Ephaptic transmission of impulses between neighbouring neurons (i.e. coupling of adjacent nerve fibres due to local exchange of ions or local electric fields) leading to excessive or abnormal firing.

1. HEMIFACIAL SPASM:
PATHOPHYSIOLOGY AND
MANAGEMENT
DR LOMESH WANKHEDE
SR NEUROSURGERY

2. INTRODUCTION
Hemifacial spasm:
• movement disorder of the seventh cranial nerve
• brief or persistent, intermittent twitching of the muscles innervated
by the facial nerve.
• usually unilaterally, beginning in the periorbital musculature, but
later on progressing to involve the perioral, platysma and other
muscles of facial expression as well.

3. • Although benign illness, embarrassment and social withdrawal
• and in severe cases even functional blindness due to involuntary eye
closure.

5. EPIDEMIOLOGY
• Prevalence 11 per 100,000
• 2:1 female preponderance
• Begins in fifth to sixth decades, 1 to 6% <30 years, age < 40 years
should prompt search for an underlying secondary cause
• usually sporadic, and familial rare, Bilateral rare (1%)

6. PATHOPHYSIOLOGY
• Root exit/entry zone of a nerve - junction betn the central and
peripheral nerve segments of a cranial nerve. There is a transition
from the central oligodendroglial cells to the peripheral Schwann
cells.
• lack an epineurium, being protected by an arachnoid membrane only.
• Highly susceptible to injury
• mc cause for HFS : ectatic or aberrant blood vessel, which compresses
the facial nerve at this root entry/exit zone leading to local
demyelination

7. 1. Nerve Origin Hypothesis Or The Peripheral Theory:
• Ephaptic transmission of impulses between neighbouring neurons
(i.e. coupling of adjacent nerve fibres due to local exchange of ions or
local electric fields) leading to excessive or abnormal firing.
• Myelination is a natural inhibitor of ephaptic transmission and the
demyelination leads to HFS.
2. Nuclear Origin Hypothesis Or The Central Theory : HFS may results
from the hyperexcitability of the facial motor nucleus due to irritative
feedback from peripheral lesions of the nerve

8. ETIOLOGY
Primary HFS: compression by an aberrant or ectatic vessel,
• anterior inferior Cerebellar artery or
• PICA
• vertebral artery
• vein
• motor analogue of trigeminal neuralgia

11. secondary HFS:
1. Cerebellopontine angle tumours — acoustic neuroma, meningioma
2. Epidermoid, arachnoid cyst, lipoma
3. Arteriovenous malformations — fistulas, venous angiomas and
arterial aneurysms
4. Brainstem lesions — stroke, trauma, demyelinating disorders
5. Infections — otitis media, tubercular meningitis
6. Parotid tumours
7. Bell's palsy

12. CLINICAL FEATURES
• Begins mc in the orbicularis oculi muscle (90%), brief repetitive
contractions of which lead to sudden, involuntary eye closure. This is
typically associated with elevation of the eyebrows — the ‘other
Babinski sign.
• persist during sleep
• paroxysmal clicking sounds in the ear - stapedius muscle
• increase during stress, reading, speaking and sometimes eating while
they abate with relaxation techniques
• natural history of the disease - chronic one with gradual worsening,
spontaneous resolution in less than 10% of cases

13. INVESTIGATIONS
• Diagnosis mainly a clinical one.
• Electromyography(to rule out facial nerve lesions resulting in
denervation),
• MRI
• surgical intervention is being planned need an MR Angiography (with
special high resolution sequences like CISS — constructive
interference in steady state)

15. Differential diagnoses
1. Blepharospasm
2. Tardive dyskinesias
3. Motor tics
4. Psychogenic hemifacial spasm
5. Focal cortical seizures involving the facial muscles
6. Aberrant regeneration after facial nerve injury.

16. • Blepharospam: bilateral synchronous contractions of the orbicularis
oculi. classical differentiation is the lowering of the eyebrow on
closure of eyes (Charcot's sign), whereas there is raising of eyebrows
with each contraction in cases of hemifacial spasm(the other Babinski
sign).
• Tardive dyskinesia - history of exposure to neuroleptic agents or
dopaminergic antagonists, stereotypical movements of the face
(perioral region), neck, trunk, and limbs.

