Pain Can Be Neuritis And Not Laminitis
10 Foot Neuritis Signs in your Horse (Neuritis/Neuropathy):
1. Hoof test ok but foot sore.
2. No increased pulses but foot sore. Radiographs same as in the past or are even improved (less rotation) but foot sore.
3. Talented farrier sees improved foot from past but foot sore.
4. Talented farrier does routine hoof trim and horse is sore 1-2 days after – this is not an error, this is a sign of Neuritis.
5. Middle of the winter and no grass or on dirt lot with no grass and suddenly foot sore. Ouchy across rocks/gravel/hard ground, the others are ok on. Allodynia – excess pain response to normal stimuli.
6. Middle of winter standing in snow or very cold over 5 days in a row and suddenly foot sore. Note: Icy therapy which helps treat Laminitis is all around the horse but is sore due to this is Neuritis and not Laminitis.
7. Bute of little help – did help in the past but even on it daily for weeks is still foot sore.
8. Stall rest/DMSO IV/Ace which helped in the past not helping now.
9. Shoes/Boots do help some but less than 50%.
10. Lame for months and months even after trying many things.
These 10 signs are Neuritis caused by past Laminitis and not new/acute Laminitis.
What happens to horse’s nerves in Laminitis resulting in neuritis?
1. Direct irritation and damage to the nerves by high levels of insulin. “Insulin Neuritis Syndrome seen in people starting insulin therapy.” Dr. Vinik, 2004, CME, Diab. Neuro.
2. Insulin Resistance leads to:
A. “A reduction of neurotrophic signaling which contributes to nerve pathogenesis.” Dr. Hosseini, 2013, Oxid. Med. Insulin’s usual action is to promote nerve growth, but Insulin Resistance blocks insulin’s normal function.
B. “In neuron, Insulin Resistance disruptions of pathways leads to mitochondrial dysfunction, oxidative stress and dysfunctions or death of the nerve.” Dr. Hosseini, 2013, Oxid. Med.
3. Less blood flow (vasoconstriction) to nerves damages them. Insulin at high levels causes vasoconstriction.
A. “Blood vessel endothelial dysfunction” seen in diabetic people with neuropathy.” Dr. DeVriese, 2000, Br. J. Pharm.
B. “Oxidative stress and inflammatory activity reduce nerve blood flow.” Dr. Kellogg, 2006, Antiox/Redux Signal.
C. “Selective COX2 inhibition helped in preventing nerve blood flow and nerve conduction velocity deficits in experimental neuropathy.” Dr. Pop-Busvi, 2002, Diabetes, University of Michigan.
D. “Neuropathy is a microvascular complication of diabetes.” Dr. Hosseini, 2013, Oxid. Med.
4. Physical crushing of nerves.
A. In all Laminitis, bone density is lost. This leads to nerves not being protected by being exposed to more shear forces and in horses shifting weight and pressing harder on areas of foot, leading to nerves bearing more weight.
B. As blood flow is lost, coffin bone can sink and press on nerves.
C. As horses founder (rotate), the shifting coffin bone smashes the nerves/blood vessels.
D. In human medicine they are looking into neuroma formation in diabetic people’s feet – very possible in horses also. Damaged nerves hypertrophy into bundles of tissue creating pain.
5. Inflammatory mediators create damage to nerves both locally in the foot and in the spinal cord.
A. “Oxidative stress and reactive oxygen species lead to progressive nerve damage, dysfunction, and loss.” Dr. Hosseini, 2003, Oxid. Med.
B. Blocking COX2 helped in preventing nerve blood flow and nerve conductive velocity deficits. Dr. Pop-Busvi, 2002, Diabetes. COX2 is an enzyme creating prostaglandins. Certain medicines like Equioxx and Previcox are COX2 specific blockers, to lower prostaglandins.
C. “PGF2-alpha, PGE2 (prostaglandins) are vasoconstricting.” Dr. Kellogg, 2005. So when the horse is inflamed there is less blood flow to the feet and nerves in the feet.
D. COX2 inactivation had “protective effects against nerve function and biochemical deficits, shows support for major contribution of the COX2 pathway activations/enhancement oxidative stress relationship in diabetic neuropathy.” Dr. Kellogg, 2006. He also, by inactivating COX2, lowered prostaglandins by 5 times and also nerve catalase by 4 times and lipid peroxidation by 2 times.
E. *** “Evidence that inflammation in COX2 is major pathway accounting for 75% of PGE2 prostaglandins.” Dr. Gross, 2002, AJ Phys.; Dr. Langenbach, 1999, Ann. NY.
