Activated protein C resistance in patients with arterial ischemic stroke

BACKGROUND

Activated C protein resistance (APC-R) has recently been reported to be a common cause of thrombophilia; it may be acquired or caused by a genetic defect (factor V Leiden mutation). It is clear that there is an association between APC-R and venous thrombosis. It has been suggested that there is a possible relationship of APC-R with arterial ischemic stroke (IS), but case-control studies have not given enough clues for considering APC-R as a main risk factor.

OBJECTIVES

To assess the incidence of APC-R in patients with IS of several ethiologies in Buenos Aires.

PATIENTS AND METHODS

Seventy-two patients with IS were assessed for signs or symptoms of previous clinical thrombophilia and the presence of vascular risk factors (RF). They were searched for APC-R (COATEST, APC resistance-V, with a predilution of the samples) test. Determinations were carried out between 1 to 4 months after the ischemic episode. The plasma of 50 healthy control subjects (blood donors) was used as controls.

RESULTS

None of the patients had signs of previous thrombophilia; 57 (79.2%) had RF for IS, and 3 (4.2%) had APC-R (all of them with RF). One subject in the control group (2%) showed a low APC response (1/50). The occurrence of APC-R among patients with stroke was not significantly higher when compared with the occurrence of APC-R among the control subjects.

CONCLUSIONS

In the present series, the incidence of factor V Leiden related APC-R in the group with IS was similar to the healthy population. Other risk factors were associated in patients showing APC-R.

[Hypophonia in lacunar stroke]

INTRODUCTION

Hypophonia has been defined as a reduction in speech volume. It is an uncommon finding in acute stroke, mainly related to multiple deep infarcts.

CLINICAL CASE

An 82 year old hypertensive woman was admitted to our hospital presenting acute right sided weakness and low speech volume. She was hypophonic and unable to yell. Language was fluent without paraphasic errors. A diffusion weighted magnetic resonance showed a small hyperintense lesion in the left corona radiata. No other lesions were detected.

CONCLUSIONS

Although, the precise anatomic area involved in the brain has not been clearly precised yet, hypophonia may be also due to isolated lacunar affecting the penetrating arteries in the corona radiata. Further studies are necessary to better understand the nature and the prognosis of this phenomenon.

Variable patterns of anti-GM(1) IgM-antibody populations defined by affinity and fine specificity in patients with motor syndromes: evidence for their random origin

Elevated titers of serum antibodies against GM(1)-ganglioside are associated with a variety of autoimmune neuropathies. Although much evidence indicates that these autoantibodies play a primary role in the disease processes, the mechanism of their appearance is unclear. Low-affinity anti-GM(1) antibodies of the IgM isotype are part of the normal human immunological repertoire. In patients with motor syndromes, we found that in addition to the usual anti-GM(1) antibodies, the sera contain IgM-antibodies that recognize GM(1) with higher affinity and/or different specificity. This latter type of antibodies was not detected in other autoimmune diseases. We studied the fine specificity of both normal and motor disease-associated antibodies using HPTLC-immunostaining of GM(1) and structurally related glycolipids, soluble antigen binding inhibition, and GM(1) affinity columns. Normal low-affinity anti-GM(1) antibodies cross-react with GA(1) and/or GD(1b). In the motor syndrome patients, different populations of antibodies characterized by their affinity and cross-reactivity were detected. Although one population is relatively common (low affinity, not cross-reacting with GA(1) and GD(1b)), there are remarkably few sera having the same set of populations. These results suggest that the appearance of the new antibody populations is a random process. When the different antibody populations were analyzed in relation to the three-dimensional structure of GM(1), a restricted area of the GM(1) oligosaccharide (the terminal Galbeta1-3GalNAc) was found to be involved in binding of normal anti-GM(1) antibodies. Patient antibodies recognize slightly different areas, including additional regions of the GM(1) molecule such as the NeuNAc residue. We hypothesize that disease-associated antibodies may originate by spontaneous mutation of normal occurring antibodies.

Southern Buenos Aires stroke project

BACKGROUND

Ethnic differences and vascular risk factors are the major determinants of stroke subtypes. Nevertheless, specific data from undeveloped countries is difficult to obtain. Natives from South America may have a higher frequency of penetrating small vessel disease and hemorrhagic stroke. However, there are few studies in South America supporting these findings.

OBJECTIVE

We analyze demographic, ethnic, risk factors, clinical characteristics, and stroke subtypes in all patients with acute stroke admitted to our hospital.

METHODS

We studied all consecutive acute stroke patients admitted to the Ramos Mejia Hospital in Buenos Aires from 1997 to 1999. Our hospital serves a determined population of Southern Buenos Aires. Data were collected prospectively on patients' admission in a form especially designed for this study including vascular risk factors, clinical features, epidemiological characteristics, and neuroradiological findings. Stroke subtypes were determined according to the TOAST classification.

RESULTS

Among 361 acute stroke patients, 31% had hemorrhagic stroke. It was more frequent among Natives (34%) than Caucasians (27%) (P<0.002). Ischemic stroke subtypes were as follows: 105 (42%) patients had lacunar, 31 (12%) atherosclerotic stroke, 53 (21%) cardioembolic infarction, and 16 (6%) other causes of stroke. Forty-five (18%) patients were classified as undetermined. Small vessel disease was higher among Caucasians (35%) than Natives (24%).

CONCLUSIONS

Penetrating artery disease (42%) and intracranial hemorrhage (31%) were the most common stroke subtypes, being more frequent than reported in the literature. Natives had significantly higher frequency of hemorrhagic stroke than Caucasians.

[Magnetic resonance and clinical and electroencephalographical localization in focal epilepsy]

Magnetic Resonance Imaging (MRI) is the method of choice to search for epileptogenic lesions. We correlated MRI findings with the epileptogenic zone (EZ) depicted by clinical and electroencephalographic (EEG) data. We studied 400 clinical records of patients who had been submitted to MRI studies and we analyzed, retrospectively, their ictal semiology, EEG characteristics and response to treatment. They were classified into 3 groups: A) temporal lobe epilepsy, B) frontal lobe epilepsy and C) parieto-occipital epilepsy. We included 155 patients: Group A) 68 cases (43.9%), 28 men (41.1%), mean age 32 +/- 11 years old, abnormal IMR in 44 (64.7%), refractory to treatment 48 (70.5%). Group B) 68 cases (43.9%), 38 men (55.8%), mean age 30 +/- 15 years old, abnormal IMR in 26 (38.2%), refractory to treatment 30 (44.1%). Group C) 19 cases (12.2%), 13 men (68.4%), mean age 27 +/- 11 years old, abnormal IMR in 11 (57.8%), refractory to treatment 12 (63.1%). Results showed that there were higher possibilities of detecting lesions which correlate with EZ in temporal than in frontal or parieto-occipital lobes epilepsy. The chances to find abnormalities on the MRI were 5 times higher in refractory patients than in those who were non-refractory.

