Myotonic dystrophy: a neglected cause of mental retardation

Speech and language abnormalities in myotonic dystrophy: An overview

Myotonic dystrophy (DM) is an autosomal dominant neuromuscular and multisystem disease that is divided into two types, DM1 and DM2, according to mutations in DMPK and CNBP genes, respectively. DM patients may manifest with various speech and language abnormalities. In this review, we had an overview on speech and language abnormalities in both DM1 and DM2. Our literature search highlights that irrespective of age, all DM patients (i.e. congenital, juvenile, and adult onset DM1 as well as DM2 patients) exhibit various degrees of speech impairments. These problems are related to both cognitive dysfunction (e.g. difficulties in written and spoken language) and bulbar/vocal muscles weakness and myotonia. DM1 adult patients have also a significant decrease in speech rate and performance due to myotonia and flaccid dysarthria, which can improve with warming up. Weakness, tiredness, and hypotonia of oral and velopharyngeal muscles can cause flaccid dysarthria. Hearing impairment also plays a role in affecting speech recognition in DM2. A better understanding of different aspects of speech and language abnormalities in DM patients may provide better characterization of these abnormalities as markers that can be potentially used as outcome measures in natural history studies or clinical trials.

A 5-year follow-up study of an atypical case of myotonic dystrophy

This study presents 5-year follow-up data on NG, a woman with adult onset myotonic dystrophy and progressive cognitive decline who was first described by Wilson et al. The extent of the cognitive impairment is atypical of symptom-onset in adulthood and of paternal inheritance, both of which apply to this case. Together, the present and earlier studies report the results of regular neuropsychological assessments over a 16-year period. Severe impairment in executive functioning, episodic and semantic memory were apparent early in the history, while visuospatial skills and working memory were only mildly impaired after 16 years of follow-up. There was also a progressive dyslexia, initially characterized by the regularization errors typical of surface dyslexia, but subsequently dominated by visual/phonological reading errors. This pattern of impairment is not typical of myotonic dystrophy but resembles semantic dementia. Whilst the deficits may be attributable wholly to myotonic dystrophy pathology, the co-existence of a form of semantic dementia is also possible. It is noted that the aggregation of tau protein is a neuropathological feature common to both diseases.

Myotonic dystrophy type I in childhood Long-term evolution in patients surviving the neonatal period

In a retrospective study, 32 patients with myotonic dystrophy, including congenital (n=17) and infantile/juvenile forms (n=15) were studied during a long follow-up lasting 7-28 years (median: 17 years). The clinical presentation was extremely variable; however, a continuum did exist between severe and less severe congenital forms, and later-onset forms, without genotype-phenotype correlation. We observed some unusual presentations, such as 3 cases of isolated club-feet during the neonatal period, and 7 patients (23%) with a completely isolated mental deficiency, language delay and school failure, who only completed the clinical picture several years later. Wechsler scale testing was performed in all cases, and repeated with 8 patients. It demonstrated a decrease in intellectual abilities in 5 patients, suggesting the possibility of a degenerative cerebral process occurring in these children. This decrease has also been reported in some adult cases. This study illustrates the extremely heterogeneous clinical presentation of myotonic dystrophy in childhood.

Evaluation of two infants with myotonic dystrophy by the McFie's diagram from the results of WISC

In this paper the authors disclose the result of a research carried out on two brothers whose parents were first cousins, being the gene transmitted by the father. The psychological test Wechsler Intelligence Scale of Children (WISC) was used in two occasions in order to assess the verbal and non-verbal skills. FRM and IRM were nine and eleven-year-old respectively, in the first examination, being the former thirteen and the latter fifteen-year-old on the second one. A comparison between the McFie's diagram and the WISC scores was made: the McFie's diagram showed the impairment severity in each cortical lobe when the left hemisphere was compared with the right one. The McFie's diagram was made from WISC's scores: the McFie's diagram showed the impairment severity in each cortical lobe when the left hemisphere was compared with the right one. On the second examination the performance was worse than in the first, mainly in the non-verbal aspects. The IRM's diagram showed a reduction in the right frontal and parietal lobes. In the FRM's diagram a reduction in the left frontal, temporal and parietal lobes, and also, in the right parietal lobe was found. The visual-spatial constructive aspects showed greatest impairment in this result.

Mechanisms of sustained ventricular tachycardia in myotonic dystrophy: implications for catheter ablation

BACKGROUND

Ventricular arrhythmias have been documented and linked to the high incidence of sudden death seen in patients with myotonic dystrophy. However, their precise mechanism is unknown, and their definitive therapy remains to be established.

