Exogenous Spinal Trauma_clinical Assessment And Initial Management

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Vol. 21, No. 12 December 1999

Refereed Peer Review

FOCAL POINT ★ Accurate clinical assessment and immobilization of animals with spinal trauma are important for successful patient management.

KEY FACTS ■ Animals that are suspected of having an unstable vertebral segment should be rigidly immobilized as quickly as possible. ■ Clinical assessment should be done cautiously to avoid iatrogenic damage to the spinal cord. ■ When a nervous system injury is suspected, a complete neurologic assessment is mandatory to determine the location and severity of nervous tissue damage. ■ Because vertebral fractures and subluxations can be subtle and visually difficult to assess, good-quality, well-positioned radiographs are essential. ■ Methylprednisolone sodium succinate should be administered as soon as possible after an animal has sustained spinal injury.

Exogenous Spinal Trauma: Clinical Assessment and Initial Management Washington State University

Rodney S. Bagley, DVM Michael L. Harrington, DVM, MS Gena M. Silver, DVM, MS

Anthony J. Cambridge, BVMS Rebecca L. Connors, LVT Michael P. Moore, DVM, MS

ABSTRACT: Spinal trauma is a common cause of spinal cord dysfunction in dogs and cats. When the spine is subjected to exogenous injury, the resultant impact often causes vertebral fracture or luxation. Because each spinal injury is unique, treatment guidelines must be individualized. This article reviews clinical assessment and management of spinal trauma.

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pinal trauma, a common cause of spinal cord dysfunction in dogs and cats,1–8 can occur from exogenous or endogenous spinal injury. Intervertebral disk extrusion remains the most common endogenous cause, whereas automobile-related injury is the most common exogenous cause. Falls, trauma from falling objects, and projectile damage are also common. External impacts often result in vertebral fracture, subluxation, or luxation. This articles focuses on the clinical management and treatment of small animals with exogenous spinal injuries that result in vertebral fracture or luxation.

PATHOPHYSIOLOGY The pathophysiologic changes that occur in the spinal cord after external impact have been reviewed.1–7 Briefly, there are two major injuries: the primary mechanical injury and the resultant pathophysiologic sequelae or secondary injury. The primary injury usually includes shearing and disruption of axonal processes, nerve cell bodies, and supporting structures (e.g., glial cells, vascular elements), resulting in physiologic or morphologic disruption of nervous impulses. Any change in the vertebral canal diameter may cause spinal cord displacement, compression, and increased intraspinal pressure. Nervous impulses in this area may be disrupted because of increasing pressure applied to the axons and nerves or from ischemia caused by alteration in spinal cord blood flow or hemorrhage. These increased pressures set in motion numerous pathophysiologic consequences, including is-

