IVDH Consensus Statement – Medical Management Data

In July 2022, the ACVIM Consensus Statement on the diagnosis and management of acute canine thoracolumbar intervertebral (IVD) disc extrusion was published. This is the first of two installments about this consensus statement as a TidBit Tuesday. For this one, we will discuss the expected outcomes from medical vs. surgical management and what entails medical management. Enjoy!

The recommendations by the committee were graded as being supported by high, medium and low levels of evidence. Recommendations with high level of confidence include multiple randomized controlled trials with concordant findings. The evidence strongly supports the conclusions. Medium level of confidence includes retrospective studies with concordant findings, or small placebo-controlled trials. The evidence suggest that the findings are likely to be real. Lastly, low levels of confidence include isolated or small retrospective studies or single non-controlled trials. The evidence suggests that the findings might be real.

Medical vs. Surgical IVD extrusion management

A very helpful table was presented to help guide appropriate treatment for dogs presenting with signs consistent with TL IVD extrusion. The “%” represent the % of dogs that respond favorably to medical (M) or surgical (S) treatment.

·         Pain only: M 80%, S 98.5% à lateral extrusion may lead to reduced response to medical management.

·         Non-ambulatory paraparesis: M 81%, S 93% à level of recovery was less with medical management.

·         Paraplegia with deep pain: M 60%, S 93% à medical recovery is prolonged and less complete.

·         Paraplegia loss of deep pain: M 21%, S 61%

This is based on moderate level of evidence.  The statement here is “In paraplegic deep pain negative dogs, success with medical management is largely poor with an increased frequency of progressive myelomalacia. Surgical management is recommended.” – moderate to high level evidence.

What is medical management?

“At least 4 weeks of restricted activity is recommended, putatively to promote the healing of the annulus fibrosus. This period should include confinement to a restricted area 9crate, ideally, or small room without furniture) except when performing rehabilitation exercises or outdoor toileting. There should be no off-leash walking, no jumping on or off furniture and no access to stairs during this time”. This statement was supported by low level evidence. Corticosteroids are NOT recommended (moderate level evidence). Dogs with NSAIDs had a higher quality of life score than those on corticosteroids but NO STUDIES specifically address the use (or no use) of NSAIDS. Pain management is discussed, but no recommendations were made because of the lack of studies evaluating different medication protocols. Acupuncture was noted to be good adjunctive treatment for medical management but is not a recommended substitution for surgical management. What are my typical recommendations? For an uncomplicated T3-L3 myelopathy without MRI, with a strong suspicion of IVDH, I recommend NSAIDs, muscle relaxants and most importantly, cage rest for at least 3 weeks.

I hope this was enlightening. Please reach out with questions and stay tuned for the next update on the consensus statement. I hope you have a wonderful week. I am enjoying our tiptoe into fall and hope you are too!

Cervical Disc Herniation Associated Myoclonus in Dogs

Intervertebral disc herniation (IVDH) is the most common cause of cervical pain in small breed dogs. The most common clinical presentation is cervical pain with a normal neurologic examination, however in a few dogs gait deficits, paw replacement deficits, or reflex deficits can seen. Myoclonus, or a sudden onset, repetitive muscle contraction is seen in about 4% of dogs in a recent study from France. This muscle contraction is frequently confused for seizure behavior by clients so be on the look out for it! The classic presentation is a small breed dog that stops an activity, demonstrates myoclonus, and then resumes it's activity. Other signs of cervical pain (yelping, low head carriage, reduced range of motion) are often present when clients are questioned, so be sure to ask! 

What is the Significance of Cervical Myoclonus with IVDH?

The presence of myoclonus did not change the prognosis or outcome for the 20 patients in the recent study (JAVMA 2023: 261:4: 511-516.). Surgical correction resulted in less recurrence of signs, and immediate resolution in the post operative period compared to medical management. Approximately 25% of of medically treated dogs experienced another episode of myoclonus considered to be distinct from the original presentation. Medical management consisted of NSAIDs, gabapentin and, for some, tramadol. 

What is the Take Away?

• Myoclonus can occur with mechanical or chemical irritation of cervical nerve roots 

• Myoclonus does not affect prognosis

• Surgical management remains the recommended treatment for rapid resolution of signs of pain and reduction in relapse/recurrance

• French Bulldogs were over represented in this study!! (Again - See TidBit Tuesday in March for the list of Frenchie spinal cord diseases

As always, thank you for reading! I am thrilled to see the lovely weather on the horizon this week and hope you have a chance to enjoy some of it, too. 

Pug Myelopathies

Did you know that Pugs are commonly diagnosed with T3-L3 myelopathies? There are so many to chose from I thought I'd take this TidBit Tuesday and discuss some of the more common ones. 

Intervertebral disc herniation

Dis herniation is a common etiology of a T3-L3 myelopathy in many dogs, and Pugs are no exception. Type I and Type II disc herniations have been diagnosed in Pug dogs in the thoracolumbar region. Clinical signs include acute (or chronic if type II) variably painful (but often WITH signs of discomfort in this breed), pelvic limb proprioceptive ataxia followed by paraparesis. Signs can progress to paraplegia with loss of deep pain. Surgical and medical correction have been shown to be useful for Pug dogs and depend on the severity of the clinical signs.

Subarachnoid diverticulum

Subarachnoid diverticulum (SAD) can be described as cystic accumulations of fluid in the subarachnoid space around the spinal cord. Pugs are cited as among the most common breeds to be diagnosed with SAD. Clinical signs are slow in onset and often include incontinence early in the clinical course. Dogs with SAD are not typically painful. Medical and surgical management have been tried however neither approach appears to be an overwhelming success. Medical management is typically my preferred approach. 

