TRIGEMINAL NEURALGIA Dr Haris PSOMR Introduction Disorder characterized

TRIGEMINAL NEURALGIA Dr. Haris PS/OMR

Introduction Ø Disorder characterized by lancinating attacks of severe facial pain Ø Diagnosis based primarily on a history of characteristic pain attacks that are consistent with specific research & clinical criteria Dr. Haris PS/OMR

l In majority of patients, clinical examination, imaging and lab tests are unremarkable – Classic TN l In a smaller group, signs & symptoms secondary to another disease affecting the trigeminal system – Symptomatic TN Dr. Haris PS/OMR

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 Dr. Haris PS/OMR

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 Dr. Haris PS/OMR

- 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 Dr. Haris PS/OMR

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) Dr. Haris PS/OMR

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 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. Dr. Haris PS/OMR

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 Dr. Haris PS/OMR

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 Dr. Haris PS/OMR

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) Dr. Haris PS/OMR

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. ” Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

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. ” Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

- Pain confined to trigeminal zone Most frequently in 3 rd division Less frequently in 2 nd or in both divisions Pain attacks are stereotyped Unilateral Bilateral in MS Clinical sensory examination is normal Dr. Haris PS/OMR

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 Dr. Haris PS/OMR

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 Dr. Haris PS/OMR

Medical Management and Treatment TN unique – majority of patients respond to treatment and may have total elimination of pain attacks Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

Routine therapy begins with single agent, in gradually increasing doses until pain attacks are suppressed or satisfactorily reduced. Carbamazepine (CBZ) Baclofen (BCF) Lamotrigine (LTG) Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

Surgical options Highly effective and well tolerated Cumulative risk of multiple pharmacological agents may exceed the risk of surgical complications, especially in the elderly Dr. Haris PS/OMR

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. Dr. Haris PS/OMR

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 - Dr. Haris PS/OMR

2. Posterior fossa exploration and MVD - More complex and invasive - Directly treats the hypothetical cause while minimizing any sensory damage Dr. Haris PS/OMR

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 - - Dr. Haris PS/OMR

ü RFL for patients who are elderly or medically frail. ü Posterior fossa exploration and MVD for younger healthier patients who can tolerate the longer more invasive surgical procedure. ü 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 Dr. Haris PS/OMR

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 - f. MRI – potential future diagnostic tool Dr. Haris PS/OMR