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Biomedical subjects

M de Carvalho

Publications and source records attributed to M de Carvalho.

At least 19 recordsLinked to original sources
PubMed2001

Allgrove syndrome in adulthood.

A 35-year-old man with a past history of achalasia developed progressive spastic tetraparesis, distal limb atrophy, dysarthria, and dysphagia. A clinical diagnosis of amyotrophic lateral sclerosis (ALS) was considered before neurophysiological investigation, which disclosed a polyneuropathy and a prolonged central conduction time. One year later, the patient developed dysautonomic symptoms. Following confirmation of adrenal insufficiency, a diagnosis of Allgrove syndrome was made. This is a rare case, and we emphasize its clinical similarity with ALS.

Adult↗
PubMed2000

Nerve conduction studies in amyotrophic lateral sclerosis.

We studied 137 ulnar nerves and abductor digiti minimi (ADM) muscles in 70 patients with amyotrophic lateral sclerosis (ALS), and correlated the results with ADM strength graded on the Medical Research Council (MRC) scale, to address the potential value of a standardized neurophysiological assessment of this nerve-muscle system. The ulnar nerves of 35 normal subjects matched for age, gender, and height served as controls. Reduced compound muscle action potential (CMAP) amplitude and area in the ADM muscle recordings correlated strongly with weakness. Distal motor latency, proximal conduction time, and F-wave frequency were abnormal with minimally detectable weakness. In weaker ADM muscles, conduction velocities and F-wave latencies were also abnormal. Conduction block was never observed and sensory potentials were normal. An "ALS neurophysiological index" was derived from these ulnar nerve studies and consisted of the expression: (CMAP amplitude/DML) x F frequency -, where F frequency was expressed as the number of F responses recorded in 20 trials. This index was strongly correlated with ADM weakness (r = 0.74, P < 0.001). Neurophysiological studies restricted to a single nerve-muscle system, the ulnar nerve/ADM, appear potentially useful in objectively assessing change in ALS.

Adult↗
PubMed2000

New transthyretin mutation V28M in a Portuguese kindred with amyloid polyneuropathy.

A 62-year-old Portuguese man, with no history of familial amyloid polyneuropathy (FAP), and a 2(1/2)-year history of tingling in the toes and sexual dysfunction was found neurophysiologically to have a sensory-motor axonal polyneuropathy. Autonomic tests showed slight sympathetic and marked parasympathetic involvement. Heart, kidney, and eyes were normal. Single strand conformation polymorphism (SSCP) mutation analysis for the transthyretin (TTR) gene was performed. The SSCP pattern suggested the presence of a mutation in exon 2, but was different from the pattern observed for a control representing the most common TTR mutation associated with FAP, i.e., TTR V30M. DNA sequencing analysis revealed an A-to-G transition in the first base of codon 28 normally encoding a valine, giving rise to a methionine residue. The presence of this extra methionine was confirmed by peptide mapping and mass spectrometry analysis. Biopsy of nerve and skin of the propositus showed amyloid deposits that were immunoreactive for TTR. This is a new variant TTR related to late-onset amyloid neuropathy with autonomic dysfunction. This case confirms that TTR mutation screening should be considered in patients with a clinical disorder consistent with amyloid neuropathy even in the absence of a family history.

Adult↗
PubMed2000

Neurophysiological features of fasciculation potentials evoked by transcranial magnetic stimulation in amyotrophic lateral sclerosis.

We report 13 patients with amyotrophic lateral sclerosis in whom fasciculation potentials (FPs) driven by transcranial magnetic stimulation (TMS) were recorded. A total of 18 different FPs were analyzed. TMS-driven fasciculations had a simple morphology and were stable. Complex potentials were never cortically driven. Recruitment by a slight voluntary contraction was verified in 7 of 13 tested FPs. FPs were driven by threshold stimuli in 7 of 10 patients and by stimuli 5% below threshold in 3 of 6. Mapping demonstrated that FPs were driven in an area close to the center of gravity of the muscle cortical area. In one case FPs were evoked from most of the cortical representation area of a very weak muscle. Three other patients with profuse fasciculations associated with other clinical conditions were also studied. No TMS evoked fasciculation was observed in this group. The results of this systematic study suggest that cortically evoked FPs arise centrally, at spinal cord or even more proximally, and can represent a marker of increased corticomotor excitability, which is predominant at an earlier phase but can persist as the disease progresses.

