What is Blepharospasm?
Blepharospasm is a progressive neurological condition characterised by abnormal, involuntary contractions and spasms of the eyelids. The term can be applied to any abnormal twitching of blinking of the eyelid, regardless of the underlying causes. Secondary blepharospasm is associated with another condition or syndrome, such as dry eyes, tardive dyskinesia, or Tourette’s syndrome. It must be differentiated from Benign Essential Blepharospasm (BEB), a type of focal cranial dystonia that involves increased contraction of the eyelid muscles leading to involuntary eyelid closure. Despite having normal eyes, patients with BEB may experience visual disturbances or blindness due to the forced closure of the eyelids.
Early Stage Symptoms:
Blepharospasm symptoms may start gradually, beginning with eye irritation or increased blink rate. In the early stages, it is often triggered by precipitating irritants or stressors, including fatigue, corneal or eyelid irritation, bright lights, and emotional tension. The symptoms often occur frequently during daytime and subside during sleep. Some patients experience absence of symptoms for a few hours upon waking up. As the condition progresses, twitching and spams may intensify and the eyelids may remain shut for several hours, leaving the patient functionally blind. Roughly, 20% of patients will start with a single eye involvement, but all patients will develop bilateral involvement later on.
- Increasing difficulty in keeping the eyes open
- Abnormal tearing
- Ocular pain
- Sensitivity to light
- Spasms that may be alleviated by sensory tricks (pinching the neck, humming, talking, sleeping etc.)
- Visual disturbances
- Psychiatric symptoms (anxiety, depression, and psychosis)
- Other abnormal movements (tics) of the head and neck
Causes of Blepharospasm
The condition was first regarded as a psychopathologic disorder. For several centuries, patients with blepharospasm were considered mentally unstable and were kept in mental asylums. It was only accepted as a type of focal dystonia in the 1970s. The cause of BEB is still unknown; the widely accepted view is due to abnormal functioning of the basal ganglia—a part of the brain that controls the muscles. Dry eye is frequently seen as a precipitating factor. Hereditary predisposition has also been reported to play a role.
Proposed Mechanism and Pathophysiology:
- Overactivity of the facial nerve
- Ion channel problems
- Sensitisation of the trigeminal system
- Family history of tremor or dystonia
- Medications for Parkinson’s disease
- Head or facial trauma
- Irritants: dry eyes, inflammation, bright lights, and meningeal irritation
There is no definitive studies or tests to diagnose blepharospasm. The physician may come up with the diagnosis by ruling out other conditions (diagnosis of exclusion). Clinical diagnosis is made by careful history taking and physical exam. Neurological tests and imaging are of limited use for this condition, and as such, are rarely included in the work-up.
Blepharospasm Treatment Options
There is no available cure for blepharospasm, and most treatment plans only involve the alleviation of symptoms. Management for secondary blepharospasm begins with treatment of any underlying disorder such as conjunctivitis, blepharitis, or corneal irritation. Other treatment options include oral medications and surgery. Pharmacological therapy often produces unpredictable results; symptom relief is short term and only benefits up to 15% of cases.
Botulinum toxin is the treatment of choice for BEB. Many studies have demonstrated the safety and efficacy of neurotoxin injection for blepharospasm. The success rate for this treatment is over 90%. Patients with apraxia of eyelid opening do not respond well to botulinum toxin.
- Botulinum toxin is first diluted to a concentration of 2.5 to 5 units per 0.1mL.
- The starting dose is 12–15 units per side if higher doses are not required.
- Using a 30 or 32G needle, the orbicularis muscle is injected at 4–8 sites per side.
- Avoid the inferomedial orbicularis muscle and the meridian of the eye to avoid diffusion to the levator palpebrae with ptosis, and interference with the lacrimal drainage apparatus.
- The onset of action is about 2–3 days and peaks at 7–10 days.
- The effects of botulinum toxin last up to 3–4 months.
- The patient must follow-up after a month and may undergo reinjection after 3–4 months.
Side Effects and Complications
Most adverse events are transient and self-limiting. These include:
- Discomfort and bruising;
- Dry eyes and partial ptosis;
- Lagophthalmos—the inability to close the eyelids completely;
- And diplopia (rare)—double vision.