Myasthenia gravis and Werlhof's disease

A case of Werlhof's disease (immune thrombocytopenia) associated with myasthenia gravis is described. The two disorders developed within a few months of each other. The immunological and practical aspects of the association are discussed.

[Physical examination--measurement of muscle strength]

Measuring muscle strength and establishing paretic symptoms are done first of all by having the patient perform actions or movements that require normal muscle strength. Measuring or grading the strength of separate muscle groups is usually done by means of the so-called Medical Research Council (MRC) scale that runs from 0 to 5, with the movement against gravity as an important criterion. This scale is not very valid in tract 4 (more strength than needed to overcome gravity, but still subnormal). Using a manual dynamometer or a fixed dynamometer it is possible to measure the strength of most clinically important muscle groups of the extremities and to compare them with values found in a normal population. For following the individual patient with a neuromuscular disorder, strength measurement with the dynamometer is more reliable than grading using the MRC scale.

Myasthenia gravis on the Dutch antilles: an epidemiological study

We carried out an epidemiological study on the prevalence and annual incidence of myasthenia gravis on tropical islands Curaçao and Aruba in the period 1980-1995. Twenty-one patients (seven men and 14 women) were identified. The point prevalence increased from 29 per million in 1980 to about 70 per million in 1990-1995; the annual incidence over the total period was 4.7 per million. The female:male ratio was 2:1; purely ocular cases (2/21) comprised 9.5% and thymomas (4/21), 19%. These data are in accordance with most other epidemiological studies in non-tropical areas. No other studies on myasthenia gravis in tropical areas have been reported.

[Physical diagnosis--signs of lumbosacral irritation]

Lasègue's test is a clinical test to demonstrate lumbosacral radicular irritation. Published evidence gives a high sensitivity (0.80-0.97) for a low lumbar disc protrusion but a low specificity (about 0.4) since this test is also positive in ischialgia due to other causes. A crossed Lasègue test had a high specificity (> or = 0.90) for presence of a (ruptured) disc prolapse. There is little or no literature about the reversed Lasègue and provocation by intra-abdominal pressure. The reproducibility of the Lasègue test is moderate (kappa about 0.55).

[A series of articles on the usefulness and uselessness of physical diagnostics; comment]

The sensitivity, specificity and reproducibility (especially the interassessor variation) of many physical diagnostic tests taught in the medical curricula appear not to have been established. Nevertheless, many of these tests are mentioned as end terms in the General plan 1994 medical education. A series of articles in this journal will be concerned with tests from physical diagnostics, with reference to usefulness and uselessness: sensitivity, specificity and reproducibility.

[Favorable results of plasmapheresis in severe myasthenia gravis]

OBJECTIVE

Evaluation of the additional effect of plasma exchange in treatment with steroids of severe myasthenia gravis.

DESIGN

Retrospective study.

SETTING

Department of Neurology, University Hospital of Groningen, the Netherlands.

PATIENTS AND METHODS

The clinical course was analysed in 24 patients with a total of 28 plasma exchange treatments. Prednisone was introduced or its maintenance dose was increased in 19 cases. Another 13 patients with severe myasthenia gravis were included to study the effect of prednisone monotherapy.

RESULTS

Of the patients treated with plasma exchange and steroids 71% improved within the first week of treatment as against only 15% of the patients treated with prednisone monotherapy. After two weeks of plasma exchange plus prednisone or prednisone monotherapy, 88% and 69%, respectively were ameliorated. None of the patients receiving plasma exchange deteriorated or experienced adverse effects or complications due to plasma exchange. Of the patients receiving prednisone monotherapy 31% deteriorated in the first week of treatment.

CONCLUSION

Patients with severe myasthenia gravis may safely be treated with plasma exchange in combination with prednisone. In our patient group, a state of rapid aggravation was cut short more quickly by prednisone plus plasma exchange than by prednisone monotherapy.