Adult↗
PubMed2000

Pathophysiological significance of fasciculations in the early diagnosis of ALS.

In amyotrophic lateral sclerosis (ALS), muscles with preserved strength can have fasciculation potentials (FPs) as the only abnormality. The FPs in strong muscles are predominantly simple and stable, and can often be recruited by a slight voluntary contraction. In weak and atrophic muscles, the FPs are generally complex and unstable, tend to have a slower firing rate and are not recruited by voluntary contraction. Macro-electromyography studies suggest that these FPs are part of a more complex motor unit, as opposed to simple FPs which can represent all the motor unit. FPs driven by transcranial magnetic stimulation (TMS) were observed in 13 ALS patients. TMS-driven fasciculations had a simple morphology and were stable. Complex potentials were never cortically driven. These observations strengthen the conviction that fasciculations in ALS can have different origins. Simple, stable FPs arise proximally and are probably related to excitotoxicity phenomena, while complex, unstable FPs are most likely to originate in distal axonal sprouts that are associated with the reinnervation process. Some ALS patients with fatigue and mild weakness can have profuse fasciculations at an early phase in the evolution of the disease. Patients with denervation localized in one region and diffuse FPs should be strongly suspected of having ALS. With this strategy it should be possible to shorten the diagnosis time.

Aged↗
PubMed1999

Respiratory disorders in ALS: sleep and exercise studies.

Sleep disruption in ALS/MND is related to hypoventilation and nocturnal O(2) saturation. Maximal inspiratory pressure (PI(max)) proved sensitive in predicting nocturnal O(2) saturation. However, PI(max) is highly dependent on patient collaboration; on the other hand Mouth Occlusion Pressure (MOP) is a reliable, non-volitional parameter index of central respiratory drive. Since exercise testing (ET) is also part of the assessment of ventilatory regulation the authors aimed to determine whether MOP and ET are sensitive and reliable parameters predictive of nocturnal O(2) saturation and clinical evolution. We conducted a Polysomnographic (PSG) study in two groups of 14 patients, selected according to their MOP level. Patients performed at admission an ET, Respiratory Function tests (RFT) and clinical evaluation with Norris spinal and bulbar scores (SNS and BNS). All patients in Group I (Low MOP) had decreased O(2) saturation during ET (P<0.001). Correlation study showed correlation between ET and MOP (R=0.6); PI(max) slope and PE(max) slope correlated with ET (R=-0.4; -0.6), respectively. ET also correlated with nocturnal O(2) saturation and SNS slope (R=0.8; -0.5), respectively. SNS and BNS slopes correlated with nocturnal O(2) saturation (R=-0.4; -0.7), respectively. The best correlations found were between MOP slope and BNS slope and SNS slope (R=0.8; 0.7), respectively. The high predictive values of MOP and ET at admission to nocturnal O(2) saturation (predicted value=80%) suggested the need of nocturnal pulse oximetry as a standard procedure. MOP and ET should also be used in evaluation protocols of ALS/MND.

Adult↗
PubMed1999

Can amyotrophic lateral sclerosis patients with respiratory insufficiency exercise?

