Trigeminal Neuralgia

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  1. Symptoms: more common in women; occurs more commonly in people over 50; lancinating or electrical pain confined to the trigeminal nerve distribution on one side; more frequently involves the lower face than the forehead and eye and is more common on the right than the left; pain may start at a trigger spot on the skin or when the mouth is stimulated by a touch, gust of wind, or cold or hot liquid; pain may typically start in the upper or lower teeth on one side causing the patient to seek dental treatment
  2. Etiology: frequently caused by vascular compression of the trigeminal sensory root at its entry into the pons; most commonly the superior cerebellar artery (76%), followed by AICA (10%); damage to the nerve root may cause ephaptic transmission (short circuiting) causing the lancinating pain. Other causes include demyelination as in multiple sclerosis, or nerve compression by tumors or vascular malformations.
  3. Treatment: See "Radiosurgery for Trigeminal Neuralgia"
    1. medical: Tegretol and Gabapentin (Neurontin) may help control pain (Tegretol is more effective). Other drugs include dilantin, baclofen, trileptal, and klonopin. Lyrica has been less effective. Side effects are more common in elderly patients who may not tolerate higher doses.
    2. injection (peripheral rhizotomy) along the trigeminal pathway: retrogasserian glycerol injection is effective in approximately 80-85% of patients and can last for years. Alcohol injection anywhere along the peripheral tract is typically effective for several months.
    3. radiofrequency thermocoagulation:
      1. complications: blindness in ipsilateral eye (cause unknown); hypertension, bradycardia and/or hypotension is very common (have atropine ready); arterial injury to carotid or accessory meningeal artery; pareshesias or dysesthesias, anesthesia dolorosa; herpes simplex eruptions occur in 31% of patients
      2. technique: 2.5 cm lateral to the corner of the mouth in AP aiming toward the medial side of the pupil and 2.5 cm anterior to the anterior aspect of the ear canal along the zygoma on the lateral view.  Too lateral placement will put the needle in the subtemporal space.  Too medial can end up in the cavernous sinus.  The typical volume of the trigeminal cistern is 0.2 to 0.4 ml measured on contrast cisternography.
    4. radiosurgery
    5. microvascular decompression
      1. 90% efficacy with recurrence less than 2% per year after 5 years
      2. complications: hearing loss, facial numbness, CSF leak are most common
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