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IN THIS NEWSLETTER:

Juvenile Pubic Symphysidoesis

Devocalization

The Role of Fenestration in Disc Disease

Corticosteroids, Neurological Disease and Colonic Perforation


Map of Our Location

Overview of Services

Information for Professionals

Online Resources

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Newsletter, 2003 Vol. 9. Issue 4

CORTICOSTEROIDS, NEUROLOGICAL DISEASE AND COLONC PERFORATION

A 5.25 kg, 5 year old male (neutered) Dachshund-mix presented to the Veterinary Surgical Referral Center for hindlimb paralysis on 8/26/03.  He had presented to the referring veterinarian 3 days earlier for lethargy, "not acting like himself, and difficulty using the left rear leg.  He had a serum chemistry profile and CBC done, with all results normal.  Deramaxx and Glycoflex were prescribed.  On 8/25 he was rechecked and was losing hindlimb motor control.  He was given SoluDeltaCortef i.v. 100 mg initially as a bolus and again 5 hours later.  He was sent for a surgical consult the next day.

On presentation here, there was hindlimb paralysis with no voluntary motor movement to the rear limbs.  Reflexes were UMN in nature and deep pain sensation was intact.  After initial evaluation and consultation with the owner, he was admitted for a myelogram and possible surgical decompression of a suspected thoracolumbar disc herniation.  Preoperatively, he was given 12 mg Dexasone SP i.v.  The myelogram showed a lesion at the level of T12-13, compatible with a ruptured disc.  The dog was taken to surgery where a left sided hemilaminectomy was done to decompress his spinal cord.  A ruptured disc was identified and removed.  Postoperatively, he was placed on a continuous drip of intravenous fluids with the addition of SoluDeltaCortef at a rate of 1mg/lb/hr for 24 hours.  He was hospitalized for 2 days then returned to the referring veterinarian's office on 8/28/03. On 9/2/03 the dog began vomiting acutely that afternoon.  Later that night he was brought in to the local emergency clinic, dead on arrival.  A necropsy was subsequently done at OSU and a perforating ulcer found in the colon wall, just caudal to the cecum.

Colonic perforation is a rare, but well described complication that seems to be compounded by the combined use of corticosteroids and concurrent neurologic disease.  It is uniformly fatal.  In the case above, the prior use of a non-steroidal anti-inflammatory drug (Deramaxx) may have contributed to the colonic perforation.

In reviewing the literature, the following findings are reported by Toombs, et. al.

1) nonambulatory neurosurgical patients treated with dexamethasone, especially males, appear to be at the greatest risk for development of colonic perforation; 2) colonic perforation is preceded or attended by variable nonspecific signs -most frequently depression, anorexia, and emesis; 3) the complication is associated with a 100% mortality and clinical signs precede death by an average of 24 hours; 4) antemortem diagnosis and treatment of the complication are difficult and appear to have no effect in reducing mortality; and 5) a prophylactic approach to gastrointestinal complications is warranted in high-risk patients - (a) use prednisone instead of dexamethasone; (b) limit treatment with corticosteroids to as short a time as possible; (c) avoid successive or concurrent use of multiple drugs with known ulcerogenic potential; (d) correct fecal retention problems before surgery; (e) avoid enemas during the first week after surgery; and (f) manage urine retention by continuous bladder decompression (closed urine drainage system) rather than repeated manual expression of the bladder.

This case is presented as a cautionary example of a fatal complication associated with treatment of a herniated disc. Dexamethasone was used in this instance as there was a manufacturer's back order on SoluMedrol, our preferred drug in acute spinal injury. The use of Deramaxx may or may not have been a contributing factor. Prolonged use of steroids in spinal cord injury should be avoided, especially dexamethasone.
 
