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Review Paper: Long Term Outcome of Cervical Dorsal Laminectomy to treat Wobbler Syndrome: 47 cases (2003-2017)

Introduction                                            

Wobbler syndrome is a progressive, heterogenous, neurological disease characterised by a variety of signs including paraparesis, tetra-paresis, ataxia, thoracic limb lameness and neck pain.

fig. 1 – MRI T2W sagittal slice of caudal cervical spine in a 7-year-old Rottweiler. There are two protruding discs at Ce5 & Ce6, consistent with a diagnosis of Disc Associated Wobbler Syndrome.

Aetiology may be classified as either disc associated (DAWS fig.1 see above) where the primary pathology is deformation of degenerate intervertebral discs, or bone associated (BAWS, also known as Osseous Associated Wobbler Syndrome OAWS, figs 2 & 3 below) where there is malformation of the neural canal, including changes to the facets joints, pedicle and vertebral bodies.

fig. 2: MRI T2W transverse slice of cervical spine in a 9-year-old Wire-Haired Pointer at the level of the Ce3 vertebral body. Note:- dorsoventral diameter of the neural canal, with normal cross sectional cord morphology.

fig. 3: T2W transverse slice of the same patient fig.2, at the level of the Ce2 disc. There is dorsoventral narrowing of the neural canal, with significant cord compression. Note the disc itself is well-hydrated. These changes are consistent with BAWS.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BAWS is usually seen in juvenile or young-adult large/ giant breeds, whereas DAWS is normally seen in middle-aged or older large breeds e.g. Dobermann Pinchers.

Most surgeons agree that decompression, distraction or stabilisation (or a combination of all three) is essential to long-term success1.  However, there is no consensus on the optimal technique for management of compressive cervical spinal lesions, reflecting their diverse array of underlying causes.

fig. 4: Intraoperative photograph of continuous dorsal laminectomy in a Great Dane.

There is an ever-expanding list of procedures and implants which claim to meet the above surgical goals, including dorsal laminectomy (fig. 4, above) as a continuous, multi- or single site procedure, ventral slot, disc replacement and distraction/ fusion.  However, published long-term outcomes show that regardless of the technique employed, recurrence of signs is seen in 15-40% of cases2,3,4.

The clinical records of all animals undergoing  cervical dorsal laminectomy at Downs Veterinary Referrals between 2003-2017 were reviewed.   All patients were operated on by the author.   Patient signalment, severity of presenting signs, diagnosis and peri-operative morbidity were assessed, with particular emphasis on DAWS and BAWS. Long term outcomes were obtained by telephone interview of owners.

 

Signalment                                                    

A wide range of breeds were presented.  However, large/ giant breeds were over-represented: Dobermann Pinchers (12/47),  Rottweilers (7), Great Danes (5), Bernese Mountain Dogs and Labrador Retrievers (each 4).

Age at first presentation ranged from six months to 10 years.  The mean age of DAWS cases was 7.1 years, whereas the mean age of BAWS cases was 2.9 years.

Sex ratio was heavily weighted towards males (35:12).

 

Correlation between age and outcome:           

17 cases were less than 5 years of age at presentation.  Of these, 15 (88%) made a full recovery, with a mean post-operative time to walking of 1.8 days.

28 cases were greater than 5 years of age at presentation.  Of these, 24 (86%) made a full recovery, with a mean post-operative time to walking of 3.75 days.

 

 

Correlation between severity and outcome:                                               

Of the 33 ambulatory cases, 29 (88%) made a full recovery, with a mean post-operative time to walking of 2.5 days

Of the 14 non-ambulatory cases, 11 (79%) made a full recovery, with a mean post-operative time to walking of 4.2 days

 

Diagnosis           

number of cases

DAWS                                            22

BAWS                                             14

Intervertebral disc disease         9 (single site, extrusion/ deformation)

Trauma                                            1

Sub-arachnoid cyst                        1

 

With both DAWS & BAWS, there was no correlation between the number of joints  affected (range 1-5) and perioperative morbidity or long-term outcome.

 

Recurrence

86% of DAWS cases made a full recovery, with one showing recurrence of signs two years later.  Mean time to walking post-op was 3.63 days.

Similarly, 86% of BAWS cases made a full recovery, with two cases showing recurrence, both two years later.  Mean time to walking post-op was 1.9 days.

In all three cases of recurrence, the patient was euthanased without further investigations.

 

Perioperative Mortality                        

Three cases died in the perioperative period.  All of these occurred prior to the routine placement of active drains prior to closure.  There were no further perioperative deaths after this modifcation.  A further two cases were euthanased 1-2 weeks after surgery due to issues with prolonged recumbent nursing (aggression, costs, etc).

 

Long-Term Outcome                                 

Five cases were lost to follow-up.  Of the remaining 34 cases that remain free of signs (or died/ were euthanased due to other causes) 12 cases were free of signs for greater than 4 years, 11 cases between 3-4 years, five cases between 2-3 years, three cases between 1-2 years and five cases remain free of signs up to one year after surgery.

 

Conclusions                                                 

The above data suggests that recurrence rate (8.1%) for DAWS/BAWS cases managed with dorsal laminectomy compares favourably to published results.

Age at presentation does not appear to influence surgical success rate, but recovery times were relatively prolonged in the older cohort.

Increased severity of signs at presentation both reduced the likelihood of success and prolonged recovery times.

No difference was found in the long-term success rate of DAWS cases and BAWS cases, but the latter recovered slightly more quickly (probably due to lower age at presentation).

On the basis of the above analysis, we would recommend dorsal laminectomy as a suitable long-term solution to all compressive lesions of the cervical spine amenable to surgery.

 

 

References

  1. De Decker, S. (2017) Medical Management of Compressive Spinal Disorders, Proceedings of the Third British Veterinary Neurology Society Annual Meeting.
  2. Garosi, L. S. (2010) Cervical Spondylomyelopathy Congress Proceedings BSAVA
  3. Sharp, N., Wheeler, S. (2005) Cervical spondylomyelopathy. Small Animal Spinal Disorders: Diagnosis and Surgery. 2nd ed. Edinburg: Elsevier Mosby: 211–246.
  4. Olby, N.J. (2003) Update on Canine Wobbler Surgery Conference Proceedings ACVIM