F. “PGE2 prostaglandin, Thromboxane is not unique to COX2 pathway in normal circumstances but in pro-inflammatory conditions such as diabetes, their function is mainly via COX2.” Dr. Kellogg, 2002.
G. Inflammatory path cross talk makes painful events. Prostaglandins made by COX2 enzymes are able to increase LOX enzymes on a different pathway and LOX products like HETE can increase only COX2 enzymes (but not COX1) “Cross activation greatly augments progress of neuropathy.” Dr. Xu, 2006, Kidney Int.
H. See how a Cox2 blocker helped in lowering peripheral neuropathy in an animal study. Also see how Gabapentin Family Med also helps. Click here to see: Etodolac, a Cyclooxygenase-2 Inhibitor, Attenuates Paclitaxel-Induced Peripheral Neuorpathy.
I. In Spinal Cord See below why Equioxx/Previcox helps so much in Neuritis.
• “Higher release of spinal COX2 protein and prolonged release of PGE2 in response to stimuli in diabetics.” Freshwater Diabetes 2002.
• In this study, this higher level of COX2 in the spinal area created hyperalgesia (overreaction to painful stimuli). This hyperalgesia seen 1 week of creating diabetes in lab animals and “it increased with duration of diabetes.” Dr. Ramos, 2007, Diabetes. Dr. Reilly – So longer inflamed, probably more and more sensitive to stimuli which is what we see often in horses.
• If just did spinal inhibitors of COX2 (not whole body, not at limbs), did see “significant alleviations of hyperalgesia.” Demonstrated animals sore not just at feet for example, but painful feet also due to spinal cord inflammation as well.
• Dr. Orsini, Head of the Laminitis Institute, alluded to this in his study of Equioxx in arthritic horses. “Improvement by day 7-14 in Osteoarthritis horses may have reflected in the past a neural effect such as a central down regulation of Allodynia associated with chronic pain.” AJVR, 2012.
• Dr. Bevtone, in a study, “COX2 involved in central nervous system pain responses and COX2 actually in CNS is increased in peripheral inflammation.” and “COXib medications (like Equioxx and Previcox) cross blood brain barrier they may provide analgesia centrally as well as peripherally.” JAVMA, 2008.
• Why Cox-2 blocker like Firocoxib (Equioxx/Previcox) needs to be used in early Laminitis pain. In a carbohydrate overload study testing various cytokines, inflammatory marks, the Cox-2 expression in laminar tissues was the one seen – not white cell cytokines, not nitric oxide enzymes. The Heiro program of pain relief over the last 5 years is in total agreement with this 2014 university study. Click here to see study: Laminar Inflammatory events in lean and obese ponies…
How to Help Stop Neuritis Pain In The Feet Of These Horses? 3 Steps.
1. Need to control high insulin – if this is not done, you are throwing Dixie cups of water on a forest fire. Slow/steady hay eating plus ration balancers with extra protein plus HEIRO = SUCCESS.
Eventually after testing, will slowly start a turn out program.
2. Physically protect feet – shoes, boots, casts, pads, impression material – to allow nerves to rest. Confine to a small area for 1 week.
A. COX2 blocking agents are most effective. 640 times more COX2 specific (Firocoxib in Equioxx). Dr. Orsini, 2012, AJVR.
B. The key is to get high levels into the horse quickly, then drop dose down but extend its use. Early on, we would get great effect then stop or cut the dose – big mistake, the horse would be sorer than before. Avoid the black hole by using COX2 blockers 21 days in a row.
C. Most of these horses have been on Bute/pulled off, but in our treatments, we will combine Bute (mostly COX1 blocking) with Firocoxib TOGETHER for just 3 short days then go 2 more weeks with Firocoxib.
D. Often COX2 medications like Equioxx or Previcox are used but at doses too small to stop nerve pain. Arthritis dosages are not helpful in the beginning of therapy.
Plan for a 1000 pound horse:
Days 4-7– No Bute. Equioxx Tablet at 1 in AM and 1 in PM.
Days 8-21 – 1 Equioxx Tablet in AM only.
Note: Fully aware that dose of Equioxx is higher than arthritis dose. This dose is highly effective for nerve pain. Often people will tell us “we tried Equioxx already” but did not do at this dosage and not in combination with Bute. Need to block COX1 and COX2 at the same time in the beginning.