METHODS AND RESULTS

We studied 6 consecutive patients with myotonic dystrophy and sustained ventricular tachycardia by means of cardiac electrophysiological testing. Particular attention was paid to establish whether bundle-branch reentry was the tachycardia mechanism, and when such was the case, radiofrequency catheter ablation of either the right or left bundle branch was performed. Clinical tachycardia was inducible in all patients and had a bundle-branch reentrant mechanism. In 1 patient, 2 other morphologies of sustained tachycardia were also inducible, neither of which had ever been clinically documented, and both had a bundle-branch reentrant mechanism. Ventricular tachycardia was no longer inducible after bundle-branch ablation, except for a nonclinically documented and nonsustained ventricular tachycardia in the only patient who had apparent structural heart disease.

CONCLUSIONS

A high clinical suspicion of bundle-branch reentrant tachycardia is justified in patients with myotonic dystrophy who exhibit wide QRS complex tachycardia or tachycardia-related symptoms. Because catheter ablation will easily and effectively abolish bundle-branch reentrant tachycardia, myotonic dystrophy should always be considered in patients with sustained ventricular tachycardia. This is especially true if no apparent heart disease is found.

Involvement of the central nervous system in myotonic dystrophy

To investigate the etiological factors responsible for intellectual impairment and mood changes in patients with myotonic dystrophy (DM), we evaluated 14 patients with DM by means of neuropsychological evaluation and magnetic resonance images (MRI). There were significant differences between patients and controls in regard to the Barthel index, Zung's depression scale, attention, verbal fluency and digit span. All patients had ventricular enlargement and white matter abnormalities on MRI. However, the severity was variable and there was no difference in neuropsychological testing between patients with mild ventricular dilatation and those with severe dilatation. On the other hand, significant differences were present between patients with mild white matter lesions and those with severe white matter abnormalities in regard to verbal fluency and attention. Neuropathologic examination of an autopsied brain showed an increase in the interfascicular space of the white matter which produced pallor on myelin staining. The present findings suggested that the white matter abnormalities were the cause of cognitive impairment among patients with DM.

Presentation, clinical course, and outcome of the congenital form of myotonic dystrophy

We report the clinical experience of 18 patients with the congenital form of myotonic dystrophy, the majority of whom were diagnosed during the neonatal period and monitored from 5 to 14 years. Prematurity associated with congenital myotonic dystrophy gives rise to the severest clinical manifestations. Among them, respiratory involvement is common and is the leading cause of death in the neonatal period. Weakness and foot deformities secondary to muscle involvement are the predominant clinical features of this group of patients from birth to age 3 or 4 years. Once muscle strength improves, learning disabilities and behavioral disturbances become the main clinical problems. All our patients, when tested after 5 years of age, had intelligence quotients under 65, clearly below the average intelligence quotient of their mothers (IQ = 80). There is no relationship between the degree of mothers' and patients' disease. No patient has presented problems with routine immunizations, and no complications were observed in the 7 patients who underwent surgery under general anesthesia. Among the surviving patients, no correlation can be established between severity of disease in the neonatal period and the magnitude of sequelae as teenagers. Mental and behavioral disturbances are the factors which mainly influence the long-term management and prognosis of this cohort of individuals.

Positron emission tomography in myotonic dystrophy

Regional cerebral glucose metabolism (rCMRG1) was studied in three patients with myotonic dystrophy by positron emission tomography with 18F-2-fluoro-2-deoxy-D-glucose as the radiotracer. Clinically, all patients presented an organic personality syndrome. Impairment of rCMRG1 was found in all cortical and subcortical regions, particularly in the frontal cortex and the lentiform nucleus. The results suggest that the organic personality changes that occur in myotonic dystrophy reflect widespread cerebral pathology. The metabolic pattern was similar to that seen in normal aging but was qualitatively more severe and is therefore consistent with the classification of myotonic dystrophy as a progeric disease.

Relative disease severity in siblings with myotonic dystrophy

Myotonic dystrophy is an autosomal dominant disorder in which an early-onset form is characteristically inherited from the mother. We studied 17 affected sibling pairs from 15 families in which two or more affected children were born to mothers with myotonic dystrophy. Later-born affected children suffered more severe disease than their first-born siblings in 13 of 17 sibling pairs. Later-born affected siblings displayed significantly more neonatal feeding difficulties, later age when first sitting alone, later age when first walking alone, and a higher incidence of scoliosis. The overall difference in disease severity between affected siblings increased as the age difference between them increased, suggesting that increasing maternal age is a factor in the relative disease severity of affected children. These findings may have relevance for genetic counseling.

