Reciprocal inhibition between the forearm muscles in patients with paroxysmal kinesigenic dyskinesia

The Pathogenesis of Paroxysmal Kinesigenic Dyskinesia: Current Concepts

Paroxysmal kinesigenic dyskinesia (PKD) is a movement disorder characterized by recurrent and transient episodes of involuntary movements, including dystonia, chorea, ballism, or a combination of these, which are typically triggered by sudden voluntary movement. Disturbance of the basal ganglia-thalamo-cortical circuit has long been considered the cause of involuntary movements. Impairment of the gating function of the basal ganglia can cause an aberrant output toward the thalamus, which in turn leads to excessive activation of the cerebral cortex. Structural and functional abnormalities in the basal ganglia, thalamus, and cortex and abnormal connections between these brain regions have been found in patients with PKD. Recent studies have highlighted the role of the cerebellum in PKD. Insufficient suppression from the cerebellar cortex to the deep cerebellar nuclei could lead to overexcitation of the thalamocortical pathway. Therefore, this literature review aims to provide a comprehensive overview of the current research progress to explore the neural circuits and pathogenesis of PKD and promote further understanding and outlook on the pathophysiological mechanism of movement disorders. © 2023 International Parkinson and Movement Disorder Society.

Transcallosal conduction in paroxysmal kinesigenic dyskinesia

OBJECTIVES

Detecting whether a possible disequilibrium between the excitatory and inhibitory interhemispheric interactions in paroxysmal kinesigenic dyskinesia (PKD) exists.

METHODS

This study assessed measures of motor threshold, motor evoked potential latency, the cortical silent period, the ipsilateral silent period and the transcallosal conduction time (TCT) in PKD patients. Data were compared between the clinically affected hemisphere (aH) and the fellow hemisphere (fH).

RESULTS

The transcallosal conduction time from the aH to the fH was 11.8 ms (range = 2.3-20.7) and 13.6 ms (range = 2.8-67.7) from the fH to the aH. The difference in TCT in the affected side was significant (p = .019).

CONCLUSION

The findings demonstrated that, although inhibitory interneurons act normally and symmetrically between the motor cortices and transcallosal inhibition was normal and symmetrical between both sides, the onset of transcallosal inhibition was asymmetrical. The affected hemisphere's inhibition toward the unaffected hemisphere is faster compared to the inhibition provided by the fellow hemisphere. These results are consistent with an inhibitory deficit in the level of interhemispheric interactions.

SIGNIFICANCE

This study revealed a defect in inhibition of the motor axis could be responsible in the pathological mechanisms of kinesigenic dyskinesia.

PRRT2 gene mutations: from paroxysmal dyskinesia to episodic ataxia and hemiplegic migraine

OBJECTIVE

The proline-rich transmembrane protein (PRRT2) gene was recently identified using exome sequencing as the cause of autosomal dominant paroxysmal kinesigenic dyskinesia (PKD) with or without infantile convulsions (IC) (PKD/IC syndrome). Episodic neurologic disorders, such as epilepsy, migraine, and paroxysmal movement disorders, often coexist and are thought to have a shared channel-related etiology. To investigate further the frequency, spectrum, and phenotype of PRRT2 mutations, we analyzed this gene in 3 large series of episodic neurologic disorders with PKD/IC, episodic ataxia (EA), and hemiplegic migraine (HM).

METHODS

The PRRT2 gene was sequenced in 58 family probands/sporadic individuals with PKD/IC, 182 with EA, 128 with HM, and 475 UK and 96 Asian controls.

RESULTS

PRRT2 genetic mutations were identified in 28 out of 58 individuals with PKD/IC (48%), 1/182 individuals with EA, and 1/128 individuals with HM. A number of loss-of-function and coding missense mutations were identified; the most common mutation found was the p.R217Pfs*8 insertion. Males were more frequently affected than females (ratio 52:32). There was a high proportion of PRRT2 mutations found in families and sporadic cases with PKD associated with migraine or HM (10 out of 28). One family had EA with HM and another large family had typical HM alone.

