Autosomal dominant nocturnal frontal lobe epilepsy: an electroclinical study of a Norwegian family with ten affected members

Precision treatment with nicotine in autosomal dominant sleep-related hypermotor epilepsy (ADSHE): An observational study of clinical outcome and serum cotinine levels in 17 patients

PURPOSE

To report the clinical outcome of nicotine exposure in patients with autosomal dominant sleep-related hypermotor epilepsy (ADSHE), along with serum concentrations of the major nicotine metabolite cotinine.

METHODS

We recruited 17 ADSHE patients with CHRNA4 mutations (12 with p.S280F and 5 with p.L291 dup). Clinical characteristics were collected from hospital records. A telephone interview was performed on the use and seizure-reducing effect of nicotine applying a six-point rating scale from "none" to very good". Serum concentrations of cotinine were measured in 14 nicotine users.

RESULTS

All patients but one had ever used nicotine. Nine had used snuff; seven were current users. Eleven had used transdermal nicotine; nine were current users. Seven reported long-lasting seizure control, all used nicotine, four transdermal nicotine and three snuff. In 78% of patients using continuous transdermal nicotine, the effect was rated as good or very good. Cotinine concentrations were 453 ± 196 (mean ± SD) nmol/l in seven patients using transdermal nicotine only vs. 1241 ± 494 nmol/l in seven using other forms of nicotine. No correlation with seizure control was found. Three patients experienced improvement with transdermal delivery compared to snuff.

CONCLUSION

This is the hitherto largest observational study supporting a favorable effect of nicotine in this specific seizure disorder. Better seizure control from transdermal nicotine compared to only day-time consumption suggests benefit from exposure throughout the night. According to current clinical experience, patients with uncontrolled ADSHE harboring relevant mutations should be offered precision treatment with transdermal nicotine.

Nicotine: A Targeted Therapy for Epilepsy Due to nAChR Gene Variants

OBJECTIVE

Genetic variants of the neuronal nicotinic acetylcholine receptor (nAChR) cause autosomal dominant sleep-related hypermotor epilepsy. Approximately 30% of autosomal dominant sleep-related hypermotor epilepsy patients are medically intractable. In preclinical models, pathogenic nAChR variants cause a gain of function mutation with sensitivity to acetylcholine antagonists and agonists. Nicotine modifies the activity of nAChRs and can be used as targeted therapy.

METHODS

We reviewed next-generation sequencing epilepsy panels from a single laboratory (GeneDx) from patients at Children's Medical Center Dallas between 2011 and 2015 and identified patients with nAChR variants. Retrospective review of records included variant details, medical history, neuroimaging findings, and treatment history.

RESULTS

Twenty-one patients were identified. Four patients were prescribed nicotine patches for intractable seizures. Three of 4 patients had a clinical response, with >50% seizure reduction.

CONCLUSIONS

Treatment with a nicotine patch can be an effective therapy in epilepsy patients with nAChR gene variants. We propose consideration of transdermal nicotine treatment in intractable epilepsy with known nAChR variants as an experimental therapy. Further clinical trials are needed to fully define therapeutic effects.

Emerging role of the KCNT1 Slack channel in intellectual disability

The sodium-activated potassium KNa channels Slack and Slick are encoded by KCNT1 and KCNT2, respectively. These channels are found in neurons throughout the brain, and are responsible for a delayed outward current termed I KNa. These currents integrate into shaping neuronal excitability, as well as adaptation in response to maintained stimulation. Abnormal Slack channel activity may play a role in Fragile X syndrome, the most common cause for intellectual disability and inherited autism. Slack channels interact directly with the fragile X mental retardation protein (FMRP) and I KNa is reduced in animal models of Fragile X syndrome that lack FMRP. Human Slack mutations that alter channel activity can also lead to intellectual disability, as has been found for several childhood epileptic disorders. Ongoing research is elucidating the relationship between mutant Slack channel activity, development of early onset epilepsies and intellectual impairment. This review describes the emerging role of Slack channels in intellectual disability, coupled with an overview of the physiological role of neuronal I KNa currents.