[Partial non convulsive epileptic status as initial presentation of limbic encephalitis]

INTRODUCTION

Limbic encephalitis is an unusual presentation of paraneoplastic syndrome, which includes among its symptoms seizures.

CLINICAL CASE

We report a case with a rare presentation of limbic encephalitis as initial symptom of small cell lung carcinoma. A 69 year-old woman presented with partial non convulsive status epilepticus and neuropsychiatric disturbances. Chest radiography and computed tomography showed mediastinal lymphadenopathy and lung nodules. Subsequently, small cell lung carcinoma was diagnosed by lymph node biopsy. The cerebrospinal fluid study was normal. The electroencephalography and magnetic resonance imaging (MRI) findings had distinctive features compatible with temporo-limbic dysfunction. The anti-Hu antibodies were negative. The neuropsychiatric symptoms improved significantly after systemic chemotherapy and adjuvant radiotherapy. A serial follow-up MRI of the head showed no evidence of intracranial metastasis three months after the diagnosis of cancer. Limbic encephalitis may be an initial manifestation of lung cancer. Paraneoplastic limbic encephalitis is considered a remote effect of cancer commonly associated with anti-neuronal antibodies (anti-Hu) and small cell lung carcinoma.

CONCLUSIONS

Status epilepticus could be an early sign of limbic encephalitis. The absence of anti-Hu antibodies does not rule out the presence of an underlying small cell lung carcinoma in patients with a clinical diagnosis of limbic encephalitis. Greater awareness for diagnosis and early treatment of the primary tumor offers the best chance for improvement in patients with lung cancer presenting with limbic encephalitis.

Multiple simultaneous intracerebral hemorrhages: clinical features and outcome

BACKGROUND

The simultaneous occurrence of intracerebral hemorrhages in different arterial territories is an uncommon clinical event. Its predisposing factors and pathophysiological mechanisms are not clearly defined.

OBJECTIVE

To analyze the frequency, risk factors, clinical features, neuroimaging findings, and outcome of multiple simultaneous intracerebral hemorrhages (SIHs).

PATIENTS AND METHODS

We studied all patients with acute stroke admitted to our hospital from July 18, 1997, through December 18, 1999. Multiple SIHs were defined as the presence of 2 or more intracerebral hemorrhages affecting different arterial territories with identical computed tomographic density profiles. Patients with a history of traumatic brain injury were excluded from this study. Diagnostic investigation included routine blood and urine tests, coagulation studies, a chest radiograph, electrocardiogram, 2-dimensional transthoracic echocardiography, and computed tomography of the head without contrast medium. Disability was assessed using the National Institutes of Health Stroke Scale and Modified Rankin Scale.

RESULTS

Among 142 patients with hemorrhagic stroke, we found 4 (2.8%) with SIHs. All 4 patients had a history of uncontrolled arterial hypertension. We excluded other potential causes of multiple SIHs by using appropriate diagnostic tests. The most common clinical manifestations were headache and weakness. Localization of hematomas was supratentorial, except for one patient who had both infratentorial and supratentorial hemorrhages. The mean National Institutes of Health score on admission was 15 and the Modified Rankin Scale score was higher than 4 at 3 months.

CONCLUSIONS

In our study, all patients with multiple SIHs had arterial hypertension and a poor outcome. Additional analytic studies, including new imaging techniques, can help to elucidate the association between arterial hypertension and multiple SIHs, risk factors, and underlying mechanisms of this clinical condition.

[Chronic inflammatory demyelinating polyneuropathy. Findings in 30 patients]

Chronic demyelinating inflammatory polineuropathy (CIDP) is a disease which was recognized several years ago. However, the mechanism underlying its pathogenesis remains poorly understood. Nevertheless, there are some clues which strongly suggest that it constitutes an autoimmune disease. Since 1992 we have studied 30 cases. All them were clinically assessed and submitted to laboratory investigations encompassing nerve conduction studies, sera proteins immunoelectrophoresis, spinal fluid analysis and sural nerve biopsies. Upon clinical examination the usual findings were weakness, muscle atrophy, absence or diminished tendon jerks, paresthesias and hyposthesias. Electrophysiological studies disclosed marked slowing of the nerve conduction velocities, suggesting demyelination. Sera immunoelectrophoresis detected monoclonal gammopathy in 17% of the studied patients, which was not associated with lymphoproliferative illnesses. Of the patients 79% had increased levels of spinal fluid proteins. Seventeen patients gave their consent for performing a sural nerve biopsy; all the samples showed demyelination. In conclusion, we think that CDIP is a disease which can be recognized when the clinical assessment, the nerve conduction studies and the spinal fluid findings suggest the diagnosis. Although nerve biopsy may be strongly supporting, we believe that it has to be performed only if doubts arise from the clinical, electrophysiological or spinal fluid observations. It is worth noting that its early detection may benefit the patient through the administration of the right therapy precluding the eventual sequelae of the disease.

[Fluctuation in bilateral thalamic infarction: diffusion study using magnetic resonance]

INTRODUCTION

Bilateral paramedian thalamic infarcts are uncommon. The most frequent clinical manifestations are acute impairment of consciousness, oculomotor abnormalities and cognitive disturbances. A fluctuating course has not been previously reported.

CLINICAL CASE

A 66 year-old woman with a past history of arterial hypertension and diabetes was admitted to our hospital presenting four episodes of decreased consciousness and vertical gaze paresis. Neurological examination between episodes was unremarkable. Diffusion-weighted magnetic resonance imaging revealed high-signal lesions in both paramedian thalamic areas.

CONCLUSIONS

Fluctuating impairment of consciousness may be a clinical presentation of bilateral paramedian thalamic infarction. Atheromatous occlusion of the mouth of the paramedian thalamic penetrating artery is the most common cause. Neurological findings and diffusion-weighted images may help to define the extension and the underlying pathophysiological mechanism.

