Auditory startle response is normal in juvenile myoclonic epilepsy

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.

Evaluation of startle response and prepulse inhibition based on changes in the range of vertical pressure force of the feet on the ground: a preliminary study

The aim of the study was to evaluate the possibility of estimating a startle response and sensorimotor gating based on changes in the range of vertical pressure force of the feet on the ground during a dynamometric examination. The study encompassed 13 healthy and physically fit men (age: 23.3 ± 2.0 years; height: 178.0 ± 6.1 cm; and weight: 76.1 ± 9.0 kg). The inhibitory mechanisms of startle reflex were used as the measure of sensorimotor gating. It was triggered by a strong acoustic stimulus (106 dB SPL, 40 ms), which was preceded by a similar, weaker signal (80 dB SPL, 20 ms). Startle reflex was evaluated using a piezoelectric force platform. The results of the conducted study show that the range of vertical pressure force of the feet caused by the reaction to a strong acoustic stimulus is significantly smaller when this stimulus is preceded by a signal of lower intensity (prepulse). Such assessment is only possible with the participants' eyes open. The generalized startle response of a person may be estimated using a force platform, based on changes in the range of vertical pressure force of the feet on the ground, which are caused by unexpected acoustic stimuli. There is a strong indication that using a force platform to evaluate sensorimotor gating could be used as an alternative to electromyographic examinations.

Startle Response in Progressive Myoclonic Epilepsy

Cortical reflex myoclonus is a typical feature of progressive myoclonic epilepsy (PME) in which it is accompanied by other types of mostly drug-resistant seizures and progressive neurological signs. Although PME is characterized by cortical hyperexcitability, studies have demonstrated atrophy and degenerative changes in the brainstem in various types of PME. Thus, we have questioned whether any stimuli may trigger a hyperactive response of brainstem reticular formation in PME and investigated the startle reflex in individuals with PME. We recorded the auditory startle response (ASR) and the startle response to somatosensory inputs (SSS) in patients with PME, and compared the results with healthy volunteers and patients with other types of drug-resistant epilepsy. All patients were using antiepileptic drugs (AEDs), 12 were on multiple AEDs. The probability of ASR was significantly lower and mean onset latency was longer in patients with PME compared with other groups. SSS responses over all muscles were low in both the PME and drug-resistant epilepsy groups; however, the differences were not statistically significant. The presence of a response over the biceps brachii muscle was zero in the PME group and showed a borderline difference compared with the other groups. Decreased probability and prolonged latencies of ASR in PME indicate inhibition of reflex circuit. A trend for decreased responses of SSS suggests hypoactive SSS in both PME and other epilepsy groups. Hypoactive ASR in PME and hypoactive SSS in both PME and other epilepsies may be attributed to the degeneration of pontine reticular nuclei in PME and functional inhibition by AEDs in both disorders.

Assessment of Startle Response and Its Prepulse Inhibition Using Posturography: Pilot Study

Purpose. The aim of this study was to evaluate the possibility of using static posturography in the assessment of sensorimotor gating. Subjects and Methods. Fourteen subjects took part in the experiment. The inhibitory mechanisms of startle reflex were used as the measure of sensorimotor gating. It was evoked by a strong acoustic stimulus (106 dB SPL, 40 ms) which was preceded by the weaker similar signal (80 dB SPL, 20 ms). A stabilographic platform was used to measure sensorimotor gating. Results. Results of static posturography show that the postural sway caused by the reaction to a strong acoustic stimulus is significantly smaller when this stimulus is preceded by the signal of lower intensity (prepulse). Such assessment is only possible in eyes open conditions. Conclusions. Static posturography can be simple and effective method used for diagnosis of sensorimotor gating in humans.