Meningomyelitis and Neoplasia

Any and all breeds are at risk for these two diseases and Pugs are not overrepresented in this group. That said, clinical signs would include acute or chronic onset of signs with paraparesis and proprioceptive ataxia in the pelvic limbs. Treatment is medical for meningoencephalitis and medical, surgical or with radiation therapy for neoplasia. 

Degenerative Myelopathy

Degenerative myelopathy (DM) is caused by a genetic predisposition to demyelination of the T3-L3 spinal cord segments. Pugs are over represented and either confirmed or strongly suspected to have a mutation of the SOD1 gene (I cannot remember if it has been confirmed, yet!), like  German Shepherd dogs. Clinical signs include a slowly progressive, non-painful, proprioceptive ataxia that progresses to paraparesis, then paraplegia. If not euthanized, pets can progress to tetraparesis and eventually respiratory failure. A diagnosis is made through findings of a normal MRI and CSF analysis along with appropriate clinical signs. Genetic testing can be useful but isn't a stand alone test. 

Constrictive myelopathy

This is the new kid on the block. First published several years ago, constrictive myelopathy is caused by a fibrous band of tissue that circles the spinal cord and causes a constriction to CSF flow and compression of spinal cord tracts. Constrictive myelopathy is now thought to form due to a lack of development (hypoplasia) of the articular processes of the TL vertebra. If you imagine the articular processes are the "hands" that hold the vertebra together, supported by muscles and ligaments, becomes easy to see how hypoplastic articular processes might result in vertebral instability. This instability would then result in fibrotic tissue forming to help "stabilize" the joint. Sadly, this fibrous tissue then causes spinal cord constriction. To make matters worse, SAD can also form secondary to chronic spinal cord trauma so these poor dogs can have constrictive myelopathy secondary to hypoplastic facets and SAD in their T3-L3 spinal cord segments. Yikes. A diagnosis is made on MRI. A recent study (https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.16639?) evaluated the incidence of constrictive myelopathy alone, or in combination with other spinal cord diseases in a group of Pug dogs. They found only constrictive myelopathy in 3 dogs, constrictive myelopathy combined with IVDH in 17 dogs and IVDH only in 9 dogs, IVDH + SAD in 2 dogs and articular process dysplasia in ALL 32 dogs!

Summary:
Pug dogs are at risk for many causes of paraparesis and proprioceptive ataxia. A detail neurologic examination, history , and appropriate diagnostic imaging and spinal tap can help determine the underlying etiology and subsequently direct treatment most specifically. 

I hope this TidBit doesn't give you the impression that I am anti-Pug - I adore these little dogs. BUT,  I recognize their predisposition to specific spinal cord diseases when assessing them clinically. Remember, not all dogs with pelvic limb weakness have a disc herniation! 
Have a great week!

Large Breed Dogs and Disc Herniation

A little background...

Dogs greater than 10 kg experience type 2 disc herniation more frequently than type 1 disc herniation. (Refresher: Type 1 = acute extrusion of the center of the disc; Type 2 = bulge of outer ring of the disc into the spinal canal.) An estimated 10-30% of the time large breed dogs have type 1, depending on the study.

How is a type 1 disc herniation different for a large breed dog?

The answer is rather obvious, but glossed over frequently. They are bigger! That means nursing care is harder, surgery takes longer and is more extensive, and as a result there can be a greater expense for some of our larger dogs.

Does the prognosis change for a medium to large breed dog?

Yes. Dr. Woelfel from NCSU recently published data from a cohort of dogs > 10 kg that had both acute disc herniation and extensive spinal cord hemorrhage.

(Spinal cord hemorrhage occurs infrequently for large and small breed dogs and was shown in a few studies to have a minimal effect on prognosis as a stand alone feature. Meaning, the prognosis was still mostly based on the presence or absence of deep pain and didn't depend on spinal cord hemorrhage identified on advanced imaging.)

Okay, back to big dogs with disc herniation and spinal cord hemorrhage. The NCSU study reported a worse prognosis, and a higher complication rate, compared to overall data for small breed and chondrodystrophic dogs.

The details in summary:

• No deep pain before surgery, recovery about 38% (general population: 50%)

• Deep pain present before surgery, recovery rate about 77% (general population:90-95%)

• Complication rate was about 24% (general population: 10-15%)

Post Operative Complications Noted in the Referenced Study

• Decubital ulcers

• Pneumonia

• Self-mutilation

• Fever of unknown origin

• MDR UTI

• Sudden death

• Progressive myelomalacia

What is the take home message?

When talking with an owner of a medium to large breed dog with acute onset paraplegia, I suggest emphasizing the need for intense at-home nursing care, possible complications (along with the higher incidence) and a realistic prognosis if the dog is diagnosed with a disc herniation on advanced imaging. Remember that other differential diagnoses can cause acute onset paraplegia! Please do not interpret this paragraph as a call for euthanasia for large breed dogs with acute paraplegia. A 38% recovery rate is not zero! But a honest, open, vet-to-client discussion is the best way to achieve an informed decision for the client.

Not sure if you are interpreting the neurologic examination appropriately? Not sure if you are doing the neurologic examination properly? Please reach out! I am happy to work with you to help guide your clients in a compassionate and informed way.

Happy Easter to those that celebrated last weekend. We welcomed spring with big smiles around my house this weekend!

Reference: Woelfel, CW, Robertson, JB, Mariani, CL, Muñana, KR, Early, PJ, Olby, NJ. Outcomes and prognostic indicators in 59 paraplegic medium to large breed dogs with extensive epidural hemorrhage secondary to thoracolumbar disc extrusion. Veterinary Surgery. 2021; 50: 527– 536. https://doi.org/10.1111/vsu.13592

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!!