Adult onset myoclonic Huntington's disease

International Guidelines for the Treatment of Huntington's Disease

The European Huntington's Disease Network (EHDN) commissioned an international task force to provide global evidence-based recommendations for everyday clinical practice for treatment of Huntington's disease (HD). The objectives of such guidelines are to standardize pharmacological, surgical and non-pharmacological treatment regimen and improve care and quality of life of patients. A formalized consensus method, adapted from the French Health Authority recommendations was used. First, national committees (French and English Experts) reviewed all studies published between 1965 and 2015 included dealing with HD symptoms classified in motor, cognitive, psychiatric, and somatic categories. Quality grades were attributed to these studies based on levels of scientific evidence. Provisional recommendations were formulated based on the strength and the accumulation of scientific evidence available. When evidence was not available, recommendations were framed based on professional agreement. A European Steering committee supervised the writing of the final recommendations through a consensus process involving two rounds of online questionnaire completion with international multidisciplinary HD health professionals. Patients' associations were invited to review the guidelines including the HD symptoms. Two hundred and nineteen statements were retained in the final guidelines. We suggest to use this adapted method associating evidence base-medicine and expert consensus to other rare diseases.

Myoclonus and epilepsy

Epileptic myoclonus can be defined as an elementary electroclinical manifestation of epilepsy involving descending neurons, whose spatial (spread) or temporal (self-sustained repetition) amplification can trigger overt epileptic activity and can be classified as cortical (positive and negative), secondarily generalized, thalamo-cortical, and reticular. Cortical epileptic myoclonus represents a fragment of partial or symptomatic generalized epilepsy; thalamo-cortical epileptic myoclonus is a fragment of idiopathic generalized epilepsy. Reflex reticular myoclonus represents the clinical counterpart of fragments of hypersynchronous epileptic activity of neurons in the brainstem reticular formation. Epileptic myoclonus, in the setting of an epilepsy syndrome, can be only one component of a seizure, the only seizure manifestations, one of the multiple seizure types or a more stable condition that is manifested in a nonparoxysmal fashion and mimics a movement disorder. This complex correlation is more obvious in patients with epilepsia partialis continua in which cortical myoclonus and overt focal motor seizures usually start in the same somatic (and cortical) region. In patients with cortical tremor this correlation is less obvious and requires neurophysiological studies to be demonstrated.

Genetics of inherited human epilepsies

Major advances have recently been made in our understanding of the genetic basis of monogenic inherited epilepsies. Progress has been particularly spectacular with respect to idiopathic epilepsies, with the discovery that mutations in ion channel subunits are implicated. However, important advances have also been made in many inherited symptomatic epilepsies, for which direct molecular diagnosis is now possible, simplifying previously complex investigations, it is expected that identification of the genes implicated in familial forms of epilepsies will lead to a better understanding of the underlying pathophysiological mechanisms of these disorders and to the development of experimental models and new therapeutic strategies, in this article, we review the clinical and genetic data concerning most of the inherited human epilepsies.

Huntington's Disease and Striatal Signaling

Huntington’s Disease (HD) is the most frequent neurodegenerative disease caused by an expansion of polyglutamines (CAG). The main clinical manifestations of HD are chorea, cognitive impairment, and psychiatric disorders. The transmission of HD is autosomal dominant with a complete penetrance. HD has a single genetic cause, a well-defined neuropathology, and informative pre-manifest genetic testing of the disease is available. Striatal atrophy begins as early as 15 years before disease onset and continues throughout the period of manifest illness. Therefore, patients could theoretically benefit from therapy at early stages of the disease. One important characteristic of HD is the striatal vulnerability to neurodegeneration, despite similar expression of the protein in other brain areas. Aggregation of the mutated Huntingtin (HTT), impaired axonal transport, excitotoxicity, transcriptional dysregulation as well as mitochondrial dysfunction, and energy deficits, are all part of the cellular events that underlie neuronal dysfunction and striatal death. Among these non-exclusive mechanisms, an alteration of striatal signaling is thought to orchestrate the downstream events involved in the cascade of striatal dysfunction.

