisposing factor to entrapment syndromes. Carpal tunnel syndrome (CTS) is the most frequent entrapment neuropathy; females and old people are most frequently affected (Comi et al., 1978). Prevalence of CTS in diabetics and associated risk factors were studied in 401 patients (208 males and 193 females) with insulin-dependent and non-insulin-dependent diabetes using electrophysiological techniques. Median nerve sensory and motor conduction velocity, ulnar and peroneal nerve motor conduction velocity and sural nerve sensory conduction velocity were investigated in all patients. Diagnostic criteria for CTS were the presence of delayed median nerve sensory conduction velocity in the palm-wrist tract and of increased distal motor latency. Polyneuropathy was defined by slowing-down of conduction velocity in two or more nerves. Forty-five patients (11.2%), 36 females and 9 males, showed CTS. One-hundred-sixty-eight patients (41.8%), 74 females and 94 males, were suffering from peripheral neuropathy. The strongest risk factors for CTS, in order of importance, were: female sex, older age and presence of neuropathy. Polyneuropathy but not CTS was related to duration of diabetes.

Adolescent↗

Clinical and instrumental diagnosis of autonomic neuropathy in insulin-dependent diabetes.

The author report a study of the relationship between symptomatic autonomic neuropathy and the response to simple cardiovascular autonomic tests (Valsalva maneuver, handgrip-test, detection of postural hypotension), in a large series of insulin-dependent diabetics (IDD). Symptoms of autonomic neuropathy were referred by 28 out of 130 IDD, prevalence and severity showed a clear relationship with the duration of diabetes. Only 4 out of 36 patients examined showed a pathologic response to the handgrip-test, while an abnormal Valsalva maneuver was evident in 24 out of 113 IDD. The data show that while the recognition of symptoms indicating a widespread autonomic derangement is rather easy, the diagnosis of autonomic neuropathy may be more difficult in the presence of mild or unspecific symptoms. The Valsalva maneuver exhibited the higher frequency of abnormal responses suggesting that the parasympathetic cardiovascular regulation may be impaired earlier than the sympathetic one. This early subclinical autonomic neuropathy may be due to metabolic or functional factors. Even if clinical consequences of an autonomic derangement of cardiovascular regulation may be serious, in our opinion subclinical impairment, being detectable in a large proportion of patients within the first year of disease, is unlikely to have a short-term severe prognostic value.

Adolescent↗

Evaluation of central nervous conduction by visual evoked potentials in insulin-dependent diabetic children. Metabolic and clinical correlations.

Peripheral neuropathy is a well-known complication of diabetes, but few data are available on central lesions. Visual evoked potentials (VEPs) seem a reliable and feasible technique for detecting a conduction delay in the central nervous system. Seventy-one insulin-dependent type 1 diabetic children (mean age 15 +/- 3 years) and 33 controls were investigated for central neuropathy. We used a pattern of reversal stimulation with television display of a checker board pattern (15 min and 30 min check size). The latencies of the positive peak (P100 wave) were significantly lengthened in 17 patients (27%) but no correlation was found between VEPs and age, duration of diabetes, insulin requirement and HbA1 level. A negative correlation was found between VEPs and peripheral nervous conduction velocity. VEPs measurement seems a simple and reliable technique for detecting early alterations in CNS function in diabetics. Our data suggest that central and peripheral nervous alterations progress simultaneously.

Adolescent↗

The objective assessment of visual contrast sensitivity by pattern reversal visual evoked potentials in diabetes.

Recent studies have described abnormalities of visual evoked potentials and pattern electroretinography in diabetics without retinopathy. The visual contrast sensitivity, determined by psychophysical tests, has proved to be abnormal in diabetic patients with and without clinical retinopathy. In this study we evaluated contrast sensitivity function using both electrophysiologic and psychophysical methods. The objective assessment of functional visual contrast sensitivity was superior to psychophysical evaluation in the detection of contrast sensitivity alterations. No relationships were found between contrast sensitivity dysfunction and abnormalities of pattern electroretinography or fluorescein angiography. Our data suggest that functional visual deficits might precede background retinopathy and that the involvement of foveal function is early and very frequent in diabetic patients, even if they have normal visual acuity.

Adolescent↗

A nested PCR method to detect Listeria monocytogenes in artificially contaminated blood specimens.

A nested PCR-based test was developed for the detection of Listeria monocytogenes in blood specimens from patients with listeriosis. Two pairs of oligonucleotide primers were designed to amplify a 1395-bp and a 453-bp fragment of the iap gene of L. monocytogenes. Amplified products were analysed with gel electrophoresis and stained with ethidium bromide. The PCR method described could be routinely used to diagnose listeriosis.

Animals↗

Transcranial magnetic stimulation and silent period in spasmodic torticollis.

