Web-Vet Neurology Specialists
Intervertebral Disc Disease
Herniation of degenerate nucleus pulposus can result in sudden onset of clinical signs ranging from spinal pain to the loss of motor function and pain sensation. This is most common in the thoracolumbar spinal column but can affect the cervical spinal cord as well. Whilst most reports in the veterinary literature relate to dogs, intervertebral disc extrusions are also reported in cats
Herniation of the nucleus pulposus through the annulus of the disc and extrusion of nuclear material into the spinal canal, resulting in concussion of the spinal cord and concurrent compression. Genetic investigations have identified an FGF4 retrogene insertion on chromosome 12 associated with the development of Hansen Type I intervertebral disc extrusions and chondrodystrophy across several dog breeds.
Pathophysiology
Pathologic Features of the Intervertebral Disc in Young Nova Scotia Duck Tolling Retrievers Confirms Chondrodystrophy Degenerative Phenotype Associated With Genotype
Chondrodystrophy results in predictable and progressive biochemical and structural changes to the intervertebral disc, resulting in early onset degeneration and dystrophic mineralization of the disc, common in multiple dog breeds. This can result in disc herniation. A mutation responsible for chondrodystrophy in dogs has been identified as an aberrant fibroblast growth factor 4 (FGF4) retrogene insertion on chromosome 12 (CFA12) and is associated with short stature of the Nova Scotia Duck Tolling Retriever.
This study found that in discs isolated from 2 dogs with the CFA12 FGF4 genotype, the nucleus pulposus was largely replaced by cartilaginous tissue consistent with premature chondroid degeneration of the intervertebral disc .
Clinical Characteristics & Diagnosis
The aim of this study was to compare the clinical presentation, MRI changes, and clinical outcome of dogs with acute thoracolumbar intervertebral disc herniation (TL-IVDH) with and without epidural hemorrhage (EH).
63 of 160 (39%) dogs with TL-IVDH had confirmed EH. French Bulldogs were significantly overrepresented. Dogs with EH were more likely to present with clinical signs less than 48 hours and were more likely to be non-ambulatory on presentation.
Magnetic resonance imaging features of canine intradural/extramedullary intervertebral disc extrusion in seven cases
Intradural/extramedullary disc extrusion is the least common type of intervertebral disc herniation in veterinary medicine, characterized by extruded disc material within the intradural space.
The aim of this study was to describe the high field (1.5T) MRI characteristics of surgically confirmed intradural/extramedullary disc extrusions.
A “Y sign” (division of the dura and arachnoid layers) maybe a reliable MRI feature for identifying intradural/extramedullary disc extrusions based on this MRI study. As the arachnoid is peeled from the dura by the disc herniation there is a splitting of the arachnoid mater and the ventral dura. The intradural disc material will be surrounded by CSF signal intensity, giving the appearance of a Y, which can be identified from the T2-weighted sagittal images.
This study aimed to describe the clinical and imaging characteristics of tentatively diagnosed IIVDE in dogs to assess the prognostic utility of neurological grade and MRI findings. The authors found that this type of disc extrusion is commonly experienced after physical activity or trauma and most frequently affects the cranial-cervical and thoracolumbar regions of non-chondrodystrophic dog breeds. MRI characteristics included T2 hyperintense, T1 hypointense, intramedullary linear tracts with reduced disc volume, and a cleft of the annulus fibrosus.
Neurological score at admission emerged as a more useful prognostic indicator than MRI findings, such as the presence of hemorrhage, in dogs with suspected IIVDE.
This retrospective study aimed to describe the clinical presentation, MRI findings, and long-term outcome after medical or surgical treatment of dogs presenting with foraminal and far lateral thoracolumbar intervertebral disc herniations.
The study evaluated 37 dogs of which, Dachshunds and mixed breeds were most affected. Median age at presentation and duration of clinical signs were 6 years and 14 days, respectively. Pain was the most frequent clinical finding (92%), particularly on spinal palpation and/or hip manipulation, followed by pelvic limb lameness (71%). Eighty-seven percent of herniations occurred at L5-L6 or L6-L7. A good to excellent outcome was seen in 95% of surgically and 90% of medically treated dogs
Also check out the webinar on this paper - click this link to watch.
