Inner ear dysfunction in myotonic dystrophy type 1

OBJECTIVES

Myotonic dystrophy type 1 is associated with various oculomotor, vestibular, and auditory abnormalities. However, auditory system investigation has been mainly performed with the subjective method of pure-tone audiometry. In this study, a detailed vestibular and audiological evaluation was undertaken, including the objective and more sensitive method of transiently evoked otoacoustic emissions (TEOAEs).

MATERIALS AND METHODS

Twenty-four patients with genetically diagnosed myotonic dystrophy type 1 and 21 controls were studied. Audiological and vestibular investigations included pure-tone audiometry, tympanometry, auditory brainstem responses (ABRs), TEOAEs, and electronystagmography.

RESULTS

Hearing impairment was evident in 15 (62.5%) patients and in nine of them (37.5%) ABR abnormalities were found. However, subclinical cochlear damage was found in all patients, as evidenced by absent emissions or lower otoacoustic emission amplitude. Vestibular hypesthesia was found in nine patients (37.5%), accompanied by spontaneous nystagmus in four of them (15.6%).

CONCLUSIONS

Auditory and vestibular abnormalities are quite common in patients with myotonic dystrophy type 1. However, it appears that subclinical cochlear damage is an ubiquitous finding of the disease.

Huntington's disease in Greece: the experience of 14 years

A large scale genetic and epidemiological study of Huntington's disease (HD) was carried out in Greece from January 1995 to December 2008. Diagnostic testing was carried out in 461 symptomatic individuals, while 256 were tested for presymptomatic purposes. The diagnosis of HD with a CAG expansion ≥ 36 was confirmed in 278 symptomatic individuals. The prevalence of HD in Greece was estimated at approximately 2.5 to 5.4:100,000, while the mean minimum incidence was estimated at 2.2 to 4.4 per million per year. The molecular diagnosis of HD was confirmed in the majority of patients (84.4%) sent for confirmation. The false-positive cases 15.6% were characterized by the absence of a family history of HD and the presence of an atypical clinical picture. The uptake of predictive testing for HD was 8.6%. A prenatal test was requested in six pregnancies. The findings of our study do not differ significantly from those of similar studies from other European countries despite the relative genetic isolation of Greece. Of interest is the identification of clusters of HD in Greece. The presence or absence of a family history of HD should be interpreted cautiously, during the diagnostic process.

Absence of aprataxin gene mutations in a Greek cohort with sporadic early onset ataxia and normal GAA triplets in frataxin gene

Phenotype of patients with the aprataxin gene mutation varies and according to previous studies, screening of aprataxin gene could be useful, once frataxin gene mutation is excluded in patients with normal GAA expansion in frataxin gene. In the present study, we sought to determine possible causative mutations in aprataxin gene (all exons and flanking intronic sequences) in 14 Greek patients with sporadic cerebellar ataxia all but one without GAA expansion in frataxin gene (1 patient was heterozygous). No detectable point mutation or deletion was found in the aprataxin gene of all the patients. Our results do not confirm the previous studies. This difference may be attributed to the different populations studied and possible different genetic background. It is still questionable whether the screening for aprataxin mutation in Greek patients' Friedreich ataxia phenotype is of clinical importance; larger, multicenter studies are necessary to clarify this issue.

Genotyping of presenilin-1 polymorphism in amyotrophic lateral sclerosis

The mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis are not fully understood. Recent studies suggest that apoptosis is involved in the abnormal neural death that occurs in this devastating disease. Presenilin-1, a transmembrane protein, seems to be implicated in apoptosis. To determine whether presenilin-1 intron 8 polymorphism has an influence in the course of amyotrophic lateral sclerosis, we examined this polymorphism genotypes in a large group of patients (n = 72) with amyotrophic lateral sclerosis and in a random sample of 213 healthy individuals. The results showed a significant difference in genotype (P < 0.04) and allele (P < 0.03) distribution between patients controls. These results suggest a possible intervention of presenilin-1 in the pathogenesis of amyotrophic lateral sclerosis.

Apolipoprotein E epsilon4 allele as a genetic risk factor for left ventricular failure in homozygous beta-thalassemia

In homozygous beta-thalassemia, the organ damage is mainly attributed to excessive iron deposition through the formation of oxygen free radicals. Despite appropriate transfusion and chelation therapy and low ferritin levels, patients still develop organ failure, heart failure being the main cause of death. This study was designed to determine whether the decreased antioxidant activity of the apolipoprotein E (APOE) 4 allele could represent a genetic risk factor for the development of left ventricular failure (LVF) in beta-thalassemia homozygotes. A total of 251 Greek beta-thalassemia homozygotes were studied. Patients were divided in three groups: group A (n = 151) with no cardiac impairment, group C (n = 47) with LVF, and 53 patients with LV dilatation and normal LV systolic function constituted the group B. DNA was obtained from all patients, and the polymerase chain reaction was used to analyze the polymorphism at the APOE locus. The APOE allele frequencies were compared with those of a Greek control sample of 216 healthy blood donors. Patients with no cardiac impairment had an APOE 4 allele frequency (7.9%) not different from population controls (6.5%, P > .05), while patients with LVF had a significantly higher frequency of APOE 4 (12.8%) than the controls (P < .05, odds ratio = 2.11, 95% confidence interval 1.03 to 4.32). The APOE 4 allele may represent an important genetic risk factor for the development of organ damage in homozygous beta-thalassemia.