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chemia, further hemorrhage, tional persons to help transand edema.1–7 port the animal can miniBecause gray matter normize the chance of additionmally receives proportionalal injury. ly higher blood flow than After the animal arrives does white matter, ischemicat the veterinary clinic, it related damage often occurs should be rigidly immobito gray matter first. Central lized to decrease the risk of hemorrhagic necrosis is the further mechanical damage pathologic consequence. All to the spinal cord.4 It is important to quickly obtain a these events lead to a selfcomplete history of the inperpetuating process of jury; significant information damage to the spinal cord includes whether the owner that often is equally, if not Figure 1A witnessed the accident, how more, detrimental than the long ago it occurred, and initial mechanical injury; what movement the animal this is referred to as the second injury theory.1–7 Putative was capable of immediately mediators of this self-perafter the trauma. For exampetuating process include ple, was the dog able to walk? excitatory neurotransmitHas it been able to urinate on ters, endorphins, catecholaits own? mines, lipid peroxidation, During the initial evaluaand free radicals released aftion, the animal should reter the initial insult. main in the same position as Based on this informathat on admission (usually tion, two therapeutic conlateral or sternal recumbensiderations become para- Figure 1B cy). Excessive manipulation mount when treating a should be avoided. If the spinal injury with fracture Figure 1— (A) A dog with spinal trauma that has been immo- history strongly suggests spior luxation. One is to pre- bilized using a backboard. (B) The head can also be taped if a nal trauma or if the animal vent further mechanical cervical lesion is suspected. is struggling to move, it damage to the spinal cord should be immediately reby stabilizing the vertebral column.4 The second constrained and immobilized by being firmly taped to a sideration is to stop or hinder the development of secrigid backboard or similar structure (Figure 1). A spinal ondary pathophysiologic events that perpetuate the trauma board (8 to 10 inches wide by 4 to 5 feet long magnitude of spinal damage. Much of current medical by 1 to 2 inches deep) works well; but any rigid, movtherapeutic efforts have been directed at counterbalancable surface can be used. Before securing the animal, ing or neutralizing the effects of these by-products of the board should be weighed so that an accurate weight trauma. of the animal can be recorded later. If thoracolumbar vertebral trauma is suspected, the animal can be seCLINICAL ASSESSMENT cured to the board by placing tape over the scapular Immobilization and femoral trochanter regions. If a cervical injury is Owners often witness traumatic spinal injuries; howsuspected, the head should also be secured. ever, some animals are found acutely dysfunctional Physical, Neurologic, and Musculoskeletal without a known traumatic history. When owners conBecause spinal injury frequently occurs in concert with tact the veterinary office for advice on transporting an multiorgan trauma, other life-threatening injuries should injured animal, they should be advised to be cautious be identified as quickly as possible. A standardized, because traumatized animals may become uncharacterisstereotypical physical examination should be conducted9; tically aggressive. Animals with spinal injuries should be critical care physical diagnosis checklists may be useful. placed on a rigid, movable surface. If a board or other Specific assessments include respiratory and heart rates, rigid device is not available, the animal can be transportheart rhythm, degree of peripheral perfusion (capillary reed in a blanket or slinglike apparatus. Recruiting addiSECOND INJURY THEORY ■ TRANSPORTATION ■ SPINAL TRAUMA BOARD

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fill time, coolness of limbs), the cranial nerves, spinal reability to move voluntarily, flexes, and cutaneous trunci and level of consciousness. reflexes are assessed and the The level of consciousness spine is palpated for hypersignificantly influences subseesthesia. Finding an area of quent neurologic evaluation focal spinal hyperesthesia is (e.g., if the animal is poorly an important clue that spinal responsive because of inadeinjury may have occurred. quate perfusion to the brain, Deep Pain Sensation assessment of deep pain senThe initial assessment sation will be difficult). should conclude with analyWhen a nervous system insis of deep pain sensation. jury is suspected, a complete neurologic assessment is man- Figure 2—A dog exhibiting the Schiff-Sherrington posture af- The presence or absence of ter being hit by a car. Note the thoracic limb extension. deep pain sensation has madatory to determine the lojor ramifications for the cation and severity of nerprognosis. Using a hemostat, a painful stimulus should vous tissue damage. However, if the animal has an be applied to affected digits; testing for skin sensation unstable vertebral fracture, the normal manipulations only will not confirm retention of deep pain sensation. and standard neurologic examination may not be possiDeep pain sensation is intact if the animal reacts by voble. The examination and diagnostic sequence as well calizing or turning toward the stimulus, often attemptas mobilization method therefore need to be modified ing to bite the examiner. However, simply pulling the to accommodate possible unstable vertebral fracture. foot away from the stimulus does not indicate conIf the animal is mentally alert but unable to move, scious recognition of deep pain. Misinterpretation of immediate concerns should be directed toward the neuthis withdrawal reflex may lead to a falsely optimistic rologic and musculoskeletal systems. Observing the anprognosis. imal’s posture can be helpful in determining whether a To evaluate the animal’s opposite (down) side, a secneurologic abnormality exists. For example, Schiffond backboard can be placed on the upside of the aniSherrington posture is characterized by thoracic limb mal and the animal flipped over and secured to the secextension and an inability to move the pelvic limbs ond backboard. The same techniques should be normally (Figure 2).8,10 Spinal reflexes in the pelvic limbs are usually normal. This results from a lesion in followed as those already described. the thoracolumbar spinal segments that interrupts the After spinal trauma has been established, the severiascending inhibitory impulses originating from border ty of injury needs to be determined before developing cells in the lumbar gray matter and terminating on cells a management strategy and discussing a realistic progresponsible for extension of the thoracic limbs. The nosis with the owner. The severity of a spinal cord inthoracic limbs are otherwise neurologically normal. Aljury is usually graded according to clinical findings though Schiff-Sherrington posture usually occurs in an(Table I). Animals with less severe trauma (painful imals with severe spinal cord injuries, this posture alone only; mildly paretic) are more often managed without does not indicate that the spinal lesion is irreversible. surgical intervention.13 Animals with more severe neurologic impairment (nonambulatory paretic or paraThe presence or absence of deep pain sensation in the lyzed) are usually considered for surgical stabilization. pelvic limbs is a more important prognostic indicator. It is important to recognize, however, that scientific Voluntary movement indicates that some nervous imdata supporting many current treatment recommenpulses are traversing the injured spinal area. It is imperadations are lacking. Individual clinical experience with tive, however, to differentiate voluntary from reflex the various treatments is often the overriding factor in movements. Reflex movements occur when animals are decision making. Anecdotal experiences, however, are touched or physically stimulated, whereas voluntary difficult to prove without case-controlled studies. Unmovements are made without external stimulation. Talkfortunately, individual assessments based on clinical ing to the animal or calling its name may result in atexperience and owner wishes remain the guiding tempts to move its limbs or wag its tail. Such stimulation forces behind management decisions in animals with should be attempted only while the animal remains respinal trauma. strained. Until definitively proven otherwise, voluntary Animals lacking deep pain sensation are less likely to movement should be assumed to be absent. return to normal function.4 If animals with interverteThe animal should be in lateral recumbency when SCHIFF-SHERRINGTON POSTURE ■ VOLUNTARY VERSUS REFLEX MOVEMENTS ■ SEVERITY OF INJURY

