Prognostic Indicators for Acute Myelopathy

Acute Paraplegia: When to ship for surgery, treat medically or consider euthanasia

It happens to all of us (perhaps to me, more than you). Monday morning, 9 am, we are presented with a dachshund (Shih Tzu, Corgi...pick your top chondrodystrophic breed) after the dog became acutely non-ambulatory over night.

You perform a neurologic examination (self high-five!) and determine that the dog has a T3-L3 myelopathy with spinal pain at the TL junction.

What do you do next?

To be clear, a T3-L3 myelopathy does NOT equal a type I disc herniation. It means the dog may have a type I disc herniation or it could have a fibrocartilaginous embolic myelopathy (FCEM), acute non-compressive nucleus pulposus extrusion (ANNPE) or in rare cases meningomyelitis. (Yes, even dachshunds can get meningomyelitis!)
If we play the odds, that chondrodystrophic dog likely has a disc herniation. What, if any, prognostic indicators can you provide to the client?

Thankfully, an article out of Frontiers in Veterinary Science entitled "Prognostic Factors in Canine Acute Intervertebral Disc Disease" was published in November 2020 for just this purpose! (1) Here are some key points from the article. (The entire article is available as an open access article if you wish to read it in it's entirety. I highly recommend doing so if you are in the habit of seeing paraplegic dogs.)

Prognostic Indicator Key Points:

• Recovery following medical management (only) for dogs with paraplegia (loss of all voluntary motor) and loss of deep pain perception (DPP) is about 22.4%.

• Recovery following medical management (only) for dogs with paraplegia and intact DPP is 56%.

• Recovery following surgical management for dogs with paraplegia and loss of DPP is about 61%.

  • 25% recovered at 2 weeks

  • 42% recovered by 4-6 weeks

  • 53% recovered by 12 weeks

• Recovery following surgical management for dogs with paraplegia and intact DPP is about 93%.

*** Did you catch that?? DPP is a prognostic indicator! Dogs without DPP do worse long-term compared to dogs with intact DPP. They are also have a 10x higher likelihood of developing progressive myelomalacia which is a fatal secondary outcome from acute spinal cord injury.

What exactly does "recovery" mean? It means walking without support but it DOESN'T mean walking normally or complete continence. Dogs may (and often do) have fecal or urinary incontinence consistently or occasionally following severe spinal cord injury.

Other Key Points:

• Spinal shock can be more commonly associated with long-term fecal incontinence but does not seem to affect the ability to recover ambulation.

• Age, breed and weight are not associated with prognosis...mostly. Some studies have found heavier dogs have a worse prognosis, other's haven't. My take - bigger dogs are harder to care for but that doesn't mean they cannot recover.

• Reduced pelvic limb reflexes due to a L4-S3 lesion (not associated with spinal shock) has a higher likelihood of incontinence long-term.

When do you send a dog for surgery?

1) if the dog is non-ambulatory or paraplegic and the clients have a desire and financial ability to pursue surgery. Surgery with imaging costs $2000-5000 USD, depending on the specialty referral center.
2) Rapidly progressive signs (E.g.: dog was walking at 8 am, and is paraplegic at 10 am, with loss of deep pain by noon) and clients wish to pursue surgical intervention if indicated after imaging.

My plea...

Please don't send clients several hours to a specialist for surgery only to discover that the cost is prohibitively expensive. It is heart breaking for everyone and unnecessarily stressful for the dog. Call me and I'll happily talk with you about consult/medical management choices or sadly advocate humane euthanasia for the dog, if it is the best option.

Stay Safe, Keep Keeping On and Have A Good Week!

(1) Olby Natasha J., da Costa Ronaldo C., Levine Jon M., Stein Veronika M. Prognostic Factors in Canine Acute Intervertebral Disc Disease; Frontiers in Veterinary Science. 2020:7 p 913.

Monoparesis following Vehicular Trauma

How do you sort out a cat or dog with thoracic limb monoparesis following trauma?

This is an important question. First, let's review the innervation to the front leg. (Get back here - it's not that bad!) There are two important nerves that guide weight bearing and movement in the front leg:
1) Musculocutaneous - exits spinal cord segments C6-8. Important innervation is biceps muscle but it does a few others. The important action is flexion of the elbow and extension of the shoulder
2) Radial - exits spinal cord segments C7-T1 +/- 2. Innervates triceps and the muscles on the cranial distal limb that extend the carpus. The important action is extension of the elbow and carpus for weight-bearing.

So, to weight bear there must be an intact radial nerve. To move the limb forward there must be an intact musculocutaneous nerve. The other nerves (supra and subscapular, axillary, median and ulnar) are important too, but not as important. If you want to remember only two nerves, remember radial and musculocutaneous.