Intellectual functions and personality in subjects with noncongenital myotonic muscular dystrophy

Mental retardation and personality disorders are commonly described among the symptoms of myotonic dystrophy. Nevertheless, this tendency is not supported by systematic studies performed on large samples, whose results are controversial. We studied the cognitive functions and personalities of a group of 28 patients, in whom myotonic dystrophy had commenced in juvenile or adult life. The severity of the disease was variable, but all subjects were self-sufficient. Only 7.1% of subjects showed low intelligence with deterioration of perceptual-motor functions. This was not correlated with the severity of their disease. Women had a substantially lower mean Wechsler-Bellevue score than men. The personality function study of the entire group showed no change of psychiatric relevance but did present a depressive attitude with marked somatic concern and difficulties in establishing relationships in social life.

Neuropsychological profile in myotonic dystrophy

Twenty patients with myotonic dystrophy underwent neuropsychological evaluation. Performances were analysed with respect to general cognitive profile, family patterns of cognitive impairment, relation with sex, age, extent of muscular involvement, and sex of affected parent. Results showed severe intellectual deficit in 50% of patients and selective impairment of visuospatial and constructional functions. Female patients showed significantly worse global intellectual status than males. No difference in intellectual level was observed in patients with respect to age, extent of muscular involvement and sex of affected parent. No family pattern of cognitive impairment could be identified. Our results show that an extensive neuropsychological battery can reveal the existence of selective mental impairment. It may provide further data on cognitive impairment onset, progression and relation to muscular involvement.

Congenital myotonic dystrophy in children--a review of ten years' experience

A review of the anaesthetic management of children with congenital myotonic dystrophy anaesthetised at the Royal Children's Hospital over the past ten years is presented. Seven children underwent a total of fourteen anaesthetics. Anaesthetic considerations must include the degree of muscle weakness and hypotonia altering muscle relaxant requirements, aspiration risk due to palatopharyngeal dysfunction, and cardiomyopathy. Succinylcholine caused muscle contracture in a patient without clinical myotonia. This drug should be avoided. Although a low threshold to institute postoperative respiratory support must exist when treating neonates and infants, the older children did not clinically exhibit increased sensitivity to respiratory depressant drugs.

Cerebral ventricular dilation in congenital myotonic dystrophy

Ultrasonography or computed tomography scanning of the brain was performed in 10 infants with congenital myotonic dystrophy between the age of 1 day and 2 months, and showed intracranial abnormalities in all. Ventricular dilation was diagnosed in eight (80%), subarachnoid hemorrhage in one, and white matter infarcts in one. The common finding of ventricular dilation is probably related to developmental brain abnormality dating back to fetal life, because it was already present in three infants scanned on the first day of life. Neonatal asphyxia was present in seven infants, associated with intraventricular hemorrhage in two. The relationship between these changes and mental retardation, which is a common feature in this disease, is unclear.

Evaluation of information-processing speed and neuropsychological functioning in patients with myotonic dystrophy

Patients with myotonic dystrophy (MD) were compared to a control group, matched to the patients in important demographic variables including IQ, on the Sternberg Memory Scanning procedure, to investigate the hypothesis of a selective change in speed of information processing in MD patients. The neuropsychological functioning of these MD patients was also compared to normative data to provide a descriptive picture of their abilities; these results were correlated to the factors of age of onset and duration of the disease. Finally, the MD patients were also compared to the defined control group on the neuropsychological measures. There was little evidence of selective slowness of information processing or particular deficit independent of overall IQ. Neuropsychologically, the MD patients as a group performed at the low average level. There was, however, a wide range of abilities, suggesting that MD patients are not a unitary group in terms of neuropsychological functioning. Age of onset of the disease was important, at least for certain results. Further research of the neuropsychological functioning of MD patients must account for the wide range of results, with more precise measures of actual onset of the disease and muscular weakness, in a longitudinal evaluation.

