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!!