17. • Motor tics are involuntary, brief, repetitive, stereotyped, movements
which can be willfully suppressed which most commonly manifest as
blinking or facial twitching
• Focal cortical seizures involving the facial muscles are continuous,
repetitive, stereotyped movements of the face and head may be seen
in focal motor seizures and may require an electroencephalogram to
differentiate
• Psychogenic hemifacial spasm is characterised by non-patterned
facial movements that vary in intensity and frequency, and are easily
distractible

18. Treatment
• DRUGS:
• carbamazepine, clonazepam, gabapentin
• other drugs like baclofen, anticholinergics and haloperidol
• Botulinum toxin therapy: prevents the calcium-mediated release of
acetylcholine at the nerve terminal preventing impulse generation -
functional reversible paralysis.
• toxin is diluted to a minimal concentration to minimize diffusion and
injected subcutaneously. improvements in as many as 75–100% of
individuals with hemifacial spasm

19. • Therapeutic effect 3–6 days after injection and last around 2–3
months.
• major limiting factor is the cost of therapy and need for repeat
injections at an interval of three to six months.
• mild facial paresis (23%), diplopia (17%), and ptosis (15%)
• botulinum toxin has led to improvement in the symptoms of
depression in these patients, reduced social embarrassment for the
individual, facial feedback hypothesis

20. SURGERY
• surgery is the only modality which can offer complete cure
• procedure of choice is microvascular decompression
• success report of up to 90% in some case series
• surgical option for those patients who either are not responding to
botulinum toxin therapy or prefer to opt for a permanent cure for the
condition.
• patients who are in reasonably good health and are generally younger
than 70 years are potential surgical candidates

21. Positioning
• Lateral or park bench positioning, under general anesthesia, and the
head is secured in three-point pin fixation placed in the lateral
decubitus position.
• A gel roll is placed in the axilla of the dependent side, all pressure
points are padded, and the nondependent arm is supported by a
padded armrest.
• The neck is slightly flexed, head is turned 10 to 20 degrees from the
affected side, vertex of the head is turned 10 to 20 degrees toward
the floor.
• patient is secured to the operative table with straps

23. Incision
• incision is vertical and located 3 to 5 mm medial to the mastoid notch
• approximately 8 cm long that is centered two thirds above and one
third below the mastoid notch.

24. • craniectomy (2.5-3 cm) should extend superiorly to the transverse sinus
and laterally to expose the sigmoid sinus
• dura then is opened in an inverted L-shaped manner 3 to 5 mm parallel to
the sigmoid and transverse sinuses
• retractor is placed beneath the cerebellum, and the cerebellum is elevated
at its inferior lateral margin rather than retracting it from lateral to medial.
The latter may cause traction injuries to the seventh and eighth nerves.
• retractor can be advanced anteriorly under direct vision until the spinal
part of cranial nerve XI comes into view. The arachnoid at this area is
opened sharply, which allows further elevation of the cerebellum and
exposure of the remaining nerves of the jugular foramen

26. • the dissection is carried out just above the ninth nerve, and by
sharply dividing the arachnoid, the cerebellum is gently elevated.
• Proceeding laterally to medially in this manner, the choroid plexus
emanating from the lateral recess of the fourth ventricle soon comes
into view. Its elevation exposes the root entry zone of the seventh
and eighth nerves at the brain stem.
• facial nerve is visible in front of the eighth nerve with its origin slightly
inferior. facial nerve usually has a slightly gray coloration compared
with the pure white appearance of the eighth nerve.

28. • After carefully dissecting the vessel free of the nerve and using the
utmost care not to manipulate either the seventh or the eighth nerve,
an Ivalon sponge or shredded teflon prosthesis is fashioned to fit
between the two

30. • complications:
• post-operative infections
• general anaesthesia complications
• recurrence of disease (20%),
• hearing loss (7–26%),
• transient or permanent facial nerve paralysis,
• CSF leakage (3%).

31. RADIOSURGERY
• Fraioli MF et al. Treatment of Idiopathic Hemifacial Spasm with
radiosuregery … Minim Invas Neurosurg 2010; 53: 34 – 36
Radiosurgery, with a single dose of 8 Gy, was used in the first
patient affected by idiopathic hemifacial spasm and autoimmune
polyneuropathy with severe hypoacusia; hypofractionated stereotactic
radiotherapy, with 15 Gy in 5 fractions of 3 Gy each, was preferred in the
other 2 cases. In all patients, the target consisted of the vestibulocochlear-
facial bundle immediately before its entry into the internal acoustic foramen.
• Results: A marked improvement of symptoms was observed in 2 patients,
and almost complete disappearance in the other case, with no
complications, particularly, auditory.

33. •Thank you