Photic Blink Reflex in People With Blepharospasm and Increased Blinking

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.

- INCLUSION CRITERIA:

- Must be 18 years or older

- For patients only: fulfill the criteria of

- Primary BPS (either focal or related to segmental dystonia) in accordance with
published criteria or

- Excessive involuntary eyelid closure without sustained OO spasms in accordance
with Conte et al + having a resting blink rate above 15 blinks per minute.

- Ability to give informed consent.

- Ability to comply with all study procedures.

- Agree to consume no caffeine or alcohol for 12 hours before participating in the
testing visits.

EXCLUSION CRITERIA:

Any of the following will exclude PATIENTS from the study:

- Secondary causes of excessive involuntary eyelid closure such as ophthalmologist
disorders involving the ocular surface, tear film, or eyelids.

- Any evidence suggesting a psychogenic movement disorder such as persisting unilateral
or asymmetric symptoms, paroxysmal symptoms, and other inconsistencies such as pain,
associated somatizations, blinking diminished by distraction, unusual sensory tricks,
or unexpected response.

- Botulinum toxin treatment < 3 months prior to a testing visit.

- History of chronic exposure (>3 month) to dopamine receptor blocking agents before the
onset of increased blinking alone or BPS.

Any of the following will exclude BOTH patients and healthy controls from the study:

- Has any major medical problem other than increased blinking or dystonia in patient
groups (such as decompensated chronic diseases or conditions that cause serious
disability such as congestive heart failure/NYHA score greater than or equal to 2,
severe COPD, advanced neoplasia, severe arthritis, HIV/AIDS, blindness).

- Employees, staff or fellows of HMCS in NINDS.

- Has used illegal drugs within the past 6 months based on history. The intent is to
exclude those with drug use that may affect study results.

- Self-reported consumption of more than 7 alcoholic drinks a week in the case of a
woman and 14 alcoholic drinks a week in the case of a man.

- Abnormal findings on neurologic exam (other than increased blinking or dystonia in
patient groups).

- Presence of anatomical or functional eyelid abnormalities other than involuntary
eyelid closure or OOs spasms (including apraxia of eyelid opening, and other disorders
such as tics or tardive syndromes).

- Has a neurologic disorder other than increased blinking or dystonia.

- Has major depression or any major mental disorders (axis I disorders).

- Has had a head injury where there was a loss of consciousness for more than a few
seconds.

- Has a deep brain stimulator, pacemaker or other implantable electronic device subject
to malfunction by electrical stimulation.