Hemifacial spasm (HFS)

Definition

A condition of intermittent, painless, involuntary, spasmodic contractions of muscles innervated by the facial nerve in one side of the face only.

May be limited to the upper or lower half of the face only,

Excess lacrimation may be present.

3 following criteria:

Not a sequela of facial palsy;
Chronic in evolution and limiting;
Normal investigations except for the presence of a vascular compression of the seventh CN, generally at its REZ.

Natural history

HFS usually begins with rare contractions of the orbicularis oculi, and slowly progresses to involve the entire half of the face and increases in frequency until the ability to see out of the affected eye is impaired.

Associated (occasionally)

Trigeminal neuralgia,

Geniculate neuralgia;

Painful Tic convulsif = HFS + Trigenubak neuralgia

Vestibular and/or cochlear nerve dysfunction.

Auditory function testing reveals abnormal acoustic middle ear reflex in almost half of patients, indicating some degree of VIII compromise.

Meige’s syndrome: hemifacial spasm with oral movements.

Numbers

More common in women

Lt > Rt

Annual incidence 1/100,000

Prevalence 11/100,000

Presents after the teenage years.

Aetiologies

Primary

Vascular compression syndrome:

The most common etiology (much more common than with trigeminal neuralgia)
Compression of the facial nerve at the root exit zone (REZ) by a vessel,

Artery (Most common)

AICA (pre- or postmeatal): Most common
Elongated PICA,
SCA,
Tortuous VA
Cochlear artery
Dolichoectatic basilar artery
AICA branches

Aneurysm,
Vascular malformation,
Veins (rare)

Idiopathic

Secondary

Tumour compressing the nerve (rare)

Benign tumours or a cyst in the cerebellopontine angle,
Parotid tumours

Multiple sclerosis
Adhesions
Osseous skull deformities

Pagets
Chari malformations

Infection

Otitis media
TB meningitis

Can follow some cases of Bell’s palsy

Pathophysiology

Peripheral theory

Cross (ephaptic) conduction at the compressed REZ,

HFS due to aberrant connections between arterial sympathetic plexus and facial nerve. Sympathetic activity during stress results in an increase in HFS symptoms.

Zheng 2012

Central theory

Hyperexcitability of facial motor nucleus due to irritative feedback from peripheral nerve
Pulsatile compression of the facial nerve at REZ → functional changes (hyperactivity) in the facial motor nucleus,

Vessel compression

AICA 43%
PICA 31%
Vertebral Artery 23%
Multiple compressions being found in as many as 40%

Offending vessel approaches the nerve at a right angle, and causes grooving in the nerve.
Transition zone 2.5mm from brainstem

May be provoked by

Variety of peripheral stimuli
Emotional events conveyed via brainstem reticular formation

Electrophysiology evidence

Spasm
Synkinesis

Where stimulation of one branch of the facial nerve results in delayed discharges through another branch (average latency: 11 mSec)

Lateral spread evoked responses

Presentation

Typical HFS

Onset in the orbicularis oculi, and progressing downward over the face
Compression: on the antero-caudal aspect of the VII/VIII nerve complex;

Atypical HFS

Beginning in the buccal muscles and progressing upward over the face
Compression at rostral or posterior to VII

Involuntary strictly unilateral tonic and/or clonic contractions of the facial muscle and platysma

Babinski - 2 sign

During contractions, the eyebrow raises while the eye is closed. Patients without the condition cannot reproduce this

Spasms cannot be voluntarily suppressed

Spasm persist during sleep

HFS and palatal myoclonus are the only involuntary movement disorders that persist during sleep.

Vessels contacting the REZ of the

Vestibular nerve

Vertigo

Cochlear nerve

Tinnitus or hearing loss

Patients with this condition is that the spasms are often wrongly thought initially to be psychogenic

Patient can hear clicking sounds or muffled sounds in ear ? Stapedius muscle activity

Evaluation

In typical cases of HFS, the diagnostic work-up is negative.

Most patients should have MRI of the posterior fossa (CT scan is less sensitive here) to R/O tumors or AVMs.

The neurovascular compression responsible for HFS usually cannot be identified on angiography.