Symptomatic treatment of Huntington disease

Huntington disease (HD) is a progressive heredoneurodegenerative disease manifested by chorea and other hyperkinetic (dystonia, myoclonus, tics) and hypokinetic (parkinsonism) movement disorders. In addition, a variety of psychiatric and behavioral symptoms, along with cognitive decline, contribute significantly to the patient's disability. Because there are no effective neuroprotective therapies that delay the progression of the disease, symptomatic treatment remains the cornerstone of medical management. Several classes of medications have been used to ameliorate the various symptoms of HD, including typical and atypical neuroleptics, dopamine depleters, antidepressants, antiglutamatergic drugs, GABA agonists, antiepileptic medications, acetylcholinesterase inhibitors, and botulinum toxin. Recently, surgical approaches including pallidotomy, deep brain stimulation, and fetal cell transplants have been used for the symptomatic treatment of HD. The selected therapy must be customized to the needs of each patient, minimizing the potential adverse effects. The primary aim of this article is to review the role of the different therapies, both available and investigational, for the treatment of the motor, psychiatric, behavioral, and cognitive symptoms of HD, and to examine their impact on the patient's functionality and quality of life.

Myoclonus and extrapyramidal diseases

Parkinsonism or dystonia are associated with myoclonus in several extrapyramidal diseases. Although the latter symptom is not always prominent, stimulus-sensitive, distal, or focal reflex myoclonus is frequently observed. This review will consider the clinical and electrophysiological features of myoclonus in Parkinson's disease, multiple system atrophy, corticobasal degeneration, progressive supranuclear palsy, Huntington's disease, dentatorubral-pallidoluysian atrophy, Lewy body dementia, and myoclonus with dystonia. The evidence of a long-latency reflex response, the presence of giant somatosensory evoked potentials, and the demonstration of a back-averaged premyoclonus focal cortical EEG activity often lead to classify myoclonus as a cortical phenomenon. However, a subcortical origin cannot always be ruled out.

Seminar on choreas

Chorea is one of the major types of involuntary movement disorders originating from dysfunctional neuronal networks interconnecting the basal ganglia and frontal cortical motor areas. The syndrome is characterised by a continuous flow of random, brief, involuntary muscle contractions and can result from a wide variety of causes. Diagnostic work-up can be straightforward in patients with a positive family history of Huntington's disease or acute-onset hemichorea in patients with lacunar stroke, but it can be a challenging and complex task in rare autoimmune or genetic choreas. Principles of management focus on establishing an aetiological classification and, if possible, removal of the cause. Preventive strategies may be possible in Huntington's disease where genetic counselling plays a major part. In this review we summarise the current understanding of the neuroanatomy and pathophysiology of chorea, its major aetiological classes, and principles of diagnostic work-up and management.

Huntington’s disease

Although available treatments for Huntington's disease (HD) are imperfect, thoughtful application can positively impact quality of life. Dopamine antagonists can provide control of the troublesome hyperkinetic movements. These agents can also diminish the frequency of hallucinations and delusions when symptoms of psychosis occur. Classical neuroleptics have the widest utilization, although atypical antipsychotics are being increasingly used. Suppression of choreiform movements has also been reported with amantadine and tetrabenazine, which is not currently approved in the United States but under investigation. Alteration in mood can be successfully managed with a variety of antidepressant medications. Superior tolerability and value in the management of a variety of behavioral disturbances have lead to extensive use of serotonin reuptake inhibitors. Modest disturbance of mood can sometimes be addressed with anticonvulsant medications. Considered a manifestation of advanced disease, dementia is less commonly addressed therapeutically. However, gathering experience suggests improved cognitive function can occur with cholinesterase inhibitor therapy. Frequently overlooked is the value of rehabilitation services in the management of diverse symptoms. Although the value of a dysphagia evaluation is apparent, the benefit to be derived from physical and occupational therapy involvement cannot be overstated. Current therapeutic trials will undoubtedly provide additional therapies to moderate symptoms, but once the mechanism(s) of selective striatal projection neuron degeneration are delineated, a revolution in the management of HD will occur.

Dose-dependent improvement of myoclonic hyperkinesia due to Valproic acid in eight Huntington's Disease patients: a case series

Background

Chorea in Huntington's Disease (HD) is usually treated with antidopaminergic neuroleptics like haloperidol, olanzapine and tiaprid or dopamine depleting drugs like tetrabenazine. Some patients with hyperkinesia, however, react to treatment with antidopaminergic drugs by developing extrapyramidal side effects. In earlier studies valproic acid showed no beneficial effect on involuntary choreatic movements. Myoclonus is rare in HD and is often overseen or misdiagnosed as chorea.