OBJECTIVE: Our objective was to study the corticobulbar projections to neck muscles in cervical dystonia. DESIGN: We compared both the motor evoked potentials and the electromyographic silent period after transcranial magnetic stimulation from sternocleidomastoid and trapezius muscles in a group of 13 patients with spasmodic torticollis with those of 20 healthy volunteers. RESULTS: With the target muscle at rest, no changes of motor threshold, motor evoked potentials latency, and amplitude were observed in dystonic patients. With facilitation, the mean amplitude of the motor evoked potentials was increased in patients compared with controls, the significant difference being for the trapezius muscle, whereas the latency did not differ between groups. The cortical silent period was significantly shorter in dystonic patients than in healthy subjects in both muscles. The duration of the cortical silent period recorded from the sternocleidomastoid muscle showed a positive correlation with the degree of neurologic disability assessed by Tsui's scale. No abnormalities of both nerve conduction velocity and peripheral silent period by stimulation of accessory nerve were found. CONCLUSIONS: These results indicate an impairment of the mechanisms of inhibitory motor control in patients with spasmodic torticollis, which could be the result of a decrease of the basal ganglia inhibitory output over the motor cortex.

Adult↗

Pattern visual evoked potential mapping in Alzheimer's disease: correlations with visuospatial impairment.

We evaluated pattern visual evoked potentials (PVEPs) in patients with Alzheimer's disease (AD) and correlated the neurophysiological results with visuospatial performances in order to understand better the underlying causes of visual disturbances. Latencies and topographical distribution of PVEP components were evaluated in 20 AD patients who underwent an extensive battery of neuropsychological tests. Mean latencies of N70 and P100 were normal in AD patients, while mean latencies of N140 and P200 were significantly increased in comparison with age-matched healthy controls. The topographical distribution of PVEP components did not show any significant difference between the two groups. Visuospatial impairment was detected in 8 patients (40%). Statistically significant positive correlations were observed between P200 amplitude (posterior right hemisphere mean z score) and performance in visuospatial tests. Our data are consistent with a sparing of foveal retinocortical pathways and with the selective dysfunction of either corticocortical connections between the striate cortex and the visual associative structures or of right temporo-parieto-occipital visual analyzers.

Age of Onset↗

Correlations between cognitive impairment, middle cerebral artery flow velocity and cortical glucose metabolism in the early phase of Alzheimer's disease.

In a previous transcranial Doppler (TCD) study, we demonstrated a decrease in blood flow velocity in the proximal tract of the middle cerebral artery (MCA) in patients with Alzheimer's disease (AD). In these patients there was also an asymmetry in blood flow velocity which positively correlated with the cognitive asymmetry often seen in the early phase of AD. In this study we found a correlation between the absolute values and asymmetry indexes of MCA blood flow velocity with adjusted metabolic values and asymmetry indexes of the relative cortical frontotemporoparietal (FTP) areas, evaluated by FDG-PET, and with neuropsychological asymmetry indexes. Patients with prevalent visuospatial deficits (right hemisphere dysfunction) showed significant decreases in right MCA blood flow velocity and right FTP cortical glucose hypometabolism, whereas in patients with prevalent language deficits (left hemisphere dysfunction), these signs were observed on the other side. In AD patients, the decrease of blood flow velocity in MCA might be due to reduced metabolic demands in the temporoparietal cortical areas primarily affected by AD.

Aged↗

Non-invasive multielectrode array for high resolution sampling of scalp-recorded potential fields.

A new non-invasive electrode array has been devised to record electrical signals on the scalp. The electrodes are arranged every 10 mm in a 4 x 8 grid, thus totalling 32. Electrical coupling is assured by a column of conductor gel with a diameter of 2 mm. The electrode array has been used to record multichannel scalp potentials evoked by stimulation of the median nerve at the wrist. It was positioned on the parietal region with the midline corresponding to the external acoustic meatus. The high spatial resolution of this device allows a detailed spatial sampling of the scalp potential field where the electrical activity arising from the parietal and premotor cortex is predominant. Scalp potentials with the system are compared with those with the 10/20 system. The improved spatial resolution allows more precise localization of minimum and maximum of the potential field, though the overall distortion introduced by aliasing in the 10/20 system is not striking. Instead, the amplitudes of the fields are considerably affected by insufficient spatial sampling.

Analog-Digital Conversion↗

Temporal segmentation and multiple-source analysis of short-latency median nerve SEPs.

Short-latency (10-50 ms) median nerve somatosensory evoked potentials (SEPs) from four normal subjects were analysed by means of temporal segmentation techniques and source derivation methods. In each case the responses were recorded using 32 electrodes. Dipolar optimization was carried out with a time-varying technique, using three different approaches: regional source estimation, spherical source estimation (one radial and one tangential component), and multiple dipolar approach. This was to assess the relative influence on the dipolar solution of the different optimization techniques. The effect of the different number of channels in the estimation procedures has been also investigated. The methods of optimization are crucial, particularly for the orientation of P22. In all cases the source location estimated with the 32-electrode montage was shifted towards the centre of the spheres.

Computer Simulation↗

Magnetization-transfer histogram analysis of the cervical cord in patients with multiple sclerosis.

