1. Differentiating Trigeminal Neuropathy From Trigeminal Neuralgia
Does It Even Matter?
Justin Sandall, D.O.
Vanderbilt University Medical Center
Department of Anesthesiology, CA-2

2. Case Presentation
26 y/o female w/a history of chronic migraine HA, depression and hypothyroidism presents for evaluation of L sided facial pain. 
She relates a history of migraines since the age of 11; occurred infrequently until beginning college in 2001 at which time they increased in frequency to 2-3x/month. 
~1 year ago she had her typical migraine which "didn't go away."  She now has a constant, throbbing/boring pain in her L periorbital/frontal area with occ. radiation to the L maxilla. 
She also has intermittent sharp, lancinating pains in those same areas. 
Her pain is worsened with anxiety, working out, loud noises, heat and alleviated with application of cold, migraine medications and Lyrica. Mother has noticed L sided facial swelling.
There is no association with brushing teeth, putting on makeup or wind on the face.  She denies changes in hearing, balance or coordination.  She also denies sensory changes, tearing, conjunctival effusion and ataxia. 
No h/o trauma or HSV.

3. Case Presentation
MEDICATIONS:  - Synthroid Oral Tablet 75 mcg 1 tablet by mouth daily - Betaxolol 10mg PO twice daily - Zoloft 150mg PO daily - Migrelief 2 tabs PO - Topamax 300mg OP daily - Ondansetron tab PO PRN - Indomethacin 25mg PO twice daily - Zomig Zmt 5mg PO twice daily - Lyrica 300mg - Kariva BC - Zyrtec 10mg

4. Case Presentation Relevant Physical Exam Relevant Imaging
PERRL, CN II-XII intact b/l, NTTP along trigeminal distribution w/o allodynia or hyperesthesia, no sensory deficits, TMJ NTTP b/l
Relevant Imaging
Previous work-up including CT and MRI unrevealing

5. Trigeminal Neuralgia
Most common pain syndrome referable to a cranial nerve.1
Most common in adults > 50 y/o, women slightly more than men2
Classically, pain is described as an electric shock–like, stabbing, unilateral pain with abrupt onset and termination in distribution of trigeminal nerve – usually V2/3.2,3
Intervals between attacks are pain free
Minimal or no sensory loss in the region of pain
Precipitation from trigger areas or by certain daily activities, such as eating, talking, washing the face, or cleaning the teeth3
Diagnosis is typically made by the history
Imaging is often pursued to r/o other causes of facial pain &/or to evaluate for MS, vascular compression of the trigeminal nerve etc.
Typically, 80% of patients respond to medical therapy3
1st line therapy is carbamazepine2,3,5

6. Trigeminal Neuralgia
May target trigeminal nerve at various sites with nerve blocks if unresponsive to medical therapy
Superficial V1/V2, gasserian ganglion
If responsive to local anesthetic block, may pursue trigeminal neurolysis
Most common target is the gasserian ganglion via the foramen ovale1
Studies have all used patients w/classic trigeminal neuralgia
Less premorbid depression/anxiety, more satisfied w/outcome, fewer side effect complaints, more willing to repeat procedure1
Study by Taha and Tew in 1996 evaluated RF rhizotomy w/curved electrode, RF rhizotomy, glycerol rhizotomy, balloon compression, and posterior fossa exploration (microvascular decompression, partial trigeminal rhizotomy)4
Showed initial pain relief to be 91-98% with success of procedure in 85-98% and pain recurrence in 15-54%
Glycerol rhizotomy had lowest initial pain relief, lowest procedure success and highest pain recurrence
Complications of trigeminal neurolysis can be devastating and include anesthesia dolorosa, loss of corneal sensation, keratitis, dysesthesia1

7. Trigeminal Neuropathy (included atypical trigeminal neuralgia and atypical facial pain)
Chronic or recurrent pain in the area of previous nerve injury, numbness, dysesthesias, and chronic burning sensations. Diagnostic evaluations rule out any other cause of pain.2
More likely to have sensory loss or allodynia5
Doesn’t meet White and Sweet criteria:2  
The pain is paroxysmal.
The pain is confined to the trigeminal distribution.
The pain is unilateral.
The bedside clinical sensory examination is normal.
The pain may be provoked by light touch to the face (trigger zones)
Significant clinical challenge because the symptoms of PTN respond poorly, if at all, to AED or surgical therapies commonly used in TN.1,2
Neurolytic treatment may actually worsen pain in this subgroup
More often associated with young, middle aged women and feelings of depression
Motor cortex stimulation for trigeminal neuralgia seems promising – 70% success rate compared to 50% for central pain5

8. Classic trigeminal neuralgia Rare
Intraoral or extraoral in trigeminal region
Each episode of pain lasts for seconds to minutes; refractory periods, and long periods of no pain
Sharp, shooting, moderate to very severe
Light touch provoked (e.g., eating, washing, talking)
Discrete trigger zones
Atypical trigeminal neuralgia
Sharp attacks lasting seconds to minutes, more continuous-type background pain, less likely to have complete pain remission
Sharp, shooting, moderate to severe but also dull, burning, continuous mild background pain
Light touch provoked, but continuous-type pain not so clearly provoked
May have small trigger areas, variable pattern
Trigeminal neuropathy
Very rare
Trigeminal area, but may radiate beyond
Continuous
Dull with sharp exacerbation
Areas of allodynia, light touch
Sensory loss, subjective-objective, progressive, vasodilation and swelling may occur
Adapted from Essentials of physical medicine and rehabilitation: musculoskeletal disorders, pain, and rehabilitation/ [edited by] Walter R. Frontera, Julie K. Silver, Thomas D. Rizzo Jr.—2nd ed. Chapter 90.

9. Case Resolution
26 y/o female with L sided facial pain in the setting of chronic migraine HA, h/o depression and hypothyroidism. Given the nature of her pain, her history of depression and migraine HA, her pain triggers or lack thereof and physical exam findings, this most likely is atypical facial pain secondary to trigeminal neuropathic pain in the V1/V2 distribution rather than classic trigeminal neuralgia.  It is important to make this distinction given that definitive treatment of trigeminal neuralgia (i.e. neurolytic tx) can actually worsen the pain of trigeminal neuropathy.  In addition, she almost certainly has a component of transformed migraine HA that is contributory thus one of our long-term goals will be to decrease the number of medicines she is on. 1. Atypical facial pain  2. Trigeminal neuropathic pain in the V1V2 distribution  3. Transformed migraine headache  4. H/o depression 5. Hypothyroidism 
Will schedule for superficial V1/V2 block and TPI and assess response.  Needs to be off indomethacin x7 days prior to procedure.  May benefit from Gasserian ganglion block and/or Stellate ganglion block down the road if not responsive to more conservative measures.  If responds well to the peripheral n. blocks, will use Botox for long-term control. Meanwhile

10. References
Jackson T, Gaeta R: Neurolytic blocks revisited. Current Pain and Headache Reports. 2008, 12:7-13.
Raj's practical management of pain/editors, Honorio T. Benzon…[et al.].—4th ed. Chapter 25.
Essentials of physical medicine and rehabilitation: musculoskeletal disorders, pain, and rehabilitation/ [edited by] Walter R. Frontera, Julie K. Silver, Thomas D. Rizzo Jr.—2nd ed. Chapter 90.
Taha JM, Tew JM: Comparison of surgical treatments for trigeminal neuralgia: reevaluation of radiofrequency rhizotomy. Neurosurgery 1996, 38:
McMahon: Wall and Melzack's Textbook of Pain, 5th ed. Chapter 37