CISS

Differential diagnosis

Blepharospasm

Bilateral spasmodic closure of the orbicularis oculi muscles
Eyes close and hard to open

In HS the eye open and closes almost like a tremor

More bilateral

HS is unilateral

More common in the elderly
May be associated with organic brain syndrome.
Blepharospasm is notorious for disappearing when the patient presents for medical evaluation (an effect of alerting), but may be elicited by asking the patient to gently close the eyes and then rapidly open them, following which a blepharospasm may occur.
HFS usually involves more than the ocular muscles

Facial myokymia:

Continuous facial spasm
Wiggle of the muscle of the face
May be a manifestation of an intrinsic brainstem glioma or of multiple sclerosis.
Often associated with other findings
What are the only involuntary movement disorders that persist during sleep? Hemifacial spasm and palatal myoclonus

Tardive dyskinesia

Motor tics and synkinesia after facial nerve injury

Oromandibular dystonia

Presents with involuntary, repeated, sustained muscle contractions that affect primarily the lower part of the face, the mouth, the mandible and maxilla, the tongue, and the pharynx.

Facial nerve tic

Presents with more complex, coordinated, multifocal movement patterns and switches between the right and the left of the face.
Facial nerve tic can be suppressed but HS cannot be

Simple focal seizures

Can also be confused with hemifacial spasm if they affect the facial muscles.

Hemimasticatory spasm describes painful contractions of the muscles of mastication.

Synkinesias after facial nerve paralysis also lead to activation of several muscles innervated by the facial nerve. Typically this only occurs in the context of voluntary movement.

Motor tics

Meige syndrome

In all the above conditions, movement disappears during sleep and “Babinski’s other sign” is absent.

Treatment

Medical

Poor efficacy
Monitor

Early, mild cases

Local injection of botulinum toxin (Oculinum®) may be effective in treating HFS and/or blepharospasm.

Blockade of calcium dependent acetylcholine release at neuromuscular junction → reversible paralysis of affected muscle
Clinical effects after couple of days and last 3 months

Baclofen has been advocated but is not very effective.
Carbamazepine and phenytoin are generally ineffective (vs trigeminal neuralgia)

Surgical

General information

Many ablative procedures are effective for HFS (including sectioning of divisions of the facial nerve);

However, this leaves the patient with some degree of facial paresis.

General

Endoscopic/microscopic assisted
Aim to eliminate the neurovascular conflict
Retrosigmoid craniotomy. Neuromonitoring with facial nerve EMG and auditory evoked potentials.

Enables early recognition of any change in function

Open the CPA, expose the facial nerve.
Insert Teflon pledget between the vessel and nerve. Can also use teflon sling.

Offending vessel is physically moved off of the nerve and a sponge is interposed as a cushion.
If patients have severe symptoms — early surgery is recommended. (once structural damage of facial nerve present, lower regression of symptoms following decompression)
Type of interpositioning material

Best: Sponge best (e.g. Ivalon®, polyvinyl formyl alcohol foam)
Other not good

Muscle may disappear
Teflon felt may thin.

Decompression of vessels impinging at root entry zone

Decompression distal to root entry zone is usually ineffective.

Operative risks:

Ipsilateral hearing loss:

May occur from traction injury or a vasospasm
Total hearing loss occurs in ≈ 13%

Range: 1.6–15%

Partial hearing loss: 6%

Facial weakness

Transient: 18%
Permanent facial weakness: 6%

Ataxia: 1–6%
Other complications that are minor or temporary include:

Aseptic meningitis (AKA hemogenic meningitis): 8.2%
Hoarseness or dysphagia: 14%
CSF rhinorrhoea in 0.3%
Perioral herpes in 3%

Stroke 0.1%,
Mortality 0.1%

Postoperatively

May be episodes of mild HFS, but they usually begin to diminish post op 2–3 days.
Surgical results of MVD depends on the duration of symptoms

Technique of MVD

‘Keyhole’- type retromastoid craniotomy, of 2 cm to 1.5 cm in size,
Posterior to the tip of the mastoid process so that the facial nerve be reached from below, inferolaterally to the cerebellar flocculus
Infrafloccular route chose because

NVCs are generally located ventrocaudally at brainstem.
A lateral- to- medial retraction of the cerebellar hemisphere would exert stretching on the eighth nerve with risk on hearing.

This is warned by an increase in latency of peak III and V on intraoperative BEAP recordings

Protection of 7th and 8th

Intraoperative brainstem auditory evoked potential (BAER), or more applicable, direct VIII nerve monitoring may help prevent hearing loss during MVD for 7th or 8th nerve dysfunction.

Furthermore, monitoring for the disappearance of the (delayed) synkinetic response may aid in determining when adequate decompression has been achieved
For a diagram of the normal anatomy of the CPA, see anatomy

The facial nerve should not be manipulated, and one should avoid dissection around the VII and VIII nerves near the IAC.