Differences in stroke subtypes among natives and caucasians in Boston and Buenos Aires

BACKGROUND AND PURPOSE

Several issues regarding ethnic-cultural factors, sex-related variation, and risk factors for stroke have been described in the literature. However, there have been no prospective studies comparing ethnic differences and stroke subtypes between populations from South America and North America. It has been suggested that natives from Buenos Aires, Argentina, may have higher frequency of hemorrhagic strokes and penetrating artery disease than North American subjects. The aim of this study was to validate this hypothesis.

METHODS

We studied the database of all consecutive acute stroke patients admitted to the Ramos Mejia Hospital (RMH) in Buenos Aires and to the Beth Israel Deaconess Medical Center (BIMC) in Boston, Massachusetts, from July 1997 to March 1999. Stroke subtypes were classified according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. All information on patients (demographic, clinical, and radiographic) was recorded prospective to the assessment of the stroke subtype.

RESULTS

Three hundred sixty-one and 479 stroke patients were included at RMH and BIMC stroke data banks, respectively. Coronary artery disease was significantly more frequent in BIMC (P:<0.001), whereas tobacco and alcohol intake were significantly more frequent in RMH (P:<0.001). Intracerebral hemorrhage (P:<0.001) and penetrating artery disease (P:<0.001) were significantly more frequent in the RMH registry, whereas large-artery disease (P:<0.02) and cardioembolism (P:<0.001) were more common in the BIMC data bank.

CONCLUSIONS

Penetrating artery disease and intracerebral hemorrhage were the most frequent stroke subtypes in natives from Buenos Aires. Lacunar strokes and intracerebral hemorrhage were more frequent among Caucasians from Buenos Aires than Caucasians from Boston. Poor risk factor control and dietary habits could explain these differences.

Current treatment pathways in ALS: a South American perspective

This article presents the findings relating to the South American subgroup of 60 patients in an international survey of the current diagnosis and treatment of patients with amyotrophic lateral sclerosis (ALS). The mean time between first symptoms and first consultation with a physician was 3.7 months, and mean delay in seeing a neurologist was then 5.6 months, giving a mean time from symptom onset to confirmation of diagnosis of 16.6 months. The time to confirmation of diagnosis was much longer for patients with symptoms of limb onset (17.5 months) than for those with bulbar onset (10.0 months). Cases with symptoms of upper-limb onset were diagnosed more rapidly (14.9 months) than those with symptoms of lower-limb onset (21.8 months). The diagnosis was confirmed in 48% of cases within 15 months of symptom onset, and a further 27% were diagnosed within 15-24 months; 47% of cases were confirmed within 4 months of consulation with a neurologist and a further 17% within 4-6 months. The first physician seen was the general practitioner in 47% of cases overall. When the neurologist was the first physician seen (27% of patients in Brazil, 0% in Argentina), diagnosis was achieved within 14 months in 88% of cases. EMG was performed in almost all patients. MRI and CT were widely used, which may cause delays. Announcement of the diagnosis was made immediately to 75% of patients overall. Riluzole was prescribed for 23% of patients in Brazil and for 67% of patients in Argentina.

Catalepsy after stroke

Catalepsy denotes a tendency to maintain postures. We prospectively looked for catalepsy in 216 acute stroke patients. We found five patients with cataleptic postures. They were seen on the nonparetic side in all cases. Other movement abnormalities seen in the catatonic syndrome were absent. CT scans of the head showed ischemic infarctions in the middle cerebral artery territory in the five cases. Cataleptic postures associated with hemispheric lesions due to stroke may be a more common phenomenon than is believed, and their mechanism remains to be elucidated.

Cerebral tumor-like American trypanosomiasis in acquired immunodeficiency syndrome

Cerebral tumor-like American trypanosomiasis (CTLAT) is an uncommon complication of Chagas' disease, observed only in immunosuppressed patients. We assessed 10 human immunodeficiency virus-positive patients with Chagas' disease who presented with CTLAT. All patients had neurological involvement and 6 developed intracranial hypertension. Neuroimaging studies showed supratentorial lesions in 9 patients, being single in 8. One case had infratentorial and supratentorial lesions. Low CD4+ cell counts were observed in all the cases and in 6 of them CTLAT was the first manifestation of acquired immunodeficiency syndrome. Serological tests for Chagas' disease were positive in 6 of 8 patients. Trypanosoma cruzi was identified in all brain specimens and in three cerebrospinal fluid samples. CTLAT should be considered in the differential diagnosis of intracranial mass lesions in human immunodeficiency virus-positive patients and should be added to the list of acquired immunodeficiency syndrome-defining illnesses.

Cu/Zn superoxide dismutase activity at different ages in sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive disorder resulting from degeneration of motor neurons in the brain and spinal cord. Sporadic ALS (SALS) accounts for the majority of patients and the familial form (FALS) represents fewer than 10% of all cases. Since it was found that there are Cu/Zn superoxide dismutase (SODI) gene mutations in 20% of FALS patients and that FALS and SALS patients show similar clinical features, it has been postulated that both may share a common physiopathological mechanism. We studied Cu/Zn SOD1 activity in cytosolic extracts of erythrocytes from 125 normal individuals and 40 SALS patients. We found that enzyme activity does not change with age in control subjects and tends to decrease in most SALS patients older than 60 years. A subpopulation of five SALS patients had significantly increased SOD1 activity; four of these patients over 70 years old. There was no correlation between enzyme activity and time of onset of the disease, or clinical forms of the illness. The variation in SOD1 activity in ageing SALS patients compared with younger patients suggests that they may undergo an oxidative disbalance contributing to the development of the disease.

Loss of motor units in Alzheimer's disease

Little attention has been paid in the literature to the state of the peripheral nervous system (PNS) in Alzheimer's disease (AD). We conducted a comprehensive electrophysiological study in 15 AD patients looking for functional abnormalities within their PNSs. A reduction of the number of functioning motor units (MU) was found in the thenar and soleus muscles of most of these patients without enlargement of the remaining MUs territories, while the motor and sensory conduction velocities of the peripheral nerves were preserved. These results suggest dysfunction of the spinal motoneurones in patients afflicted with this condition.

