Prof. Dr. Geert Mayer

Hephata Klinik, Dept. of Neurology, Schwalmstadt-Treysa and Philipps University Marburg, Dept. of Neurology, Marburg, Germany

Question. You are one of the authors of the European Federation of Neurological Societies (EFNS) Guidelines on Management of Narcolepsy (Billiard M, et al. Eur J Neurol 2006; 13: 1035-48). Are there any new perspectives in the pharmacological treatment of narcolepsy?
Answer. Narcolepsy is a rare disease. The problem for orphan diseases is that they provide just a small market for new substances. The costs of developing new pharmacological treatments are extremely high, due to the high standards set out by national medical agencies, which require proof of efficacy. Only two products have obtained the approval of the European Medical Association (EMA) in the last 14 years: Modafinil and sodium oxybate.
The hypothesis that narcolepsy is an autoimmune disease has stimulated treatment of early onset narcolepsy with IVIG. The few treatments performed have shown subjective improvement, which could not be confirmed with methods such as the multiple sleep latency test (MSLT) or in bringing CSF hypocretins back to normal levels. Ethical committees did not give their approval to perform a double-blind placebo-controlled study in Europe.
Histamine, which is known to have a major impact on wakefulness and cognitive performance, has been a candidate for investigation in the last 4-5 years. A histamine 3 receptor antagonist has been tested in several sleep disorders in which the main complaint is daytime sleepiness, i.e. narcolepsy, sleep apnoea and Parkinson´s disease. In all diseases, daytime sleepiness was reduced in subjective and objective ratings, whereas specific symptoms as cataplexy, hypnagogic hallucinations and sleep paralysis were not affected.

Q. Are hypocretins already available?
A. Studies in narcoleptic dogs with a phenotype comparable to human narcolepsy have been tested with intravenous and intraventricular application of hypocretin-1. Due to the short half-life of hypocretin, the benefits on cataplexy and sleepiness were extremely short, i.e. lasting up to 5 minutes. Recently a German group applied hypocretin-1 intranasally, the result being normalisation of olfactory dysfunction and stabilisation of REM sleep with a reduction in wake-to-REM transitions. Hypocretin-1 can be purchased, but it is not yet commercially available. It may only really become promising when a stable substance with a half-life that allows it to be applied three times daily can be developed.

Q. You have been one of the first clinicians to work on motor control in narcoleptic patients (Mayer G, Meier-Ewert K. J Sleep Res 1993; 2: 143-8) and you speculated that the motor disorder in REM sleep might still be in the process of developing towards a full-blown REM sleep behaviour disorder (RBD). In a possible lifelong development of a motor disorder starting in NREM sleep, might the onset of narcolepsy represent the turning point for its intrusion into REM sleep?
A. In recent years many authors have shown that narcolepsy is associated with motor disinhibition during all sleep stages. Our studies in a few multiplex families found an association with REM and NREM parasomnias in first degree relatives that was more frequent than the association with excessive daytime sleepiness. Czech narcolepsy specialists found REM sleep behaviour disorder with early onset in children with narcolepsy. The frequency of RBD in narcolepsy is estimated to range from 8-60%. This huge range suggests an overestimation. The high frequencies are instead due to subjective estimates and false attributions, since studies with polysomnography confirm a range of 8-18%. The high association with parasomnias prior to the onset of narcolepsy indicates that even prior to the onset of narcolepsy there are phenomena that indicate instability of the coupling between motor activity and sleep stages.

Q. Would you please explain the difference, if any, between narcoleptic patients with and without RBD?
A. So far we do not have enough data to state clearly whether there are any differences at all. RBD in narcoleptic patients seems to be less violent than the idiopathic RBD that occurs in elderly, multimorbid patients, who are mainly males. The detection of RBD in narcolepsy therefore strongly depends on the phenotype (reported only when strong enough to be noticed by the patients´ partners) and/or the skills of the interviewer and examiner (i.e. finding anamnestic hints of movements in sleep that go beyond leg movements, and on findings of unusual motor activity in the different sleep stages). Our own recent findings from a follow-up investigation carried out after 7-8 years show that some narcolepsy patients with RBD developed neurodegenerative signs, which could indicate that narcolepsy patients with RBD might have a similar course of the disease to that of patients with idiopathic RBD.