CONCLUSIONS

This work expands the phenotype of mutations in the PRRT2 gene to include the frequent occurrence of migraine and HM with PKD/IC, and the association of mutations with EA and HM and with familial HM alone. We have also extended the PRRT2 mutation type and frequency in PKD and other episodic neurologic disorders.

Paroxysmal choreodystonic disorders

Paroxysmal choreodystonic disorders or paroxysmal dyskinesias are a heterogeneous group of movement disorders characterized by recurrent attacks of abnormal involuntary movements. They are classified into four categories according to the precipitant, duration of attacks, and etiology: (1) paroxysmal kinesigenic dyskinesia (PKD), in which attacks are brief and induced by sudden voluntary movements; (2) paroxysmal nonkinesigenic dyskinesia (PNKD), in which attacks occur spontaneously; (3) paroxysmal exertion-induced dyskinesia (PED), in which attacks are brought on by prolonged exercise; and (4) paroxysmal hypnogenic dyskinesia (PHD), in which attacks occur during sleep. Among them, PHD is currently known to be a form of mesial frontal-lobe epilepsy, and has been given the term "autosomal-dominant nocturnal frontal lobe epilepsy" (ANDFLE) in some familiar cases with an autosomal-dominant inheritance. The clinical, etiological and pathophysiological features of PKD, PNKD, and PED are reviewed.

Extended surround inhibition in idiopathic paroxysmal kinesigenic dyskinesia

OBJECTIVE

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent attacks of dyskinesia, in which movement of one body part produces involuntary movements of other body parts. Surround inhibition (SI), a mechanism for suppression of unwanted movements, could be deficient in these patients. To test this idea, we performed a transcranial magnetic stimulation (TMS) study in drug-naive patients with PKD.

METHODS

TMS was set to be triggered by self-initiated flexion of the index finger at different intervals. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of the control TMS at rest. Normalized MEP amplitudes of the patients' self-triggered TMS sessions at different intervals were compared to those of the controls.

RESULTS

During index finger flexion, MEP amplitudes from the little finger muscle were unchanged in both the patients and normal subjects, however, post-movement MEP enhancement observed in the normal subjects was absent in patients with PKD. These results suggest that the functional operation of SI is itself preserved, but that post-movement excitation of surrounding muscles is deficient in PKD.

CONCLUSIONS

This finding may represent that the operation of SI is extended to the post-movement period, perhaps as a compensatory mechanism for preventing unwanted movement in surrounding muscles.

SIGNIFICANCE

While many types of impaired inhibition have been described previously in PKD, this is the first possible example of increased inhibition.

Channelopathy: hypothesis of a common pathophysiologic mechanism in different forms of paroxysmal dyskinesia

Paroxysmal dyskinesias are a rare heterogeneous group of neurologic disorders, characterized by transient sudden choreoathetoid or dystonic attacks without loss of consciousness. This study reports a family with six affected members in three generations, and two sporadic cases of paroxysmal dyskinesia. Familial cases of paroxysmal dyskinesia are affected by idiopathic long-lasting paroxysmal exertion-induced dyskinesia and the sporadic cases by idiopathic short-lasting paroxysmal kinesigenic dyskinesia. Familial cases also suffer from epilepsy, mainly of generalized type, with benign outcome; one sporadic case is affected by migraine. Results presented in this neurophysiologic study include electromyography, somatosensory evoked potentials by median nerve stimulation, somatosensory evoked potentials by posterior tibial nerve stimulation, motor evoked potentials by magnetic transcranial cortical stimulation, visual evoked potentials, brainstem auditory evoked potentials, blink reflex, reflex H, and electroencephalography. The clinical and neurophysiologic findings presented here suggest a condition of hyperexcitability at the muscular and brain level, perhaps as a result of an ion channel disorder, which is in agreement with reports in the literature.