Neuropsychological disturbances in frontal lobe epilepsy due to mutated nicotinic receptors

Mutations in nicotinic receptor subunits have been identified in some families with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). Normal intelligence has currently been considered the rule, although anecdotal cases with intellectual disability have been reported. We aimed to evaluate the frequency and degree of neuropsychological disorders in ADNFLE associated with nicotinic receptor mutations by testing 11 subjects from four families with a comprehensive neuropsychological assessment. General intellectual function was below the normal range in 45% of the subjects. All were abnormal in one or more executive task. Memory was either more affected than executive functions or equally affected in two thirds of subjects, suggesting a frontotemporal pattern of cognitive impairment. Cognitive dysfunction appears to be an integral part of the broad phenotype of ADNFLE with nicotinic receptor mutations, a fact that has been underestimated until now. The cognitive disorder affects executive functions as well as memory in most subjects.

Topiramate treatment for nocturnal frontal lobe epilepsy

PURPOSE

Aim of this study was to evaluate the efficacy and tolerability of the antiepileptic drug topiramate (TPM) in a sample of patients with nocturnal frontal lobe epilepsy (NFLE).

METHODS

A 24 patients with video-polysomnographically confirmed NFLE received topiramate as single or add-on therapy. They all completed diaries concerning the seizures frequency and complexity and underwent to periodic follow-up visits. We classified the patients as: seizure-free, responders or non-responders.

RESULTS

15 M; 9 F; mean age 29.3+/-10.4 years. The video-polysomnographic recordings showed a wide spectrum of seizures, ranging from repeated stereotypic brief motor attacks to prolonged attacks, with complex and bizarre behaviour; the recorded episodes occurred during non-REM sleep, both stage 2 and stage 3-4. The EEG during wakefulness was normal in all the patients, while seven of them showed epileptiform abnormalities during polysomnography. TPM was administered as single or add-on therapy from 50 to 300mg daily at bedtime. The follow-up duration ranged from 6 months to 6 years. The patients were classified as: seizure-free=6 (25%); responders (reduction of at least 50% of seizures)=15 (62.5%); non-responders=3 (12.5%). The adverse events were: weight loss (6 pts, 25%); paresthesias (3 pts, 12.5%); speech dysfunction (2 pts, 8.3%). All the adverse events disappeared within 3 months.

CONCLUSIONS

In our experience, TPM seems to be effective in about 90% of patients with NFLE. Few of them experienced transitory adverse events. TPM could be included in the options for patients with this form of epilepsy.

Tobacco habits modulate autosomal dominant nocturnal frontal lobe epilepsy

Mutations in neuronal nicotinic acetylcholine receptors have been demonstrated in autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). The beneficial effect of nicotine administration was previously reported in one single case. We investigated the influence of the tobacco habits of 22 subjects from two pedigrees with alpha4 mutations (776ins3 and S248F). Subjects were interviewed with respect to pattern of nicotine intake and seizures. Seizure freedom was significantly associated with tobacco use (P=0.024). All seven nonsmokers with manifest ADNFLE had persistent seizures. Seizure fluctuations, including long remissions, corresponded to changes in tobacco habits in several patients. One patient who recently had begun treatment with transdermal nicotine experienced improvement. We conclude that tobacco appears to be an environmental factor that influences seizure susceptibility in ADNFLE. Inactivation by desensitization of the mutant receptors by nicotine may explain the beneficial effect. The efficacy and safety of transdermal nicotine in ADNFLE should be further explored.

Participation in contact or collision sports in athletes with epilepsy, genetic risk factors, structural brain lesions, or history of craniotomy

✓Despite a plethora of guidelines for return to play following mild head injury, a discussion of when and if an athlete should be allowed to participate in contact or collision sports if he or she sustains a structural brain lesion or after a head injury requiring craniotomy is lacking. The structural lesions discussed include arachnoid cyst, Chiari malformation Type I, cavum septum pellucidum, and the presence of ventriculoperitoneal shunts. Issues unique to this population with respect to the possibility of increased risk of head injury are addressed. The population of athletes with epilepsy and certain genetic risk factors is also discussed. Finally, the ability of athletes to participate in contact or collision sports after undergoing craniotomies for traumatic or congenital abnormalities is evaluated. Several known instances of athletes returning to contact sports following craniotomy are also reviewed.

