Interventional_Procedures_for_Trigeminal_Neuralgia by Dr

Report
Interventional Procedures for
Trigeminal Neuralgia
Dr. Edmond Chung
Pain Team
QEH
Contents
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Methods
Theory
Indications
Limitations
Contraindications
Anatomy
Set up
Equipments
Contents (cont’d)
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Technique
Side Effects & Complications
Efficacy
What if the pain recurs ?
Peripheral nerve blocks
Methods
• Chemical – Glycerol
• Radiofrequency thermocoagulation of
Trigeminal Ganglion
• Maxillary & Mandibular nerve blocks
• Peripheral nerve blocks of the branches of
Trigeminal nerve – supraorbital, infraorbital,
mental nerve blocks
Indications
• Trigeminal Neuralgia refractory to noninvasive means of Rx – V1, V2 or V3
dermatomes
Contraindications
• Space-occupying lesions or microvascular
compression in brain, esp brainstem (Check CT
or MRI first!)
• Coagulopathy
• Infection
• Uncooperative patient
• Patient refusal
Anatomy
• Middle cranial fossa
• Dorsal & cranial to foramen ovale
• Medial to the gasserian ganglion is the carotid
artery & cavernous sinus
• V1 (ophthalmic part) – most medial & greatest
distance to the foramen ovale
• V2 (maxillary part) – central
• V3 (mandibular part) – most lateral & superficial
Limitations
• Pts who want to avoid numbness of face as
result of RF
• Pain in V1 dermatome
Equipments
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RF generator
RF cannulae
RF probes
RF ground electrode
X-ray Image Intensifier (C-arm)
Set Up
Technique - landmark
Technique
• Pt on horizontal recumbent position
• Head fixed on a radiolucent head rest by adhesive
bandage
• Under MAC (using TCI / TIVA technique)
• Fluoroscopic guidance
• Essential to obtain an optimal picture of foramen
ovale
• C-arm 45 deg caudal / cranial & 15-20 deg
sideways
Technique (cont’d)
• 22G 10cm RF needle with a 2mm free tip inserted
along the direction of radiation beam (tunnelvision technique)
• N.B. beware piercing of oral mucosa
• Needle advanced towards foramen ovale
• Once needle enters the foramen, a clear “give”
perceived
• Check with lateral view on the depth of
penetration – intersection of clivus & os
petrosum
Technique (cont’d)
• Sensory Stimulation
– Freq : 100 Hz
– Voltage : 0.1-0.5V
• The aim : to elicit paresthesia or pain in the division of
trigeminal nerve, which you wish to lesion
• Motor Stimulation
– Freq : 2 Hz
– Voltage : less than 1V
• If you see contractions of masseter muscle, advance
the needle deeper into the foramen ovale.
Technique (cont’d)
• Lesion mode (additional bolus of IV propofol first) :
– Lesion at 60 deg C for 60 sec
– Allow to wake up after 1st lesion  retest with pin prick or
sensory stimulation
– Adjust position of needle or advance further accordingly
– Re-institute GA
– Repeat lesioning in 5 deg C increments for 60 sec each
– At each stage, allow pt to wake up & retest with pin prick
or sensory stimulation
– Check corneal reflex
Results
• Long term (years) success rates vary from 80 –
90%
Complications
• Corneal anesthesia / hyperesthesia – 13.7%
• Dysesthesia in the treated area 5-7%
• Masseter weakness 1-2%
Morbidity & Mortality
• Low morbidity
• Can be performed on an out-patient basis
• Mortality has not been reported
What if the pain recurs ?
• For repeated RF
• To review with CT or MRI brain at intervals to
exclude SOL
• Refer to Neurosurgery for consideration of
Gamma Knife or Radiosurgery
Maxillary or Mandibular Nerve Blocks
Peripheral Nerve blocks
• Supraorbital nerve block
• Infraorbital nerve block
• Mental nerve block
Thank You

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