Methods

In this report, we present eight patients whose main symptom is myoclonic hyperkinesia. All patients were treated with valproic acid and scored by using the Unified Huntington's Disease Rating Scale (UHDRS) motor score before and after treatment. In addition to this, two patients agreed to be videotaped.

Results

In seven patients myoclonus and, therefore the UHDRS motor score improved in a dose dependent manner. In three of these patients antidopaminergic medication could be reduced.

Conclusion

In the rare subgroup of HD patients suffering from myoclonic hyperkinesia, valproic acid is a possible alternative treatment.

Huntington's disease: present treatments and future therapeutic modalities

Huntington's disease (HD) is a devastating neuropsychiatric disorder for which therapeutic interventions have been rather fruitless to date, except in a slight symptomatic relief. Even the discovery of the gene related to HD in 1993 has not effectively advanced treatments. This article is essentially a review of available double-blind, placebo-controlled trials of therapy for this condition which also includes relevant open label trials. Unfortunately, HD research has tended to concentrate on the motor aspects of the disorder, whereas the major problems are behavioural (e.g. dementia, depression, psychosis), and the chorea is often least relevant in terms of management. We conclude that there is definitely poor evidence in management of HD. The analysis of the 24 best studies fails to result in a treatment recommendation of clinical relevance. Based on data of open-label studies, or even case reports, we recommend riluzole, olanzapine and amantadine for the treatment of the movement disorders associated with HD, selective serotonin reuptake inhibitors and mirtazapine for the treatment of depression, and atypical antipsychotic drugs for HD psychosis and behavioural problems. Moreover, adjuvant psychotherapy, physiotherapy and speech therapy should be applied to supply the optimal management. Finally, some cellular mechanisms are discussed in this paper because they are essential for future neuroprotective modalities, such as minocycline, unsaturated fatty acids or riluzole.

[Myoclonus in the adult: diagnostic approach]

Myoclonus, defined as shock-like involuntary movement, may be physiological or caused by a very wide variety of hereditary and acquired conditions. Because myoclonus can originate from different disorders and lesions affecting quite varied levels of the central and peripheral nervous systems, it represents from many points of view a diagnostic challenge. Moreover, new entities have been recently individualized, such as cortical tremor, which deserve renewed attention. The aim of this review is to propose a rationale for a diagnostic approach based on clinical and electrophysiological grounds. In this setting, we successively address 1) the clinical features allowing a positive diagnosis of myoclonus; 2) the clinical clues to the etiology; 3) the relevance of the clinical context to the diagnosis; and 4) the contribution of neurophysiology. Differentiating myoclonus from tics, spasm, chorea and dystonia can be difficult, and a careful reappraisal of clinical features allowing precise identification is presented. Moreover, the topographical distribution of myoclonus, the temporal pattern of muscle recruitment, the condition of occurrence and the rhythm of the event, may provide clinical clues relevant to the diagnosis. Myoclonus without associated epilepsy, myoclonus with epilepsy, myoclonus with encephalopathy, parkinsonism and/or dementia represent overlapping clinical categories, although they remain useful for the diagnostic approach. Using electrophysiology (including back-averaging EEG, MEG, SEP, C-reflex studies) to determine the origin of myoclonus may not allow us to focus on the underlying condition. Indeed, in many instances, the myoclonus is cortical in origin, but the pathology is found elsewhere.

Safety of intrastriatal neurotransplantation for Huntington's disease patients

Fetal neural transplantation has been shown to be a feasible, safe, and according to a number of recent reports, effective treatment for Parkinson's disease (PD). Fetal striatal transplantation may be as feasible, safe, and effective a treatment for Huntington's disease (HD), a disorder for which there is currently no effective treatment. This report describes our experience with fetal striatal transplantation to adult striatum in three HD patients. Three moderately advanced, nondemented HD patients received transplantation of fetal striatal tissue. The striatal precursor was selectively obtained from the lateral ganglionic eminence. Each patient received bilateral grafts from five to eight donors, placed into the caudate nucleus (one graft on each side) and the putamen (four grafts on each side). All three patients had HD as documented by family history, DNA heterozygosity (17-20 and 48-51 repeats), magnetic resonance imaging (MRI) revealing striatal atrophy, and 2-deoxyglucose positron emission tomography revealing striatal hypometabolism. All patients had been evaluated using the Unified Huntington's Disease Rating Scale and appropriate neuropsychological tests for at least 3 months prior to transplantation. One year following transplantation, MRI of all three patients revealed that the grafts survived and grew within the striatum without displacing the surrounding tissue. No patients demonstrated adverse effects of the surgery or the associated cyclosporin immunosuppression, nor did any patient exhibit deterioration following the procedure. The limited experience provided by these three patients indicates that fetal tissue transplantation can be performed in HD patients without unexpected complications.