Myasthenia gravis: diagnosis and follow-up of 100 consecutive patients

One hundred consecutive patients with myasthenia gravis (MG) referred between 1985 and 1989 were analysed for epidemiological characteristics, evolution of early signs, delay in diagnosis, yield of diagnostic tests and effects of treatment. The female to male ratio was 1.6:1.0. Sixteen patients had a thymoma. Ocular MG occurred in 14. Associated autoimmune diseases were found in 15 patients. In 34% of the women and 10% of the men the diagnosis was delayed for more than 2 years. In the first 3 months progression was more rapid in men than in women. Anti-acetylcholine receptor antibodies were found in 94% of the patients with generalized MG and in 29% of the ocular patients. The neostigmine or the edrophonium test was positive in 84% of the generalized and in 60% of the ocular patients. Electromyography was diagnostic in 71% of the generalized and in 42% of the ocular patients tested. Thymectomy was performed in 56 patients (12 with thymomas). Fifty-one per cent were treated with one or more immunosuppressive drugs, at any time. After a mean follow-up of 9.6 years after onset remissions had occurred in 43%, considerable improvement in 25%, moderate improvement in 20% and 12% remained unchanged. There were no deaths due to MG. Thirty-six per cent remained dependent on immunosuppressive drugs. Medication-free remission was most frequent (35%) in the early-onset (< 50 years) group. Side-effects of pyridostigmine were noted in 34% of 99 patients, of prednisone in 65% of 49 patients, and of azathioprine in 54% of 28 patients, but these necessitated stopping the drug in only 1%, 10% and 14% respectively.

[Quantification and evaluation of 5 neurological equilibrium tests in test subjects and patients]

OBJECTIVE

Quantification and evaluation of five neurological balance tests as part of the routine neurological examination in order to obtain objective test results for healthy individuals and several neurological patient groups.

SETTING

Department of neurology, University Hospital Groningen, the Netherlands.

DESIGN

Prospective, controlled study.

METHODS

220 subjects (113 healthy individuals and 107 neurological patients) participated in a balance test investigation comprising gang board, Romberg's test, tandem gait, one-leg-stance, hopping. Tests were performed on a hopscotch (3 meters long, divided in 6 rectangles of 20 by 50 cm) and using a stopwatch to register times and faults.

RESULTS

All five quantified tests were feasible for healthy individuals. Up to the age of 70 results gradually declined, above 70 a strong decline was observed. Patients with gait and balance disorders performed less well in all tests except the Romberg's test.

CONCLUSIONS

Taking into account a strict standardisation of these five existing tests standard values were obtained for a fast and simple quantification of balance in the routine neurological examination, which can also be used to monitor progress. Especially the results obtained in tandem gait, one-leg-stance and hopping differ significantly between healthy individuals and patients. The gang board appears to be useful for quantifying serious balance disorders. Romberg's test is a specific test for the perceptual sensibility and does not belong in the routine neurological examination of balance.

The clinical spectrum of limb girdle muscular dystrophy. A survey in The Netherlands

A cross-sectional study was performed in the Netherlands to define the clinical characteristics of the various subtypes within the broad and heterogeneous entity of limb girdle muscular dystrophy (LGMD). An attempt was made to include all known cases of LGMD in the Netherlands. Out of the reported 200 patients, 105 who fulfilled strictly defined criteria were included. Forty-nine patients, mostly suffering from dystrophinopathies and facioscapulohumeral muscular dystrophy, appeared to be misdiagnosed. Thirty-four cases were sporadic, 42 patients came from autosomal recessive and 29 from autosomal dominant families. The estimated prevalence of LGMD in the Netherlands was at least 8.1 x 10(-6). The clinical features of the autosomal recessive and sporadic cases were indistinguishable from those of the autosomal dominant patients, although calf hypertrophy was seen more frequently, and the course of the disease was more severe in autosomal recessive and sporadic cases. The pectoralis, iliopsoas and gluteal muscles, hip adductors and hamstrings were the most affected muscles. Distal muscle involvement occurred late in the course of the disease. Facial weakness was a rare phenomenon. The severity of the clinical picture was correlated with a deteriorating lung function. All autosomal dominantly inherited cases showed a mild course, although in two families life-expectancy was reduced because of concomitant cardiac involvement.