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bral disk disease have decompressive surgery within 48 hours of losing deep pain sensation, they have approximately a 50% or greater chance of walking eventually.14 In contrast, we have found that animals that lose deep pain sensation after suffering spinal trauma have considerably less than a 50% chance of recovery. If deep pain sensation has been lost for 48 hours or longer, there is virtually no chance of functional recovery. Furthermore, if deep pain sensation is absent in an animal with 100% or greater displacement of the vertebral canal, the prognosis for walking is hopeless (Figure 3).

DIAGNOSTIC TESTING If a vertebral injury is suspected, survey radiographs of the affected area should be taken before continuing the examination. Vertebral fractures and subluxations can be subtle and visually difficult to assess. Thus good-quality, well-positioned radiographs are essential.11,12 Initial radiographic assessment of obvious displacements of the vertebrae can be done while the animal is awake and immobilized. Sedation may be necessary in some animals; however, it may influence the results of further neurologic examination. Animals should be sedated only after determining the extent and severity of the trauma. Survey radiographs provide a static record of the position of the vertebrae. Information regarding how extensive the displacement of vertebrae was at the time of injury and before radiog-

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TABLE I Grading Scale for Assessing Treatment of Spinal Injuriesa Grade

Condition

8 7 6 5 4

Normal Pain only Paresis (walking) Paresis (not walking) Paraplegia (urination and deep pain sensation intact) Paraplegia (urination absent and deep pain sensation intact) Paraplegia (deep pain sensation absent <48 hr) Paraplegia (deep pain sensation absent >48 hr)

3 2 1 aFrom

least to most severely injured.

Figure 3A

Figure 3B Figure 3—(A) Survey radiograph of a dog that lacks deep pain

sensation in the pelvic limbs. There is greater than 100% displacement of the vertebral canal L3-4. (B) Sagittal T2-weighted magnetic resonance image of the same area. The spinal cord has been severed at this location.

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raphy, however, may not be appreciated from a single image. Because of the strong paraspinal musculature, vertebrae can be displaced acutely at the time of injury and subsequently pulled back to a more normal position. This possibility should be considered in patients with vertebral trauma when clinical signs appear worse than that suggested by radiography. Disturbances to adjacent soft tissue (e.g., paraspinal muscle disruption, hematoma) may provide radiographic clues to the location of injury. The degree of displacement of the vertebral canal on radiographs is less important in determining prognosis than is the degree of neurologic impairment.