Genetic screening for Huntington's disease in Chinese patients with involuntary movements

The diagnosis of Huntington's disease (HD) can be confirmed by detecting the expanded CAG repeat in the IT15 gene. Besides chorea, patients with HD may present with a variety of bizarre involuntary movements, resulting in confusion in making the diagnosis. Under such conditions, genetic analysis is the final confirmatory test. To determine if any patient with involuntary movements of undetermined etiology might be related to HD, we did genetic analysis on 22 patients and identified three with expanded CAG repeat. We could not obtain family history of HD in these patients due to adoption, early death of parents, or a vague history. All three patients were among the group with generalized chorea, but one had additional marked dystonic posturing. Together with four clinically recognizable HD patients, the relative frequency of HD among the 103 patients with choreiform movements in this hospital is 6.8%.

Huntington's disease

Huntington's disease is a genetically inherited degenerative neuropsychiatric disorder, characterized by motor alterations, including involuntary movements such as chorea, dementia and psychiatric disturbances. In this article, the authors review the clinical features of the disease. They also analyze some genetic and pathophysiologic aspects, that can help to improve our understanding of this disorder involving the basal ganglia.

Cortical Myoclonus in Huntington's disease associated with an enlarged somatosensory evoked potential

We report the electrophysiologic findings of myoclonus in a patient with Huntington's disease (HD). This patient was studied postoperatively after a bilateral fetal cell transplant in his striatum. Incomplete transient improvement was seen in the myoclonus, followed by gradual deterioration. The myoclonus itself had a cortical correlate and was associated with an enlarged somatosensory evoked potential (SEP), consistent with the presence of cortical reflex myoclonus. An enlarged SEP has not been previously reported in myoclonus associated with HD. The postulated mechanisms for myoclonus, when it occurs in HD, have differed in the literature. The reason for the transient improvement of the myoclonus following transplantation is unclear, but this case raises the possibility that basal ganglia circuits may modulate cortical myoclonic activity.

Myoclonus in corticobasal degeneration

Five patients with unilateral myoclonus and a clinical diagnosis of corticobasal degeneration (CBD) were studied. All patients showed enhanced long-loop responses in their myoclonic arms without enlarged somatosensory potentials. The cortical relay time of the long-loop responses was studied in three patients, in two of whom it was < 2 ms, even in the nonmyoclonic arm. Myoclonus in CBD is probably related to an enhanced long-loop reflex whose pathway is unlikely to be the same as that in classic cortical reflex myoclonus.

Tourettism associated with Huntington's disease

The identification of the gene for Huntington's disease (HD) has made it possible to diagnose patients with HD who present with unusual or atypical features. We describe a 41-year-old man whose initial manifestation of HD was dominated by the presence of motor and vocal tics and other features of Tourette's syndrome. This case illustrates the broad range of clinical manifestation of HD and the usefulness of testing for the HD mutation in selected cases with familial movement disorders.

Cortical myoclonus in Huntington's disease

We describe three patients with Huntington's disease, from two families, in whom myoclonus was the predominant clinical feature. The diagnosis was confirmed at autopsy in two cases and by DNA analysis in all three. These patients all presented before the age of 30 years and were the offspring of affected fathers. Neurophysiological studies documented generalised and multifocal action myoclonus of cortical origin that was strikingly stimulus sensitive, without enlargement of the cortical somatosensory evoked potential. The myoclonus improved with piracetam therapy in one patient and a combination of sodium valproate and clonazepam in the other two. Cortical reflex myoclonus is a rare but disabling component of the complex movement disorder of Huntington's disease, which may lead to substantial diagnostic difficulties.