Acquired blepharoptosis

A review is given of the aetiology and possible treatment of acquired (non-congenital), blepharoptosis, which is a common but not specific sign of neurological disease. The diagnostic categories of upper eyelid drooping are scheduled as (a) pseudo-ptosis due to a local process or overactivity of eye closure, including blepharospasm, and (b) true ptosis due to a paresis of the eyelid levators (m. tarsalis superior or m. levator palpebrae) or to a disinsertion of the m. levator palpebrae (aponeurotic ptosis). A paresis of the m. tarsalis is due to a lesion in the central, intermediate or peripheral neuron of the sympathetic chain and constitutes one of the components of Horner's syndrome. A paresis of the m. levator palpebrae may be due to a failure in central innervation, in oculomotor (n.III) function, in neuromuscular transmission or to a lesion in the muscle itself.

Familial hypokalemic periodic paralysis. Clinical, diagnostic and therapeutic aspects

Five generations of a family with hypokalemic periodic paralysis (HOPP) were studied. Of the 120 screened family members, 64 were found to have HOPP of which 38 were suffering from attacks. In the other 26 the diagnosis was made on account of vacuolar myopathy, a reduced muscle fiber conduction velocity or the signs of permanent muscle weakness (PMW) in combination with (grand)children with attacks. Applying these criteria skipping of generations did not occur in this family. When defined properly, PMW was found in all patients at older age, independent of the previous occurrence of paralytic attacks. Dynamometry and muscle CT-scanning appeared valuable in the diagnosis and the progression of PMW. In 2 patients autopsy was performed. Characteristics vacuolization was found in the striated muscle tissue in various degrees. Heart and smooth muscle tissue were not involved. Therapy is limited. Potassium salts shortening and preventing the paralytic attacks are tolerated well. Acetazolamide is more effective in the prevention of the paralytic attacks, but is not tolerated very well. HOPP can be considered as a myopathy characterized by PMW at older age in all patients, combined with paralytic attacks in more than half the patients.

[Use of alternative treatments by patients with myasthenia gravis]

OBJECTIVE

To analyse the use of alternative treatments by patients before and after myasthenia gravis was diagnosed, and the influence on the diagnostic delay.

DESIGN

Retrospective study.

SETTING

University Hospital Groningen, Netherlands.

METHOD

A questionnaire was sent to 90 consecutive patients with myasthenia gravis to inquire about their use of alternative treatments.

RESULTS

Of the 72 respondents 18 had used alternative treatments. Of these 11 had even done so before diagnosis. The most important reason for the use was the lack of understanding and trust that these patients said they experienced from their regular doctors. Almost all patients discontinued alternative treatment when it became clear that it had no effect. Compared with those not using alternatives, the diagnosis was delayed in the group of patients using alternative treatments, but not significantly.

CONCLUSION

More attention for patients with chronic and undefined complaints may shorten the delay in diagnosing and treating myasthenia gravis adequately.

[Unterberger's test not useful in testing of vesitibular function]

OBJECTIVE

Quantification of the stepping test in routine neurological examination.

SETTING

University Hospital Groningen, the Netherlands.

DESIGN

Prospective, controlled study.

METHODS

The stepping test was assessed in 41 healthy subjects, in 7 subjects with artificially induced vertigo and in 83 patients with disturbances of gait or equilibrium resulting from different affections of the central nervous system. Displacement and rotation to the right or the left side were measured. The different groups were then compared with each other.

RESULTS

We found a great inter- and intra-individual variation in direction and width of rotation and in displacement. The results of the test are not influenced by right(+)-or left(-)-handedness or by dominance of the right or the left leg.

CONCLUSION

The current test does not appear to be useful for detection of abnormalities in the vestibular system or for distinguishing normal individuals from patients.