Now that we have that over with, let's put this to practice. Here is the scenario: You are presented with a 1 year old cat with a history of vehicular trauma a few days ago. The cat is presented dragging the left thoracic limb, unable to bear weight. When you watch it walk you can see advancement of the shoulder and elbow but it is minimal.
Question: What nerve is affected MOST?
Answer: Radial
Question: What spinal cord segment does the radial nerve arise from?
Answer: C8-T1 or 2.

Really good question: What is this cat's lesion localization?
Answer: Let's do a neurologic examination! :)

Neurologic exam:
Mentation: BAR
Cranial nerves: normal (note Horner's can be seen with thoracic limb injuries but isn't seen in this cat).
Reflexes: Absent triceps, absent withdrawal of the left thoracic limb. Unable to detect bicep or extensor carpi reflex (hey, it's a cat, give me a break!). All other limbs have normal withdrawal and pelvic limbs have normal patellar reflexes.
Palpation: non painful
Proprioceptive testing: absent tactile placing left thoracic limb, absent tactile placing left PELVIC limb, normal entire right side.
Gait: left thoracic limb monoparesis as previously described.

Now you can properly answer the previous question.
With absent radial nerve and diminished musculocutaneous innervation to the left leg, we KNOW the lesion must involve C6-T2, correct? (It's absent because of the missing withdrawal reflex - mediated through largely the radial nerve but also musculocutaneous too.) The real question here is this: is the injury in the plexus only or is there evidence of spinal cord involvement? To answer that question, you must look downstream from the affected segment. This means, look at the left pelvic limb. This limb has absent tactile placement so there has been disruption to the spinal cord tract going from the brain to the left pelvic limb, and back again.
Answer: This cat has a C8-T2 spinal cord lesion.

The differential list must now include things that affect the spinal cord such as avulsion and a disc herniation, hematoma or hemorrhage. Your diagnostic plan would include advanced imaging of the spinal cord. If the lesion localization had been peripheral plexus (not spinal cord) you would consider a brachial plexus avulsion only and advanced imaging would not be indicated. Knowing the lesion localization can markedly change your differential diagnoses, diagnostic plan and ultimately treatment and recovery!

Not sure about this case? Feel free to email me! This TidBit Tuesday is a slightly altered version of a real case seen recently. Keep those consults coming so we can share the knowledge folks! Please email/call/text me to schedule a consult or hop on my website and utilize the online scheduler to find the best time.

Have a good week!

C Reactive Protein and Discospondylitis

C-Reactive Protein and Discospondylitis

What is C-Reactive Protein (CRP)?

It is an acute phase protein that has been used in other inflammatory conditions such as SRMA, IMPA or inflammatory bowel disease to support or monitor the clinical response to treatment. 

Is it elevated with Discospondylitis?

Short answer: yes.
Long answer: It was elevated in most dogs in a recent study that were diagnosed with bacterial discospondylitis, but not all. In 8 dogs they measured it again 4-6 weeks into antibiotic treatment and it was normal in all 8 dogs. 

What can we do with this information in practice?

When faced with a patient with discospondylitis you can use CRP to support the radiographic evidence of discospondylitis. I would NOT suggest using this as a disease monitoring tool for dogs with discospondylitis because, as the authors point out, the intervertebral disc is a very immune privileged area of the body therefore infection could persist that is not reflected in the CRP. One of the dogs, in the study quoted above,  with normal CRP, had a recurrence of signs after stopping antibiotics. This suggests that CRP may not be a good long-term monitoring tool. 

That's all for this week! Have a safe, happy week and keep those consults coming! 

Nye G, Liebel FX, Harcourt-Brown T. C-reactive protein in dogs with suspected bacterial diskospondylitis: 16 cases (2010-2019). Vet Rec Open. 2020;7(1):e000386. Published 2020 Jul 20. doi:10.1136/vetreco-2019-000386

The Five Types of Disc Herniation

The Five Types of Disc Herniation (that we know of!)

1. Dystrophic calcification secondary to chondroid degeneration of nucleus pulposus (NP), called a Hanson Type I. This causes mechanical stress on the outer annulus fibrosus (AF), leading to rupture of individual collagenous strands of AF and eventually full failure.

2. Fibrous degeneration occurs when fibers of disc split leading to accumulation of tissue fluid and plasma between them. Over time the mechanical pressure exerted by NP causes thickening of the AF dorsally, causing protrusion. (Hanson Type II).

3. ANNPE (Acute noncompressive nucleus pulposus extrusion) - this is normal NP that is exploded into the canal, usually during activity. Also called a traumatic disc herniation.

4. AHNPE (Acute hydrated nucleus pulposus extrusion) – An apparently normally hydrated NP that is compressive and often located ventral to the cord, often in the neck.

   1. Significantly more neuro deficits and less signs of cervical pain with AHNPE compared to other causes of cervical myelopathy.

