Interictal myoclonus with paroxysmal kinesigenic dyskinesia

Paroxysmal dyskinesias

Paroxysmal dyskinesias are a rare group of movement disorders affecting both adults and children. Based on the events that precipitate the abnormal movements, they are subdivided into paroxysmal kinesigenic dyskinesia (PKD), precipitated by sudden voluntary movements; paroxysmal nonkinesigenic dyskinesia (PNKD), which occurs at rest; paroxysmal exertion-induced dyskinesia (PED), occurring after prolonged exercise; and paroxysmal hypnogenic dyskinesia (PHD), which occurs in sleep. Paroxysmal dyskinesias can be sporadic, familial (autosomal dominant inheritance), or secondary to other disorders. Recent genetic discoveries may aid us in elucidating the pathophysiology of these disorders. PKD has been linked to the pericentromeric region of chromosome 16, PNKD is associated with mutations in the myofibrillogenesis regulator 1 (MR-1) gene on the long arm of chromosome 2 (2q32-36 locus), and PED is associated with mutations in the glucose transporter gene, GLUT1, responsible for glucose transport across the blood-brain barrier. Lifestyle modification to avoid precipitating factors is important in the management of paroxysmal dyskinesias. Medical therapies have not been examined in controlled trials. Nevertheless, anticonvulsants have been found to be extremely effective in treating PKD and are sometimes useful in other types, suggesting that these disorders may indeed represent forms of channelopathies. Drugs such as acetazolamide, anticholinergics, levodopa, and tetrabenazine have been inconsistently successful. In rare cases with medically refractory symptoms, deep brain stimulation has also been employed. Development of successful treatments for the different paroxysmal dyskinesias rests on elucidating the pathophysiology and targeting therapy to treat the underlying perturbation.

[Paroxysmal kinesigenic dyskinesia: a channelopathy? Study of 19 cases]

INTRODUCTION

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by brief episodes of dystonia and choreoathetosis triggered by sudden voluntary movements. Disease onset is seen in the first or second decade. The attacks typically last less than one minute. Three autosomal dominant PKD loci are identified: EKD1, EKD2 and EKD3. EKD1 has an overlap with the locus of the "Infantile Convulsion and Choreoathetosis (ICCA) syndrome". The favorable natural history, the episodic nature of the symptoms and their sensitivity to anticonvulsant therapy suggest channelopathy as a mechanism of PKD.

PATIENTS AND METHODS

We reviewed the clinical features, the family history, the treatment response, the evolution and the technical investigations in 19 affected individuals.

RESULTS

All cases were idiopathic. Ten patients had a positive familial history. Three patients suffered from ICCA syndrome. Some atypical features were seen, such as the association of kinesigenic and nonkinesigenic attacks and the presence of migraine, ataxia, seizures and myoclonus. Acetazolamide responsiveness was seen in two patients.

CONCLUSION

The coexistence of PKD and nonkinesigenic dyskinesia in several patients confirms the earlier described presence of intermediary forms, nonrepresented in the current classification of paroxysmal dyskinesias. Our study results suggest channel dysfunction and basal ganglia involvement in the pathophysiology of PKD.

Visual hallucinations and symptoms of REM sleep behavior disorder in Parkinsonian tauopathies

BACKGROUND

In Parkinsonism, visual hallucinations (VH) and REM sleep behavior disorder (RBD) have been thought to indicate underlying synucleinopathy.

OBJECTIVES

We tested the validity of this hypothesis by searching for VH and RBD symptoms in Parkinsonism related to tauopathies.

METHODS

Patients with progressive supranuclear palsy or corticobasal degeneration were identified via a clinical data bank.

RESULTS

Of 53 patients who expressed study interest by telephone, 44 returned questionnaires. VH occurred in 16% of patients. Similarly, acting out of dreams occurred in 16% of patients. Neither VH nor RBD symptoms were linked to disease duration or dopaminergic medication and there was no mutual association.

CONCLUSION

VH and RBD symptoms also occur in Parkinsonism related to tauopathies, thus refuting the initial hypothesis.