From the Guidelines
Hemifacial spasm is most commonly caused by vascular compression of the facial nerve, usually within the centrally myelinated portion of the nerve. This condition is characterized by involuntary muscle contractions on one side of the face, typically beginning with intermittent twitching around the eye and progressing downward to involve other facial muscles. The primary cause of hemifacial spasm is compression of the facial nerve by an aberrant or ectatic blood vessel, most commonly at the root exit zone where the nerve leaves the brainstem 1.
Causes of Hemifacial Spasm
- Vascular compression of the facial nerve by an aberrant or ectatic blood vessel
- Tumors, such as acoustic neuromas or meningiomas
- Vascular malformations
- Aneurysms
- Inflammatory conditions that affect the facial nerve
- Rarely, hemifacial spasm may develop following Bell's palsy or facial trauma as the nerve regenerates improperly
- Some cases are associated with multiple sclerosis or brainstem lesions
The diagnosis of hemifacial spasm typically involves MRI with special attention to the cerebellopontine angle to identify vascular compression or other structural causes 1. Understanding the specific cause is crucial for determining appropriate treatment, which may include medications like carbamazepine or botulinum toxin injections for symptom management, or microvascular decompression surgery to address the underlying compression in suitable candidates. A thorough patient history and physical examination are essential to exclude identifiable causes of facial paresis or paralysis 1.
From the Research
Causes of Hemifacial Spasm (HFS)
- HFS is generally accepted to be caused by pulsatile vascular compression upon the facial nerve root exit zone 2
- The primary culprit vessels found to cause HFS include the anterior inferior cerebellar artery, posterior inferior cerebellar artery, vertebral artery, or a large vein 2
- In some cases, HFS can be caused by tumors at the cerebellopontine angle (CPA) or vascular malformations 3
- Vascular compression of the VII cranial nerve at its root exit zone from the brainstem is also a known cause of HFS 4
- Double compression (DC) in both the root exit zone (REZ) and the cisternal portion (CP) can also cause HFS 5
- Multivessel compression may be challenging and require more than conventional microvascular decompression 6
Types of Vascular Compression
- Neurovascular compression can be categorized into different anatomical portions of the facial nerve, including the root exit point, attached segment, root detachment point, and distal cisternal portion 2
- The severity of compression can be defined as mild (contact without indentation of nerve), moderate (indentation), or severe (deviation of the nerve course) 2
- Multiple compressing vessels can be found in some cases of HFS 2