Dystonia

INDEX

 

Blepharospasm is a dystonia of the facial musculature that ranges in severity from an increased blink rate to disabling contractions with pain and visual dysfunction. Blepharospasm is characterized by excessive contraction of the orbicularis oculi muscles, and patients often may attempt eyebrow elevation to overcome the problem.

Meige’s syndrome or segmental cranial dystonia is the association of blepharospasm with oromandibular and sometimes cervical or laryngeal dystonia.

Figure 1. Basic terms of the components of orbicularis oculi

Anatomy

The orbicularis oculi muscle lies in a plane just deep to the subcutaneous tissue; the skin of the eyelids is the thinnest skin in the body and contains very little subcutaneous fat. Thus, the orbicularis oculi muscle may lie just 1 mm below the surface of the skin. The muscle is divided into orbital and palpebral parts:

- Orbital portion forms a wide circle around the orbital rims and interdigitates with other facial muscles. It is under voluntary control and is responsible for tight closure of the eyelids.
- Palpebral part involuntarily and gently closes the eye during blinking and sleep and is further divided into:

Figure 2. Potential preseptal and pretarsal injection sites

 

Treatment
It is recommended to avoid injection:

Commonly a combination of the pretarsal and preseptal injections is useful:

Dose: typically 2-2.5 units Botulinum: total of 5 injections per eye (12. 5 u); total 25 units for both eyes.

 

Figure 3. Commonly used approach, combining pretarsal and preseptal sites.

References