The authors have shown in a recent paper that survival with amyotrophic lateral sclerosis (ALS) can be increased by the use of non-invasive methods of assisted ventilation (Bipap). However, the progression of muscle weakness was not affected and the quality of life was not positively enhanced. In ALS, reduced physical activity may partially be secondary to alveolar hypoventilation syndrome. This leads to deconditioning of ALS/motor neuron disease (ALS/MND) patients. The authors decided to investigate the possibility of reducing motor decline by exercising these patients to the anaerobic threshold, but simultaneously compensating the respiratory insufficiency with the Bipap STD. We conducted a controlled single blind study, exercising eight consecutive ALS/MND patients and used a control group of 12 ALS/MND patients. The patients were all evaluated during a 1 year period. Respiratory function tests (RFT) were performed at entry and then at 6 month intervals. Barthel, Functional Independent Mobility scale (FIM) and Spinal and Bulbar Norris scores were recorded every 3 months. There was a significant difference between the two groups with respect to FIM scores (P<0.03), but not Barthel scores (P<0.8). A slower clinical course (Spinal Norris score P<0.02) and a significant difference in the slope of the RFT (P<0.008) were observed in the treated group, suggesting that exercise may be beneficial in ALS patients once Bipap is used to control peripheral and muscle oxygenation.

Adult↗
PubMed1999

Multifocal motor neuropathy mimicking motor neuron disease: nine cases.

Multifocal motor neuropathy with persistent conduction block (MMN) is a rare clinical entity, mimicking motor neuron disease (MND). In order to research which are the most frequent nerves and segments where conduction block (CB) can be identified, we reviewed the clinical and neurophysiological data of nine patients with MMN who were studied and followed by the authors. Weakness and muscle atrophy of the dominant hand was the most frequent presentation. Lower limbs were involved later in the disease evolution. The ulnar and median nerves were the most affected nerves. They had conduction blocks mostly at the forearm and at Erb's point-elbow (or above elbow) segments. Both common peroneal and tibial nerves were frequently affected at their distal segments, but proximal segments were also probably involved. The presence of anti-GM1 antibodies was variable, and their determination was not essential for the diagnosis of MMN. Eight patients given IV immunoglobulin therapy had no disease progression. One patient was responsive to corticosteroids. The CB identification in our patients allowed us to clearly distinguish MMN from MND. The good prognosis and need for management with IV immunoglobulin, support the crucial role of a careful neurophysiological study to diagnose this clinical entity.

Adult↗
PubMed1999

Reflex sympathetic dystrophy associated with amyotrophic lateral sclerosis.

Reflex sympathetic dystrophy (RSD) is a syndrome characterised by severe distal pain and vasomotor changes. It is believed to be caused by sympathetic nervous system overactivity. Trauma is the most frequent precipitant event. An association with amyotrophic lateral sclerosis (ALS) has been reported only once. We report three patients with ALS in whom the occurrence of RSD, in one of them at a very early clinical stage, seemed to have precipitated a more rapid clinical evolution. New sprouting re-innervating fibres have abnormal ion channels which might increase the risk of RSD. On the other hand, motor changes have been described in RSD, as well as motor strength improvement after RSD treatment. The complex relation of ALS with RSD is discussed. In all ALS patients pain followed by further loss of function should prompt a search for RSD.

Aged↗
PubMed1999

Cortical muscle representation in amyotrophic lateral sclerosis patients: changes with disease evolution.

Transcranial magnetic stimulation (TMS) mapping was performed regularly on 11 patients with amyotrophic lateral sclerosis (ALS). Map area decreased by 25% (P = 0.03) and normalized volume decreased by 47% (P = 0.01) in those patients who were mapped four times over a period of 11.6 months. The center of gravity (CoG) position moved randomly along the interaural line by distances larger than could be explained by experimental error (P = 0.002). Central conduction time, threshold, and motor evoked potential:compound muscle action potential (MEP:CMAP) amplitude ratio did not change significantly with time (P > 0.05). There were significant linear correlations between strength and CMAP amplitude and between map area and volume. No correlation was found between strength or CMAP amplitude and area or volume. The changes in map parameters were attributed primarily to loss of cortical cells. These results indicate that map parameters may be more sensitive to cortical neuronal loss than other TMS parameters.

Adult↗
PubMed1999

Variation in diagnostic strategy of the EMG examination--a multicentre study.