5. FCE (Fibrocartilaginous embolism): a piece of NP that becomes dislodged and finds its way into the vasculature surrounding the spinal cord. This can be into venous or arterial blood vessels. The end result is an acute shift in blood flow at the level of the spinal cord.

Match the clinical sign with the type of disc herniation

A. Chronic, progressive ataxia progressing to paresis
B. Acute, non-progressive unilateral weakness affecting one leg, or one side (hemiparesis)
C. Acute, progressive, painful ataxia progressing to paresis in a chondrodystrophic dog
D. Acute non-progressive ataxia and paresis affecting both sides of the body (paraparesis or tetraparesis)
E. Acute, rapidly progressive tetraparesis and ataxia of all four limbs with minimal cervical pain

If you answered...
Type I: C
Type II: A
ANNPE: D
AHNPE: E
FCE: B

you are correct!

Based on the clinical picture, it can be very difficult to distinguish Type I from ANNPE, and AHNPE. Typically, type I is painful (but not always), and the other two are minimally to non-painful. 

Which of these require surgery?

Any disc herniation that results in compression of the spinal cord with associated clinical signs could be considered for surgical correction. This statement would then suggest that Type I, Type II and AHNPE could be surgically corrected. Therefore, any patient with signs of a progressive or painful myelopathy should be evaluated for diagnostic imaging (typically MRI) for possible surgical intervention whenever possible.

Bonus question:
Can you name two diseases that are commonly diagnosed instead of a type I or type II disc herniation? Scroll to the bottom for the answer!

Change is coming! Starting in September I will have new fees, and new availability.  I am happy to accommodate outside of these hours whenever possible so please reach out if you cannot find a suitable time using the online scheduler. ( https://barnesveterinaryservices.com/ )

New Hours (Starting September 8th)
Monday 11a-1p, 4-5p
Tuesday 3-4p
Wednesday 11a-1p, 2-4p
Thursday 2-4p
Friday 12-1p
Saturday 9-11a

Bonus Question Answer
 Meningoencephalomyelitis (a.k.a meningitis), and neoplasia. Keep these two on your differential diagnoses list when you suspect a disc herniation!!

The Genetics of Disc Herniation

What is the deal with chondrodystrophy, anyway?

Chondrodystrophic dogs are born to have short stature, and abnormal aging of the intervertebral discs. It's what makes a Dachshund or French Bulldog look like, well, a Dachshund or French Bulldog! I'm sure it comes as no surprise that there is a genetic reason why they look this way. But, did you know that someone has sorted out the genetic mutation that has been linked to chondrodystrophy and disc herniations?

What is the genetic mutation and what does it mean?

Several studies in 2019 (and earlier) looked at copies of 12-FGF4RG and 18-FGF4RG status in chondrodystrophic dogs and found that if a dog carried at least 1 copy of the 12-FGF4RG gene they were significantly smaller, younger and more likely to have radiographically calcified discs than those without. Furthermore, 12-FGF4RG was the only factor identified in multivariate logistic regression models that contributed to needing disc herniation surgery in mixed breed dogs. Mixed breed dogs? (You ask.) Yes, Dachshunds and French bulldogs, specifically, have such a high rate of carrying 1 or 2 copies of the 12-FGF4RG gene that it's impossible to say with the relative risk of disease is for these breeds with the mutation. In other words, if every Dachshund has the mutation is it actually related to disc herniation? Not sure yet. One study found that non-Dachshund and French Bulldogs had between a 5.1-15.1 fold increase of disc herniation if they had at least 1 copy of this gene. 

What do I do with this information?

If you have a neutered animal, nothing. It might predict the risk of disc herniation in that animal but that animal is already born, and presumably loved, so this information is not actionable. If you have a client considering breeding you may be faced with the results of this genetic information and asked the question above.  My opinion? There are specific breed risks so either read the published data on risk for the specific breed in question, or reach out to me and I'll gladly pass along the information. It's in a handy table, but not my data so I don't feel comfortable including it in the TidBit Tuesday mailer. If possible, breeders should try to breed dogs with zero or 1 copy to dogs with 1 or zero copies of the mutation to reduce it's presence in the breed. *This doesn't apply to Dachshunds or French Bulldogs for the above mentioned reasons!

Keep those chondrodystrophic dogs fit, healthy, and leading low impact lifestyles! It won't eliminate the risk of a disc herniation but it may make recovery easier. 

Batcher K, Dickinson P, et al. Phenotypic Effects of FGF4 Retrogenes on IVDD in Dogs. Genes (Basel) 2019; 10(6): 435.

Do you have a case you'd like to discuss with me? Feel free to email, text, or call me! I'm still trying to see mostly video consults whenever possible but I'm gradually increasing the live consults performed. Either way, I look forward to (continuing) to work with you!