Recurrent Cervical Pain

Imagine with me that you are presented with a 10 kg small breed dog on Tuesday morning with a history of neck pain. This dog had a history of neck pain 1 year ago that underwent full work up, at your local University or specialty hospital, and was diagnosed with a disc herniation. The clients pursued surgery, and recovery was smooth and complete. The clients were thrilled...until yesterday. Now, they're angry.

How likely is it that this dog has herniated ANOTHER disc in it's neck?

It is a good question, and one that we have some recent data that might help answer this question. A study out of the UK looked at the recurrence rate of cervical pain in dogs that had a prior disc herniation diagnosed via advanced imaging.
119 dogs in the study, 36 dogs had signs of recurrent neck pain or a cervical myelopathy.

• 36/119 had medical management following diagnosis of IVDH

  • 13/36 (36%) had a recurrence of signs

  • Recurrence was more likely at the same intervertebral disc space

• 83/119 had surgical correction following diagnosis of IVDH
  

  • 27/83 (33%) had a recurrence of signs

  • Recurrence was more likely at neighboring intervertebral disc space to the original disc herniation

• Surgical correction did not decrease the odds of recurrence in this study. Important: We don't know if these dogs underwent surgical fenestration at the time of their first surgery, or not.

• Recurrence was within 2 years of the original diagnosis of a disc herniation for 80% of the dogs in this study. (Note: this means that 20% it was longer than 2 years!)

** We don't know that every one of the dogs had a second disc herniation but the few that did have work up did have a disc herniation confirmed.

The data reported in this study suggests that medical and surgical correction of cervical disc herniations does not change the risk of new onset cervical pain. Reported ranges in the literature for recurrence of cervical pain with surgical correction are between <10-30% (and probably more towards the 0-15% range in the cervical spine) so it is at the high end of reported recurrence. Reported recurrence with medical management is slightly more difficult to track but may be in the 30-40% range. Therefore, it is surprising that the authors saw a similar recurrence for medical vs surgical correction. This may come down to the surgical correction performed, which we don't know from this study. We do know that none of the dogs with surgical correction had a recurrence at the site of correction.

What should we tell the client before us? Surgical correction for a ruptured disc corrects the issue at that disc, but may not address degeneration at distant sites. Sadly, their pet may be faced with a recurrence of another disc herniation. If they're up for another workup and possible surgery, it's time to start the process for referral. If they'd like to give medical management a try, get started on some pain management and bed rest (avoid those steroids if you can in these cases!) and keep a close eye on the dog. Weekly neurologic exam would be recommended, if possible.

Link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/jsap.13480

This Tidbit took a slightly different approach than my usual updates. I typically try to pull 1-2 key points from an article that I find useful, and that I think you'll find useful. This time, I decided to represent a study that wasn't highly powered, that also didn't provide clear, convincing data to support a specific question. We all like black and white scientific data that we can read, digest and apply but honestly, that is a minority of what I read on a daily basis. This TidBit had more "waffling" in it because I wasn't fully convinced the data provided would change my practice. How did this report strike you? Did you find it useful, or not? As always, thanks for reading!

Have a great week and keep those consults rolling!

Managing a Pain in the Neck

Cervical pain can present with or without concurrent neurologic deficits and therefore maybe secondary to neurologic or non-neurologic disease.

Animals with neurologic deficits in addition to neck pain have a neuroanatomic lesion localization (C1-T2 myelopathy) which includes the region of pain.

Deficits noted in the C1-T2 lesion localization may include proprioceptive ataxia of all four limbs, tetraparesis (or plegia), reduced or absent postural reactions in all four limbs, +/- reflex deficits of the thoracic limbs. Postural reactions are often more severe in the pelvic limbs than thoracic limbs with a C1-T2 myelopathy therefore this finding should not dissuade you from this lesion localization. Rarely noted neurologic deficits may include unilateral Horner’s syndrome and unilaterally absent cutaneous trunci. With acute, peracute and severe cervical injury respiratory failure (lack of inspiration) can be seen secondary to damage to the phrenic nerve (driving diaphragmatic function) and/or damage to the upper motor neurons that regulate the intercostal innervation. A lesion localization of a C1-T2 myelopathy indicates neurologic damage, and therefore diseases affecting the nervous system should be considered for these patients. See the section below discussing differential diagnoses for animals with a C1-T2 myelopathy lesion localization.

Animals with cervical pain without neurologic deficits cannot have a neuroanatomic lesion localization because they do not necessarily have neurologic disease.

Therefore, the diagnosis written in the record should be “cervical pain”. These animals may have neurologic disease; however, diseases outside of the nervous system should also be included on a differential diagnoses list.

Differential Diagnoses (not a complete, textbook list...just the more common ones)
** Many differential diagnoses listed below may start with signs of neck pain ONLY, without evidence of a myelopathy and then may or may not progress to signs of a myelopathy.