Further studies on HTLV-I associated myelopathy in Argentina

We report 10 HTLV-I virus seropositive subjects, eight of them with HTLV-I associated myelopathy (HAM), two of them also infected with HIV as well as two asymptomatic HTLV-I+ relatives of two unrelated patients. HTLV-I is endemic in several tropical areas, where it causes different neurological diseases. Only few patients have been reported in our country since 1994. We studied 8 patients, who fulfilled the clinical criteria for chronic spastic paraplegia, and 2 other non-symptomatic HTLV-I seropositive relatives, with electromyography (EMG), motor and sensory conduction velocities (NCV), somatosensory, visual and brainstem auditory evoked potentials (SSEP, VEP and BAEP), Magnetic Resonance Images (MRI) and cerobrospinal fluid (CSF) analysis. The latter was carried out only in seven symptomatic patients. In every case positive ELISA tests for HTLV-I/II were confirmed by Western Blot. The two asymptomatic persons were clinically and electromyographically assessed, one of them was also submitted to SSEPs studies. Three patients were males. Patient's ages ranged from 5 to 65 years old. All symptomatic patients showed muscular weakness, spasticity with pyramidal signs and sphincter disturbances. Five of them had paresthesias and 2 had burning pain on their feet. The EMGs and the NCVs were normal in 7 patients and in the 2 asymptomatic ones. SSEPs, obtained by stimulating the posterior tibial nerves, were impaired in 7 patients and in the asymptomatic person who received the procedure. The 7 symptomatic patients who underwent lumbar puncture had positive tests for HTLV-I in CSF, 3 out of these 7 patients had also high protein levels and 4 had increased number of lymphocytes. In 2 patients intrathecal IgG production could also be demonstrated. MRI were normal in 7 patients and in the 2 asymptomatics, the exception being a female who had bilateral hyperintense lesions in cerebral white matter in T2. In conclusion, tropical spastic paraparesis is apparently a rare disorder in Argentina. However, some cases have been reported recently. Most probably, its prevalence is currently underestimated. Its diagnosis should be considered in every patient with progressive spastic paraplegia.

Lower motor neuron syndrome associated with anti-GM1 antibodies

It has been recently recognized that increased titers of serum anti-GM1 antibodies may be associated with motoneurone diseases or with multiple motor neuropathy with or without conduction block and also with chronic sensorimotor neuropathy and Guillain-Barré syndrome. Santoro et al. were the first to note that anti-GM1 antibodies were able to bind to the nodes of Ranvier of the sural nerve of a patient with clinical signs and symptoms mostly resembling amyotrophic lateral sclerosis who also showed, in nerve conduction studies, multifocal motor nerve fibers conduction block and serum IGM anti-GM1 antibodies. The two patients presented in this report had asymetrical motor neurone disease with signs and symptoms of lower motoneurone involvement, and other signs, in the first patient, which suggested the existence of upper motoneurone damage. Besides, the second patient also had clinical sensory impairment in the lower limbs. Electrophysiologically, none of them had nerve conduction block but both showed inexcitable median and sural nerve sensory fibers. Both had high titers of anti-GM1. A sural biopsy of both patients showed immunoglobulins into the sensory fibers. However, we do not know whether the anti-GM1 antibodies bind to a cross-reactive glycolipid other than the GM1 itself. In any case, it seems that the presence of anti-GM1 antibodies might be a marker signalling a potentially treatable immune disorder which may have signs of lower and upper motor neurone disease and, also, clinical and electrophysiological evidences of peripheral sensory involvement.

[Severe cardiac failure in Kearns-Sayre syndrome]

Mitochondrial disorders are a group of diseases that can affect virtually all organ systems. A 19 year old man was seen in 1993 with neurologic abnormalities consisting of impaired function of muscles, diplopia, progressive loss of vision, impaired phonation and swallowing, during the last 10 years. Physical examination disclosed moderate wasting of the four limb muscles, mild motor weakness of neck muscles, symmetrical hyporeflexia, cerebellar dysfunction, severe external ophtalmoplegia and ptosis. Fundii oculi examination showed retinitis pigmentosa. The electromyogram demonstrated myopathic changes with normal nerve conduction velocities. The cerebrospinal fluid was normal, except for a mild increase in lactic acid. Histochemical study of a muscle biopsy specimen demonstrated ragged red fibers and increase of the subsarcolemal oxidative activity of mitochondriae. The diagnosis of Kearns-Sayre disease was confirmed and he was discharged advising physical therapy. On February 1995, he was again admitted, this time with right cardiac failure and worsening of all his previous symptoms and signs. He complained of myalgias and his muscle weakness was more striking on clinical examination. Echocardiography showed biventricular dilatation and left ventricular hypertrophy with preserved systolic function. A new muscle biopsy revealed an heteroplasmic deletion of 5 Kb with 80% of mutant mitochondrial DNA. In brief, we report a patient with the clinical phenotype of Kearns-Sayre syndrome who presented an acute congestive cardiac failure due to cardiomyopathy, an association which has seldom been, reported in the literature.

Reliability of the NINDS Myotatic Reflex Scale

The assessment of deep tendon reflexes is useful for localization and diagnosis of neurologic disorders, but only a few studies have evaluated their reliability. We assessed the reliability of four neurologists, instructed in two different countries, in using the National Institute of Neurological Disorders and Stroke (NINDS) Myotatic Reflex Scale. To evaluate the role of training in using the scale, the neurologists randomly and blindly evaluated a total of 80 patients, 40 before and 40 after a training session. Inter- and intraobserver reliability were measured with kappa statistics. Our results showed substantial to near-perfect intraobserver reliability, and moderate-to-substantial interobserver reliability of the NINDS Myotatic Reflex Scale. The reproducibility was better for reflexes in the lower than in the upper extremities. Neither educational background nor the training session influenced the reliability of our results. The NINDS Myotatic Reflex Scale has sufficient reliability to be adopted as a universal scale.

The effect of levodopa on the habituation of the acoustic-palpebral reflex in Parkinson's disease

The aim of the present study was to assess the habituation of the blink responses evoked by repetitive auditory stimuli in patients with Parkinson's disease in different clinical states. We studied 28 parkinsonian patients. Eighteen patients without motor fluctuations were studied off and on levodopa, on two different sessions, one week apart. The remaining 10 parkinsonians had the wearing off phenomenon and were studied while being off their medication and while ON and OFF, as determined clinically, after a single dose of levodopa. Twelve age-matched controls were also studied in a single session. Unilateral auditory 1 kHz, 105 dB stimuli were delivered at a frequency of 0.2 Hz. The number of responses (R) from the orbicularis oculi was registered. R values were significantly smaller in controls and in treated parkinsonians than in untreated patients. R was also significantly smaller when ON than at baseline and when OFF in parkinsonians with the wearing off phenomenon. These results suggest a failure of the inhibition of the acoustic-palpebral reflex in Parkinson's disease. The improvement with levodopa and the similarities between the clinical and the electrophysiological changes suggest a dopaminergic role in the inhibition of this brainstem reflex.