Newsletter, 2003 Vol. 9. Issue 3

THE ROLE OF FENESTRATION IN DISC DISEASE

Fenestration, or the ablation of the nucleus pulposus of the intervertebral disc, remains a controversial technique in veterinary medicine.  Promoted as a method to prevent or diminish the chance of a disc rupturing, fenestration of cervical and/or thoracolumbar intervertebral discs involves either surgical removal of the intervertebral disc’s nucleus, or ablation of the nucleus with a laser.  In this discussion, we will use the terms surgical fenestration and laser disc ablation interchangeably.

Many times, surgical fenestration is performed in conjunction with decompression of a ruptured disc, although the rationale for that remains unclear as the incidence of extruded discs (second incidence) at other levels following decompressive surgery has been reported to be only 2.67% (Brown, et al.)  While fenestration alone has been used for dogs with acute, severe neurological signs (paresis, paralysis), fenestration alone runs contrary to the recommendations of most neurologists and surgeons in these situations, where definitive decompressive surgery is suggested.

How effective is fenestration?  A recent study of 277 cases in which laser disc ablation was used shows that only 3.4% of the dogs had a recurrence of paresis or paralysis following laser surgery (Bartels, et al).  While this recurrence rate is lower than that reported for other disc fenestration techniques, it is higher than the figure reported by Brown for recurrence rates in the 187 cases studied following surgical decompression.  Additionally, of interest in the study of dogs undergoing laser disc ablation was that 18.7% of owners reported that > 4 weeks after the ablation procedure, their dogs had clinical signs attributable to orthopedic, soft tissue or neurologic disease.  These dogs were not included in the 3.4% recurrent paresis/paralysis group.  The true incidence of recurrence, if we do not only measure paresis and paralysis, may be much higher than the 3.4% figure reported, however; that remains unknown at present.  Further studies which could include CT examination or MRI or a myelogram are needed to document recurrence of disc symptoms following ablation or fenestration.

So when is it appropriate to recommend fenestration of intervertebral discs?  It seems prudent to stick with the requirements which the doctors at OSU have developed to identify appropriate candidates for laser disc ablation.  Dogs undergoing either surgical fenestration or laser ablation should be free of neurological signs.  They should not have back pain, paresis or paralysis for a period of 2 to 4 weeks before undergoing fenestration or ablation.  They should be off of all steroidal anti-inflammatory drugs for the same period of time.  Dogs who have had stable neurological abnormalities for the same period of time could be considered as candidates for fenestration or ablation.
Acute cervical or thoracolumbar disc protrusions or herniations resulting in clinical signs of neck or back pain, paresis, or paralysis are not candidates for fenestration or laser disc ablation and should undergo a definitive decompressive surgery as indicated by a myelogram or CT examination of the spinal cord.    Fenestration or ablation should be recommended as prophylactic procedures only, and the owners counseled that as with all medical procedures, they are not 100% effective.

If you have questions about disc disease or would like suggestions for managing neurological cases, please give us a call.
 
  

Newsletter, 2003 Vol. 9. Issue 2
DEVOCALIZATION

At one point or another in our career, a client will request that we “de-bark” their pet.  Reasons can be varied, with probably the most unusual request we have had being the fact that the client had a court order to either have their dog de-barked, or euthanize the animal!  Fortunately for this pet, they opted to have her de-barked.

Suppression of barking has been attempted by various means, including surgical techniques and conditioning methods most often utilizing electrical collars to negatively condition the dog.  Collars can be effective, but many times the dog becomes wise to the fact that when the collar is off, he/she is free to bark with impunity!  In other cases, the pet may have a long hair coat preventing effective contact or the proper transmission of electrical impulses, rendering the collar ineffective.  Some dogs bark despite an effective stimulus from the collar.

Surgical means of suppression of vocalization are often disappointing, as barking can recur.  Removal of vocal folds via an oral approach has traditionally been the most commonly used surgical method to de-bark.  Many times a ventral web of connective tissue develops as well as scarring along the excision line on the vocal folds which allows the dog to produce noise similar to a bark. 

The barkless Basenji has a larynx that differs from other breeds, in that they have shallow ventricles filled by thick and solid mucosal folds.  A technique described in the literature that we have used with success, and currently recommend as the technique of choice in de-barking dogs, is removal of the mucosa of the ventricles.  Consistent devocalization of dogs is expected with this procedure.