CORTICOSTEROID THERAPY Corticosteroid therapy is an important adjunctive therapy for humans and animals with spinal trauma.15–24 Ideally, corticosteroids are administered as soon as possible after a spinal injury, either before or during radiographic evaluation. A multicenter study in humans also suggested that methylprednisolone sodium succinate (MSS) administered up to 8 hours after spinal trauma was beneficial. 16 Experimental studies in small animals have suggested that after spinal trauma, the time frame in which MSS is helpful may be less (possibly as little as 1 hour).15–24 This information suggests that recommendations in human trials regarding the benefit of MSS may be too long, thus emphasizing the need to administer

SURVEY RADIOGRAPHY ■ DEGREE OF DISPLACEMENT ■ DRUG THERAPY

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MSS to small animals as quickly for 4 to 6 weeks may be a satisas possible. Other corticosterfactory or equally beneficial oids (e.g., dexamethasone)25 have treatment for animals with not been proven effective treatspinal trauma.32,33 External support bandages or casts have also ment of experimental spinal been successful as nonsurgical trauma and have been associated treatment of animals. 34 The with significant complications in goals of external support should clinically affected animals with be immobilization of the vertespinal disease.26–28 In studies in humans, a 30bral segments above and below mg/kg intravenous (IV) bolus the damaged area. This support of MSS was administered inishould be as rigid as possible to tially, followed by 5.4-mg/kg/ ensure that minimal, and idealhour IV for the next 23 hours ly no, motion of the vertebral as a constant-rate infusion in an column occurs around the afattempt to keep high levels of fected area. the drug in the injured cord for Figure 4A First, a soft bandage should a longer period. This regimen, be extended above or below the however, is labor intensive and thoracic limbs for thoracolumrequires 24-hour monitoring of bar and cervical fractures, rethe animal. An alternative but spectively. Cast padding covexperimentally unproved protoered by cling gauze and elastic col is MSS as an initial bolus wrap works well as the initial (time 0) at a dose of 30 mg/kg bandage. A plaster or fiberglass IV, with additional doses of 15 cast can then be molded to the mg/kg IV at 2 and 6 hours after shape of the spine and used for the initial dose. rigid support; however, we preIf MSS is administered too fer using aluminum rods bent quickly to an awakened aniin a rectangular shape and conmal, vomiting often occurs. If Figure 4B toured to the curvature of the MSS is given too rapidly to an spine (Figure 4). The ends of animal under general anesthe- Figure 4—(A) A dog with an L-1 fracture that has had the rectangular configuration sia, hypotension often is noted. an external spinal splint applied. The handles are helpful can then be bent outward and when moving the dog. (B) A male dog with a T13-L1 In addition, a primary compliused as handles that will assist luxation that has had an external spinal splint applied. A cation of MSS administration waterproof pad has also been applied to the ventral as- during manipulation, physical to dogs with spinal injury is pect of the bandage to minimize the possibility of urine therapy, and walking. Additional gastrointestinal ulceration.26–30 soaking the bandage. handles can be fashioned with Acute death has also been notthe bandage to serve the same ed experimentally with bolus purpose (Figure 5). The casting injections of MSS; however, this is very rare in clinical material or aluminum rods should be secured to the soft practice.31 Regardless, we advise administering IV MSS wrap with bandage material (e.g., white porous tape). over a period of approximately 5 to 10 minutes. In animals with a cranial cervical fracture, the bandage should be extended upward and over the animal’s NONSURGICAL TREATMENT head to the level of the eyes (Figure 5). Holes can be Treatment of spinal trauma can be separated into surcut in the bandage to allow the ears to protrude norgical and nonsurgical categories, although combined mally. If external support is applied after surgery, the modalities may be appropriate. Whether to use either bandage material immediately overlying the incision or both of these treatments depends on numerous faccan be cut open to allow visual inspection of the incitors, including anecdotal experiences of the examiner sion. With lower lumbar and lumbosacral fractures, esand such nonmedical factors as owner finances. pecially in male dogs, the penis or vulva should not be In general, major indications for surgery are reduction bandaged. To prevent males from urinating on the banof spinal instability and alleviation of spinal cord comdage, a plastic shield cut from a used IV fluid bag or pression. In some instances, however, cage confinement waterproof pads can be ventrally secured to the banMETHYLPREDNISOLONE SODIUM SUCCINATE ■ EXTERNAL SUPPORT ■ BANDAGING

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REFERENCES

Figure 5—A dog with a C-2 fracture was wrapped in a sup-

port bandage with handles.

