Neurotransmitter – Riley

h2 - CopyRiley, 2 year-old male Cocker Spaniel, was referred by Apple Valley Animal Hospital for left side weakness and concern for spinal cord lesion.

Presenting Complaint/History:

Riley was playing vigorously in yard, yelped and was then very weak on the left side. He was referred for left side weakness and concern for spinal cord lesion.

Exam Findings:

Riley was ambulatory but would drag and scuff his left thoracic and left pelvic limb and had left side postural reactions (hopping, paw flip test) delays along with decreased withdrawal response and tone on the left thoracic limb. Although bright and responsive and non-painful, Riley’s left pupil was too small and the left third eyelid elevated.

Localization / Assessment:

Left side cervical spinal cord based on left side weakness and postural deficit. The decreased tone and reflex made a lesion within the intumescence or C6-T2 region the most likely. Furthermore, the miosis and prolapsed nictitans were thought to be from disease of the Horner’s tract as it passes through cervical spinal cord. Lastly, because there was no discomfort on exam, a lesion within the spinal cord was suspected.


MRI showed disease within the spinal cord just above the C4 disk space on the left consistent with a high velocity, low volume hydrated disk extrusion or acute non-compressive nucleus pulposus extrusion from C4-C5 disk (Figure 1).

xrayFigure 1 Cross sectional MRI at level of C4-C5 disk space. The round white circle is signal from the arachnoid space which surround the spinal cord. The triangular white spot (blue arrow) within the left side of the spinal cord is from contusion secondary to a low volume, high velocity disk extrusion. The cross sectional volume of disease on MRI is even better than neurological exam findings in predicting outcome and when lesion less than 90% of total area of spinal cord there is a 93% chance of returning to walking (see reference below).



De Risio L, et al. Association of clinical and MRI findings with outcome in dogs with presumptive acute non-compressive nucleus pulposus extrusion: 42 cases (200-2007). JAVMA 2009 Feb 12: 234 (4): 494- 504


Low volume high velocity nucleus pulposus (disk) extrusion at C3-C4.


Traumatic disc extrusions have several common synonyms in veterinary literature including acute non-compressive nucleus pulposus extrusions, low volume high velocity disc extrusions, and Type 3 disc extrusions. They occur from vigorous activity or trauma where the normal intervertebral disc is placed under stress which exceeds it structural capacity and a small amount of nuclear material is extruded under high pressure and velocity. The extruded disc material strikes the spinal cord causing a contusion and clinical signs. This mimics the clinical course of fibrocartilagenous embolism (FCE) and the two diseases are often indistinguishable unless the MRI is closely scrutinized. Prognosis for each disease is similar and interestingly the prognosis is best predicted by MRI (Figure 1). Treatment is predominantly directed at bladder management with phenoxybenzamine or prazosin and valium, pain medication if needed, two weeks rest and physical therapy if needed. Although the disease is from disk extrusion there is no compression and therefore no need for surgery.

Horner’s syndrome is from a lack of sympathetic influence to the eye and features miosis, enopthalmos, ptosis, 3rd eyelid elevation and dilation of the scleral blood vessels.

The pathway, a circuitous one, starts in brainstem, runs down cervical spinal cord, leaves the vertebral column in the thoracic spine and runs back up the neck entering the skull where it passes adjacent to the middle ear in route to the eye.


At a recheck several months later, Riley had made a full recovery and was still pain-free.

Take Home Points:

1. Two common, non-surgical diseases of the inside of the spinal cord are called low volume, high velocity traumatic disk extrusions and FCE

2. Diagnosis and prognosis is made with MRI and cross sectional area strongest predictor of outcome

3. Bladder management (expression, drug therapy), restricted activity, and physical therapy / rehab are hallmarks of therapy in cat and dogs

4. Horner’s syndrome, when noted with spinal cord disease, localizes lesion to the cervical spinal cord and typically involves non-surgical lesions of the inside of the spinal cord.

For more information or to discuss this case please contact Dr. Bush.

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