BACKGROUND AND PURPOSE: Previous studies have failed to show significant correlations between the number and extent of T2 spinal cord lesions and the clinical status of multiple sclerosis (MS) patients. We evaluated 1) whether it is feasible to create magnetization transfer-ratio (MTR) histograms of the cervical cord in patients with MS by using two different acquisition schemes, and 2) whether cervical cord MTR histogram metrics were different from those of healthy control subjects and between MS patients with and without locomotor disability. METHODS: We obtained two sets of gradient-echo sequences with and without a saturation pulse from 90 MS patients and 20 sex- and age-matched healthy control subjects. One set consisted of 20 axial, contiguous slices with a thickness equal to 5 mm. The other set consisted of 17 sagittal slices with a thickness equal to 3 mm and an interslice gap equal to 0.3 mm. After image coregistration and removal of tissues around the cervical cord, MTR histograms were created. The average MTR, the peak height, and the peak position of the histograms were measured. All of these measurements were from the whole of the cervical cord, thus including both MS lesions and normal-appearing tissue. RESULTS: When comparing the MTR histograms obtained using axial, contiguous, 5-mm-thick slices, MS patients had significantly lower average cervical cord MTR and peak height than did control subjects. When comparing the MTR histograms obtained using sagittal, 3-mm-thick slices, MS patients also had significantly lower average cervical cord MTR and peak location than did control subjects. Patients with locomotor disability had significantly lower average cord MTR and peak location than those without. CONCLUSION: This study shows that it is feasible to obtain MTR histograms of the cervical cord from MS patients by using different acquisition schemes. Our results also suggest that the assessment of MS cervical cord damage, achieved using MTR histograms, may lead to a better understanding of the clinical manifestations of the disease.

Adult↗

A comparison of MR imaging with fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences in the assessment of patients with multiple sclerosis.

BACKGROUND AND PURPOSE: Fast fluid-attenuated inversion-recovery (FLAIR) sequences are sensitive for detecting lesions in patients with multiple sclerosis (MS). More rapid fast-FLAIR imaging of the brain can be achieved by the concomitant use of half-Fourier acquisition single-shot turbo spin-echo (HASTE-FLAIR) and echo-planar imaging (EPI-FLAIR). The present study was performed in a large cohort of subjects to assess and compare the number and volume of brain lesions detected by the fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences in patients with MS. METHODS: Fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences were obtained from 46 consecutive MS patients. Lesions seen on each type of sequence were counted and classified by consensus by two observers. Lesion volumes were measured using a semiautomated segmentation technique based on local thresholding. RESULTS: The quality of the fast-FLAIR images was significantly better than that of HASTE-FLAIR and EPI-FLAIR images. Fast-FLAIR revealed significantly more lesions and higher lesion volumes than did HASTE-FLAIR and EPI-FLAIR. A similar number of large lesions was detected by the three sequences, but HASTE-FLAIR and EPI-FLAIR showed significantly fewer small and intermediate lesions than did fast-FLAIR. The number of lesions seen on HASTE-FLAIR and EPI-FLAIR images was similar. CONCLUSION: HASTE-FLAIR and EPI-FLAIR sequences revealed as many large MS lesions as fast-FLAIR. Because their acquisition times are only a fraction of that needed for fast-FLAIR sequences, they may be useful for making a rapid diagnosis of MS in uncooperative patients. Their reduced ability to detect smaller lesions indicates that they should not be used as a routine approach to imaging patients with MS.

Adult↗

Prognostic value of MR and magnetization transfer imaging findings in patients with clinically isolated syndromes suggestive of multiple sclerosis at presentation.

BACKGROUND AND PURPOSE: The extent of abnormalities on T2-weighted MR images of the brain of patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) at presentation is associated with an increased risk of developing clinically definite MS (CDMS). We evaluated whether subtle changes outside T2-visible lesions are present in the brain of these patients and whether their extent increases the risk of subsequent development of CDMS. METHODS: Dual-echo, T1-weighted, and magnetization transfer (MT) images of the brain were obtained from 24 patients with CIS at presentation. These patients were followed up for a mean period of 33 months (range, 25-42 months). Twenty age- and sex-matched healthy volunteers served as control subjects. To create MT histograms of the normal-appearing brain tissue (NABT), macroscopic lesions were segmented from dual-echo images, were superimposed automatically, and were nulled out from the coregistered and scalp-stripped MT ratio (MTR) maps. The following MTR histogram-derived measures were considered: average MTR, MTR(25), MTR(50), MTR(75), peak height, and peak position. T2 and T1 lesion loads, average lesion MTR, and brain volume were also measured. RESULTS: Patients with CIS had lower average NABT-MTR (P < .0001) and peak position (P = .002) than did control volunteers, but patient brain size was similar to that of volunteers. At follow-up, 10 (41%) patients developed CDMS. Patients who developed CDMS during the follow-up period had higher T2 lesion volume (P = .003) and lower average NABT-MTR (P = .005) and peak position (P = .006) than did those who did not develop CDMS. T2 lesion volume (odd ratio, 3.54; P = .0005) and average NABT-MTR (odd ratio, 0.81; P = .01) were independent predictors of the subsequent development of CDMS. CONCLUSION: Subtle changes occur outside lesions visible on conventional MR images among patients with CIS suggestive of MS at presentation. The greater the extent of such abnormalities is, the higher is the risk of subsequent development of CDMS.

Adult↗