A recent webinar with Dr Paul Freeman on the subject of IVDD opened up multiple questions on the current recommended treatment protocols for these patients. Primarily, Dr Paul Freeman questions whether the early surgical intervention actually does result in improved outcomes for patients with Hansen Type I IVDD.
Here we’ll discuss some of the questions Dr Freeman brought up in his lecture, as well as a few additional points.
IVD herniation can occur in canine patients in five distinct presentations. The most common type of IVDD is Hansen Type I. This is also the presentation that raises the most questions when it comes to how we treat these patients for the best chance of recovery.
Let’s dive into canine intervertebral disc disease, and what we know about its occurrence.
Understanding IVDD
We are all familiar with the analogy of the IVD to a jelly doughnut; the outside of the doughnut is the annulus fibrosus, the structure that determines the shape of the disc, and the jelly is the nucleus pulposus, the inner gelatinous substance with a high-water concentration that allows the disc to absorb shock. The cartilaginous end plates connect the disc to the bony vertebral body on either side. While we like to think of the disc and the vertebrae as separate, they are really a continuation of one another, and we need to consider them as a single unit.
When the disc degenerates, the annulus becomes harder and more brittle until it ruptures, while the nucleus loses its gelatinous quality and calcifies.
Disc Herniation
The disc can herniate into the vertebral canal in one of two ways.
A disc protrusion occurs when the annulus remains intact, but the shape deforms and bulges into the spinal canal compressing the spinal cord.
An extrusion occurs when the annulus ruptures and the nucleus escapes into the spinal canal.
The primary and secondary consequences
In the event of an IVD lesion, there will be both a primary injury and a secondary injury for us to consider. The primary injury occurs when the nucleus pulposus impacts the spinal cord, leading to haemorrhage and oedema in the region. Alternatively, the primary injury may occur when the spinal cord is compressed because of protruding or extruding disc material.
The secondary injury occurs as a cascade of events following the initial injury and can result in necrosis and apoptosis of the spinal cord.
Speedy decompression of the spinal cord through surgical intervention aims to minimise the secondary damage to the spinal cord by directly treating the primary injury.
The Five Presentations of IVDD
We are familiar with two main types of IVDD, briefly described above, but there are also a few additional presentations. The five types are:
- Hansen Type I IVDD
This is an acute extrusion of the nucleus pulposus through a rupture in the annulus fibrosis. The extrusion may cause both contusion and compression of the spinal cord, with compression often quite significant.
It generally occurs in chondrodystrophic dogs, including dachshunds, between the ages of 3 and 7 years as an acute or subacute presentation that progresses over a few days. The clinical severity and presentation can have a very wide range, with a good prognosis of recovery for all but the most severely affected dogs.
- Hansen Type 2 IVDD
This is a chronic protrusion of the disc, as the annulus stays intact but bulges into the vertebral canal, resulting in compression of the spinal cord. This usually occurs at multiple vertebral levels, making it challenging to determine which vertebral levels are responsible for the clinical presentation or symptoms of the patient.
A mixed presentation
The herniation may be both acute and chronic, with a combination of chondroid and fibroid disc degeneration.
- Acute Non-Compressive Nucleus Pulposus Extrusion (ANNPE)
An acute rupture of the annulus fibrosus leads to the escape of the liquid nucleus that causes contusion but no compression. This can only be managed non-surgically.
MRI of Intradural-Extramedullary Intervertebral Disc Extrusion in Dogs
- Hydrated Nucleus Pulposus Extrusion (HNPE)
In this condition, the annulus fibrosus ruptures with herniation of normal or partially degenerated nucleus pulposus. This is a high-pressure rupture that results in more contusion than compression and is more common in the cervical region. It can be managed surgically or non-surgically.
- ANNPE and HNPE
Both of these conditions can occur as per-acute conditions in middle-aged or older dogs, with border collies over-represented. These conditions tend to be non-painful, although the symptoms can sometimes begin with the patient yelping in pain during vigorous activity.