The aim of this retrospective study was to describe MRI features of paraspinal muscle signal alteration in 103 dogs with acute thoracolumbar intervertebral disk extrusion and to investigate an association of the signal alterations with neurological grade, type and location of intervertebral disk extrusion, degree of spinal cord compression, and presence of epidural hemorrhage.
Paraspinal muscle signal alterations were visible in 37 dogs affecting the epaxial and or hypaxial musculature. All signal alterations were hyperintense on T2-weighted images and iso- or hypointense in T1-weighted images. Signal void in T2* was not observed in any dog. Post-contrast images showed enhancement in 45%. There was neither an association with degree of compression nor epidural hemorrhage. Intervertebral disk extrusion caudal to L1 and a higher neurological grade was associated with the presence of muscle changes.
Nerve root signature (NRS) presents as elevation of the limb in a non-weight bearing position while standing, which is believed to be a manifestation of pain resulting from entrapment or irritation of the spinal nerve or nerve root. NRS is commonly found in association with Intervertebral Disc Herniation (IVDH). However, it can also occur due to neoplasia, trauma, bony proliferative changes, and inflammatory conditions.
This study describes the clinical and magnetic resonance imaging (MRI) findings in dogs with NRS associated with cervical IVDH and found that 42% of cases actually were associated with C2-C3 through C4-C5 disc sites. Most commonly the disc lesions seen on MRI were lateralised or foraminal in location.
Therapy & Prognosis - Dogs
ACVIM Consensus Statement on Acute Canine TL Intervertebral Disc Extrusion
Although there is much literature available on IVDE, the majority of it is observational. Consensus statements are important to review available literature, weigh the evidence and generate recommendations for management as well as highlight some areas of opportunity for further exploration (see image above). If you want to know more about the state of knowledge on IVDE and potential areas of research, have a read of this paper published in JVIM
Prognostic Factors in Canine Acute Intervertebral Disc Disease
This review article addresses what is known about predicting the prognosis in dogs with acute intervertebral disc disease.
Important prognostic considerations are recovery of ambulation, return of urinary and fecal continence, resolution of pain and, on the negative side, development of progressive myelomalacia. Initial injury severity affects prognosis as does type of IVDE, particularly when considering recovery of continence. Overall, loss of deep pain perception signals a worse outcome. When considering Hansen type 1 IVDE, the prognosis is altered by the choice of surgical vs. medical therapy. Cross-sectional area and length of T2 hyperintensity and loss of HASTE signal on MRI have also been associated with outcome.
There is a general perception that French bulldogs with severe thoracolumbar disc extrusions (TL-IVEDE) have a poor rate of recovery especially when compared to Dachshunds and other chondrodystrophic breeds. This recent paper evaluates the rate of recovery of nociception-negative French bulldogs with TL-IVDE.
Thirty-seven French bulldogs with absent nociception were evaluated and 14 of 37 (38%) regained deep pain perception by the time of discharge; only 19% with L4-S3 lesions regained deep pain perception compared to 11 of 21 (52%) of dogs with T3-L3 lesions!
The video above is one of the lucky Frenchies which can be seen to have regained motor function shortly after surgery.
The goals of this retrospective case-control cross-sectional study were to (1) compare the success rate of routine surgical decompression in dogs with disc extrusion with epidural hemorrhage (DEEH) compression compared to Modified Frankel Score (MFS) matched dogs with non-hemorrhagic disk extrusions; (2) evaluate the extent of spinal cord compression on MRI compared to final patient outcomes in DEEH compression and (3) determine the surgical compression to decompression ratio and its relation to patient outcomes in cases of DEEH compression. A total of 143 dogs were included in this study.
The study supports the finding that when a similar level of surgical decompression is achieved, dogs with DEEH compression have similar outcomes to dogs with non-hemorrhagic IVDE for similar degrees of neurological dysfunction. Overall, the presenting Modified Frankel Score, rather than the extent of extradural compression visualised on MRI or presence of hemorrhage predicts functional outcome.
The objective of this study was to compare the proportions of dogs with thoracolumbar disc extrusion that lose pelvic limb pain perception if surgery is performed on the day of admission or delayed overnight.
273 dogs were subdivided into two groups: early surgery (spinal decompression between their examination at day of admission and the following morning), and delayed surgery (did not undergo surgery between admission and the following morning). The proportion of dogs that lost pelvic limb pain perception overnight was compared between the early and delayed surgery groups.
