TRIGEMINAL NEURALGIA

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• TRIGEMINAL NEURALGIA

dr shabeel pn
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Introduction

• Disorder characterized by lancinating 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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• In majority of patients, clinical exam-ination,
  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 physio-logic
  changes following partial nerve injury, Devor et
  al proposed ignition hypothesis.
• A trigeminal injury induces physiologic changes
  that result in a population of hyper-excitable
  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 andPhysical 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
• 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, and also
  associated with vascular compression.
• 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)
• 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
• Pain has at least one of the following
  characteristics
• 1. intense, sharp, superficial or stabbing
• 2. precipitated from trigger areas or by
  trigger factors
• Attacks are stereotyped in individual patient.
• There is no clinically evident neurological
  deficit.
• 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)
• 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.
• Pain has at least one of the following
  characteristics
• 1. Intense, sharp, superficial or stabbing
• 2. Precipitated from trigger areas or by
  trigger factors.
• Attacks are stereotyped in individual patient.
• 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 thats
  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 therapyPrimary drug therapy

• Bergouignan, 1942 found that the anticonvulsant
  phenytoin effectively controlled attacks of TN
• 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
  AEDs, 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
• Percutaneous stereotactic radiofrequency thermal
  lesioning of the trigeminal ganglion and/or root
  (RFL)
• Posterior fossa exploration and microvascular
  decompression (MVD) of the trigeminal root
• 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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• RFL
• - Produce mild injury to the sensory fibers in
  the trigeminal root.
• Minimally invasive
• Controls symptoms in gt 85 of patients
• Principal side effect sensory loss and
  occasional dysesthesia

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• Posterior fossa exploration and MVD
• More complex and invasive
• Directly treats the hypothetical cause while
  minimizing any sensory damage

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• 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 patho-physiology
  of the disorder remain unanswered
• Development of drugs specific for TN
• Lack of objective testing remains as a problem
• fMRI potential future diagnostic tool