Trigeminal Neuralgia

Trigeminal neuralgia (TN) is an often chronic and recurring pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain syndrome involving the sensory distribution of the trigeminal nerve (cranial nerve (CN) V). The pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain is typically unilateral and described as an acute, sharp, electric- shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock–like pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain involving the maxillary or mandibular areas and often associated with spasm of facial muscles. Trigeminal neuralgia occurs in multiple, short-acting episodes. Most cases are usually due to vascular compression of the trigeminal nerve, although secondary causes can be from aneurysms, neuromas, or other neurologic disorders. A detailed history is the hallmark for diagnosis. Neuroimaging with MRI is useful to determine the exact pathology involving the trigeminal nerve root. The 1st line of therapy is pharmacologic (carbamazepine). Other treatment options include botulinum toxin injections or surgical procedures in refractory cases.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

Trigeminal neuralgia (TN) is a disorder presenting with recurrent, sharp pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain in the distribution of the trigeminal nerve.

Anatomy of the trigeminal nerve

Trigeminal nerve (cranial nerve (CN) V):

  • The largest of all the cranial nerves Cranial nerves There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain. Overview of the Cranial Nerves
  • Starts at the mid-lateral surface of the pons
  • Sensory ganglion (Gasser ganglion) reside in the floor of the middle cranial fossa.

3 major divisions of CN V:

  • Ophthalmic (V1): 
    • Exits the cranium via the superior orbital fissure
    • Purely sensory
    • Sensory innervation of the forehead, eyes, and nose Nose The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Anatomy of the Nose
  • Maxillary (V2):
    • Exits the cranium via the foramen rotundum
    • Purely sensory
    • Innervation of the lower eyelid, teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth, nasal cavity, gums of the upper jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint, palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Oral Cavity: Palate, and tonsils 
    • Autonomic innervation of the lacrimal and nasal glands
  • Mandibular (V3): 
    • Exits the cranium via the foramen ovale
    • Sensory and motor
    • Motor innervation of the muscles of mastication
    • Sensory supply of the teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth, gums of the lower jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint, buccal mucosa, dorsum of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Oral Cavity: Lips and Tongue, and external acoustic meatus

Epidemiology

  • Annual incidence: 4–5 per 100,000
  • Ratio of men to women: 1:1.5 
  • Onset is typically after 40 years old, but may occur at any age.

Etiology

  • Classic TN: 
    • Approximately 75% of cases result from vascular (artery or vein) compression of the trigeminal nerve at the entry zone of the root. 
    • The compression is commonly caused by a branch of the superior cerebellar artery.
  • Secondary TN: 
    • 15% of cases are caused by an underlying disease.
    • Common causes include:
      • Multiple sclerosis Multiple Sclerosis Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. Multiple Sclerosis
      • Vestibular schwannoma Vestibular schwannoma Acoustic neuroma, also referred to as vestibular schwannoma, is a benign tumor arising from Schwann cells of the vestibular component of the cranial nerve VIII. Acoustic neuroma forms within the internal auditory meatus and extends into the cerebellopontine angle. Acoustic Neuroma (acoustic neuroma)
      • Meningioma Meningioma Meningiomas are slow-growing tumors that arise from the meninges of the brain and spinal cord. The vast majority are benign. These tumors commonly occur in individuals with a history of high doses of skull radiation, head trauma, and neurofibromatosis 2. Meningioma
      • An epidermoid cyst or other cyst
      • Arteriovenous malformation
      • Aneurysms
  • 10% are classified as idiopathic TN (unidentified cause).