Clinical manifestations of peripheral nervous system involvement in human chronic Chagas disease

We conducted a clinical and electromyographical study in patients with Chagas' disease in the indeterminate or chronic stages of the illness. Altogether 841 patients were examined. Only 511 were admitted within the protocol; the remainder patients were rejected because they showed other causes able to damage the nervous system. Fifty two (10.17%) out of the 511 patients showed signs and symptoms of peripheral nervous system involvement in the form of sensory impairment and diminished tendon jerks suggesting the presence of neuropathy. Forty five of them were submitted to a conventional electromyographical examination. Fifteen of them showed normal results, while the remainder 30 disclosed a reduced interference pattern, being most of the remaining motor unit potentials fragmented or poliphasic, reduced sensory and motor conduction velocities and diminished amplitude of the sensory action potential. The findings suggest that some chagasic patients in the indeterminate or chronic stages of the disease may develop a clinical mild sensory-motor peripheral neuropathy.

Peripheral nervous system involvement in human and experimental chronic American trypanosomiasis

An electrophysiological and histological study of the muscle and the peripheral nervous system (PNS) was carried out in chronic human American trypanosomiasis (Chagas' disease) and in an experimental Chagas' disease (Chd) mouse model. Altogether 995 patients with chronic Chd and 261 mice, experimentally infected with RA and CA-I parasite strains, were investigated. Results were compared with matched controls. Techniques employed in humans were: clinical assessment, conventional electromyography (EMG), estimated number of motor units, motor and sensory nerve conduction velocities, repetitive nerve stimulation and muscle and sural nerve biopsies. In mice conventional EMG, sciatic nerve conduction time, sciatic nerve action potential amplitude, in vitro miniature end-plate potentials (MEPPs) and end-plate potentials (EPPs) recordings, muscle, nerve and spinal cord histology and identification of cell phenotypes within the inflammatory infiltrates were the employed procedures. Out of 511 patients submitted to clinical examination, 52 disclosed signs and symptoms of mixed peripheral neuropathy. By employing electrophysiological techniques, it could be shown that about 30% of the investigated patients had one or more of the following features: diminished interference pattern, most of the remainder motor unit potentials being (MUPs) polyphasic; reduced number of functional motor units in the thenar, hypothenar, soleus and/or edb muscles; slow sensory and motor nerve conduction velocities; low sensory action potential amplitude and impairement of neuromuscular transmission. In mice, MUPs duration and amplitude were increased at later stages of the infection, nerve conduction was slow, nerve action potentials were of low amplitude, mepps were of low amplitude and double epps were frequently found. Muscle histology in humans with chronic Chd showed type I and type II grouping, atrophic angular fibers and targetoid muscle fibers. In mice perivascular mononuclear cells infiltrates, small round fibers, muscle fibers necrosis, atrophic angular fibers, type II muscle fibers grouping and grouped muscle fibers atrophy were found. Sural nerve samples showed segmental and paranodal demyelination and axonal loss. The same features were observed in mice nerves, also in this model mononuclear cells infiltrates at the nerve, dorsal root ganglia and meninges surrounding the spinal cord were observed. Muscle and nervous tissues infiltrates were mainly composed of T lymphocytes with predominance of CD8 or CD4 subsets according to the parasites strain employed for infecting the animals. These findings suggest that the skeletal muscle and the PNS may be involved in chronic American trypanosomiasis.

Early onset Alzheimer's disease in a South American pedigree from Argentina

We report the clinical, SPET, immunohistochemical and DNA features of an early-onset familial Alzheimer's disease (FAD) in an Argentine pedigree of South American indian ethnic background. Pedigree spans 5 generations comprising more than 110 biological relatives. Clinical data supported the diagnosis of early onset FAD (mean age at onset 38.9 years) in 10 family members, including 3 with pathological confirmation (mean age at death 48.5). The pattern of transmission suggested autosomal dominant inheritance. Prominent features were mood changes, early language impairment, myoclonus, seizures and cerebellar signs. SPET displayed bilateral frontal, temporo-parietal and cerebellar hypoperfusion in early stages and in an asymptomatic member at risk, suggesting that SPET may have predictive value in this family. Immunohistochemistry showed beta amyloid deposits within neuritic plaques and vessel walls and no anti-PrP immunoreactivity. DNA analysis showed no abnormalities in the beta amyloid precursor protein gene. The identification of additional genetic defects in well characterized independent FAD pedigrees will contribute to the understanding of the pathogenesis of Alzheimer's disease.

[Persistent cerebellar ataxia after toxic administration of diphenylhydantoin]

Diphenylhydantoin (DFH) is known to yield cerebellar ataxia in chronically treated epileptic patient due to cerebellar atrophy with loss of Purkinje cells. Little attention has been paid in the literature to the acute DFH intoxication bearing cerebellar symptoms. We report a patient afflicted with complex partial seizures due to a left temporal cyst, who has been treated during the last two years with DFH 100 mg/day. Due to the refractory characteristics of his seizures he was put on DFH 400 mg daily, and developed a pancerebellar syndrome. After surgical removal of the cyst his seizures entirely faded away and his cerebellar signs improved. Nevertheless his neurological examination still showed trunkal and lower limbs ataxia. After one year of follow up his neurological picture did not change, while he was seizures free. TC and MRI did not show cerebellar atrophy.

[Cerebellar syndrome caused by amiodarone]

Amidarone (AMD) is an antiarrhythmic drug with side effects on the nervous system. Cerebellum is seldom involved: We describe the case of a 56 years old male patient with a history of 4 month of cerebellar involvement characterized by gait unsteadiness, ataxia, nistagmus and vertigo. He was on treatment with AMD because of ventricular arrythmia. The cerebellar syndrome progressively disappeared after drug withdrawal and he was symptoms-free 4 months later. Similar symptoms appeared after another one month of automedication with the same drug. Structural lesions, metabolic, nutritional deficiencies or toxics were excluded. Mechanisms of cerebellar toxicity of AMD are yet unknown. The knowledge of the toxic effects of this drug, widely used in our country, would allow its early recognition.

