Neuropathic Pain / Nerve Pain
What is Neuropathic Pain (NP)?
Neuropathic pain is initiated or caused by a lesion or dysfunction of the nervous system (IASP), often without clinically distinct lesions or diseases. Early and accurate diagnosis and proper treatment can prevent the nervous system from adapting improperly and worsening into chronic pain syndrome.
What is Episodic Neuropathic Pain?
Severe pain that feels like a puncture, stabbing or electric shock-like pain due to sudden seizures which lasts for several seconds to several minutes, is called neuralgia. This pain can also be triggered by light touches or movements in the face or mouth.
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Trigeminal neuralgia
Intense stabbing or electric shock-like pain occurs one side of the face and mouth which suddenly appears and then disappears after several seconds to minutes. There is a period of no pain at all between the onset of pain. Neuralgia can happen abruptly at any time triggered by normal activities like washing your face, brushing, shaving, talking, eating, etc.
Cause: Trigeminal nerve damage
Diagnosis method: medical history examination, neurological examination, head and neck MRI
Treatment
Drug therapy: carbamazepine or oxcarbazepine, lamotrigine, baclofen, phenytoin, gabapentin, pregabalin, valproate, tizanidine, tocainide
Surgical therapy: cryotherapy, neurectomy or alcohol injection, microvascular decompression, radiofrequency thermocoagulation, balloon compression, glycerol rhizotomy, gamma knife surgery
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Glossopharyngeal neuralgia (GPN)
It is usually unilateral, with 25% being bilateral. Short, moderate electric shock like pain, appears and disappears suddenly in the ears, under the angular area of the jaw, under the tongue, and in the throat. Pain can be triggered by coughing, swallowing food, touching your gums or blowing your nose, touching your ears, etc.
Cause: damage to the glossopharyngeal nerve and vagus nerve
Diagnosis method: medical history examination, neurological examination, head and neck CT or MRI
Treatment
Drug therapy: carbamazepine or oxcarbazepine, local anesthetic
Surgical therapy: microvascular decompression, intracranial sectioning of the glossopharyngeal nerve and the upper rootlets of the vagus nerve, gamma-knife surgery
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Occipital neuralgia (ON)
Severe pain like a sudden stabbing of one or both sides, occurs in the back and lower areas of the head.
Cause: laryngeal nerve damage
Diagnosis method: medical history test, neurological examination, differential diagnosis for cervical spine injury or pain associated with neck and shoulder muscles
Treatment: injection therapy- local anesthetics and corticosteroids
What is Continuous Neuropathic Pain?
A pain that occurs continuously with various pain intensity from low to high. Pain is mainly mild to moderate and has no period when the pain stops completely.
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Peripheral trigeminal traumatic neuropathy, Anesthesia dolorasa
Usually occurs unilaterally with mild to moderate dull pain or moderate to severe burning or stabbing pain in the face or mouth. Patient with neurological dysfunction may experience symptoms such as: feeling sensitive (positive: hyperalgesia, allodynia), negative (hypoesthesia, hypoalgesia), or a tingling sensation. Patients often pinpoint the pain area.
Cause: It occurs mainly within 3-6 months after damage of the trigeminal nerve from mechanical, chemical, thermal, and irradiation trauma. Trauma of the peripheral trigeminal nerve can also be caused by surgical procedures such as root canal treatment, tooth extraction, and implant placement. There is no known correlation between peripheral trigeminal nerve damage and surgical procedures found yet, but it has been reported that about 5% of patients who had the surgical procedures might experience pain due to trauma of the nerve.
Differential Diagnosis: Neuropathic pain is mistakenly diagnosed a disease of teeth or gum and receives unnecessary medical/dental treatments such as neurological treatment, RCT, extraction, exploratory surgery, apical apex resection, etc. We see a lot of cases that get better after receiving treatment in our clinic.
Diagnosis method: medical history examination, neurological examination, quantitative sensory testing, advanced neurophysiological testing, X-ray, CT, MRI, psychiatric examination
Treatment
Drug therapy: topical anesthesia, antidepressants, anticonvulsants
Surgical therapy: microsurgical repair, dorsal root entry zone lesioning (DREZ), sensory thalamic neurostimulation.