Surgery is done under general anesthesia using aseptic surgical technique.  Broad-spectrum antibiotic coverage is administered prophylactically prior to surgery, and my preference is to continue antibiotics for 10 days postoperatively.

The goal of surgery is to remove, or extirpate, the mucosal lining of the ventricle.  Ventral laryngotomy is performed to allow surgical access to the lumen of the larynx.  Incisions are made along the edge of the vestibular fold and the edge of the vocal fold, with removal of the vestibular mucosa done using a combination of blunt and sharp dissection.  Once all of the mucosa has been removed, the mucosal edges are sutured closed.  Laryngotomy closure is routine and the animal is observed carefully during the postoperative period, with care taken to recover the dog in a “head-down” position so that any bleeding which may occur results in blood running out the animal’s nose rather than down the airway.

Results are expected to be good.  In the largest series of cases I am aware of in which this technique has been reported, 47 of 49 dogs operated were termed successful long-term results.  Dogs will resume the attempt to bark, and the owner must be made aware of this, however; only a hoarse, low volume noise is expected to be heard.

If you have questions about this or any other surgical procedure, please feel free to give our office a call.
 
 
Newsletter, 2003 Vol. 9, Issue 1

JUVENILE PUBIC SYMPHYSIODESIS (JPS) IN DYSPLASTIC PUPPIES

Canine hip dysplasia is a commonly occurring orthopedic condition seen mostly in large breed dogs.  Treatments for hip dysplasia range from conservative medical therapy to surgical procedures designed to either re-shape or replace the hip joint.  Salvage procedures such as femoral head and neck ostectomy are designed to allow dogs to have a pain-free, albeit usually abnormal, gait.  Most of these surgical procedures are performed after a diagnosis of hip dysplasia has been made and clinical symptoms are noted.

Juvenile Pubic Symphysiodesis, or JPS for short, has recently been described in dogs by Dueland and his group at the University of Wisconsin.  Initial results have been described and appear promising enough to warrant offering this technique in clinical patients.  In this procedure, the pubic symphysis is fused prematurely through the use of electrocautery applied to the rapidly dividing cells of the symphysis.  By fusing the pubic symphysis, the acetabulum is subsequently rotated ventrally as the animal matures, gradually increasing the femoral head coverage within the acetabulum and improving coxofemoral joint congruity.

Patient selection is key to achieving optimal results, as it is with many surgical procedures.  The puppy must still be immature and growing rapidly - patients in the Wisconsin study were between 12 and 24 weeks of age.  The hip joints should also have demonstrable laxity.  This means that palpation of the hips should become a routine part of the puppy examination when puppies from breeds “at risk” are seen for routine vaccination procedures in your practice.  Sedation is not necessary as laxity can be detected in the awake patient, with practice.  In the study, distraction index (DI) was measured and puppies with a DI greater than 0.30 were treated with JPS.  Theoretically, all susceptible puppies could be treated.

The surgery involves exposure of the pubic symphysis and the application of a calculated dose of electrocautery (40 watts) for 12 to 20 seconds, depending upon pubic size.

Results initially have been encouraging, with JPS dogs showing improvement in all measurements at one and two years of age.  Improvements were seen in DI, laxity, Norberg angles, and force plate analysis among other variables measured in these dogs.  Radiographic evaluation of DJD in these hips shows that while 71% of controls were worsened, in the JPS group 69% were improved or did not progress.

JPS appears to be promising in the properly selected patient.  Our current suggestion is that all puppies at-risk for hip dysplasia be palpated at examination the first time seen in your office.  Those which fall into the age group 12 to 24 weeks, have palpable laxity (Ortolani sign), or come from a mating which has produced dysplastic pups before, are candidates for the procedure.  Morbidity is low and most patients can go home the same day.  The owner must also consent to having the puppy neutered, either the same day or at a later date.  If you have questions about the JPS procedure, please give our office a call.