Experimental Chagas' disease: electrophysiology and cell composition of the neuromyopathic inflammatory lesions in mice infected with a myotropic and a pantropic strain of Trypanosoma cruzi

C3H/HeN mice infected with the pantropic/reticulotropic Trypanosoma cruzi RA strain disclosed electromyographic signs (EMG) of neuropathic damage, while those infected with the myotropic CA-I strain showed EMG suggestive of primary muscle involvement. Although both strains induced inflammatory infiltrates in hamstring muscles (HM), damage was more severe in mice infected with CA-I. In sciatic nerves (SN) of mice infected with the RA strain, increased inflammatory changes, amastigote nests, and myelin digestion chambers were consistently found during the course of infection. On the other hand, the CA-I strain produced minor inflammatory changes without detectable amastigotes in such tissue. The RA strain induced chronic leptomeningitis in spinal cord (SC), while infiltrates were limited to spinal roots and dorsal ganglia in animals infected with CA-I. In mice infected with RA, phenotypic analysis of inflammatory lesions showed a consistent predominance of CD8+ T cells in nervous tissue throughout the course of infection and in HM during the chronic phase whereas natural killer cells were detected at 120 and 270 days pi. In mice infected with CA-I, a predominance of CD8+ cells in SN was only detected during the acute phase and in HM during the late chronic phase; B lymphocytes bearing surface IgM were present in all studied tissues at 270 days pi. In addition, positive fluorescence for mouse IgG was observed at 120 days pi in muscle interstitium. These results strongly suggest that T. cruzi strain-dependent mechanisms are involved in the development of neuromyopathic damage.

Cognitive impairment in human chronic Chagas' disease

We proposed to investigate subclinical cognitive impairment secondary to chronic Chagas' disease (CCD). No similar study was previously done. The neuropsychological performance of 45 chronic Chagasic patients and 26 matched controls (age, education place and years of residency in endemic area) was compared using the Mini Mental State Exam (MMSE), Weschler Memory Scale (WMS) and the Weschler Adult Intelligent Scale (WAIS). Non-parametric tests and Chi2 were used to compare group means and multivariate statistics in two way frequency tables for measures of independence and association of categorical variables with the disease.

RESULTS

Chagasic patients showed lower MMSE scores (p < .004), poor orientation (p < .004), and attention (p < .007). Lower WMS MQ were associated with CCD (Chi2 5.9; p < .01; Fisher test p < .02). Lower WAIS IQ were associated with CCD (Chi2 6.3, p < .01; Fisher test p < .01) being the digit symbol (p < .03), picture completion (p < .03), picture arrangement (p < .01) and object assembly (p < .03) subtests the most affected. The impairment in non-verbal reasoning, speed of information processing, problem solving, learning and sequencing observed in chronic Chagas disease patients resembles the cognitive dysfunction associated with white matter disease.

Multiple sclerosis: assessment of lesional levels by means of transcranial stimulation

Conduction in the Pyramidal Tracts (PTs) was studied in 30 healthy volunteers and 17 patients with definite Multiple Sclerosis. Central motor conduction time (CMCT) was assessed employing unipolar electrical transcranial stimulation and studies of the peripheral conduction time. Fourteen out of the seventeen studied patients showed CMCT abnormalities. No significative correlation was found between the intensity of muscle weakness and the slowness of conduction in the corresponding PTs. Subclinical abnormalities were detected in more than half of the studied patients. CMCT slowness showed a good correlation with the time course of the disease in the cortico-cervical (CCT) but not in the cortico-lumbar (CLT) tracts. Evidence favoring the existence of two different lesional levels along the PSs was found in 9 out of the 14 patients studied with recordings in the hand and leg muscles. Two patterns of abnormalities gave support to this conclusion. The first consisted of slowed conduction or inexcitability in both the CCT and CLT at one side, while only one of the contralateral PTs was impaired. In the second one, the 4 explored PTs showed a slowed conduction, but in addition, CMCT difference between the CLT and CCT was longer than normal. Both patterns suggest that one lesional level could be situated between the internal capsula and the lower cervical cord and the other in the spine below the 8th cervical methamera or in the corona radiata.

Central motor conduction in human chronic Chagas' disease

The possible involvement of spinal alpha motor neurons, dorsal root ganglia and sensory fibers in human chronic Chagas' disease was previously demonstrated. More recently neuropsychological and sensory evoked potentials studies suggest the existence of central nervous system abnormalities in these patients. We assessed the state of central motor pathways in 46 patients with chronic Chagas' disease and 30 healthy volunteers by means of percutaneous cortical and spinal electrical stimulation. No significative slowness in pyramidal tracts (PT) conduction was found when comparing both groups. Neither any individual patient exhibited abnormally delayed PT conduction values beyond the upper normal limit of the healthy volunteers. These results suggest that, in contrast with other neural systems, the large myelinated PT fibers are usually spared in human chronic Chagas' disease.

[Neurocysticercosis in a hospital of the city of Buenos Aires: study of 11 cases]

Eleven patients with diagnosis of possible neurocistycercosis were studied in our Department since 1986. All of them were adults. Eight were Bolivian citizens. The commonest neurological clinical manifestation were seizures and/or headache. Brain CT scans showed cystic lesions and calcifications in 5 patients, only calcifications in 3, enlarged ventricles in 2 and an isolated frontal cystic lesion in 1. Six out of 7 patients who were submitted to spinal fluid ELISA test showed positive response for cysticercosis. Patients were put on praziquantel (50 mg/Kg/d) or albendazol (15 mg/Kg/d) with good outcome for all them. Surgery was carried on for treatment of enlarged ventricles (2 patients) and for a like-expansive lesion (1 patient). The aim of this work is to underscore the fact that in Buenos Aires city, which previously was not within the endemic latin american area for cysticercosis, is now possible to find patients with the neurological manifestations of this parasitosis, most probably due to migration of people coming from the north provinces or from countries situated at its border where the disease is endemic.

Influence of feelings of burden on the caregiver's perception of the patient's functional status

We studied the correlation between the caregiver's feelings of burden and the cognitive, behavioral and functional impairment of demented patients. We attempted to show the influence of caregiver's feelings of burden on their perception of the patients' functional status and to establish the predictors of feelings of burden. Twenty-five probable Alzheimer disease patients (NINCDS-ADRDA criteria) were assessed on cognitive measures and functional status (DAFS). The caregiver's index of burden (CIB), obtained from an adapted version of the Zarit Burden Interview, was correlated with the caregiver's report on the patient's instrumental activities of daily living (IADL) and physical self-maintenance functions (ADL); total and partial DAFS scores, and patient's cognitive and behavioral problems rated with the Functional Dementia Scale (FDS). The CIB correlated with the caregiver's report on the patient's behavioral disturbances (r = 0.71, p < 0.001) and physical self-maintenance activities (r = 0.62, p < 0.001), but not with cognitive impairment, IADL and the DAFS. The patients showed better functional performance in the direct assessment than in that reported by their caregivers (mainly in shopping, feeding, dressing, and ambulation). Thus, burden may foster a growing intolerance of the caregiver, inducing an underestimation of the patient's actual functional competence. The caregiver's report on the patient's behavioral problems was the best predictor of feelings of burden (P = 19,9, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[Schwannomatosis: report of a new case]

Schwannomatosis is a rare disorder, still not quite well defined, seldom described in the literature. In this paper we report the case of male. Patient, 52 years old, who in the last 30 years developed five subcutaneous tumors within his limbs peripheral nerves, which histologically proved to be schwannomas. A brain computed tomography showed a partially calcified tumor in the left temporal lobe which most likely was a meningioma. A thorough clinical examination was unable to find signs of type I or type II neurofibromatosis. The present condition, probably a form of phacomatosis, has to be distinguished from neurofibromatosis and is considered as an independent clinical entity whose origin still awaits further detailed investigations.

