Photic Blink Reflex in People With Blepharospasm and Increased Blinking

Blepharospasm Clinical Trial

Official title: Study of the Photic Blink Reflex in Patients With Blepharospasm and Increased Blinking

Status Terminated

Clinical Trial Summary

Background:

Some people who have increased blinking may later develop blepharospasm. Blepharospasm is a neurological disorder that causes involuntary closing of the eyes. Researchers want to learn more about how eyes close in response to different stimuli. They want to study this in healthy people, people with increased blinking, and people with blepharospasm.

Objective:

To learn how light exposure affects people with blepharospasm.

Eligibility:

People ages 18 and older with blepharospasm or increased blinking, and healthy volunteers

Design:

Participants will be screened with:

Medical history

Physical exam

Neurological exam

Participants will have up to 5 visits. The number of visits will depend on the number of tests they opt to have. They can opt to have up to 4 tests. Visits last 60-90 minutes. They cannot drink alcohol or caffeinated drinks for at least 12 hours before visits. Visits could include the following tests:

Evaluation of eyelid movements. This will be video recorded.

Electromyography: Small sticky electrodes are placed on the lower eyelid skin. These are attached to wires. Muscle activity is recorded during blink reflex procedures.

Electrical stimulation: An electrode is placed close to the eyebrow. It will deliver small electrical shocks. The strength of the shocks will be enough to provoke a blink.

Photic stimulation: A lamp is placed in front of the face. It will deliver single or paired flashes. The flashes will be at various intervals and intensities. Participants will wear a patch over one eye during this test.

Combination of electrical and photic stimulation

Clinical Trial Description

Objective:

• The purpose of the first study of this protocol is to improve understanding of the role played by light sensitivity in the pathophysiology of blepharospasm (BPS).

• As a characteristic feature of BPS, the electrocutaneous blink reflex recovery cycle (EBR rc) shows an increased recovery index of R2 compared with healthy subjects.

• In the first study proposed under this protocol we will study the recovery cycle of the blink reflex evoked by a light stimulus (PBR rc) and the effect of a light stimulus on the EBR (MBR rc) in patient with BPS. Since photophobia and increased blinking are common symptoms in this group of patients, we will look for possible correlations between neurophysiological data and the Light Sensitivity Questionnaire (LSQ) or the Blink rate (Brt). The second study proposed under this protocol will explore the PBR rc and the MBR rc in patients with increased blinking alone, a condition indicated as a possible precursor of BPS.

Study population:

We plan to recruit 24 patients with blepharospasm, 24 healthy volunteers (HVs) and 24 patients with increased blinking alone.

Design:

In two different studies, we will compare all the results from the EBR rc, PBR rc and MBR rc between BPS patients (first study) or increased blinking patients (second study) and HVs. We will also look for possible correlation between the neurophysiologic data and the clinical scales acquired during a clinical assessment. In the EBR rc procedure, the supraorbital nerve will be stimulated with paired electrical stimuli at varying ISIs and the EMG response from the orbicularis oculi muscles will be recorded. In the PBR rc procedure, paired light stimuli will be given at varying interstimulus intervals (ISIs) and the EMG responses from the orbicularis oculi will be recorded. In the MBR rc study a weak light stimulation will be given at varying ISIs before an electrical stimulation of the supraorbital nerve. Each experimental procedure will last about 1 hour. There will be one screening visit and up to 4 testing visits per participant. However, participant can either undergo all the experimental procedures or participate in only some of them and will be allowed to participate in two experimental procedures per testing visit.

Outcome measurements:

• EBR rc, PBR rc, MBR rc: the electromyography (EMG) responses at different interstimulus intervals (ISIs).

• Blink rate: number of eye blinks per minute.

• LQs: the total score of the Light Questionnaire Scale.

These results will be compared between the two patient groups and HVs. We will look for possible correlations between neurophysiological and clinical data. ;

Related Conditions & MeSH terms

• Blepharospasm

• NCT number: NCT03263000
• Study type: Observational
• Source: National Institutes of Health Clinical Center (CC)
• Status: Terminated
• Start date: October 30, 2017
• Completion date: April 24, 2019