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Traumatic spinal cord injury (Proceedings)

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Nov 01, 2010

     • Primary injury
          o Direct parenchymal and vascular damage
          o Occurs immediately as a result of traumatic event

     • Secondary injury
          o Result of biochemical cascades initiated by primary injury
          o Includes ATP depletion, increases in intracellular Na+ and Ca2+ as well as extracellular excitatory neurotransmitters, production of oxygen free radicals, increased cytokine production, accumulation of nitric oxide, lactic acidosis and activation of arachidonic acid, kinin, complement, coagulation and fibrinolytic cascades
          o Results in further damage to nervous tissue
          o Therapy directed at minimizing secondary injury

     • Initial neurologic evaluation
          o Important components of neurologic exam
               ▪ Motor/Posture – ambulatory vs. recumbent, muscle tone and voluntary movements, Schiff-Sherrington posture
               ▪ Segmental reflexes – tendon, withdrawal, panniculus and perineal reflexes
               ▪ Pain perception – assessed via behavioral response to a noxious stimulus
                    » Superficial – elicited from pinch of the skin/SQ tissues
                    » Deep – elicited from pinch of bone/digit
               ▪ Mentation and cranial nerve evaluation can generally be performed without significant patient manipulation
          o Scoring system has been described for acute spinal cord injury in dogs
          o Initial neurologic status may improve following immediate stabilization

     • Management of TSCI
          o Immobilization
          o Hemodynamic stabilization
               ▪ Resuscitation for maintenance of normotension, adequate oxygen levels
                    » Often concurrent injuries involving other areas – cardiovascular, respiratory, abdominal, brain trauma
               ▪ CBC, chemistry panel, electrolytes, UA and thoracic radiographs can help define extent of injuries
          o Analgesia
          o Imaging
               ▪ Radiographs – screening lateral views safe; VD views only with a horizontal beam technique if potential for instability exists
               ▪ CT – excellent bone detail, evidence of hemorrhage may be seen
               ▪ Myelography – used to evaluate potential spinal cord compression
               ▪ MRI – for evaluation of extrinsic and intrinsic spinal cord lesions
          o Medical management to reduce secondary injury
               ▪ Corticosteroids
                    » Use controversial in human and veterinary medicine
                    » Methylprednisolone has been extensively evaluated; evidence suggests benefit related more to free radical scavenging than anti-inflammatory properties; other commonly used steroids (e.g. prednisone, dexamethasone) do not have free radical scavenging capabilities
                    » National Acute Spinal Cord Injury Study trials in humans
                        o Small improvements (in motor scores at 6 weeks and pinprick and touch sensation at 6 months post injury) noted in TSCI patients administered methylprednisolone within 8 hours of injury; detrimental >8h; no difference in outcome vs. control groups at 1 year; increased risk of pneumonia and trend towards sepsis with methylprednisolone therapy
                    » A study in dogs showed timely surgical decompression of acute compressive spinal cord injury was more effective for improving neurologic recovery than methylprednisolone without surgery
                    » A study of dachshunds administered methylprednisolone and having surgical decompression following IVD herniation showed increased post-operative complications (melena, diarrhea, emesis, hematemesis and anorexia) and higher medical bills vs. dogs not receiving methylprednisolone Polyethylene glycol (PEG)
                    » Use shown to be safe in dogs
                    » Ongoing studies for evaluation of efficacy in spinal cord injury
               ▪ N-acetylcysteine has been investigated to prevent oxidative secondary injury in dogs, but did not prove to have clinical benefit in a randomized blinded placebo-controlled clinical trial