Differential Diagnoses (not a complete, textbook list...just the more common ones)
** Many differential diagnoses listed below may start with signs of neck pain ONLY, without evidence of a myelopathy and then may or may not progress to signs of a myelopathy.

1. Acute/peracute onset clinical signs:

   1. C1-C2 subluxation (congenital or traumatic)

   2. Intervertebral disc herniation (type I)

   3. Traumatic fracture/subluxation non-C1-C2

   4. Meningomyelitis

   5. Discospondylitis/osteomyelitis

2. Slow/subacute onset clinical signs

   1. Discospondylitis

   2. Vertebral or neural neoplasia (note: intramedullary neoplasia is commonly non-painful. Any involvement of the meninges can result in cervical pain.)

   3. Intervertebral disc herniation type II

   4. Syringohydromyelia

   5. Cervical spondylomyelopathy (AKA Wobbler’s syndrome)

   6. Meningomyelitis

3. Acute, non-progressive clinical signs

   1. Fibrocartilagenous embolism (note: this may be painful in the first 24 hours, however most become non-painful after 24 hours.)

   2. Syringohydromyelia

What do you do?

First, a neurologic examination. If the animal has neurologic deficits, referable to the cervical region, localize the lesion. (Self promotion plug here....remember if you're not confident with a neurologic examination, please call for a consult!)

Radiographs are useful if trauma or subluxation is a primary differential diagnoses. Treatment should follow with your differential diagnoses list. If the pet is poorly or non-ambulatory a consultation or referral to a neurologist is recommended ASAP.

Thanks for reading! I hope you have a great start to 2022. Keep those consults coming!

Steroid Responsive Meningitis-Arteritis

It's a cold Tuesday morning and your first patient today is a painful, 6 month old Boxer dog. You dutifully run through the differential diagnoses in your head as you walk into the room. What you see when you arrive is a depressed, febrile Boxer puppy trying really hard not to move their head or neck and wincing when doing so.
After examination you find the dog has the following neurologic examination findings:
Mentation: QAR, especially for this normally hyperactive puppy
Cranial nerves: normal
Gait: stiff, stilted gait but no evidence of paresis, ataxia or lameness. (Although lameness and paresis CAN happen with steroid responsive meningitis-arteritis, a.k.a. SRMA)
Postural reactions: normal paw replacement in all four limbs
Reflexes: normal in all four limbs, normal c. trunci and perineal (you did a great job!)
Palpation: Oh how the dog winces with cervical palpation! (Don't do cervical ROM on this dog, okay?)

Neuroanatomic lesion localization: Well...technically the neurologic examination is all normal, right? So all you can say is "cervical pain" on the record. No neuroanatomic lesion localization when they are neurologically normal.

Differential diagnoses: Trauma, fracture, subluxation, muscle strain, infection/polyarthritis, and yes, SRMA.

What is SRMA?

It is an immune mediated disease that affects the vasculature of the meningitis, and sometimes the joints and it typically affects dogs < 2 years of age, with large breed dogs and beagle dogs over represented.

How do you diagnose it?

First, rule out other causes (radiographs, spinal MRI). Next, perform a spinal tap and identify a neutrophilic pleocytosis (often with a SUBSTANCIALLY increased cell count!). Third, rule out infectious diseases that cause meningitis in your area of practice. For most of us in Wisconsin, this is Neospora (toxoplasma if cat), fungi, and bacterial causes.

What is the recommended treatment?

Steroids at 1-2 mg/kg PO q12h, depending on the literature. I start with 1 mg/kg PO q12h for 30 days and then reassess the CSF. Some studies suggest doing this dose, or a slightly tapered dose, for up to 3 months and then reassessing the CSF. When normal, a gradual taper over 3-6 months is common. Relapses can occur in up to 80% of the studies published but my experience has been a much lower recurrence rate.
A recent study by Giraud et al* found a lower relapse rate with the addition of azathioprine. They used 2 mg/kg PO q24h x 1 month and then tapered from there to an every other day dosing interval for 2 months for a total of 3 months of treatment. The authors suggested that the addition of azathioprine allowed them to reduce the prednisone dosage sooner and more rapidly, thus reducing long-term side effects. Over 80% of the dogs in this study were in clinical remission within the 2 year follow-up time without signs of relapse.
Azathioprine was also reported to have exceptionally long survival times when used in combination with steroids to treat meningitis of unknown etiology (MUE), another immune mediated CNS disease. So...perhaps we're on to something here! Interestingly, azathioprine was suspected not to cross the blood brain barrier initially. Hummm...

Key Points:

• SRMA is often treatable, but relapses do occur.

• A CSF tap is needed to confirm the diagnosis however MRI is often performed before CSF to rule out physical/structural abnormalities. This helps to decrease the risk of harm from a spinal tap.

• Steroids are the mainstay of treatment but azathioprine may be added to allow a more rapid reduction of steroids (thus reducing long-term side effects from steroids).

Have a great week and stay safe out there! It's been a snowy few weeks here in Wisconsin so drive safely if you're out and about!