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Persistent idiopathic facial pain: PIFP, Atypical facial pain
It is a pain that is constantly felt on the surface or deep within the face and mouth, with mild to moderate severity. Duration of pain tends to be about 2 hours a day for more than 3 months and clinically, neurologic deficit may not appear. However, experience of numbness has been reported in more than 60% of patients. In many cases, patient cannot accurately pinpoint the pain area. Pain usually is dull and aching and symptoms may become worse over time.
Cause: It is caused by surgical treatment or trauma in the face or mouth, and the pain persists for no specific reason after the wound is healed.
Diagnosis method: medical history examination, neurological examination, quantitative sensory testing, advanced neurophysiological testing, X-ray, CT, MRI, psychiatric examination
Treatment
Drug therapy: tricyclic antidepressants (amitriptyline, desipramine, nortriptyline), anticonvulsants (gabapentin, pregabalin), serotonin noradrenaline reuptake inhibitors (venlafaxine, duloxetine, milnacipran), topical lidocaine, and analgesics (opioids, tramadol).
Surgical therapy: Various surgical therapies are being performed, but the US FDA does not permit it for chronic pain.
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Burning mouth syndrome (BMS, glossodynia )
Burning pain occurs in the mucous membrane of the mouth, including the tongue, without a specific cause and lasts for months to years. Usually, the burning pain increases gradually during the day, peaking in the evening.
Area: Mainly on the upper and lower sides of the tongue and the side or lower part, the front part of the roof of the mouth, the lower lip, and the other parts of the oral cavity including the inside of the cheek
Cause: BMS is caused by nerve damage to the tongue or oral cavity or by secondary effects of oral or systemic diseases.
Pain is increased by stress, fatigue, and spicy or irritating food. It is associated with emotional factors such as anxiety and depression, especially in postmenopausal women.
Treatment: Drug therapy is mainly used.
Clonazepam, anxiolytics (diazepam, chlordiazepoxide), low-level laser therapy, antidepressants (amitriptyline, trazodone, paroxetine, milnacipran), anticonvulsants (gabapentin, topiramate), salivary stimulants (pilocarpine), dopulinum topamine type Aagonists (pramixamine type A), and Botulinum type A
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Peripheral neuritis
It is a peripheral neuropathy caused by inflammation.
Inflammation may directly damage the peripheral nerves through inflammatory cytokines, or may result from mechanical pressure from inflammatory edema.
Cause: It is usually caused by invasive treatment such as nerve treatment, extraction, implant placement, and chronic pain may occur if peri-implantitis affects the nerve trunk. In addition, symptoms may result from arthropathy of the jaw, sinusitis, and early malignant tumors.
Treatment: Treatment with anti-inflammatory drugs (corticosteroids or NSAIDs) is effective early in the onset.
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Shingles (Herpes zoster: HZ, shingles)
It usually appears after the 60's and causes blisters in the facial skin or mouth unilaterally with severe pain. Within 1-5 days of onset, symptoms may include malaise, headache, sensitivity to light, sensitivity to skin irritation, and fever.
Cause: Recurrence after infection with a virus (varicella-zoster virus: VZV). Virus stays latent in the dorsal muscle ganglion or cranial ganglion, and is manifested by stimulation such as stress or trauma.
Diagnostic method: clinical examination, polymerase chain reaction testing, viral culture, direct immunofluorescence antigen staining
Treatment: The treatment goal is to relieve pain, promote healing, and prevent complication such as neuralgia or secondary infection after herpes. Recently, shingles vaccination has been used effectively.
Drug therapy: Antivirals (acyclovir, valacyclovir, famciclovir), Nonopioid analgesics: acetaminophen or NSIADs, Opioids, Corticosteroids, antidepressants (amitriptyline, desipramine, venlafaxine, bupropion), gabapentinoids (gabapentin, pregabalin)
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Postherpetic neuralgia (PHN)
Neuropathic pain caused by the shingles virus, which occurs in 20% in 60s, 30% in 80s and above, and rarely occurs in 50s or younger. Neurological dysfunction (hyperalgesia, allodynia, dysesthesia) may appear.
Cause: Shingles, nerve damage
Treatment: Vaccine vaccination is effectively used, and drug treatment is mainly used after an outbreak. Nonopioid analgesics, Opioids, Corticosteroids, antidepressants, gabapentinoids.
<Orofacial pain, AAOP, Sixth edition p6 Fig 1-2>.