Clinical and genetic aspects of idiopathic epilepsies in childhood

The identification of the first genes associated with idiopathic epilepsy has been an important breakthrough in the field of epilepsy research. In almost all cases these genes were found to encode components of voltage- or ligand-gated ion channels or functionally related structures. For many other idiopathic syndromes, there is linkage evidence to one or more chromosomes, but the genes have not yet been identified. Identification of the responsible genes and their gene products will further increase the knowledge of the pathogenic mechanisms involved in epilepsy, and will hopefully facilitate the development of drug targets for the effective treatment of epilepsy. This review gives an overview of the clinical characteristics and an update of genetic research of those idiopathic childhood epilepsies for which genes have been identified and the monogenic idiopathic childhood epilepsies for which mapping data are available.

Recent advances on autosomal dominant nocturnal frontal lobe epilepsy: "understanding the nicotinic acetylcholine receptor (nAChR)"

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is characterized by clusters of nocturnal motor seizures, which are often stereotyped and brief. They vary from simple arousals during sleep to dramatic, bizarre, hyperkinetic events with tonic or dystonic features. A minority of patients may experience aura. This disease is caused by various mutations of genes coding for subunits of neuronal acetylcholine receptor comprising the sodium/potassium ion channel. Recent advances in molecular genetics have provided the means for a better understanding of human epileptogenesis at a molecular level, which can facilitate clinical diagnosis and provides a more rational basis of therapy of this form of epilepsy. In this review, we report the recent data in the genetics of ADNFLE.

Evidence for a fourth locus for autosomal dominant nocturnal frontal lobe epilepsy

Mutations responsible for autosomal dominant nocturnal frontal lobe epilepsy have been identified in two members of the neuronal nicotinic acetylcholine receptor gene family: CHRNA4(ENFL1 locus) and CHRNB2 (ENFL3 locus) coding for alpha4 and beta2 subunit, respectively. However, mutations in these genes account for only a minority (less than 10%) of cases. For a third ADNFLE locus (ENFL2) on chromosome 15q24 the gene was not identified. The involvement of the three loci in the pathogenesis of ADNFLE was investigated in 12 unrelated Italian families, selected on the basis of anamnestic and video-polysomnographic data. Compliant family members were typed for polymorphic markers spanning the analyzed chromosome regions. Linkage analyses excluded association of all chromosome regions with ADNFLE in 72% of cases. In two, four and one families it was impossible to ascertain or exclude association with ENFL1, ENFL2, or ENFL3, respectively, however, no mutations have been detected in the nicotinic receptor genes located in these regions. These data strongly suggest that ENFL1, ENFL2 and ENFL3 are minor loci for the disease and point to the existence of at least a fourth locus for ADNFLE.

Temporal evolution and prognostic significance of postoperative spikes after selective amygdala-hippocampectomy

The purpose of this study was to quantify the temporal evolution and to determine the prognostic significance of spikes on serial postoperative EEGs after selective amygdala-hippocampectomy. The authors performed postoperative EEGs 4 months, 1 year, and 2 years after surgery in 31 patients with unilateral mesial temporal lobe epilepsy. Spike frequency was determined ipsilateral to the resection (group I, no spikes; group II, 1 to 10 spikes; group III, 11 to 20 spikes; group IV, more than 21 spikes during the 30-minute recording). The temporal evolution of postoperative spike frequency was assessed, and these parameters were correlated with surgical outcome. Twenty-two patients showed spikes on postoperative EEG. Spike frequency decreased over time in 14 patients, while no changes or minimal changes occurred in seven patients, and spike frequency increased in one patient. Nine patients had no spikes. There was no correlation between occurrence, frequency, and temporal evolution of spikes with postoperative seizure control. The authors' results demonstrate a progressive decrease of spike frequency during the postoperative period after selective amygdala-hippocampectomy, although occurrence, frequency, and temporal evolution of postoperative spikes had no implications on surgical outcome.

Familial partial epilepsy with variable foci in a Dutch family: clinical characteristics and confirmation of linkage to chromosome 22q

PURPOSE

Three forms of idiopathic partial epilepsy with autosomal dominant inheritance have been described: (a) autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE); (b) autosomal dominant lateral temporal epilepsy (ADLTE) or partial epilepsy with auditory features (ADPEAF); and (c) familial partial epilepsy with variable foci (FPEVF). Here we describe linkage analysis in a Dutch four-generation family with epilepsy fulfilling criteria of both ADNFLE and FPEVF.

