Post on 13-Jan-2017
Trigeminal Neuralgia
Shikher ShresthaNINAS
History..
Aretaeus of Cappodocia provided one of the earliest descriptions in 2nd century – First account of TN
1756 – The French surgeon Nicholas Andre coined the term “tic douloureux”
1773 – Fothergill described typical features of TN
1820s – Charles Bell attributed this to disease of V nerve
Introduction
Stereotyped, repetitive, unilateral, electric shock like facial pain triggered by non-noxious stimulation with clear pain-free intervals
Excruciatingly painful
50-70 yrs (median age: 67 yrs)
4-5 per 100,000 population
Rt. Side face more common (rt:lf::3:2)
Women:Men::2:1 to 4:3
Etiology
Compression of trigeminal nerve at its exits from the pons by adjacent artery or vein
Cerebellopontine angle tumors 1-2%
AVM
Multiple sclerosis 1-8% - usually bilateral
Pathogenesis
Neural compression by a blood vessel or tumor nerve root demyelination
Demyelination by MS
Demyelination ephaptic transmission or ectopic impulse generation between denuded axons
Calvin et. Al. Comprehensive theory
Utilized two known physiological mechanisms
Trigeminal dorsal root reflex
Repetitive firing of extra action potentials from a focal region of altered axonal size or myelination
Centralist concept and Peripheralist concept
Centralist concept:
altered central connectivity and neuronal hyperactivity caused by deafferentation
Peripheralist concept:
altered peripheral sensitivity to chemical and mechanical stimuli
No theory postulated explains all the aspect like
pain free periods of variable time
triggering of pain by non noxious stimulus
separation of trigger areas from the painful region
response to anticonvulsant
N.B> decompression of the root may relieve pain by facilitating remyelination
IHS criteria for Trigeminal Neuralgia
Clinical Features
Tic douloureux – almost exclusively diagnosed by history
Confined to distribution of oneOr more divisions of trigeminal n.
Lower part of the face more Commonly affected
V2 or its combination with other Division accounts to ~45% cases
V1 – least affected division
Clinical Features continued..
Unpredictable and sudden onset of pain
Severe in degree and short in duration
Many paroxysms of pain within a single hour
Such bouts may go on for days, with some fluctuation In frequency from hour to hour and day to day.
Natural remissions become less frequent and less prolonged with time
Progression of Trigeminal Neuralgia..
Clinical Features contd..
Trigger zones – sensitive areas in face, which when touched cause an attack of pain. Even Gentle breeze can trigger.
Lancinating, lightening like or electrical in quality – likened to the pain experienced when a dentist drills into the pulp of a tooth
Bilateral tic pain – 3% pts. – Although no pt. has bilateral pain during the same episode.
Dentists often seen first – history of multiple tooth extractions!!!tooth in upper jaw – radiation to orbit or face with headache
on the same sidetooth in lower jaw – pain in mandibular region and deep in ear
If prior ablative procedures – pain may have different characteristics
DDx: Atypical pain should also be considered
Atypical paindeep, burning, continual without jabbing onsetradiates behind the ear, down onto the neck, across opp.
Maxilla patient clutch the face unlike trigeminal n. patients who shield their face without touching itMyofascial pain –muscle of mastication and TMJ pain – lateral face
aching, burning or cramping pains, associated with tenderness to palpation of involved muscles
Differential Diagnoses to be considered..
Diagnosis
No imaging or physiological studies currently available substitutes for history
Neurological exam – normal except mild sensory changes in a minority of patients in the region of their pain
IF MS or CPA tumor – clinical findings, which heralds the underlying cause
Diagnosis - MRI
. traditionally normal
. identification of etiological cause as in MS or CPA
. Chiari malformation – trigeminal neuralgia due to venous or arterial compression of cranial n. along tonsillar ectopia
. Recent MRI and MRA – anatomical relation of arteries and venous
structures with the trigeminal nerve at the root entry zone in the CPA
used as a preoperative adjunct than for diagnostic purpose
Continued development may lead to its ability to discern vascular
impingement
Treatment..
Few or no randomized trials comparing medical, surgical and interventional techniques
For secondary trigeminal neuralgia – cause is treated
For Classical trigeminal neuralgia
MedicationSurgery
Medications..
Drugs with anticonvulsive properties rather than analgesics
Carbamazepine, Phenytoin and Gabapentine – reduce or control pain
Oxcarbamazepine, Lamotrigine and baclofen – beneficial but very limited evidence
Carbamazepine
First line treatment – CarbamazepineBegun as 200mg/d and increased as tolerated to 200mg tds-qid or moreDoses higher than 1800mg/d is no more effective70% patients – symptomatic improvement
Goal – to reach the smallest dose to provide adequate pain relief
AE: lethargy, sluggish thinking and imbalanceinterferes with production of blood elements and alter
hepatic fxn
When pain free for several weeks should be tapered over weeks
Phenytoin
100mg tds
IV has been used for acute exacerbations
25% obtain satisfactory pain relief – has been shown to correlate with phenytoin blood level
Coadministered carbamazepine can raise serum phenytoin concentrations whereas phenytoin can decrease the half life of carbamazepine
Other agents..
