TRIGEMINAL NEURALGIA
Introduction

Disorder characterized by
attacks of severe facial pain

Diagnosis based primarily on a history of
characteristic pain attacks that are
consistent with specific research & clinical
criteria
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lancinating

In majority of patients, clinical examination, imaging and lab tests are
unremarkable – Classic TN

In a smaller group, signs & symptoms
secondary to another disease affecting the
trigeminal system – Symptomatic TN
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Nicolas Andre, 1756
“Tic douloureux”
commented that it was exclusive &
distinctive from all other diseases
John Fothergill, 1773
outlined major clinical features, clearly
establishing the disorder as a discrete
syndrome
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Epidemiology and Demographics
- Incidence of approx 4 in 100,000
Familial cases also reported
-
Majority of cases occur spontaneously
-
Slight female predominance
-
Over age 50
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-
Pain typically consists of lancinating
paroxysms
Mostly in Second & Third trigeminal
divisions
Right side most often involved
Pain attacks stereotyped
Symptom free between attacks
Chronic disorder, most patients will
experience pain attacks for years unless
appropriately treated
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Etiology and Pathogenesis
Cause – not known
Injury to the nerve root – an initiating factor?
(Benign tumors and vascular anomalies
that compress the trigeminal nerve root
can
produce
symptoms
clinically
indistinguishable from classic TN)
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Based on the morphologic and physiologic changes following partial nerve injury,
Devor et al proposed “ignition hypothesis”.
A trigeminal injury induces physiologic
changes that result in a population of hyperexcitable and functionally linked primary
sensory neurons. The discharge of any
individual neuron of this group can quickly
spread to activate the entire population.
Such a discharge could underlie the
sudden jolt of pain in TN attack.
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Clinical Presentation and
Physical Findings
Diagnosis of TN based on distinctive signs &
symptoms.
White & Sweet articulated diagnostic criteria
for TN.
Consists of 5 major clinical features that
define the diagnosis of TN
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Sweet diagnostic criteria
1.
2.
3.
4.
5.
Pain is paroxysmal
The pain may be provoked by light touch
to the face (trigger zones)
The pain is confined to the trigeminal
distribution
The pain is unilateral
The clinical sensory examination is
normal
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Patients who did not meet all the criteria
rarely benefited.
The Sweet criteria were incorporated into
the criteria published by IASP & IHS.
ICHD II (IHS) subdivides Trigeminal
Neuralgia (code 13.1) into,
- Classic TN (code 13.1.1)
- Symptomatic TN (code 13.1.2)
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Classic TN (13.1.1)
Most common form- idiopathic,
associated with vascular compression.
and
also
“a unilateral disorder characterized by brief electric
shock-like pains, abrupt in onset and termination, limited
to the distribution of one or more divisions of trigeminal
nerve. Pain is commonly evoked by trivial stimuli
including washing, shaving, smoking, talking and/or
brushing the teeth (trigger factors) and frequently occurs
spontaneously. Small areas in the nasolabial fold and/or
chin may be particularly susceptible to the precipitation
of pain (trigger areas). The pains usually remit for
variable periods.”
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ICHD Criteria for Classical TN (13.1.1)
A.
Paroxysmal attacks of pain lasting from a fraction of a
second to 2 minutes, affecting one or more divisions of
the trigeminal nerve and fulfilling criteria B and C
B.
Pain has at least one of the following characteristics:
1. intense, sharp, superficial or stabbing
2. precipitated from trigger areas or by trigger factors
C.
Attacks are stereotyped in individual patient.
D.
There is no clinically evident neurological deficit.
E.
Not attribute to another disorder.
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Symptomatic TN (13.1.2)
- Results from another disease process
(MS or a cerebellopontine angle tumor)
“Pain indistinguishable from 13.1.1
classic TN but caused by a demonstrable
structural lesion other than vascular
compression.”
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ICHD Criteria for Symptomatic TN (13.1.2)
A.
Paroxysmal attacks of pain lasting from a fraction of a
second to 2 minutes, with or without persistence of
aching between paroxysms, affecting one or more
divisions of trigeminal nerve and fulfilling criteria B and C.
B.
Pain has at least one of the following characteristics:
1. Intense, sharp, superficial or stabbing
2. Precipitated from trigger areas or by trigger factors.
C.
Attacks are stereotyped in individual patient.
D.
A causative lesion, other than vascular compression, has