METHODS

Clinical characteristics and results of EEG, computed tomography (CT), and magnetic resonance imaging (MRI) were evaluated in a family with autosomal dominantly inherited partial epilepsy with apparent incomplete penetrance. Linkage analysis was performed with markers of the ADNFLE (1p21, 15q24, 20q13.3) and FPEVF (2q, 22q11-q12) loci.

RESULTS

Epilepsy was diagnosed in 10 relatives. Age at onset ranged from 3 months to 24 years. Seizures were mostly tonic, tonic-clonic, or hyperkinetic, with a wide variety in symptoms and severity. Most interictal EEGs showed no abnormalities, but some showed frontal, central, and/or temporal spikes and spike-wave complexes. From two patients, an ictal EEG was available, showing frontotemporal abnormalities in one and frontal and central abnormalities in the other. Linkage analysis with the known loci for ADNFLE and FPEVF revealed linkage to chromosome 22q in this family.

CONCLUSIONS

The clinical characteristics of this family fulfilled criteria of both ADNFLE and FPEVF. The frequent occurrence of seizures during daytime and the observation of interictal EEG abnormalities originating from different cortical areas were more in agreement with FPEVF. The observed linkage to chromosome 22q supported the diagnosis of FPEVF and confirmed that this locus is responsible for this syndrome.

Schizophrenia, psychotic illness and other psychiatric symptoms in families with autosomal dominant nocturnal frontal lobe epilepsy caused by different mutations

OBJECTIVES

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is characterized by a strong family history of epileptic seizures, which predominantly occur during sleep. ADNFLE has been associated with mutations in two genes coding for the nicotinic acetylcholine receptor (CHRNA4 and CHRNB2). Thus far, three different mutations have been detected in the CHRNA4 gene, and two in the CHRNB2 gene. The aim of this study was to compare the frequency of psychiatric disorders in two ADNFLE families with different CHRNA4 mutations (776ins3 and Ser248Phe).

METHODS

Information was gathered from hospital charts and therapists, and the family members were assessed by clinical interviews and structured clinical interviews.

RESULTS

Of the 10 individuals diagnosed with epilepsy in the CHRNA4-776ins3 family, at least four had been in contact with psychiatric services. One individual had schizophrenia, while another family member had experienced at least two severe psychotic episodes, and had been taking antipsychotic medications for years. The third family member had been hospitalized at least three times for psychiatric problems. The fourth family member needs help with activities of daily living due to incapacitating apathy, although she does not have a psychiatric diagnosis. Such accumulation of psychiatric problems was not seen in the family with the Ser248Phe mutation.

CONCLUSION

These findings suggest that there may be an association between the 776ins3 mutation and the psychiatric symptoms, a hypothesis that needs further testing.

Sleep-related epilepsy

Sleep is important for the general health of all, but is particularly essential for individuals with epilepsy. In these patients, a complex relationship exists between seizures and sleep, and both must be considered for optimal care. In this review, recent advances in the field of epilepsy and sleep are considered. These include sleep disorders with a specific relationship to epilepsy, the influences of sleep and sleep deprivation on interictal epileptiform discharges, detrimental effects of seizures on sleep, and the effects (good and bad) of epilepsy treatments on sleep.

Absence of alpha7-containing neuronal nicotinic acetylcholine receptors does not prevent nicotine-induced seizures