Treatment is primarily conservative, relying on rehabilitation and physiotherapy.
Surgical vs conservative treatment approaches
In his lecture, Dr Paul Freeman raises the question of whether decompressive surgery is necessary for the successful recovery of these patients. There is conflicting evidence in the canine patient population on whether decompressive surgery is more effective than alternative treatment options.
So far, very little correlation has been found between the degree of compression found on imaging and the neurological deficits or treatment outcomes of the patient.
Anecdotally, we like to make the claim that dogs that undergo decompressive surgery experience more rapid recovery, but there is very little evidence to support this statement.
While there are dogs that are conservatively managed that do deteriorate with time, there are also conservatively managed patients that make a full recovery.
The questions unanswered
For Dr Freeman, there are too many questions about IVDD (particularly Type I IVDD) that remain unanswered. These unknowns have made him question whether early surgical decompression is in the best interest of these patients and whether we may successfully help the body to recover through conservative management.
Some of the big questions raised by Dr Freeman include:
- Why is there no association between spinal cord compression and the severity of signs or outcomes?
- Why should residual compression after surgical intervention sometimes delay recovery, even when we know we leave disc material behind most of the time?
- Why is the evidence on rapid decompression so mixed, when experimental evidence would suggest this is important?
- Why is there such a difference between published recovery rates of deep-pain negative dogs treated surgically and medically – but only among this group?
A quest to find answers
These unanswered questions have led Dr Freeman and his team to develop an IVDD research group, where one of the studies being conducted is a prospective MRI-confirmed study of dogs with IVDD managed medically. They aim to follow the natural course of the disease over a three-month period to determine whether the extruded disc material resorbs with time, and how the presence of this material correlates with the recovery of the patients.
They also hope to determine what the actual recovery rate is of medically managed deep-pain negative dogs and to avoid the unnecessary euthanasia of dogs owned by clients who cannot afford surgery.
Which group of dogs really do require surgical decompression?
In his webinar, Dr Freeman shares the preliminary results collected up until the point of his lecture, with some very thought-provoking findings.
You can watch this webinar in the Onlinepethealth Small Animal Membership.
In conclusion
Dr Freeman’s work highlights that there are still many components of the progression of IVDD that we do not understand. For this reason, our treatment recommendations and approaches may not be meeting the individual needs of the patients we see – especially the group of patients that cannot undergo surgical intervention.
Wiggleless back braces
A note on Wiggleless back braces. For certain conservatively managed cases of neurological dysfunction, a back brace can help provide protection, stability and support to the patient. Read more about how the brace can be used in practice.
Rest in rehabilitation
There is no real consensus on rest when it comes to the conservative management of IVDD. General recommendations for rest vary from four to eight weeks, with varying degrees of restriction throughout that time period. Read more about how we can support dogs that require a period of cage rest or exercise restriction.
Resources
- Intervertebral Disc Disease: Where Are We Now, Dr Paul Freeman
- Physiotherapy for Fibrocartilaginous Embolism, Helen Nicholson
- Assessment of the Neurological Dog, Marinette Teeling
- Techniques to Try and Why they Work, Helen Nicholson
- Common Neurological Conditions, Dr Ryan Gallagher
- Assistive Devices for Neuro Cases, Marti Drum
- Motor Learning in Rehabilitation, Amie Hesbach
- What, Why and How of Tone Modulation, Amie Hesbach
- Rehabilitation Treatment Progression, Amie Hesbach
- Troubleshooting the Neurological Patient, Lowri Davies
- Hydrotherapy for Neurological Cases Part 1 & 2, Angela Griffiths
- Neurodynamic Mobilisation in Animal Physical Therapy, Sabine Hárrer
- The Neurological Dog, Marinette Teeling
- MRI of Intradural-Extramedullary Intervertebral Disc Extrusion in Dogs
- Timing of Surgery for Dogs with Thoracolumbar Intervertebral Disc Extrusion
- Comparing and contrasting FCEM and ANNPE in dogs using MRI
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