Hemifacial spasm
[6] The intermittent twitching of the eyelid, which can result in forced closure of the eye which gradually spreads to the muscles of the lower part of the face (Typical form- See Image).
Experts have linked hemifacial spasm to facial nerve injury, Bell's palsy and tumors.
The first proposed theory is ephaptic transmission, which is electrical activity crossing from one demyelinated neuron to another resulting in a false synapse.
[8] The second theory involves abnormal activity of axons at the facial nerve root end zone secondary to compressive damage/demyelination.
There appears to be an autosomal dominant pattern of inheritance in these families with low penetrance, and except for a younger age at onset, the clinical features overlap with the idiopathic cases.
Evaluation of single-nucleotide polymorphisms in genes related to vascular change causing compression of blood vessels did not show an association with hemifacial spasm.
Diagnosis begins with a complete neurological exam, including an electromyography (EMG: a test that measures and records electrical activity generated in muscle at rest and in response to muscle contraction), magnetic resonance imaging (MRI: a test that uses magnetic waves to make pictures of structures inside the head), computed tomography (CT scan: a type of x-ray that uses a computer to make pictures of structures inside the head), and angiography (an x-ray exam of the blood vessels when they are filled with a contrast material).
In one study, only 25% of the CT scans showed the abnormality in hemifacial spasm patients, whilst more than half of the MRI imaging demonstrated a vascular anomaly.
MRI imaging is recommended as the initial screening procedure in the assessment of patients with hemifacial spasm.
[15] Microsurgical decompression and botulinum toxin injections are the current main treatments used for hemifacial spasm.
[18] Observational data from studies (the updated review in 2020 did not find any randomized controlled trials) indicates that botulinum toxin is safe and effective in the treatment of hemifacial spasm with success rates of between 76–100%.
Sometimes as a temporary measure, medical treatment can be offered to patients with very mild cases or those who are reluctant to have surgery or botulinum toxin injections.
[26] In another study of 2050 patients who had presented with hemifacial spasm between 1986 and 2009, only nine cases were caused by a cerebellopontine angle syndrome, an incidence of 0.44%.
[4][27][8] Additional advances in understanding the etiology and improving treatments for hemifacial spasm did not occur until the mid-seventies.
The results illustrated nerve-vessel conflicts (or cholesteatoma) to be located at the root exit zone of the facial nerve in all cases.
Biopsies of the root exit zone demonstrated degeneration of axons, denuded axis cylinder and interrupted myelin.