Nicotine is the primary addictive component in tobacco, and at relatively low doses it affects cardiovascular responses, locomotor activity, thermoregulation, learning, memory, and attention. At higher doses nicotine produces seizures. The mechanisms underlying the convulsive effects of nicotine are not known, but studies conducted on a number of inbred strains of mice have indicated a positive correlation between the number of alpha-bungarotoxin (alpha-BTX) binding sites in the hippocampus and the sensitivity to nicotine-induced seizures. Because alpha7-containing neuronal nicotinic acetylcholine receptors (nAChRs) represent the major binding site for alpha-BTX, mice lacking the alpha7 nAChR subunit were predicted to be less sensitive to the convulsive effects of nicotine. To test this hypothesis, we injected nicotine intraperitoneally in alpha7 mutant mice and found that the dose-response curve for nicotine-induced seizures was similar in the alpha7 +/+, alpha7 +/- and alpha7 -/- mice. The retained sensitivity to the convulsant effects of nicotine could not be explained by the presence of cholinergic compensatory mechanisms such as increases in mRNA levels for other nAChR subunits, or changes in binding levels or affinity for nicotinic ligands such as epibatidine and nicotine. These findings indicate that alpha7 may not be necessary for the mechanisms underlying nicotine-induced seizures.

Sleep-related disorders in neurologic disease during childhood

Sleep disorders commonly are associated with neurologic disorders in childhood. This review discusses primary sleep disorders that affect children with primary neurologic diseases. Primary sleep disorders are discussed as they relate to the primary neurologic disease. In addition, sleep disorders secondary to neurologic disorders commonly seen in the practice of pediatric neurology are reviewed. A useful sleep history to improve diagnostic and therapeutic interventions is outlined.

The wide clinical spectrum of nocturnal frontal lobe epilepsy

Nocturnal frontal lobe epilepsy (NFLE) has become clinically relevant in recent years. NFLE represents a spectrum of clinical manifestations, ranging from brief, stereotyped, sudden arousals, often recurring several times per night, sometimes with a quasi-periodic pattern, to more complex dystonic-dyskinetic seizures and to prolonged "somnambulic" behaviour. Episodes of increasing intensity have been labelled as paroxysmal arousal (PA), nocturnal paroxysmal dystonia (NPD) and episodic nocturnal wandering (ENW). NFLE affects both sexes with a higher prevalence for men, is frequently cryptogenetic and displays a strong familial trait for parasomnias and epilepsy (NFLE). Seizures appear more frequently between 14 and 20 years of age, but can affect any age and tend to increase in frequency during life. Interictal and ictal scalp electroencephalography (EEG) are often normal, the use of sphenoidal leads may be helpful. Carbamazepine taken at night is often effective at low doses, but a third of the patients are resistant to anti-epileptic drugs (AED) treatment. A familial form, characterized by an autosomal dominant transmission, has also been described. Autosomal dominant nocturnal frontal lobe epilepsy is a genetic variant of NFLE, in itself both clinically and biologically heterogeneous. NFLE should be suspected in the presence of frequent stereotyped paroxysmal nocturnal motor events arising or persisting into adulthood. Videopolysomnography is mandatory to confirm the diagnosis.

Independent occurrence of the CHRNA4 Ser248Phe mutation in a Norwegian family with nocturnal frontal lobe epilepsy

PURPOSE

To describe the clinical features of a family from Northern Norway in which autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is associated with a Ser248Phe amino acid exchange in the second transmembrane domain of the neuronal nicotinic acetylcholine receptor alpha4 subunit (CHRNA4). We also tested for evidence of a de novo mutation or founder effect by comparing haplotypes with the original Australian family where the Ser248Phe mutation was first described.

METHODS

Clinical details were obtained from 19 family members. Personal interviews and genetic analysis were carried out in 17. Parts of the coding region of CHRNA4 were sequenced, and two known polymorphisms (bp555/FokI, bp594/CfoI) were typed by restriction analysis.

RESULTS

Eleven individuals had ADNFLE. The haplotypes of the mutation-carrying alleles of affected individuals from the Northern Norwegian and the Australian ADNFLE family are different. The phenotypic expressions are remarkably similar.

CONCLUSIONS

The Ser248Phe mutation occurred independently in both families. Given the rarity of the disease, this suggests that not only the position of a mutation in the coding sequence but also the type of an amino acid exchange is important for the etiology of ADNFLE. The phenotypic similarity of these two families with different genetic backgrounds suggests that the Ser248Phe mutation largely determines the phenotype, with relatively little influence of other background genes.