Antibodies to skeletal muscle in myasthenia gravis. Part 3. Relation with clinical course and therapy

Fluctuations of anti skeletal muscle antibodies (AMA) were studied in relation to clinical changes and fluctuations in anti acetylcholine receptor antibodies (a-AChR). Forty-two patients with generalized myasthenia gravis were studied in clinical and serological follow-up during several years under various conditions. Results from this study demonstrate that AMA fluctuate in strong relation to a-AChR, clinical course and immunosuppressive therapy. Thymomectomy resulted in an increase or de novo appearance of AMA in 10 of the 12 patients who did not receive immunosuppressive medication.

Antibodies to skeletal muscle in myasthenia gravis. Part 2. Prevalence in non-thymoma patients

Anti-skeletal muscle antibodies (AMA) were measured in 340 non-thymoma patients with myasthenia gravis (MG) by both an ELISA with citric acid muscle extract and by immunofluorescence assay. Three a-AChR negative but AMA-positive patients were found. The occurrence of AMA was related to the age at onset in patients with an onset of MG beyond 40 years and with duration of disease in patients with an earlier onset of MG. This stresses the heterogeneity of late onset and early onset MG. Serial measurements in individual patients revealed no evidence for a thymic role in the generation of AMA. There was no difference in specificity of AMA in early and late onset patients. The presence of AMA in CT-negative patients is not necessarily suggestive of a radiological shortcoming in the detection of thymoma since in 16 AMA-positive patients from our series no thymoma was found at operation or obduction.

Antibodies to skeletal muscle in myasthenia gravis. Part 1. Diagnostic value for the detection of thymoma

The role of anti-muscle antibodies (AMA) in the diagnosis of thymoma in patients with myasthenia gravis (MG) is evaluated. We compared ELISA and Western blot assay for antibodies to citric acid muscle extract (a-CAE) with an immunofluorescence assay (IF). Sera from 234 selected MG patients and 123 controls were tested. There was no essential difference between ELISA and IF. Western blot was superior in young onset patients but less useful in patients with an onset beyond the age of 40 years. Unusually high post-test probabilities were found by our patient selection criteria which seem most realistic for clinical practice. Western blot revealed no differences in specificity of AMA in thymoma and non-thymoma patients irrespective of age at onset of disease.

Potassium channels in hypokalaemic periodic paralysis: a key to the pathogenesis?

1. A possible role for the ATP-sensitive potassium channels in the pathogenesis of hypokalaemic periodic paralysis was investigated. 2. We assessed insulin release and muscle strength after intravenous glucose loading with and without the potassium channel opener pinacidil and the potassium channel blocker glibenclamide in three patients with hypokalaemic periodic paralysis and in a pair of matched control subjects for each patient. 3. A significantly higher initial insulin response (1.5-30 min) was found in the patients with hypokalaemic periodic paralysis in comparison with the control subjects. During potassium channel blocking with glibenclamide the insulin release was more enhanced in patients than in control subjects. On the other hand, the potassium channel opener pinacidil impaired the insulin release in healthy control subjects but not in patients. The serum glucose levels showed no differences between patients and control subjects. In one of the patients with hypokalaemic periodic paralysis glucose loading resulted in a fall in muscle strength, which did not occur during the administration of pinacidil. 4. These findings suggest a disturbance in the ATP-sensitive potassium channel in patients with hypokalaemic periodic paralysis, which is not limited to pancreatic beta cells, but may be also involved in the abnormal behaviour of skeletal muscle.

[Quantification of the gnostic sensitivity via measurement of the vibration threshold and of finger tip sensation]

OBJECTIVE

Quantification of vibration perception and fingertip sensation in routine neurological examination.

SETTING

Neurological Clinic, University Hospital, Groningen, the Netherlands.

DESIGN

Prospective, controlled investigation.

METHODS

Vibration perception and fingertip sensation were quantified in a large group of normal control persons of various ages and in neurological patients and compared with the usual sensory tests at routine neurological examination. The vibration perception limit was measured with a biothesiometer without accelerometer, the fingertip sensation with a device for two-point discrimination slightly modified according to Renfrew ('Renfrew meter'). Concordance of the tests was studied by calculating kappa values.