Cognitive and personality function in myotonic muscular dystrophy

Twenty-nine patients with myotonic dystrophy from 14 families were tested with the Wechsler and Shipley measures of cognitive function. Forty-one per cent of the subjects had little or no physical handicap. Approximately one-third had low Wechsler scores, whereas 7% had relatively high scores. There was a trend for affected females to have poorer cognitive function than males. Limited cognitive ability correlated with maternal inheritance of the gene and severe physical handicap, but there were individual exceptions. Strongest cognitive abilities were verbal and informational, whereas the weakest were immediate recall, abstraction and spatial manipulation and orientation. There was no evidence of intellectual decline with time. Signs of cerebral atrophy on CT scans were uncommon, occurring for certain in only one of 19 subjects. Personality profiles were also constructed for 25 myotonic subjects using interview and MMPI techniques. Forty-four per cent of the subjects had unremarkable personality profiles, 24% had mild personality difficulties and 32% had prominent personality abnormalities. Serious personality difficulty was most common in patients with low cognitive ability and advanced physical handicap. There was no "typical" personality pattern representative of the entire group. It is likely that many personality problems were the result of individuals with limited resources attempting to cope with their physically deforming and debilitating neuromuscular disorder.

Neuropsychological findings in myotonic dystrophy

Although the literature contains several references to clinically apparent cognitive deficits in patients with myotonic dystrophy (MYD), efforts to support these observations with formal testing have been lacking. The current study compared 17 MYD patients with 25 normal controls on an expanded Halstead-Reitan Battery. The MYD group scored worse than the controls on nearly every neuropsychological measure. Significant neuropsychological impairment was present even when tests of motor skills were excluded. There was no relationship between general neuropsychological impairment and degree of weakness, myotonia, or muscle atrophy in the MYD patients. These findings suggest that cognitive impairment can be an important and relatively independent component of the disability in MYD, which should be considered in the clinical evaluation and counselling of persons with this disease.

Teratogens associated with congenital contractures in humans and in animals

An evaluation of over 350 patients in a study of congenital contractures of the joints (arthrogryposis) included a review of family, pregnancy, and delivery histories for teratogenic exposures. Fifteen out of the total 350 patients studied had a possible teratogenic exposure: an infectious agent (viral or bacterial), maternal drug or toxin ingestion, chronic maternal neurologic or muscular illness, or a direct physical insult such as a structural uterine anomaly. Literature was reviewed for all human and animal cases reported with congenital contractures of the joints with an associated teratogenic insult. Those findings are discussed here.

Congenital myotonic dystrophy in Britain. II. Genetic basis

Genetic analysis of 54 sibships containing 70 patients with congenital myotonic dystrophy has shown paternal transmission in only one case, the disorder being maternally transmitted in 51 sibships. No instance of new mutation was found. At least half the sibs were unaffected; 9 sibs were affected without definite congenital involvement. No evidence for genetic heterogeneity was found, most affected mothers having few or no symptoms. There was no disturbance of sex ratio for the affected grandparents, nor in the sibships of the affected parents. The genetic data from this study and from previous published reports support the clinic evidence that the congenital form of myotonic dystrophy results from a maternal intrauterine factor affecting those individuals carrying the myotonic dystrophy gene.

Congenital myotonic dystrophy in Britain. I. Clinical aspects

A clinical and genetic study of congenital myotonic dystrophy in Britain has been carried out in 70 patients from 54 sibships. The clinical aspects are analysed here, and the existence of a syndrome clinically distinct from myotonic dystrophy of later onset is confirmed. Characteristic features included neonatal hypotonia, motor and mental retardation, and facial diplegia. A high incidence of talipes occurs at birth together with hydramnios and reduced fetal movements during pregnancy, factors suggesting prenatal onset of the disorder in many cases. Prolonged survival is the rule after infancy, but the occurrence of numerous neonatal deaths in the sibships suggests the existence of unrecognized cases dying in the neonatal period.

Intestinal absorption in myotonic dystrophy

Forty-four patients with myotonic dystrophy were subjected to various tests for intestinal absorption. A varying number of patients were subjected to the various tests. In one patient (of altogether 11 patients) a pathological vitamin A absorption test was found together with increased faecal excretion of fat and nitrogen. Two of 12 patients showed pathological D-xylose tests. The reason for this may possibly be deficient urine collection. Schilling tests were on the whole normal. Glucose tolerance tests were pathological in 26 of 35 patients. The following pathological findings were made: elevated fasting blood sugar, elevated peak level, delayed return to pretest level, biphasic response and reduced increment in blood glucose levels following loading. The biphasic response seems to be a rather characteristic finding in myotonic dystrophy. The peak concentration was in all except one case reached within 15-60 minutes. Intravenous glucose loading gave normal response curves. The pathological response on oral loading was probably often caused by intestinal motility disturbances and not by malabsorption. Malabsorption seems to be a rare feature of myotonic dystrophy.