Clinical Presentation

Main reported symptoms

  • Sudden, stabbing, unilateral facial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain:
    • Frequent unilateral pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • In rare cases (3% of individuals with TN), pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain can be active on both sides at the same time. 
    • The pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain is a severe, sharp, shooting, or electric- shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock–like sensation, lasting seconds to 2 minutes. 
    • Facial grimacing or spasm may accompany the pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain (tic douloureux).
  • Individuals report “trigger zones” (usually midline around the nose Nose The nose is the human body's primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Anatomy of the Nose and lips Lips The lips are the soft and movable most external parts of the oral cavity. The blood supply of the lips originates from the external carotid artery, and the innervation is through cranial nerves. Oral Cavity: Lips and Tongue):
    • Even nonpainful stimuli in the trigger zones can cause pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Stimuli include:
      • Chewing
      • Washing the face
      • Talking
      • Brushing the teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth
      • Shaving
      • Cold air
    • After the initial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, a refractory period may last up to several minutes.
    • Stimulation of the trigger zone will not cause pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain during the refractory period.
  • Autonomic symptoms (V1 involvement):
    • Lacrimation
    • Rhinorrhea
    • Conjunctival injection
  • TN attacks:
    • May occur for extended periods of time (weeks to months)
    • In many cases, remission can last at least 6 months.
    • Recurrence is common (frequency and severity wax and wane).
    • During periods with multiple attacks, affected individuals report depressed mood (↑ suicide Suicide Suicide is one of the leading causes of death worldwide. Patients with chronic medical conditions or psychiatric disorders are at increased risk of suicidal ideation, attempt, and/or completion. The patient assessment of suicide risk is very important as it may help to prevent a serious suicide attempt, which may result in death. Suicide risk) and disturbances in eating and sleeping.

Associated symptoms

When other neurologic conditions (e.g., multiple sclerosis or aneurysms) are present, additional symptoms may include:

  • Visual/ocular manifestations
  • Weakness
  • Neuropathy
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • Hearing loss Hearing loss Hearing loss, also known as hearing impairment, is any degree of impairment in the ability to apprehend sound as determined by audiometry to be below normal hearing thresholds. Clinical presentation may occur at birth or as a gradual loss of hearing with age, including a short-term or sudden loss at any point. Hearing Loss
  • Tinnitus
  • Cutaneous tumors

Diagnosis

Diagnosis of TN is clinical with a thorough history and physical. Further workup with imaging or laboratory studies may be required if red-flag symptoms are present.

History

  • Diagnostic criteria based on the International Classification of Headache Disorders 3rd Edition:
    • Paroxysms or attacks of unilateral facial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain are recurrent in areas supplied by 1 or more divisions of the trigeminal nerve.
    • Pain characteristics:
      • Duration: a few seconds to ≤ 2 minutes 
      • Severe intensity
      • Shooting, stabbing, sharp, or electric- shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock–like pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain 
      • Innocuous stimuli within the affected trigeminal distribution triggers the pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain.
      • No other alternative diagnosis
  • Red-flag symptoms: 
    • Age of onset < 40 years old
    • Changes in sensation
    • Deafness
    • History of skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin lesions
    • Poor response to medications (carbamazepine)

Physical examination

  • Neurologic examination findings are normal:
    • Facial sensation is intact.
    • Bulk and strength of the masseter muscles are normal.
    • Corneal reflexes are normal.
  • Any permanent area of numbness excludes the diagnosis.
  • If sensory loss is found, exclude multiple sclerosis (MS) or a structural lesion.

Ancillary studies

  • MRI:
    • Recommended to rule out nerve compression or structural brain lesion
    • High-resolution MRI with thin cuts through the region of the trigeminal ganglion + heavy T2 weighting with or without contrast 
    • Confirms morphological changes such as dislocation, distortion, atrophy, or compression of the trigeminal nerve at the origin from the pons
  • CT:
    • An alternative only when MRI is unavailable
    • Not as sensitive as MRI of the brain
  • Laboratory workup:
    • Used at baseline to monitor adverse effects from medications 
    • Includes CBC, serum electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes, and liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver function panel

Management

  • Classic and idiopathic TN:
    • 1st line-therapy: carbamazepine or oxcarbazepine:
      • Mechanism of action is inhibition of neuronal sodium channel activity to reduce the excitability of neurons.
      • 58%–100% of individuals achieve complete or partial pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain control (lack of response is a red-flag finding)
      • Common side effects: vertigo Vertigo Vertigo is defined as the perceived sensation of rotational motion while remaining still. A very common complaint in primary care and the ER, vertigo is more frequently experienced by women and its prevalence increases with age. Vertigo is classified into peripheral or central based on its etiology. Vertigo, sedation, ataxia, and nausea
    • Alternative agents (can be used individually or combined):
      • Baclofen
      • Lamotrigine
      • Gabapentin
    • Botulinum toxin injections: Consider in the elderly or if oral medications and more invasive management cannot be tolerated.
    • Surgical procedures: for individuals refractory to medical management:
      • Microvascular decompression (commonly used if unable to tolerate a major procedure)
      • Rhizotomy
      • Gamma knife radiosurgery
      • Balloon compression 
  • For secondary TN, management of the underlying etiology is critical.
  • Screen and treat comorbid psychiatric conditions (e.g., depression and anxiety).