Electrophysiological assessment of spinal cord lesions by means of transcranial cortical stimulation

Central Motor Conduction Time (CMCT) was assessed in 30 healthy volunteers and 22 patients with spinal cord lesions due to compressive, degenerative and demyelinating disease. To obtain the CMCT, electrical Transcranial Stimulation and Percutaneous Spinal Stimulation or F wave calculations were employed. Pyramidal Tract (PT) conduction was always abnormal in the clinically impaired corticospinal tracts of all the studied patients. This results correlated with the degree of muscle weakness specially in those having compressive lesions. Subclinical evidence of pyramidal damage was also observed in two patients with Multiple Sclerosis. As opposed to the other groups, patients with degenerative spinal disease, showed essentially symmetric abnormalities. An important overlap of CMCT slowness was seen among the three studied groups, suggesting that this isolated clue is not valuable enough for aetiological suspicion. Double muscle responses due to single TCS were obtained, during rest, in some patients from each group, but never in controls. This pathological feature, not reported by others, could represent the excitation of indirect corticospinal connections, partially responsible for the residual motor function after PT damage.

Peripheral motor nerve conduction studies in patients with chronic Chagas' disease

A comprehensive investigation of nerve motor conduction velocity was carried out in the ulnar nerve of 70 patients in the chronic stage of Chagas disease. It was found that 2.6% of them, had slowness of the large motor axons at distal segments and 14% at proximal segments. Twenty seven percent of them had also slowness of conduction at the smallest motor fibers. These observations signal that some patients in the chronic stage of the infection may develop a motor neuropathy.

Percutaneous cervical stimulation: effects on intraspinal structures

Changes in the amplitude of motor evoked potentials (MEPs) from percutaneous cervical stimulation (PCS) obtained at rest in the thenar muscles, and smaller than 0.8 mV, were studied under 3 different experimental conditions. A significant enhancement was observed mainly with a conditioning subthreshold transcranial stimulus and when MEPs were obtained in coincidence with weak voluntary contraction of the target muscle. Subthreshold stimulation of Ia fibers of the median nerve seemed to have a smaller facilitatory effect. It is generally accepted that PCS excites the spinal motoneuron (SMN) axons at the spinal nerve. However, our results show that other SMNs, usually not recruited, may be triggered by PCS when they receive excitatory postsynaptic potentials from the pyramidal tract (PT) or Ia fibers. This behavior suggests that low intensity PCS also exerts subthreshold excitation of the PT fibers and, perhaps, of the incoming spindle afferents, which adds its effects to the conditioning stimuli.

[Trypanosoma cruzi: induction of changes in the peripheral nervous system in different strains of mice]

This study has been designed to find an easy method to evaluate the motor unit alterations induced during experimental T. cruzi infections. Different mouse strains infected with three strains of T. cruzi were used to perform conventional needle electromyography, in one of the lower limb hamstring muscles; amplitude, duration and number of phases of single motor unit potentials were measured. The following parasite strain to mouse strain relationship was investigated, in mice inoculated intraperitoneally with bloodstream forms of T. cruzi: Tulahuen and C3H/HeN, C57Bl, Balb/c, Swiss; CA-I and C3H/HeN, Rockland, NIH; RA and C3H/HeN, Rockland. T. cruzi-induced denervating alterations were found in both C3H/HeN and C57Bl mice infected with the Tulahuen strain, as well as in C3H/HeN mice inoculated with the CA-I strain. Moreover, CA-I trypomastigotes could produce primary muscle changes in C3H/HeN and NIH mice. The technique employed in this investigation proved to be an easy and adequate way to detect changes within the motor unit during T. cruzi infection in mice.

[Diagnosis and treatment of myasthenia gravis: study of an inpatient population]

Between 1974 and 1987 we have examined 50 patients with the diagnosis of myasthenia gravis. Female preponderance (2.5: 1) was found. Also, it was observed that most of the patients were aged between 20 and 49 years. Beside the clinical examination, the following tests were performed: (1) edrofonium test, (2) supramaximal repetitive nerve stimulation, (3) serum acetylcholine antibodies titers and (4) intraperitoneal passive transference of patient's sera to mice and recording of meepp's amplitude in the phrenic-diaphragm preparation in vitro. These four tests gave positive values for myasthenia in 90 to 100% of the cases. Thymus radiological examination was carried out by pneumomediastinography, which proved to correlate with the histological picture of the gland, and computed tomography, which disclosed some discrepances with the histology. Treatment was based on anticholinesterase drugs, corticosteroids and thymectomy, being the corticosteroids the most valuable therapeutical tool. Nine patients treated with steroids disclosed transitory worsening of their signs and symptoms at very early stages after onset of corticosteroid therapy, 6 of them had a disfavorable course in their follow-up. This observation seem to have value in the early prognosis of the disease.

[Somatosensory evoked potentials in a population with chronic lead poisoning]

Eleven patients with chronic lead intoxication were submitted to somatosensory evoked potential (SEP) studies. All patients demonstrated increased lead blood levels and reduced ALA D activity in red blood cells. Three patients showed delayed spinal arrival (N13 wave), four delayed cortical arrival (N20 wave), and three prolonged central conduction time (time elapsing between N13 and N20 waves) (see table 1). No relationship was found between the abnormal findings and the levels of lead or ALA D. Time of intoxication was not related to the altered electrophysiological features either. The findings reported suggest that, beside the well known peripheral involvement in chronic lead intoxication, some patients may develop central nervous system impairment perhaps related to myelin involvement as suggested by the prolonged SEP central conduction time.