Baclofen: GABA analogCan be used alone or in combination with phenytoin or carbamazepine
Clonazepam, Valproic acid, lamotrigine, topiramate and Gabapentin
Gabapentin relieves many forms of neuropathic pain and is well tolerated
Little or no evidence to support the use of non-antiepileptic drugs in the treatment of tic douloureux
2/3rd patients – adequately managed on antiepileptic drugs1/3rd patients – can not tolerate side effects
½ of the patients – candidates for surgery
Opiods – not appropriate for long term treatment; only used while buying time while the adequate drug levels of anticonvulsant drugs comes
Acupuncture, herbs, vitamins, magnets – NO ROLE
BOTTOM LINE: Either good relief with medication or offer surgical intervention
Surgical Treatment..
No surgical procedure is warranted unless pharmacological therapy has failed inadequate pain relief or unacceptable side effects
Gasserian Gangliolysis
Objective: to selectively destroy A-δ and C fibers (nociceptive) while preserving the A-α and β fibers (touch)
Can be repeated easily if pain recurs
Associated with minimal rate of morbidity
Gasserian ganglion and adjacent sensory root of trigeminal nerve
Expectation: more permanent effect than neurectomy because neural regeneration is less likely to occur in these areas than peripheral branches
Gangliolysis contd..
Radiofrequency gangliolysisneedle inserted through the cheek into the V3 at foramen
ovalethen advanced under fluoroscopic guidance into the
gasserian ganglion and sensory root
Entry point – 2.5 cm lateral to corner of theMouth in the occlusal plane
Needle aimed toward the intersection of The coronal plane halfway between the External auditory meatus and lateral Canthus and the sagittal plane centered at thepupil
Gangliolysis contd..
The third, second and first divisions can then be stimulated in sequence by slowly advancing the needle tip
V3 encountered 1 cm after penetration of the foramen ovale, V2 is located at 2 cm and V1 at 3 cm and at the level of the clivus
Once the needle is ideally situated, the patient is awakened and the relevant nerve root stimulated to confirm stimulus provoked cutaneous paresthesia in the painful trigeminal distribution
Gangliolysis contd..
Patient is then reanesthetized and the neural destruction produced by radiofrequency current to create thermal lesion
Other options:
Fogarty catheter balloon – mechanical destruction
Glycerol injection
Goal: pain control with least neurological deficit
Gangliolysis contd..
Produces pain relief for longer period than injection or avulsion of peripheral branch
80% chance of 1 year pain relief50% chance of 5 year success25% recurrence 5 yrs5-10% no initial pain relief with early recurrence0.5% to 1% complication – meningitis, c. nerves damage, corneal anesthesia, masseter weakness and anesthesia dolorosa (total sensory loss)
Most dreaded complication – anesthesia dolorosa
Gangliolysis contd..
Balloon compression – technically easier with similar resultBradycardia anticipated during the procedureGlycopyrrolate adminstered prior to injection to counteract AECorneal hypoesthesia and anesthesia dolorosa – lower chance
Glycerol – less often performed these daysLocation of glycerol can not be precisely targetedLong term result not so good20-30% long term failure
N.B. peripheral neurectomy only indicated when gangliolysis fails
Microvascular Decompression
Jannetta developed this procedure
Involves operating microscope and microsurgical technique
Retromastoid craniectomy vessel or vessels separated from the nerve synthetic sponge or Teflon felt inserted to maintain the separation
Trigeminal nerve carefully and circumferentially inspected along its entire intracranial course from the root entry zone to its entrance laterally into Meckel’s cave
Microvascular Decompression contd..
Greater potential for producing long lasting pain relief without any facial sensory loss
It may take several days for the pain to stop after the procedure
Definitive neurovascular compression found in 88.6% cases
7.5% explorations – no pathology intraoperatively
70-80% - superior cerebellar artery compressing n.
Microvascular Decompression contd..
V2/V3 pain – compression of rostral and anterior portion of the n.
10% - AICA is the compressive vessel – compression at caudal and posterior portion of the n. closest to cn. VI; rarely by Persistent Primitive Trigeminal Artery
5-13% - due to compression by vein
70% to 80%- excellent pain relief3.5% per year recurrence
If no significant vascular compression – the main sensory root of the trigeminal n. can be partially divided adjacent to the pons (posterior trigeminal rhizotomy) – some degree of facial hypoesthesia although ophthalmic division spared due to somatotopic organization
Morbidity 5%; mortality 0.5%
Stereotaxic Radiosurgery..
Minimally invasive alternative
2 types – linear accelerators (linacs) and Gamma knife used
70-80% pain free in short term
50% relapse
60-90 Gy single session
Most patients responded within 6 months with median of 2 mo.
AE: facial dysesthesias, corneal irritation, vascular damage, hearing loss, facial paresis
Peripheral Neurectomy
Resection and avulsion of a branch of trigeminal nerve
Rarely a procedure of choice today
Complete anesthesia in the distribution of avulsed branch
Pain relief rarely lasts more than a year or so
Trigeminal Tractotomy
When all measures have failed
Sectioning of the descending trigeminal tract in the medulla
Loss of pain and temperature in the ipsilateral face; spares touch
Small suboccipital craniectomy C1/C2 laminectomy anatomic and physiologic localization and tractotomy
IN a nutshell
Not all facial pain can be discounted to trigeminal neuralgia
Do not straight away jump to surgery
Multitude of treatment modalities.. No treatment is superior .. Should be tailored to the individual patients
Thank you!!