Differential Diagnosis

  • Postherpetic neuralgia: viral reactivation of the varicella zoster virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview (VZV). Age, stress, or immunocompromised states can trigger the reactivation of the virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview. Postherpetic neuralgia presents as a painful, unilateral rash distributed in a single dermatomal distribution (often in the thoracic region or along the trigeminal distribution). Diagnosis is clinical. Management includes antiviral therapy and symptomatic treatment. 
  • Migraine Migraine Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache: a prevalent primary headache disorder characterized by episodic, moderate-to-severe headaches, which may be associated with nausea and/or vomiting and increased sensitivity to light and sound. Migraine headache Migraine Headache Migraine headache is a primary headache disorder and is among the most prevalent disorders in the world. Migraine is characterized by episodic, moderate to severe headaches that may be associated with increased sensitivity to light and sound, as well as nausea and/or vomiting. Migraine Headache is a clinical diagnosis with several variants. Management strategies include abortive therapy including NSAIDs and triptans Triptans Triptans and ergot alkaloids are agents used mainly for the management of acute migraines. The therapeutic effect is induced by binding to serotonin receptors, which causes reduced vasoactive neuropeptide release, pain conduction, and intracranial vasoconstriction. Triptans and Ergot Alkaloids to manage acute episodes, as well as preventative strategies to minimize morbidity and pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain-related disability.
  • Cluster headaches Cluster headaches Cluster headache is a primary headache disorder characterized by moderate-to-severe unilateral headaches that occur in conjunction with autonomic symptoms. Cluster headache can last from weeks to months, during which the affected individual may experience attacks up to several times a day, followed by a pain-free remission period. Cluster Headaches: a primary headache disorder characterized by moderate-to-severe unilateral headaches occurring in conjunction with autonomic symptoms. Cluster headaches Cluster headaches Cluster headache is a primary headache disorder characterized by moderate-to-severe unilateral headaches that occur in conjunction with autonomic symptoms. Cluster headache can last from weeks to months, during which the affected individual may experience attacks up to several times a day, followed by a pain-free remission period. Cluster Headaches are characterized by attacks ≤ several times per day for weeks to months, followed by a pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain-free remission period. The diagnosis is clinical and often easy to establish due to the distinct features. The 1st line of treatment involves administration of oxygen by nasal cannula and/or abortive therapy with a triptan. Preventative strategies (e.g., glucocorticoids Glucocorticoids Glucocorticoids are a class within the corticosteroid family. Glucocorticoids are chemically and functionally similar to endogenous cortisol. There are a wide array of indications, which primarily benefit from the antiinflammatory and immunosuppressive effects of this class of drugs. Glucocorticoids or verapamil) are crucial.
  • Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT): a rare form of headache characterized by bursts of severe burning/throbbing with unilateral pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain lasting a few seconds to minutes, affecting the head and around the eye or temple. Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing are also associated with autonomic nervous system Autonomic nervous system The ANS is a component of the peripheral nervous system that uses both afferent (sensory) and efferent (effector) neurons, which control the functioning of the internal organs and involuntary processes via connections with the CNS. The ANS consists of the sympathetic and parasympathetic nervous systems. Autonomic Nervous System responses such as tearing, conjunctival injection, nasal congestion, and sweating. The attacks may be relieved with corticosteroids and antiepileptic drugs, but are generally nonresponsive to the usual analgesics. Trigeminal neuralgia has a refractory period after the pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, but SUNCT does not. Neuroimaging also shows neurovascular contact in many cases of TN.

References

  1. Bennetto, L., Patel, N. K., & Fuller, G. (2007). Trigeminal neuralgia and its management. Bmj, 334(7586), 201–205

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