RESULTS

The normal values of both sensory qualities had a log-normal distribution and increased with age. The values obtained with the Renfrew meter correlated well with those of the two-point discrimination and stereognosis but were systematically higher than those indicated by Renfrew.

CONCLUSION

Both methods appear useful at routine neurological examination if certain measuring precautions are taken.

Antibodies to acetylcholine receptors in myasthenia gravis. In vitro synthesis by peripheral blood lymphocytes before and after thymectomy

Pokeweed mitogen (PWM)-driven in vitro synthesis of antibodies to the acetylcholine receptor (PSA) was studied in non-thymoma patients with myasthenia gravis. In a group of 46 patients, the occurrence of PSA was related to the presence of the thymus or, in operated patients, the absence of a clinical effect of thymectomy. Sixteen patients were followed before and soon after thymectomy. PSA disappeared in all patients, at least temporarily, between 6 weeks and 1 year afterwards, independent of the clinical course and eventual clinical effect of the operation. A recurrence was found only in one of the five patients who derived no benefit from the operation. These findings support the hypothesis that the therapeutic effect of thymectomy can be explained by removal of a source of autoreactive lymphocytes. There was no correlation between the changes in serum levels of a-AChR and clinical improvement, suggesting a minor role of circulating peripheral blood lymphocytes (PBL) and the thymus in the total production of a-AChR.

HLA type is not indicative for the effect of thymectomy in myasthenia gravis

The frequency of HLA types in a selected group of 40 patients with myasthenia gravis in relation to the effect of thymectomy and also to gender, and thymus histology was studied. As generally described we found a significant increase in the frequency of HLA-A1, HLA-B8, HLA-DR3 and HLA-DQ2 in the total group. There were no further differences between subgroups of patients, which demonstrates that HLA type is not indicative for the effect of thymectomy in myasthenia gravis.

[The effect of thymectomy in patients with myasthenia gravis without thymoma; a statistical analysis]

In order to determine the effect of thymectomy on the prognosis of patients with myasthenia gravis, an analytical-descriptive study was carried out in the Neurological Clinic of the Groningen University Hospital and the Mathematical Institute of Groningen University. In 183 patients with generalized myasthenia gravis without thymoma, with onset between 9 and 46 years of age, the severity of the disease was scored by one neurologist at fixed times (0.5, 1, 2, 3, etcetera up to 15 years) after onset. Thymectomy was performed in 144 patients at different times (0.5, 1, 2, 3, etcetera up to 7 years) after onset. Logistic regression analysis was carried out with, as the criterion for marked improvement, a decrease of the disease score by 50%. Using this criterion, age, sex, duration of the disease and severity of the disease prior to operation played no distinct parts as prognostic factors. At different periods after the onset of the disease, groups of patients operated or not (yet) operated were compared. Patients subjected to thymectomy within 5 years after onset of myasthenia gravis had a better probability of halving of the severity score than patients not subjected to operation. These data render it possible in the individual patient to make an adequate estimate of the probability of marked improvement if thymectomy is performed or postponed.

Vibration perception threshold, complaints and sensory examination in diabetic patients

The vibration perception threshold (VPT) was investigated by means of a biothesiometer among 40 patients with insulin dependent diabetes mellitus. The age as well as the duration of the disease affected the VPT. However, a correlation between the VPT and the rate of metabolic control measured through the glycolysed Hb (HbAlc) could not be demonstrated. In early stages abnormalities were already detectable in the feet. The VPT was elevated in 13 of 20 patients with sensory complaints and in 4 of 20 patients without complaints. Routine neurological examinations such as light touch and pinprick sensation were less sensitive to diagnose neuropathy. In detecting early signs of diabetic neuropathy in an outpatient population the determination of the VPT is a sensitive tool.

