Startle Response in Progressive Myoclonic Epilepsy

In depth behavioral phenotyping unravels complex motor disturbances in Cstb-/- mouse, a model for progressive myoclonus epilepsy type 1

Progressive myoclonus epilepsy type 1 (EPM1) is an autosomal recessively inherited childhood-adolescence onset neurodegenerative disease caused by mutations in the cystatin B (CSTB gene). The key clinical manifestation in EPM1 is progressive, stimulus-sensitive, in particular action-induced myoclonus. The cystatin B-deficient mouse model, Cstb-/-, has been described to present with myoclonic seizures and progressive ataxia. Here we describe results from in-depth behavioral phenotyping of the Cstb-/- mouse model in pure isogenic 129S2/SvHsd background covering ages from 1.5 to 6 months. We developed a method for software-assisted detection of myoclonus from video recordings of the Cstb-/- mice. Additionally, we observed that the mice were hyperactive and showed reduced startle response, problems in motor coordination and lack of inhibition. We were, however, not able to demonstrate an ataxic phenotype in them. This detailed behavioral phenotyping of the Cstb-/- mice reveals new aspects of this mouse model. The nature of the motor problems in the Cstb-/- mice seems to be more complex and more resembling the human phenotype than initially described.

Research Progress in the Study of Startle Reflex to Disease States

The startle reflex is considered a primitive physiological reflex, a defense response that occurs in the organism when the body feels sudden danger and uneasiness, characterized by habituation and sensitization effects, and studies on the startle reflex often deal with pre-pulse inhibition (PPI) and sensorimotor gating. Under physiological conditions, the startle reflex is stable at a certain level, and when the organism is in a pathological state, such as stroke, spinal cord injury, schizophrenia, and other diseases, the reflex undergoes a series of changes, making it closely related to the progress of disease. This paper summarizes the startle reflex in physiological and pathological states by reviewing the databases of PubMed, Web of Science, Cochrane Library, EMBASE, China Biology Medicine, China National Knowledge Infrastructure, VIP Database for Chinese Technical Periodical, Wanfang Data, and identifies and analyzes the startle reflex and excessive startle reaction disorder.

Does Valproic Acid/Na Valproate Suppress Auditory Startle Reflex in Patients With Epilepsy?

BACKGROUND AND OBJECTIVE

Auditory startle response (ASR) was normal in juvenile myoclonic epilepsy whereas it was suppressed in progressive myoclonic epilepsy. However, both groups were using valproic acid/Na valproate (VPA) in different doses. Therefore, we aimed to analyze whether VPA has an impact on ASR in a cohort of epilepsy. For this purpose, we included patients with epilepsy and analyzed ASR in patients who were using VPA.

PATIENTS AND METHOD

We included 51 consecutive patients who had epilepsy and were using VPA between January 2014 and January 2016. Two control groups of 37 epilepsy patients using other antiepileptic drugs (AEDs) and of 25 healthy subjects were also constituted. All participants underwent investigations of ASR and startle response to somatosensory inputs (SSS) under similar conditions.

RESULTS

An analysis of patients using VPA, not using VPA and healthy subjects revealed significantly longer latency and lower probability of orbicularis oculi (O.oc) and sternocleidomastoid responses after auditory stimulation, decreased total ASR probability and longer latency of O.oc response after somatosensory stimulation in patient groups compared with healthy subjects. Multivariate analysis showed type of AED had a role in the generation of abnormalities. VPA, carbamazepine, and multiple AED use caused suppression of ASR. Total ASR probability was decreased or O.oc latency got longer with longer duration of VPA use whereas serum VPA level at the time of investigation did not correlate with total ASR probability.

DISCUSSION

Both ASR and SSS are suppressed by the effect of VPA, especially in patients using for a long period and in patients using other AEDs with VPA. Given the fact that VPA leads to long-standing synaptic changes of dopaminergic transmission, abnormalities of this network may be the more likely cause.