What are the causes of blepharospasm?

Causes of Blepharospasm

Blepharospasm is primarily an adult-onset focal dystonia characterized by involuntary contractions of the orbicularis oculi muscles with largely unknown etiology, though it appears to be multifactorial in nature. 1

Primary Blepharospasm

Primary blepharospasm (also called benign essential blepharospasm or BEB) is the most common form and has the following characteristics:

• Demographics and Presentation:

  • More common in women (2.8:1 female to male ratio) 2
  • Typically presents in the fifth and sixth decades of life 3
  • 93% of patients are Caucasian 2

• Contributing Factors:

  • Stress: 72% of patients report a stressful event immediately prior to symptom development 2
  • Genetic predisposition: 32% of patients report a family history of focal dystonia 2
  • Neurological dysfunction: Believed to involve abnormal functioning in the basal ganglia and other brain circuits 1

• Clinical Variants:

  • Pure blepharospasm (50% of cases)
  • Blepharospasm with Meige's syndrome (31% of cases) - involves lower facial muscles
  • Blepharospasm with eyelid opening apraxia (4% of cases) 2

Secondary Causes

While primary blepharospasm is most common, several conditions can cause or be associated with blepharospasm:

• Ocular Surface Disease:

  • Dry eye syndrome
  • Blepharitis (inflammation of the eyelid margin)
  • Meibomian gland dysfunction 4

• Medication-Induced:

  • Though uncommon, certain medications may trigger or worsen symptoms:
    • Dopamine-blocking agents (antipsychotics)
    • Anti-emetics 2

• Neurological Disorders:

  • Parkinson's disease
  • Progressive supranuclear palsy
  • Multiple system atrophy

Exacerbating Factors

Several factors can worsen blepharospasm symptoms:

• Environmental triggers:

  • Bright light and glare (25% report preceding photophobia) 2
  • Wind
  • Air pollution
  • Reading or other visually intensive tasks

• Psychological factors:

  • Anxiety
  • Fatigue
  • Emotional stress

Diagnostic Considerations

When evaluating a patient with blepharospasm:

• Adults presenting with typical blepharospasm generally do not require extensive etiological investigation as the condition is rarely due to an identifiable underlying cause 1

• However, unilateral symptoms, particularly when associated with other neurological findings, warrant further investigation to rule out structural lesions

• The diagnosis is primarily clinical, based on history and observation of involuntary eyelid contractions

Clinical Pearls and Pitfalls

• Differential diagnosis: Distinguish from other causes of eyelid closure:

  • Hemifacial spasm (unilateral, involves other facial muscles)
  • Myokymia (fine twitching of eyelid muscles)
  • Ptosis (drooping rather than squeezing)
  • Blepharitis (inflammation rather than spasm)

• Important caveat: When blepharospasm is associated with blepharitis, treating the underlying inflammation may significantly improve the spasmodic symptoms 4

• Treatment implications: Understanding the cause helps direct therapy:

  • Primary blepharospasm typically responds to botulinum toxin injections (86% improvement rate) 5
  • Secondary forms may respond to treatment of the underlying condition

In summary, while the exact pathophysiology of blepharospasm remains incompletely understood, it appears to involve a complex interaction of genetic predisposition, environmental triggers, and neurological dysfunction, with stress being a particularly common precipitating factor.