dage, a plastic shield cut from a used IV fluid bag or waterproof pads can be ventrally secured to the bandage (Figure 4). If more protection against moisture damage is needed, a trash bag or suitable barrier can be placed over the bandage with the ends tucked into it. After completing the bandaging, the animal should be closely monitored for complications. For example, the layers of bandaging may cause an increase in the animal’s body temperature, especially if the ambient environment is warm. Thus the animal’s body temperature should be monitored often. In addition, if the bandage is too tight around the thorax or cervical area, mechanical respiratory problems may develop. External supports and bandaging should remain in place for 4 to 6 weeks or until healing is complete. The bandaging should be changed as needed, especially if the skin becomes irritated. Loose-fitting bandaging also should be replaced. Follow-up evaluations should be scheduled as necessary but ideally at 3 and 6 weeks after injury. However, more frequent visits may be required if external support bandaging needs to be changed. Radiographic reassessments of fracture healing can determine when cage confinement or external support can be terminated. Gradual return to exercise should be initiated when healing is complete. During weeks 1 to 2 of returning to exercise, short (10 to 15 minutes) leash-controlled walks should be initiated one to three times a day on surfaces with good footing. If leash walks are tolerated, the duration and number of walks during the day can be increased over the next 2 to 4 weeks. If the animal tolerates this exercise, it should be allowed free activity in enclosed activity areas (e.g., a fenced backyard).

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methylprednisolone in compression trauma to the feline spinal cord. J Neurosurg 55:200–208, 1981. Hall ED, Braughler JM: Effects of intravenous methylprednisolone on spinal cord lipid peroxidation and (Na+ + K+)ATPase activity. J Neurosurg 57:247–253, 1982. Braughler JM, Hall ED: Lactate and pyruvate metabolism in injured cat spinal cord before and after a single large intravenous dose of methylprednisolone. J Neurosurg 59:256– 261, 1983. Braughler JM, Hall ED: Uptake and elimination of methylprednisolone from contused cat spinal cord following intravenous injection of the sodium succinate ester. J Neurosurg 58:538–542, 1983. Hall ED: The neuroprotective pharmacology of methylprednisolone. J Neurosurg 76:13–22, 1992. Hoerlein BF, Redding RW, Hoff EJ, McGuire JA: Evaluation of dexamethasone, DMSO, mannitol and solcoseryl in acute spinal cord trauma. JAAHA 19:216, 1983. Moore RW, Withrow SJ: Gastrointestinal hemorrhage and pancreatitis associated with intervertebral disk disease in the dog. JAVMA 180:1443–1447, 1982. Toombs JP, Caywood DD, Lipowitz AJ, Stevens JB: Colonic perforation following neurosurgical procedures and corticosteroid therapy in four dogs. JAVMA 177:68–72, 1980. Hoerlein BF, Spano JS: Non-neurological complications following decompressive spinal cord surgery. Arch Am Coll Vet Surg 4:11–16, 1975. Siemering GB: High dose methylprednisolone sodium succinate: An adjunct to surgery for canine intervertebral disc herniation. Vet Surg 21:406, 1992.

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30. Galandiuk S, Raque G, Appel S, Polk HC Jr: The twoedged sword of large-dose steroids for spinal cord trauma. Ann Surg 218:419–427, 1993. 31. McDougal BA, Whittier FC, Cross DE: Sudden death after bolus steroid therapy for acute rejection. Transplantation Proc 8:493–495, 1976. 32. Selcer RR, Bubb WJ, Walker TL: Management of vertebral column fractures in dogs and cats: 211 cases (1977–1985). JAVMA 198:1965–1968, 1991. 33. Carberry CA, Flanders JA, Dietz AE, et al: Nonsurgical management of thoracic and lumbar spinal fractures and fracture/luxations in the dog and cat: A review of 17 cases. JAAHA 25:43–54, 1989. 34. Patterson RH, Smith GK: Backsplinting for treatment of thoracic and lumbar fracture/luxation in the dog: Principles of application and case series. VCOT 5:179–187, 1992.

About the Authors Drs. Bagley, Harrington, Silver, Cambridge, and Moore and Ms. Connors are associated with the Department of Clinical Sciences, Washington State University, College of Veterinary Medicine, Pullman, Washington. Drs. Bagley (Neurology and Internal Medicine), Harrington (Neurology), and Moore are Diplomates of the American College of Veterinary Internal Medicine. Dr. Silver is a resident in neurology and neurosurgery. Dr. Cambridge is a resident in surgery. Ms. Connors is a neurology veterinary technician.