Clinical Case Challenge: Dog with Sudden Tetraplegia and Respiratory Weakness

A 14-year-old dachshund mix named Hanna presented to Henry and Lois Foster Hospital for Small Animals (FHSA) at Cummings School of Veterinary Medicine at Tufts University with sudden paralysis of all four limbs (tetraplegia) and difficulty breathing.

History

Hanna, an otherwise healthy dog, experienced tetraplegia after jumping down from a bed to the floor. Her walking listed to one side soon after the jump, and within a few hours she was paralyzed from the neck down. When she presented at the emergency room at FHSA, she also showed signs of distressed breathing.

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Determine which diagnostics and treatments are required
Diagnostics
Upon arrival at the ER, Hanna was unable to move her legs at all. The Emergency Medicine and Critical Care (ECC) team at FHSA conducted a physical exam and detected respiratory issues as well. She was breathing from her abdomen and showing no movement in her chest wall. Bloodwork was ordered to rule out potential causes of neurological disease, such as changes in electrolytes or red blood cell counts or signs of inflammation. Results returned normal. The ECC team pulled in the Neurology service to consult on the case.

After a chest X-ray came back clear (with no metastatic lesions and no pneumonia that could indicate a cancerous cause for paralysis), Hanna underwent an MRI, revealing that an intervertebral disc in her cervical spine was herniated, and the extruded nucleus pulposus was moderately compressive. The Neurology team diagnosed Hanna with Hydrated Nucleus Pulposus Extrusion (HNPE).

HNPE can be associated with a traumatic event, in this case, the dog’s landing from the jump, and often can be managed medically. Because of the intensity of Hanna’s symptoms, the Neurology team determined that she would need ventral slot surgery.

Treatment
Dr. Andrew Shulman (he/him), neurology specialty intern at FHSA in the Department of Clinical Sciences at Cummings School, explains, “Pathophysiologically, HNPE causes bruising on the spinal cord and some compression as well. Often with time it starts to dissipate. Hanna was so severely affected, we needed to help immediately with the compression. Ventral slot procedure is commonly performed with intervertebral disc herniations in the neck.”

During the procedure, the doctors made an incision in the midline of Hanna’s neck, used a drill to create a window in the spine and intervertebral disc, and removed the herniated disc material.

“The surgery went perfectly,” says Shulman. "Sometimes we can run into severe bleeding, and sometimes we don’t get as much disc material. This surgery was quick, the approach was straightforward, and it went as well as we could have wanted.”

Despite the successful surgery, Hanna took a negative turn 24 hours post-surgery, again struggling to breathe. The criticalists in FHSA’s Intensive Care Unit ran bloodwork and found her carbon dioxide level above 60, a threshold for intervention.

“When you reach a level above 60 and can’t get the underlying cause addressed immediately, you need to put the patient on mechanical ventilation to breathe for them,” says Shulman.

Hanna was sedated and placed on a mechanical ventilator. A patient may deteriorate after ventral slot surgery for a few reasons: post-surgical bleeding, damage incurred to the spinal cord during surgery, luxation or fracture of the spine, or as in Hanna’s case, a bruise on the spinal cord from the initial disc herniation.

“With HNPEs, the disc ruptures under a lot of pressure, it hits the spinal cord and can cause a bruise. We suspected that since it came on so quickly, it took time for the bruise to get as bad as it was going to get,” says Shulman.

An MRI showed a patch of brightness on the spinal cord where the disc herniated, and no evidence of bleeding or luxation of the spine, confirming that a bruise from the original spinal cord injury was causing the breathing issues.

This type of bruising can heal on its own with time. Published data on dogs with respiratory issues due to cervical intervertebral disc herniation often need two to five days of mechanical ventilation while they heal. After one day on ventilation, Hanna showed signs of wanting to wake up.

After initially ventilating Hanna with an endotracheal tube, the ECC team recommended a tracheostomy, using the incision from surgery, to continue breathing support while allowing her to wake up, move, and eat. The longer a patient remains on machine ventilation, the higher the risk of other complications, such as ventilator-associated pneumonia.

“Hanna is otherwise a healthy girl—her kidneys, heart, and liver were functioning well,” says Shulman. “We wanted to avoid damage to other organs while the neurological function controlling her breathing recovered. The tracheostomy helped us get there faster and avoid these other consequences, especially pneumonia.”

Hanna came off sedation smoothly and immediately started eating, a positive sign. After 12 hours, the ECC team removed the tracheostomy tube. She was breathing better on her own. Hanna remained on medications for pain and anxiety, and started on caffeine to assist with respiratory function.

Within a few days, her breathing completely returned to normal, and soon after she began moving her front legs. On day nine, Hanna was ready to head home, unable to walk, but getting stronger each day. Her family continued her care at home with plenty of rest and physical rehabilitation exercises.

At Hanna’s two-week recheck, she was able to hold her weight and take a few steps. One month out, she was fully walking again, with just a bit of wobbliness.

“Hanna was walking really well, doing exactly what we wanted her to be doing,” says Shulman. “It was such a team effort between Neurology, Critical Care, the family, and Hanna. We were seeing her get better and better every time.”

Comments from Cummings School’s Neurology Service
“It’s important with cervical spinal cord injuries to keep in mind that depending on the level of the lesion, it can lead to respiratory compromise,” says Shulman. “We commonly see dogs with herniations in the thoracolumbar spine, and those don’t directly carry a risk of respiratory compromise, but when it’s in the neck, that’s a possibility when it’s more severely affected. We don’t see it with high frequency, but it’s a risk.”

Mechanical ventilation should be considered if the HNPE patient’s breathing becomes significantly compromised.

“There are ways for these dogs to get better despite the injury being so severe. Patients like Hanna are so affected neurologically that they need a ventilator. These patients can do really well afterwards, and there is a good chance that we can take them off the ventilation,” says Shulman.

After surgery, it’s up to the body to do the healing.

“The spinal cord does most of its recovery in the first one to three months, and fine-tuning of the healing can take six to nine months to complete,” says Shulman. “Hanna will continue to heal over the next several months until she reaches the full level of recovery a year after the injury. She may have wobbliness, but should still be able to do everything she wants to do—walk, run, play, and have a happy and comfortable life.”