Manejo Médico y Quirúrgico del Traumatismo Medular Agudo

Spinal cord trauma is a common problem in small animal practice. Common causes are for example trauma originated by disc herniation and contusion due to car accidents or falls from heights. Vertebrae, discs, meninges, spinal cord, or a combination of all can be damaged.

As soon as the spinal cord is traumatized, there is hemorrhage and damage to the nervous tissue, which causes a decrease in perfusion to the cord and adjacent tissue. If the disc is herniated, fractured or luxated, it will also cause compression on the spinal cord. This primary damage triggers a series of secondary events that cause the lesion to become bigger. Among the most common changes, there is destruction of the microvascular net, changes in the intracellular ion concentrations, excitotoxicity, free radical production and inflammation. The final point of this cascade is apoptosis, which can go on for a prolonged period of time after the initial trauma.

When the patient is presented with a history of trauma, a complete physical examination should be performed to evaluate the ventilation capacity, airways, cardiac and circulatory function as well.

The priority is to treat shock and any lesion that could compromise the patient's life.

The physical exam should be done carefully, since many spinal lesions can be overlooked.

A neurological exam is essential to detect if there is a lesion, its location and the patient's prognosis.

The patient should be placed in lateral recumbency and avoid movement as much as possible. Spinal reflexes, muscle tone, motor ability and deep and superficial sensibility should be evaluated.

The presence or absence of deep pain is the most important factor of the neurological exam to help us giving a prognosis. This should be assessed before applying any sedative or analgesia; if deep pain is absent, the prognosis is bad, and the owner should be warned about the possibility of the patient having a very slow recovery or even that the neurological damage is irreversible.

The presence of Schiff-Sherrington sign is of no value to the prognosis.

In general, clinical signs are not progressive, unless there is an instability of the column, hemorrhage or myelomalacia, which worsens the spinal cord's lesion.

The whole vertebral column should be palpated in order to detect fractures or luxations of the vertebrae. The possibility of more than one lesion should be considered.

Depending on the site of the lesion, there can be different degrees of ataxia or paresis.

Table 1. Neurological signs according to the site of the lesion

Radiographs should be taken once the lesion has been located. First, a lateral view to avoid moving the patient. In that same position, oblique views can be taken to be able to see joint facets. Great care should be taken when doing a ventrodorsal view, since the column can be unstable causing greater damage to the spinal cord.

In case of obvious fractures or luxation, the radiograph should be enough to have a diagnosis; however, there are cases where the results of the radiograph do not coincide with the clinical signs or there is a suspicion of bone fragments in the medullar space, or even a disc compressing the cord. These cases require advanced imaging studies like myelography, CT scans or MRI.

Myelography is an invasive procedure that requires general anesthesia. It can be performed on the same site where the radiograph was taken, meaning that in many occasions it can be done in the same premises.

It also has the advantage of giving a full view of the spinal cord and confirm if the lesion is severe.

MRI and CT studies are not invasive, but also require general anesthesia, and in most cases the patient has to be transported to a diagnostic center, which implies greater handling. The advantages of these techniques are that they allow detecting details in fractures, and joint facets with better detail and the degree of compression to the cord can be assessed. Magnetic resonance and tomography also allow the differentiation of a hematoma or edema, which changes the prognosis, since edema is easily resolved.

There is a controversy on when the ideal moment to decompress the spinal cord and stabilize the vertebrae is. Currently, veterinarians advocate doing it as soon as the patient is stable, since it is very difficult to keep them still and the lesion might worsen. So if the patient presents with neurological damage and there is instability on the imaging, the appropriate procedure to do is performing surgery as soon as possible.

There is no drug considered ideal for inflammation and avoid free radical damage. There are some studies in progress that show procedures and drugs that in a near future could be helpful in the treatment of spinal cord trauma. Among these drugs there is polyethylene glycol, calcium channel blocking agents, nervous cell transplant and stem cells.

After the initial treatment for the spinal cord trauma, the neurological assessment and the imaging studies should be performed to be able to decide if the patient is a candidate for medical or surgical treatment. Medical treatment is recommended for patients that present with pain and the lesions on the vertebrae indicate that it is stable. Those cases presenting neurological deficit and changes on the vertebrae indicate instability, are the ones where surgical treatment is preferred, since it will give the patient a better prognosis.

Medical treatment consists of keeping the patient as immobile as possible, if the region allows for this and should this be considered necessary, a cast or bandage is placed to stabilize. Minimal time is 4 weeks, plus 2 to 3 weeks of relative immobility. The patient can be kept under a regimen of NSAIDs for the first weeks. It is important to manage pain on the first days. Tramadol, fentanyl or buprenorphine can be used as analgesics. Muscle relaxants like diazepam or Robaxisal can also be used to reduce muscle spasm.

Intensive intrahospital care in these patients is warranted as they should be assisted to urinate or defecate and not allow for movements that can worsen the lesion. If the patient is not able to urinate by itself, the bladder should be emptied by compression or through a urinary catheter, three times a day. If there is a cast, it should be checked constantly to immediately detect any lesion or ulceration on the skin, particularly over the areas of the groin and armpit.

Surgical treatment is indicated when it is necessary to align, stabilize and/or decompress the spinal cord. Surgery should be done as soon as the patient is stable enough for anesthesia.

The surgical technique used will depend on the type of lesion and the structures affected.

In cases of fractures or luxation, it is recommended to align the vertebrae and fix them with pins or screws with surgical cement or plates and screws. If the imaging confirmed that there is compression, because of the presence of a disc, a shard or hematoma, besides fixation, it should be decompressed through a hemilaminectomy or a dorsal laminectomy.