Phenotypic variability in familial prion diseases due to the D178N mutation

BACKGROUND

Between January 1993 and December 2003, 19 patients with familial prion diseases due to the D178N mutation were referred to the regional epidemiological registry for spongiform encephalopathies in the Basque Country in Spain, a small community of some 2,100,000 inhabitants.

METHODS

Ten further patients belonging to the same pedigrees were retrospectively ascertained through neurological or neuropathological records. In four of the patients, the diagnosis was confirmed by analysing DNA obtained from paraffin blocks. In this article, we report on the clinical, genetic, and pathological features of the 23 patients carrying the D178N mutation confirmed by genetic molecular analysis. Haplotyping studies suggest a founder effect among Basque born families, explaining in part this unusually high incidence of the D178N mutation in a small community. Only two patients (8%) lack familial antecedents.

RESULTS

We have observed a phenotypic variability even among homozygous 129MM patients. Our findings challenge the currently accepted belief that MM homozygosity in codon 129 is always related to a fatal familial insomnia (FFI) phenotype. Indeed, seven out of 17 patients with a 129MM genotype in this series presented with a Creutzfeldt-Jakob disease (CJD) clinicopathological picture.

CONCLUSIONS

The considerable clinical and pathological overlapping observed among homozygous 129MM patients favours the view that FFI and CJD178 are the extremes of a spectrum rather than two discrete and separate entities. Other genetic or environmental factors apart from the polymorphism in codon 129 may play a role in determining the phenotypic expression of the D178N mutation in the PRNP gene.

A randomised open-label study of tiagabine given two or three times daily in refractory epilepsy

Efficacy and tolerability of tiagabine was evaluated in patients with non-controlled partial seizures in a multicentre, open-label, parallel group study. Tiagabine was administered either two (b.i.d.) or three times daily (t.i.d.) as adjunctive therapy and titrated stepwise to a target of 40 mg/day during a 12-week, fixed-schedule titration period; this was followed by a 12-week flexible continuation period. The primary efficacy endpoint was the proportion of patients completing the fixed-schedule titration period. A total of 243 patients were randomised and received treatment, 123 to b.i.d. and 120 to t.i.d. dosing. Fewer patients in the b.i.d. (76 and 62%) than in the t.i.d. (87 and 72%) group completed the fixed-schedule titration period (OR: 0.562; 95% CI: 0.309-1.008; P=0.0532). The median percentage decrease in all types of seizure (excluding status epilepticus) during the fixed schedule titration period was 33.4% for the b.i.d. and 23.8% for the t.i.d. groups (P=0.9634; Van Elteren's test). The proportion of responders was similar for the b.i.d. and t.i.d. groups. There were no significant differences between dosage regimens in the change in median seizure rates from baseline. Adverse events were more frequent during the titration than the continuation period. Most events were mild and related to the central nervous system. Although their incidence was similar between treatment groups, severity was more frequent in the b.i.d. group. Our results suggest that during titration tiagabine is better tolerated with t.i.d. dosing, but during long-term maintenance, a t.i.d. schedule is as effective and well tolerated as b.i.d.

[Status epilepticus in the elderly]

The status epilepticus in the elderly has not been considered specifically until the last few years. In this report we revised the epidemiological and clinical aspects as well as its etiology, prognostic and therapeutic implications. These group of patients have proper specific conditions. We emphasize the importance off an accurate diagnosis and specific treatment. Finally we present our personal data over pseudo-status and different types of status.

[Idiopathic cerebral gas embolism]

Air embolism to the brain is an accident that may occur in situations that favour the entrance of air into the bloodstream. The clinical diagnosis is sometimes difficult and only the computerized axial tomography may be of invaluable help. We present a rare case of air embolism occurring during sleep in which no apparent causes could be established. This woman had clinical findings of extensive infarction at the right cerebral hemisphere. The axial tomography performed during the first five days showed the presence of air bubbles persisting for three days and areas of infarction and edema during the 3rd-5th day. Magnetic resonance evidenced new areas of infarction in both hemispheres by the 12th day. Application of antiedema therapy was followed by a partial clinical recovery.

[Progressive multifocal leukoencephalopathy associated with leukopenia of unknown (iatrogenic?) origin]

Progressive multifocal leukoencephalopathy is a virtually always opportunistic infection of central nervous system caused by papova viruses, which clinically presents with symptoms and signs of involvement of different encephalic levels. We report a case with a double interest: on the one hand, both clinical features and lesions were limited to the brainstem and cerebellum; on the other hand, the disease developed in a previously healthy female in whom laboratory evidence of immunodeficiency of unknown origin was demonstrated. A reason for immunodeficiency was also not found at autopsy, being speculated that it could have been iatrogenically associated with antidepressant drugs.

[Dementia caused by miliary cerebral metastasis of a hepatocarcinoma]

Different types of tumors account for the etiology of 8.6% of all cases of dementia. Cerebral computed tomography (CT) permits the detection of most of them. The miliary metastasis variety commonly presents as dementia, and CT may then be normal. A patient with late epilepsy after cerebral infarction developed subacute dementia and he subsequently died. Post mortem study disclosed miliary cerebral metastases of a clinically unsuspected hepatocarcinoma. Cerebral CT did not detect the metastases. Although the incidence of hepatocarcinoma is increasing, we are unaware of any similar reported case, as cerebral involvement is exceptional in this condition. Despite its rarity, this case highlights the need to perform thorough neuropathological investigations in dementia.