Analyze the gait. For a refresher on upper motor neuron (UMN) versus lower motor neuron (LMN) gaits, click here.
Is he ambulatory? Are the pelvic limbs normal? Are the thoracic limbs normal? Is one side worse than the other? Are the steps long and floaty or short and choppy?
I would describe Hurcules as having “ambulatory tetraparesis with an upper-motor neuron, general proprioceptive ataxia. The thoracic limbs are worse than the pelvic limbs and the left side is more affected than the right.” Notice how he is long-strided and ‘floaty’ in the thoracic limbs, especially the left side. When he turns, he crosses over the thoracic limbs. He knuckles over in the thoracic limbs. These are hallmarks of an upper motor neuron gait.
Knowing that his mentation and cranial nerves are normal, what is your neuroanatomical localization? Is the lesion above or below the foramen magnum?
Is it cranial or caudal to the T2 spinal cord segment?
For the thoracic limbs to be affected, the lesion needs to be cranial to T2. So we’ve narrowed it from somewhere between C1 and T2. Can we do better? Let’s ask our spinal reflexes. The spinal nerves that supply the flexor withdrawal reflex originate in the C6-T2 spinal cord, travel through the brachial plexus and innervate the muscles of the thoracic limb. For the withdrawal reflex to be normal, one would suspect the lesion to be affecting the C1-C5 spinal cord (e.g., the C6-T2 spinal cord, nerve roots, nerves, muscles, etc are normal).
The spinal cord may divided based on the location of lower motor neurons supplying the musculature of the limbs. The spinal cord segments include C1-C5, C6-T2, T3-L3 and L4-S3.
So our neuroanatomical localization is the C1-C5 spinal cord.
What is our differential diagnosis? Remember the DAMNIT-V scheme. Degenerative disk disease is possible given the chronic, progressive nature. Anomalies such as syringomyelia, cysts, subarachnoid diverticula or stenosis are possible as well. Metabolic spinal cord disease is unlikely. Given his age, breed, progression and discomfort, neoplasia is possible. Name some neoplasms that affect the spinal cord of dogs–bonus points if you remember the different locations with regards to the dura mater. For a refresher, see the June 2012 Case of the Month. Inflammatory and infectious causes such as Granulomatous Meningoencephalomyelitis or Cryptococcus can cause the exact same signs as Hurcules is showing. Aseptic suppurative meningomyelitis of Boxers is a great differential, however, Hurcules is slightly older than the typical patient. Trauma and vascular (stroke) are unlikely given the waxing and waning, progressive course.
Hurcules’ complete blood count (CBC), chemistry, urinalysis and thoracic and abdominal radiographs were unremarkable.
High-field magnetic resonance imaging (MRI) of Hurcules cervical spine was performed.
The patient’s right side is on the left of the screen, as if the head were coming out of the computer screen. Note the large, contrast-enhancing (white) mass compressing the spinal cord to the right (left side of the image). This is a meningioma which was later removed.
Note the large, contrast-enhancing mass at the level of the caudal aspect of C2 and cranial aspect of C3 that appears to compress the spinal cord from the outside and push in on it. While it can be challenging to determine whether a mass is intradural-extramedullary or extradural, an intradural-extramedullary mass such as a meningioma was considered most likely.
A dorsal approach to the C1-C4 spine was performed and a left-sided hemilaminectomy was performed at C2-3. The hemilaminectomy was extended past dorsal midline to allow for adequate exposure of the mass. A durotomy was performed and a tan/grey mass was found in the subdural space. The mass was gently removed.
Hurcules did remarkably well. Here is a video of him at his suture removal appointment. He has continued to improve and has a new lease on life.
Thank you to Dr. Balko, Dr. Koscielniak and Dr. Valderrama at Faithful Companions Animal Hospital for trusting Southeast Veterinary Neurology to care for Hurcules, and thank you to his family for giving us the chance to help! If you have any questions about Hurcules’ case or any other neurological condition, please feel free to call us at (305) 274-2777.
Sagittal MRI of Hurcules' neck showing a meningioma at C2-3. This view is similar to a lateral radiograph, however, note the increased soft tissue detail and lack of superimposed structures.
Dorsal plane image of Hurcules' neck. This is a similar view as a VD radiograph. Note the large mass compressing the spinal cord toward the right (left in the image).
Axial "slice" image at the level of C2-3. This image is made in a plane perpendicular to the other two. Dorsal is toward the top of the image.