Anti-acetylcholine receptor antibodies decrease after thymectomy in patients with myasthenia gravis. Clinical correlations

Clinical course and changes in serum levels of antibodies to the acetylcholine receptor (a-AChR) were followed in 82 patients with myasthenia gravis during a period of 1-8 years after thymectomy. Decrease in a-AChR immediately after thymectomy was influenced by changes in a total IgG. Immunosuppressive medication affected serum a-AChR at all points of time. In a subgroup of 41 patients without thymoma who had no immunosuppressive drugs, there was a steady decrease in a-AChR concomitant with clinical improvement from 6 weeks after thymectomy.

The "make/break test" as a diagnostic tool in functional weakness

Strength was measured in four major muscle groups with a hand-held dynamometer. The "make" and "break" technique was used with and without encouragement, and fatiguability was tested in patients with organic weakness and patients with functional weakness. Patients with functional weakness could be distinguished from the other two groups by an increase in strength greater than 20% with the break compared with the make technique. Additionally they tend to show larger increases in strength with encouragement and their "fatiguability" was less.

Hand-held myometry: reference values

In thirteen major muscle groups of 50 healthy females and 50 males, aged 20-60 years, maximum voluntary contraction was measured with a hand-held dynamometer. The intrasession variation, the left-right variation, and the fifth and fiftieth centile values were calculated. The ratio of two observations within one session ranged from 0.85 to 1.18 and the ratio of left to right ranged from 0.82 to 1.22 (95% reference limits). In 20 volunteers the repeatability was tested after one week. The ratio of averages of three measurements in two successive weeks ranged from 0.82 to 1.23 (95% reference limits). There were only small differences between muscle groups concerning these ratios. A significant relation with age and weight/Quetelet Index could be demonstrated in some muscle groups. The mean strength of females is approximately two thirds of the strength of males. The data may be useful as reference values in the application of hand-held myometry.

Azathioprine in myasthenia gravis: observations in 41 patients and a review of literature

We report azathioprine treatment of 41 patients with myasthenia gravis, with a follow-up of more than 3 yr. The data show that azathioprine is effective in controlling the disease, both as a single drug as well as in combination with prednisone. In addition it may be steroid sparing. Older patients derived more benefit from the medicament. Side-effects could be managed fairly well, except for one patient who developed a non-Hodgkin lymphoma. Data from this study do not support the supposition that the therapeutic effect of azathioprine is dependent on macrocytosis. Fluctuations of serum levels of antibodies to the acetylcholine receptor were simultaneous with clinical changes and thus were not of predictive volume for the clinical course.

Permanent muscle weakness in familial hypokalaemic periodic paralysis. Clinical, radiological and pathological aspects

Myopathy accompanying familial hypokalaemic periodic paralysis (HPP) is much less well documented than the paralytic attacks from which the disease derives its name. Eleven affected members of a large kinship with HPP were studied clinically and radiologically for the presence of myopathy. In 4 patients muscle biopsies were also performed and in 1 of them the histological findings obtained at autopsy were compared with the CT scans of various muscles. In another patient not previously biopsied, the specimens of both amputated legs were examined histologically. The age of the studied individuals ranged from 33 to 74 yrs. The 4 youngest patients showed no clinical signs of myopathy. However, in 2 of them CT scans demonstrated discrete hypodense lesions in the leg muscles, whereas in the other 2, muscle biopsies showed a vacuolar myopathy. The other 7 patients, all older than 50 yrs, presented both clinical and CT evidence of myopathy of proximal and distal muscles ranging from very mild to very severe, males being slightly more affected than females. In all 11 patients a mean CT grading was made that was based on the abnormalities found in the different muscle groups. The myopathy appeared to be unrelated to the history of paralytic attacks, but a strong correlation was found between age and mean CT grading. It was concluded that HPP is a myopathy with permanent muscle weakness of late onset in all the patients. The expression of the paralytic attacks is variable.

Measurement of the handcoordination

The validity and reproducibility of two simple coordination-tests, the spiraltest and nailtest were examined in 113 healthy subjects, 33 patients with Parkinson's disease and 24 patients suffering from cerebellar disorders. The performances of the healthy subjects decreased significantly with age but gender had no influence. The performances of the dominant hands were significantly better. At a specificity of 90% the sensitivity was about 70% for the nailtest and about 75% for the spiraltest. For the patients with Parkinson's disease the spiraltest was more accurate than the nailtest. Since reference values are available these tests can be useful in the diagnostic process if a patient is suspected of a coordination disorder of the hands. Furthermore they are likely to give a better impression of the course of a disease affecting the coordination than if only clinical judgment is used.