OBJECTIVES: In order to improve the universal quality of the EMG examination, knowledge about the variation among physicians is needed. METHODS: The variation among physicians in diagnostic strategy or criteria for diagnosing was analysed from a multicentre database with 940 EMG examinations sampled by seven physicians from six laboratories in Europe. RESULTS: For the whole group of patients as well as for the subgroup of patients with polyneuropathy, variation among physicians in examination techniques, number of examined structures per patient and number of abnormal structures per patient required for a diagnosis was found. Some of the variation may be explained by use of different techniques, which showed differences in sensitivity, while some of the variation may be due to differences in diagnostic strategy and criteria for diagnosing. CONCLUSIONS: The study indicates a need for development and revision of international guidelines for EMG practice although implementation of standards requires caution.

Decision Making↗
PubMed1998

Fasciculation potentials: a study of amyotrophic lateral sclerosis and other neurogenic disorders.

We studied fasciculation potentials in amyotrophic lateral sclerosis (ALS), and in other neurogenic disorders, in strength and single-fiber electromyography-matched muscles. Benign fasciculations were studied in 3 normal subjects. Fasciculations were more stable and easier to recruit voluntarily in the early phase of ALS; later, fasciculations were more unstable, more complex, and less likely to be voluntarily recruited. Stable fasciculations, representing part of large, reinnervated motor units, and probably arising from distal axonal sprouts, usually had a higher firing rate than more complex and unstable fasciculations. In weak muscles in ALS, fasciculations were generally more unstable than in other neurogenic disorders. In normal-strength muscles fasciculations are less complex in ALS than in other disorders. Benign fasciculations have a high firing rate and normal morphologic parameters. In ALS fasciculations arise proximally early in the disease and distally in the later stages. Fasciculation may be important in excitotoxic cell death in ALS.

Adult↗
PubMed1998

Paralytic shellfish poisoning: clinical and electrophysiological observations.

In paralytic shellfish poisoning a mollusc contaminated with a toxin (saxitoxin) causes a potentially lethal disease, clinically characterised by gastrointestinal and neurological symptoms, of which possible respiratory depression is the most serious. The toxin acts by blocking the sodium channels. We report 9 Portuguese patients with this disease. The mollusc was identified as Mytilus edulis, contaminated with the dinoflagellate Gymnodinium catenatum, and the toxin saxitoxin. Our patients had a benign clinical course with cerebellar ataxia as the most severe neurological impairment. Eight out of 9 patients had neurophysiological investigations, the largest number so far reported. Motor and sensory conduction velocities and amplitudes were normal. The proximal conduction times, as assessed by F waves, showed delayed conduction and decreased frequency, which returned to normal in few weeks. The somatosensory evoked potentials confirmed normal peripheral and central sensory conduction. The rich vascular supply at root level of the sodium channels of the proximal motor nerves may explain the greater vulnerability to toxin damage. The typically transient and quickly reversible nerve dysfunction caused by ion channel blockade is reported.

Adult↗
PubMed1998

Can medical audit change electromyographic practice?

Considerable variation in EMG practice has been described previously. Since 1992, 7 clinical neurophysiologists from 6 European countries prospectively collected electromyographic (EMG) examinations. The aim of this study was to examine whether several years of mutual influence among physicians using medical audit resulted in a more uniform EMG practice. We studied whether there was a change in the number of examinations per patient and the techniques used from the first 12 to the last 12 EMG examinations on patients with polyneuropathy. For F-wave studies and motor nerve studies, there was a clear change towards a more uniform practice. For sensory nerve conduction studies and muscle studies, there were only minor changes. With regard to examination techniques, there was a reduction in the use of more time-consuming examination techniques (near-nerve sensory studies and quantitative muscle studies). It seems possible to change the EMG practice of individual physicians by international collaboration and medical audit. However, until now most changes have been minor and large differences in European EMG practices persist. The diversity of practices suggests a need for studies on the optimal application of existing examination techniques.

Electromyography↗