Seven of 151 dogs in the early surgery group lost pain perception overnight compared to 15 of 122 in the delayed surgery group (P= 0.025).
The aim of this retrospective analytical study was to describe the volume of postoperative residual extradural material (VREM) and the ratio of the cross-sectional area (CSA) of maximum SC compression to the CSA of SC in a compression-free intervertebral space as MRI measures of preoperative and postoperative compression (residual spinal cord compression, RSCC), and to compare these measures between the neurological outcome in a group of dogs.
The prevalence of residual extradural material in postoperative MRI studies was 100%. No significant differences in mean preoperative SC compression, mean RSCC, mean SC decompression, or VREM were found between positive and negative outcome groups.
Lumbar vertebral canal stenosis due to marked bone overgrowth after routine hemilaminectomy in a dog
Fascinating case report published in Acta Veterinaria Scandinavica of bone overgrowth after decompressive surgery for lumbar epidural hemorrhage resulting a year later in recurrence of neurological signs. Revision decompressive spinal surgery was performed with histopathology revealing normal or reactive osseous tissue. Nine-month postoperative, imaging studies showed a similar vertebral overgrowth, resulting in minimal spinal cord compression.
Lateralised / foraminal disc disease in 4 dogs with chronic cervical pain refractory to standard conservative treatment was evaluated.
Ultrasound-guided paravertebral perineural injections with methylprednisolone acetate (1 mg/kg [0.45 mg/lb]) at the C3 nerve root in dog 1 and at the C7 nerve root in the other 3 dogs were performed. Injections were repeated at intervals of 4 weeks to 3 months on the basis of clinical response. None of the dogs had any complications from the procedures. For dogs 1 and 4, there was complete resolution of lameness and signs of cervical pain following perineural injections, and for dog 3, there was complete resolution of lameness and only minimal residual cervical pain. Dog 2 did not have long-lasting improvement.
Therapy & Prognosis - Cats
The objective of this study was to describe outcomes after surgical or conservative treatment of cats with thoracolumbar and lumbosacral IVDH.
This was a retrospective cohort study evaluating outcomes of surgical (49 cats) and conservative (36 cats) management of IVDH; 7 cats were euthanized at diagnosis.
Surgical treatment resulted in 62% (6 weeks) and 74% success (6 months). Conservative treatment resulted in 54% (6 weeks) and 65% success (6 months). Neurological grade at presentation was higher in cats treated surgically (median, 2; range, 1‐5) than in those treated conservatively (median, 2; range, 0‐4; P = .001). Regardless of treatment type, cats suffering trauma were more likely to have a successful outcome 6 weeks after treatment compared with those without history of trauma. Neurological deficits remained in the majority of cats for both treatment types.
Acute Non-Compressive Nucleus Pulposus Extrusion (ANNPE)
This study aims to evaluate the outcome among paraplegic deep pain positive (DPP) and deep pain negative (DPN) dogs with either FCEM or ANNPE and factors influencing recovery.
14 dogs were initially paraplegic DPP (8 FCEM, 6 ANNPE) and 17 dogs were paraplegic DPN (11 FCEM, 6 ANNPE). Outcome was available for 26 dogs (14 DPP, 12 DPN) with a median follow-up time of 182 days (range 0–2,311) including 2 dogs euthanized at the time of diagnosis; 1 of 12 DPN dogs (8.3%) regained independent ambulation, whereas 9 of 14 DPP dogs (64.3%) regained independent ambulation. DPN dogs had a significantly higher risk of not regaining independent ambulation compared with DPP dogs. No other variables were associated with outcome.
Hydrated Nucleus
Pulposus Extrusion
This study aims to evaluate the outcome among paraplegic deep pain positive (DPP) and deep pain negative (DPN) dogs with either FCEM or ANNPE and factors influencing recovery.
14 dogs were initially paraplegic DPP (8 FCEM, 6 ANNPE) and 17 dogs were paraplegic DPN (11 FCEM, 6 ANNPE). Outcome was available for 26 dogs (14 DPP, 12 DPN) with a median follow-up time of 182 days (range 0–2,311) including 2 dogs euthanized at the time of diagnosis; 1 of 12 DPN dogs (8.3%) regained independent ambulation, whereas 9 of 14 DPP dogs (64.3%) regained independent ambulation. DPN dogs had a significantly higher risk of not regaining independent ambulation compared with DPP dogs. No other variables were associated with outcome.