The natural course of myasthenia gravis: a long term follow up study

A long term follow up study is presented of 73 patients with myasthenia gravis, living in Amsterdam between 1926 and 1965. In the period 1961-65 the annual incidence was 3.1, the prevalence 53 per million. Maximum severity of the disease occurred during the first seven years after onset in 87%. Eighteen (29%) patients died, of whom eight had a thymoma (TH). Spontaneous improvement or remission occurred at any time during the follow up. At the end of the study (1985) 16 (22%) patients were in a complete clinical remission, 13 (18%) had improved considerably (3 with prednisone), 12 (16%) had improved moderately, 12 (16%) had remained unchanged and two had deteriorated. If the early deaths are excluded the outcome is similar in the early and the late onset group without TH. Patients with TH had a less favourable course. Associated autoimmune diseases were diagnosed in 25% (n = 58). Because most of these patients were treated with anticholinesterases only, the evolution of their clinical state represents the natural course of MG.

Improvement of muscle strength in familial hypokalaemic periodic paralysis with acetazolamide

A double blind cross-over study of eight patients with familial hypokalaemic periodic paralysis was made to assess the influence of acetazolamide on muscle strength. All patients had a reduced interictal muscle fibre conduction velocity. Five patients had no attacks at the time of the study. One patient withdrew from the study because of an adverse reaction. The muscle strength of 11 muscle groups was measured with a hand-held dynamometer. The sum of force improved significantly in the seven patients (mean increase: 17%, p less than 0.05; 95% confidence interval: 7.2-26.8%). Endurance tests showed an improvement in the performance of 30 full kneebends. Surface EMG measurement showed no change in the muscle fibre conduction velocity or power spectra during treatment. The integrated EMG showed a (non significant) mean increase of 21%.

The muscle fiber conduction velocity and power spectra in familial hypokalemic periodic paralysis

Surface EMG has been used to determine the average muscle fiber conduction velocity (MFCV) and power spectra of the m. biceps of 10 patients and 15 asymptomatic offspring of a large kinship with familial hypokalemic periodic paralysis (HOPP). The MFCV of the patients was 3.37 +/- 0.35 m/sec (mean +/- SD, n = 9), the median frequency (Fmed) of the power spectra was 55.0 +/- 5.8 Hz (mean +/- SD, n = 9), both values are significantly (P0.001, Student's t-test) lower than the control values: MFCV = 4.55 +/- 0.33 m/sec; Fmed = 88.6 +/- 15.5 Hz (mean +/- SD). In 6 of the 15 asymptomatic relatives, the surface EMG results were also abnormal. It is concluded that the MFCV is reduced in familial HOPP. This results in a predominantly low-frequency content of the power spectra, thereby providing a new model for studying the relationship between the MFCV and the frequency spectrum of surface EMG. Asymptomatic relatives that have inherited the disease probably can be detected with this method.

The slow channel syndrome. Two new cases

Two patients are described with a myasthenic syndrome that presented in early adult life. One patient had 2 asymptomatic first degree relatives with similar electrophysiological findings. Both patients had abnormal fatiguability, arm weakness being prominent; neither of them responded to anticholinesterase medication. An abnormal decrement at 3 Hz stimulation was present, and a single stimulus evoked a repetitive response. Electrophysiological studies on biopsied intercostal muscle showed miniature endplate potentials of normal amplitudes but with prolonged rise and decay times. Anticholinesterase staining (Case 1) was not reduced, and showed elongation of some endplates. Ultrastructural studies (Case 2) showed degeneration of junctional folds and diffusely thickened endplate basal lamina. Calcium deposits were not observed and myopathic changes were slight. The findings are consistent with a prolonged open time of the ACh-induced ion channel.