Central motor conduction in ischaemic and hemorrhagic cerebral lesions

Electrical Transcranial Cortical Stimulation was performed in 20 healthy volunteers and 14 patients having supra- or infratentorial vascular lesions. Central Conduction Time (CCT) in the Pyramidal Tract (PT) was calculated by subtraction of the Peripheral Conduction Time and the spinal synaptic delay to the Motor Evoked Potential (MEP) latency. Twelve out of fourteen patients showed prolonged MEP latencies or CCTs in the affected corporal segments. Only in 3 cases, 2 with subcortical hematoma and other with bilateral ischaemic lesions, the PT was inexcitable. Two patients, one with a discrete cortical lesion and the other with an hemispheric cerebellar infarct showed no abnormalities in pyramidal conduction. Electrophysiological results showed a good correspondence with the degree of clinical impairment.

A sequential study of the peripheral nervous system involvement in experimental Chagas' disease

To search for the sequential compromise of the spinal cord, nerves, and skeletal muscle in mice chronically infected with Trypanosoma cruzi, animals were subjected to electromyographic investigation, end-plate recordings, and histological studies at 7, 15, 37, 60, 90, 120, 180, 270, and 360 days postinfection. Electromyographic studies showed signs of motor unit remodeling as early as 15 days postinfection, when diminished duration and amplitude of motor unit potentials pointing to a primary muscle involvement were found. Thereafter, certain features of denervation, reinnervation, and primary muscle involvement were often found to coexist. Low miniature end-plate potentials with normal frequency and acetylcholine quantum content were found in end-plate recordings made at the phrenic-diaphragm in vitro. Double end-plate potentials were observed in most of the tested muscle fibers from day 90 postinfection. All these features suggest post-synaptic damage of the end-plate and the presence of reinnervation after day 90 postinfection. Histological studies disclosed inflammatory infiltrates consisting of lymphocytes and macrophages, with vasculitis as the main lesion in the hamstring muscles; intracellular parasites were seen in 25% of the cases. Neuropathic features, as expressed by type fiber grouping and grouped muscle fiber atrophy, were found. On nerve examination epineural, perineural, and endoneural vasculitis were seen. Digestion chambers and myelin ovoids (axonal degeneration) were observed. In teased fiber preparations, segmental internodal and paranodal demyelination and remyelination were found. The lumbar inflammatory spinal cord failed to show grey or white matter infiltrates. However, spinal roots and dorsal root ganglia were densely affected by inflammatory cells.

Motor unit involvement in human acute Chagas' disease

Thirty five patients with acute Chagas' disease who demonstrated parasitaemia at the time of the investigation were submitted to a detailed electromyographical study. With their muscles at rest, 12 patients showed fibrillation potentials and/or positive sharp waves. On volitional contraction, 7 had short duration motor unit potentials (MUPs) and low polyphasic MUPs. On motor and sensory nerve fibers conduction studies, 20 disclosed values below the lower control limit within one or more nerves. Finally, 12 patients produced a muscle decremental response on nerve supramaximal repetitive stimulation. The findings signal that primary muscle involvement, neuropathy and impairement of the neuromuscular transmission, either isolated or combined, may be found in the acute stage of human Chagas' disease.

Neuromuscular transmission studies in human chronic Chagas' disease

An electrophysiological investigation of the state of the neuromuscular transmission (nmt) was carried out in 58 patients with the diagnosis of chronic Chagas' disease. On repetitive supramaximal nerve stimulation it was found that some patients did not show abnormalities, others had decremental muscle responses, others developed enhancement of the muscle evoked potential amplitudes, while some other patients combined both types of pathological responses. The findings suggest that some patients with chronic Chagas' disease develop impairment of nmt, though data obtained in this study do not give information about neither the type of impairment nor the localization (pre or postsynaptic, or both) of the damage.

Cerebral evoked potentials in human chronic Chagas' disease

Seventy five patients with the diagnosis of chronic Chagas' disease were studied by employing EPs techniques. Two of them had delayed arrival of the signal to the Erb's point and one to the spinal cord when looking at SEPs. Two patients had increment of the time interval between waves Ist and IIIrd, when studying PEATs. These findings were interpreted as due to peripheral nerve fibers damage, a feature described in previous papers. The most striking finding was the prolonged time interval between waves N13 and N20 (SEPs) found in two patients and between waves IIIrd and Vth (PEAT) seen in 7 affected subjects. These observations suggested the development of some sort of CNS involvement, perhaps related to myelin damage, in patients who reached the chronic state of the infection.

Familial congenital facial diplegia: electrophysiologic and genetic studies

A 13-year-old boy with autosomal-dominant congenital facial diplegia was evaluated by electrophysiologic and genetic investigations. Thirteen members of his family were affected over 4 generations. The electrophysiologic studies revealed blink reflex abnormalities. Both R1 and R2 responses were prolonged on the left side after ipsilateral stimulation, while R2 was also delayed by contralateral stimulation. Ipsilateral R1 and R2 were of normal latencies when the right side was stimulated. A third ipsilateral response at 63 msec of latency could be obtained when stimulating the left side. These findings suggest functional damage to the brainstem. Further support for this interpretation was provided by the prolonged time between waves I and V, bilaterally, documented by study of brainstem auditory evoked potentials.

Changes in tetrodotoxin-resistant action potentials after passive transfer of myasthenia gravis patient sera

Muscle electrical activity has been studied in mice after intraperitoneal injection of sera from myasthenia gravis (MG) patients. Myasthenic serum did not modify the electrical properties of innervated muscle fibres. The resting membrane potential and the action potential parameters remained unchanged. However, tetrodotoxin (TTX)-resistant action potentials of denervated muscles were reduced by myasthenic serum, possibly in association with receptor endocytosis induced by the immunoglobulin. However, a direct effect of MG serum on TTX-resistant sodium channels cannot be ruled out.

Tools to differentiate immunologic and non-immunologic myasthenia gravis in infancy

Twelve patients between 15 months and 13 years of age with clinical and pharmacological features of myasthenia gravis were studied. Repetitive nerve stimulation did not offer valuable information; the patients demonstrated either inspecific muscular decremental response or had normal behavior. Two clear groups of patients were identified after measurements of acetylcholine receptor (AChR) antibodies and MEPP amplitude recorded in the diaphragm of mice injected with sera from those patients. The first group included patients with positive AChR antibodies titers and decreased MEPP amplitude. The second one had negative AChR antibodies titers and MEPPs with normal amplitude. These data strongly suggest immunologic and non-immunologic mechanisms for the former and later respectively.