Q. As President of the German Sleep Society you know the socioeconomic burden of patients suffering from narcolepsy in your country. In fact you have published on that topic (Dodel R, et al. Sleep 2004; 27: 1123-8) and you pointed out that indirect costs are considerably higher than direct costs. Could you please explain this issue a little more?
A. Narcolepsy is a disabling disease depending on the severity of the symptoms. Excessive daytime sleepiness in most patients is more impairing than cataplexies. The German study on the socioeconomic burden of the disease was performed in hospitalised patients. These are the patients with the severest impairments, meaning that the data are biased and do not necessarily represent the average narcolepsy population. However, the German data have been replicated in the Danish population. The Danish studies were based on the data set of national registers, which include every diagnosed patient. Knowing that the delay in the diagnosis of narcolepsy is still about 8 years from disease onset and that the population that remains undiagnosed is estimated to be 80%, these data show a similar bias.
Most patients develop narcolepsy in their second decade. Confronted with the tight work schedule of most professions in our industrialised life, the patients cannot maintain their work performance sufficiently and constantly. They eventually come to a point where they have to take sick leave and after some time have no other choice but to apply for early retirement. The number of days of sick leave and the number of retirements adds up to the high indirect costs.

Q. Do you think the German figures could be extrapolated to the rest of the EU countries?
A. The confirmation of the German figures by the Danish figures clearly shows that the situation for narcolepsy patients is similar all over Europe. One might think that societies with a higher acceptance of sleepiness and sleep during the daytime should make it easier for narcoleptic patients. This may have been true in the past. However, all eastern and western countries have undergone a process of industrialisation that does not differ in work times and performance demands. Data from Hong Kong and even Japan show similar developments to those in the western countries, although socioeconomic data are not available there.

Q. Health-related quality of life is considerably reduced in patients with narcolepsy to varying degrees (Dodel R, et al. Sleep Med 2007; 7-8: 733-41). In your opinion what kind of measures should be integrated into healthcare guidelines in order to improve the quality of life in these patients?
A. First of all guidelines need to be accepted by health insurance companies which provide the means for diagnostic and therapeutic care of the patients. Very often guidelines are considered to be theoretical publications by scientists that do not take health economy into consideration, i.e. diagnostic procedures are considered to be too costly and clinical diagnosis as sufficient. This often results in an increase in costs, when patients have a different diagnosis and the diagnostic workup considering differential diagnosis has to be performed twice, or when co-morbid disorders are not recognised and treated. This practice possibly leads to false prevalence figures in national registries, as in the Scandinavian countries, where many narcolepsy patients with only clinical diagnoses are included.
Another major problem is that narcolepsy, even though rare, is not a life-threatening disease. The most disabling symptom - excessive daytime sleepiness - is unspecific, which makes it a matter of behavioural misconduct in the public opinion. There is still very much to do to raise awareness of narcolepsy and its societal consequences. The integration of guidelines may be important to a small extent, but more important is the integration of management of the consequences of this disease. This would include counselling for education, choice of profession, security issues at work and traffic, psychoeducation of patients and families and many more features. Much future work needs to be done in this field.

Q. You are the Secretary of the Board of the European Narcolepsy Network (EU-NN) founded in 2007. Could you please summarise the main goals of this association in the past 5 years?
A. The EU-NN is a network of European experts with the objective of promoting European scientific research in narcolepsy, hypersomnia and related fields, and of optimising medical care for patients by improving diagnostic and therapeutic measures. Close cooperation among those involved in treatment, management and research, as well as patients and their family members, is to be developed further and will facilitate the fast exchange of knowledge and information in the field. Therefore the association wants to contribute to and improve the European information and communication structures and to support the establishment of a standardised patient database. The participating centres and members are working in close collaboration and exchanging data to facilitate the progress of high standard clinical and scientific knowledge, and the spreading of this knowledge. The core of the EU-NN is a standardised core database (accessible to all members), which includes patient history data and phenotypical characteristics obtained from blood and CSF analyses. There is also a local database (accessible only to individual centres), which can be customised individually to suit the specific requests of the centres.

Q. How about the EU-NN database? How is it developing?
A. The board of the EU-NN has established the internet-based database, which took some time to integrate a basic data set. The database has entailed quite a lot of work on fine tuning it, by defining the inclusion criteria, the items and the definition of narcoleptic symptoms and co-morbidities that exceed the definitions of the given classifications of the International Classification of Sleep Disorders (ICSD2). Presently, the technical standards are defined and will soon be implemented. Due to strict inclusion criteria that focus on patients diagnosed according to the EU-NN standards, the inclusion of patients is moving forwards slowly, but steadily. Recently the EU-NN has launched its website http://www3.unil.ch/wpmu/eunn/ to provide regular information about sleep disorders, members, scientific activities and conferences. Several scientific publications have been released with a major input by the EU-NN.

Dra. Rosa Peraita-Adrados
Unidad de Sueño y Epilepsia-Neurofisiología Clínica. Hospital Universitario Gregorio Marañón. Madrid

Prof. Juan-Vicente Sanchez-Andrés
Director asociado de Revista de Neurología Departamento médico, Viguera eds.

Categorias
Sueño