been demonstrated by special investigations and/or
posterior fossa exploration.
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The pain of TN……
-
-
-
Paroxysmal attacks
Electric shock like quality
Sudden onset & severe in intensity  facial
grimace
Duration btw 1 sec and 2 min
Instantaneous electric shock sensation that’s
over in much less than a sec – ‘lightning bolt’
Symptom free btw attacks.
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Trigger zones……
A TN “trigger zone” is an area of facial skin or oral
mucosa where a low intensity mechanical
stimulation can elicit a typical pain attack.
- Only a few mm in size
- In perioral region
- First division trigger zones are very rare.
- Presence of trigger zone pathognomonic.
- May result from ephatic coupling btw partially
damaged trigeminal axons.
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-
-
Pain confined to trigeminal zone
Most frequently in 3rd division
Less frequently in 2nd or in both divisions
Pain attacks are stereotyped
Unilateral
Bilateral in MS
Clinical sensory examination is normal
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Clinical evaluation
Diagnosis based on clinical history,
supplemented by physical examination
findings and cranial imaging studies.
Detailed intraoral examination to rule out
odontogenic and non odontogenic source
for the pain
Examination of CN V, VII & VIII
Symptomatic TN from a CPA mass often
shows facial weakness and hearing loss on
that side
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Diagnostic testing
Diagnostic brain imaging to visualize
anatomic landmarks around trigeminal
ganglion and CPA
CT, MRI – to rule out CPA lesions and to
visualize subtle vascular anomalies
causing compression
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Medical Management and
Treatment
TN unique – majority of patients respond to
treatment and may have total elimination
of pain attacks
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Pharmacologic therapy
Primary drug therapy
Bergouignan,
1942
found
anticonvulsant
phenytoin
controlled attacks of TN
that
the
effectively
Similarity in mechanisms between epilepsy &
TN pain attacks.
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Routine therapy begins with single agent, in
gradually increasing doses until pain
attacks are suppressed or satisfactorily
reduced.
 Carbamazepine (CBZ)
 Baclofen (BCF)
 Lamotrigine (LTG)
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CBZ superior to Phenytoin
CBZ monotherapy provides symptom control
in up to 80% patients
BCF equally effective, better tolerated
Others
- Clonazepam, Gabapentin, Topiramate,
Oxcarbazepine, Tiagabine, Levetiracetam
and Zonisamide.
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Multiple drug therapy
-
When a patient respond only partially to
single drug therapy at dosages that evoke
side effects……
-
When patients do not satisfactorily respond
to 2 AED’s, they should be considered for
surgical interventions.
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Surgical options
Highly effective and well tolerated
Cumulative risk of multiple pharmacological
agents may exceed the risk of surgical
complications, especially in the elderly
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3 SURGICAL APPROACHES
1.
Percutaneous stereotactic radiofrequency
thermal lesioning of the trigeminal ganglion
and/or root (RFL)
2.
Posterior fossa exploration and microvascular
decompression (MVD) of the trigeminal root
3.
Gamma knife radiation to the trigeminal root
entry zone (GKR)
Produce satisfactory relief of TN symptoms in 80 –
90% of patients. Incidence of complications is
low and specific for the technique employed.
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1.
RFL
-
Produce mild injury to the sensory fibers
in the trigeminal root.
Minimally invasive
Controls symptoms in > 85% of patients
Principal side effect – sensory loss and
occasional dysesthesia
-
-
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2.
Posterior fossa exploration and MVD
-
More complex and invasive
-
Directly treats the hypothetical cause
while minimizing any sensory damage
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3.
GKR
-
Relatively recent
Employs
computerized
stereotactic
methods to concentrate gamma radiation
on the trigeminal root entry zone
Could be highly effective
Long term benefits to be established
-
-
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
RFL for patients who are elderly or medically
frail.

Posterior fossa exploration and MVD for
younger healthier patients who can tolerate the
longer more invasive surgical procedure.

GKR as an alternative to RFL in frail or elderly
patients. MVD or RFL remains the standard for
surgical treatment of younger patients who have
considerable life expectancy
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Conclusion
-
Many fundamental questions about pathophysiology of the disorder remain unanswered
-
Development of drugs specific for TN
-
Lack of objective testing remains as a problem
-
fMRI – potential future diagnostic tool
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