Vessels must be preserved, especially the cochlear artery and small perforators.

During mobilization of the compressive artery(ies), care must be taken not to avulse perforators and not to manipulate AICA as well as the labyrinthine artery.
Mechanical vasospasm → cochlear ischaemia.

A warning sign is decrease in amplitude of peak I on BEAPs recordings

Place gentle medial traction on the cerebellum (< 1cm is recommended), and incise the arachnoid membrane between the flocculus and the eighth nerve (to avoid tension on nerves that could cause post-op deficit).
The IX nerve may be followed medially from the jugular foramen to locate the origin of the VII nerve (the origin of VII is 4mm cephalad and 2mm anterior to that of the IX nerve).
The conflicting loop(s) is (are) maintained apart with a piece of material:

Teflon (PTFE Felt)

Made from bundles or balls by stripping filaments from mattress.

‘Edwards Outflow Tract Knitted PTFE’ is used to make (rigid) plates for interposition.
‘Sauvage Knitted Polyester’ is used to make (supple) sheets for interposition.

Attention should be brought not to exert any neocompressive effect on the facial and/ or the vestibulocochlear nerve, as well as not kinking the arteries.
Regular irrigation with (a few) droplets of 10% papaverine in normal saline solution is wise to release constrictive vasoreactions.

Excessive use of concentrated solution would be toxic because of the very acid pH of papaverine.

Intraop monitoring

In patients with HFS, stimulation of the facial nerve, one of its branches, gives rise to repetitive and spreading EMG responses in the facial muscles, innervated by the other branch.
Intraoperative running EMG recordings of lateral spread responses (LSR) during MVD, was advocated by Møller and Jannetta to ensure that adequate decompression has been achieved

Long-term relief was obtained even in patients in whom LSR remained present at end of MVD we doubt about that reliability of LSR monitoring (Hatem et al., 2001)

BEAP recordings

Severe spasm that does not abate suggests failure to achieve adequate decompression, and reoperation should be considered.

Surgical results

Good prognostic indicator

Shorter duration of symptoms
Younger patients do less well

High success rates spasm-free initially (90-95%),

Cure may be delayed by several months to one year

Delayed cure strongly supports that HFS is not only due to mechanical pulsations of an elongated artery against the REZ of the nerve.
Demyelination of fibres and hyperactivity in the facial motor nucleus induced by the chronic vascular compression likely play a role.
Delay could be explained by the time necessary for reversal of the plastic electrophysiological changes, especially those in the nucleus that are considered as having caused the symptoms

Resolution (Overall symptom free patients = 75-85% )

Complete resolution of spasm occurs in ≈ 85–93%.
Spasm is diminished in 9%,
Unchanged in 6%.

29 patients with complete relief,

25 (86%) had immediate post-op resolution,
4 patients took from 3 mos to 3 yrs to attain quiescence.

Recurrence

Recurrence in 25%
Return of symptoms after a period of complete resolution of HFS occurs in up to 10% of patients,

86% of recurrences happen within 2 yrs of surgery, and the risk of developing recurrence after 2 yrs of post-op relief is only ≈ 1%.

Mortality was less than of 1%

Complications

Cerebellar infarct or haemorrhagic complication: 0.50%
CNs injury

Permanent hearing loss with sufficient residual function 2.45– 15.90%
Permanent hearing loss with non sufficient residual function 1.18– 2.60%

Permanent facial nerve palsy, of any degree, initial and irreversible: 0.8 and 5.0%
Delayed facial palsy

That generally occurred around the end of the first post- op week
Present in 7.3%
This symptom— whose mechanism remains unknown – was totally reversible within several weeks to a few months in almost all patients.

Lower CNs

Hoarseness, dysphagia, swallowing difficulties,
0.44% to 2.18%

CSF leakage:

Present as

Middle ear effusion
Pseudomeningocele
Rhinorrhoea, with eventual meningitis.

Occurrence is minimized by careful tight closure.

Postop issue

Failure to relieve spasm / recurrence

Low pressure headache

Nausea and vomiting

Hearing

Swallowing

Mobilisation

Hemifacial spasm (HFS)

Definition

Natural history

Associated (occasionally)

Numbers

Aetiologies

Pathophysiology

Presentation

Evaluation

Differential diagnosis

Treatment

General information

Surgical results

Postop issue

Images