NOTE: This combination has worked on hundreds of horses in 2012-2013 but 8 horses were still sore at day 21. I would then add Gabapentin by itself and got some results but when I would extend Equioxx with Gabapentin combined would get much more improvement.
Looked into why it happened and why if your Vet wants to use Gabapentin to combine with Firocoxib:
Dr. Chizh, 2007, Brit J. Anesth. Study:
1. Gabapentin in human studies did act centrally (spinally) on pain with a 30-40% reduction in Allodynia/hyperalgesia. Dr. Cilron, 2006, Exp Rev Neurotr.
Dr. Reilly – I agree. I would get some effect in cases but it was not a “wow” and it takes about a week to work.
2. In his study, he combined a COX2 blocker with Pregabalin (Gabapentin’s brother called Lyrica).
“Pregabalin combined with COX2 specific paracoxib was more efficacious in attenuating measurements of control sensitization than paracoxib alone. Combining Gabapentin-like drugs and COX2 inhibitors may provide an efficacy benefit in chronic pain states where central sensitization is key mechanism for neuropathic pain.”
Click here to see the study: Effects of Oral Pregabalin and aprepitant on pain.
“Combinations of analgesic mechanisms could lead to improved efficacy.”
Dr. Reilly – Now I knew why it helps, where it helped. I needed it rarely, but if I did need it, will combine it.
How to dose Gabapentin?
There is a great study on Gabapentin in Horses – Click here to see Dr. Terry’s article in J. Vet Pharm. Therap., 2010, Pharmacokinetic Profile and behavioral effects of Gabapentin in the horse.
What I have learned over the years:
1. The drug has a short half life, so need 3 times a day dosing. I have tried twice a day with failure and 3 times a day with great success.
2. I have tried the 20mg/kg dose but horses seemed very sedated (“zonked” according to owners), so I tried 15mg/kg with similar results, so use a 10mg/kg, 3 times a day dosage and horses good and comfort is improved.
3. Gabapentin has a low bio-availability (16%) so it takes abut 3-5 days to see effects. Do not get upset if in 2 days you only see a little.
4. If going to work, will see it by Day 8.
5. I always combine with Equioxx Tablets at the same time. Study on site (see link) shows works better than Gabapentin-like drugs alone. 1+1=3 Synergy.
NOTE: Ponies/Minis that are 250-500 pounds dose of Bute/Firocoxib?
Bute is dropped to ¼ gram AM & PM for 3 days only (not 7). But the Firocoxib is given still at 1 Equioxx tablet in AM and 1 Equioxx Tablet in PM for 7 days, then 1 Equioxx Tablet a day for 14 more days.
We have tried doing ½ or ¼ dose used in 1000 pound horses and it often fails. We believe there is a more profound neuritis amount in these types, via multiple past laminitis event in ponies over horses which require a stronger dose.
This dose is not required in acute laminitis cases, but in ponies/minis that have chronic/long-standing painful feet for over 3 weeks and are not responding to conventional doses.
Possible mechanics of why they need a higher dose for Neuritis than arthritis per pound?
- Greater spinal aspect of pain in ponies/minis.
- COX2 induced hyperalgesia increased with duration of Diabetes in Ramos study. Ponies/minis get earlier episodes of Laminitis and more Laminitis events than horses.
- More COX2 action due to LOX pathway crosstalk requiring more COX2 blocking.
- Length of time a Laminitis horse could effect need:
“Although pain of diabetic neuropathy may resolve spontaneously, pain persisting more than 3 months is unlikely to do so and may last years.” Dr. Glaer, 1995, Neuro.
Helpful Hints to Help Avoid Nerve Pain:
1. Boots – Physical barrier between earth and foot to protect nerves – also in winter keeps feet warmer avoiding cold-induced hyperalgesia.
2. Socks inside boots – Help wick away moisture – plain white socks.
3. Leg wraps/blankets in winter to keep feet warmer.
4. Increase time inside barn in winter to keep warmer.
5. Mats if outside to, again, protect nerves. Also acts as a barrier against cold earth in winter.
6. Deep Bedding – Protecting feet.
7. Pads in soles – can use sole guard if no shoes – will help in bare feet or in shod horses, add pad prior to shoe placement.
8. Frequent picking out feet to remove stones/snow.
9. Indoor turnout with cushion, no rocks to avoid flares.
10. Shovel snow allowing a dirt area and not just standing in 6 inches of snow. Put saw dust, shaving, used straw in area for traction.
11. Don’t skip trims – huge problem setting off flares.
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