Sleep and epilepsy

Sleep disturbance in patients with epilepsy is frequently overlooked, but may contribute to decreased daytime functioning and increased seizure activity. Although complicated, the relationship between sleep and epilepsy is becoming clearer. Sleep, and particularly deep non-rapid-eye-movement sleep, increase interictal epileptiform activity. Sleep increases certain seizure types and the rate of generalization of partial seizures, however rapid-eye-movement sleep seems to suppress seizures. Sleep disorders, particularly sleep apnea, exacerbate seizures. Seizures, in turn, can disrupt sleep structure, particularly rapid-eye-movement sleep. An understanding of these relationships is important in seizure control and in maximizing the quality of life for patients with epilepsy.

Electroclinical picture of autosomal dominant nocturnal frontal lobe epilepsy in a Japanese family

PURPOSE

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is the first described partial epilepsy syndrome known to be due to a single gene mutation. We found a first Japanese ADNFLE family with a novel mutation of the neuronal nicotinic acetylcholine receptor (nAChR) alpha4 subunit (CHRNA4) gene. The aim of this report is precisely to describe the electroclinical manifestations of ADNFLE in this family and to compare these findings with those of other families reported previously in the literature.

METHODS

Three affected family members were investigated electroclinically by close clinical observation, interictal EEG, video-EEG monitoring, magnetic resonance imaging, and single-photon-emission tomography. Information about other affected family members was obtained from either the spouse or the parents. Mutations within the CHRNA4 gene were examined in seven family members.

RESULTS

The clinical manifestations and diagnostic findings in the members of this family were consistent with ADNFLE. However, there were intrafamilial and interfamilial variations in clinical features. The seizures of the patients were brief tonic seizures, with hyperventilation in children and secondarily generalized tonic-clonic convulsions in adults. The onset of the children's seizures began in infancy and early childhood. The children's seizures were sometimes provoked by movement and sound stimulation, and did not respond to antiepileptic drugs. On the other hand, the adults' seizures disappeared spontaneously or were easily controlled with carbamazepine. Three children showed hyperactivity, and two children had mild mental retardation. All patients had impaired consciousness during their seizures and no auras. A novel missense mutation (c755C>T) in exon 5 of the CHRNA4 gene was found in four affected family members.

CONCLUSIONS

The electroclinical pictures of a Japanese family with ADNFLE were basically the same as those of other families reported, but with slight differences. ADNFLE is probably not uncommon, and it is very likely that there are unidentified patients with this inherited disorder in Japan.

Recent advances in the genetics of epilepsy: insights from human and animal studies

Progress in understanding the genetics of epilepsy is proceeding at a dizzying pace. Due in large part to rapid progress in molecular genetics, gene defects underlying many of the inherited epilepsies have been mapped, and several more are likely to be added each year. In this review, we summarize the available information on the genetic basis of human epilepsies and epilepsy syndromes, and correlate these advances with rapidly expanding information about the mechanisms of epilepsy gained from both spontaneous and transgenic animal models. We also provide practical suggestions for clinicians confronted with families in which multiple members are afflicted with epilepsy.

Glutamate receptors and transporters in genetic and acquired models of epilepsy

Glutamate, the principal excitatory neurotransmitter in the brain, acts on three families of ionotropic receptor--AMPA (alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid), kainate and NMDA (N-methyl-D-aspartate) receptors and three families of metabotropic receptor (Group I: mGlu1 and mGlu5; Group II: mGlu2 and mGlu3; Group III: mGlu4, mGlu6, mGlu7 and mGlu8). Glutamate is removed from the synaptic cleft and the extracellular space by Na+-dependent transporters (GLAST/EAAT1, GLT/EAAT2, EAAC/EAAT3, EAAT4, EAAT5). In rodents, genetic manipulations relating to the expression or function of glutamate receptor proteins can induce epilepsy syndromes or raise seizure threshold. Decreased expression of glutamate transporters (EAAC knockdown, GLT knockout) can lead to seizures. In acquired epilepsy syndromes, a wide variety of changes in receptors and transporters have been described. Electrically-induced kindling in the rat is associated with functional potentiation of NMDA receptor-mediated responses at various limbic sites. Group I metabotropic responses are enhanced in the amygdala. To date, no genetic epilepsy in man has been identified in which the primary genetic defect involves glutamate receptors or transporters. Changes are found in some acquired syndromes, including enhanced NMDA receptor responses in dentate granule cells in patients with hippocampal sclerosis.