Cerebrotendinous xanthomatosis (CTX): a clinical survey of the patient population in The Netherlands

The clinical features and additional investigations of 20 Dutch patients suffering from cerebrotendinous xanthomatosis (CTX), an inborn error of metabolism in bile acid synthesis, are described. The onset was in the second or third decade. The clinical picture at the time of examination consisted of a combination of two or more of the following signs: cataract, xanthoma of a tendon, mental deterioration, pyramidal tract signs, cerebellar signs and epilepsy. Mental retardation was reported in patients. CT-scanning showed cerebellar hypodensity in 8 out of 16 patients but this feature did not correlate well with cerebellar signs. The EEG was abnormal in all but one patient. Treatment with chenodeoxycholic acid resulted in a normalization of EEG and biochemical abnormalities but not of the clinical signs. Cholic acid was equally effective but had much less side effects. The importance of a diagnosis in early life is stressed as well as the examination of clinically unaffected heterozygous relatives.

Factors influencing the relapse risk at steroid dose reduction in myasthenia gravis

In a selected group of 69 patients with myasthenia gravis treated with prednisone, the factors were studied that might have influenced the reoccurrence or exacerbation of clinical signs after initial improvement in two-thirds of the patients. It was not evident that the speed of dose reduction was responsible for the relapse in most patients. Azathioprine added to the prednisone regimen was found to reduce the relapse rate at steroid reduction. Pure ocular cases and patients who underwent thymectomy without thymoma had a higher chance to remain in remission after prednisone was stopped. Maintenance dose could be determined in 18 patients and was 0.42 mg/kg/2 d., but the difference between patients with or without azathioprine was not significant.

Intractable ventricular tachycardia in a patient with giant cell myocarditis, thymoma and myasthenia gravis

A 48-year-old man presented with a malignant thymoma in combination with myositis, myasthenia gravis, a giant cell myocarditis and recurrent intractable ventricular tachycardias. Despite various therapies (chemical, electrical and surgical), arrhythmias supervened in the presence of a normal coronary arteriogram. Active myocarditis was believed to be the mechanism of the ventricular tachycardias.

Anti-acetylcholine receptor antibodies in myasthenia gravis. Part 3. The effect of thymectomy

The clinical condition and the serum levels of antibodies to acetylcholine receptor protein were followed in 30 patients with myasthenia gravis before and in a period varying from 2 to 4 (mean 3) yr after thymectomy. Twenty-five patients improved in the 2 yr following thymectomy. A highly significant correlation was found between the change in clinical condition and the change in antibody levels. Only 3 patients improved without a fall of antibody level. Prethymectomy antibody levels were positively correlated with the severity of the clinical condition and with the degree of thymus hypertrophy.

In vitro T-cell dependent B-cell activity in myasthenia gravis

The in vitro T-cell dependent B-cell activity was analysed in 34 patients with myasthenia gravis and in 16 controls by culturing 1 X 10(6) peripheral blood lymphocytes for 8 days with or without pokeweed mitogen (PWM) and measuring the amounts of IgG and IgM released into the culture supernatant. Increased production of IgG in the unstimulated cultures was found in 20 patients, 8 of whom also produced increased amounts of IgM. Upon PWM stimulation the patients produced normal amounts of IgG. The IgM production, however, was decreased in the patient population compared to the controls. Only one of the controls produced more IgG than IgM, either unstimulated or during PWM stimulation. In contrast 10 patients produced more IgG than IgM in the unstimulated cultures and 15 patients did so during PWM stimulation. The 'spontaneous' production of immunoglobulins was not measurable before 4 days of culture and was not the result of in vivo activated B-cells. We suggest that the increased 'spontaneous' immunoglobulin production and the decreased production of IgM during PWM stimulation may be a result of abnormal T-cell activity. The abnormalities found were not related to disease activity, the presence of multiple autoantibodies in the serum, steroid therapy or previous thymectomy. Besides these abnormalities, patients not treated with immunosuppressive drugs also showed decreased PWM induced IgG synthesis.