Neurology Case of the Month: Down Shih TzuWritten on August 23, 2012 by Mark Troxel, DVM, DACVIM (Neurology) Hospital: Massachusetts Veterinary Referral Hospital

Signalment: 7yr FS Shih Tzu

History: The patient was brought in to the Emergency Department after falling down the stairs at home. She was normal prior to the fall.

Neurological Exam
Mental status: Quiet, alert, responsive
Gait/posture: Nonambulatory tetraparesis with thoracic limbs weaker than pelvic limbs and left side slightly weaker
Cranial nerves: WNL
Postural reactions: Absent CP/hopping x 4
Spinal reflexes: WNL x 4
Spinal pain: Neck pain
Muscle tone: Normal x 4
Muscle atrophy: None
Pain sensation: Normal x 4
Cutaneous trunci: Normal bilaterally

What is your neurolocalization?
What are the top differential diagnoses?

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Neurolocalization = C1-C5 with central cord syndrome (see notes below)

Differential diagnoses
• Trauma – fracture, luxation
• Traumatic disk herniation (so-called “Type III” disk – see notes below)
• Fibrocartilaginous embolism (FCE)
• Compressive disk protrusion/herniation

Diagnostics
• PCV/TS/Nova were unremarkable
• Spinal radiographs: narrowed C4-5 disk space, no evidence of fracture/luxation
• MRI: narrowed C4-5 disk space with lack of a normal hyperintense nucleus pulposus, intramedullary T2-weighted hypointensity that was also hypointense on T2*HEMO & slightly hypointense on pre-contrast T1-weighted images, no contrast enhancement observed, no evidence of spinal cord compression

• CSF: hemorrhagic CSF obtained from both lumbar & cisternal CSF tap (submitted cisternal CSF). RBC: 147,629 cells/uL, WBC: 7603 cells/uL (normal < 5), Protein: 185.9 mg/dL (normal < 25), Cytology: 2% neutrophils, 25% small to medium lymphocytes, 9% large mononuclear cells and 4% eosinophils. Erythrophagocytosis noted.

Diagnosis
Traumatic disk herniation or FCE most likely

Treatment
The patient was treated with pain medications for the first 48 hours. Professional physical therapy, as well as at-home PT exercises, were started. Corticosteroids were not given to this patient. Administration of corticosteroids is controversial and there is limited data on its effectiveness in peer-reviewed veterinary literature.

Prognosis
Fair – approximately 75% of dogs with traumatic disk herniation / FCE will recover the ability to walk

Outcome
The patient was brought in for recheck exam 2 weeks after the injury. During that time, she regained the ability to walk without assistance with only mild ataxia in all 4 legs.

Notes
1. In central cord syndrome, there is weakness in the thoracic limbs that is worse than the pelvic limbs. This is because there is disease within the spinal cord parenchyma that is affecting the more centrally located LMNs and white matter tracts to the thoracic limbs more than the peripherally located white matter tracts to the pelvic limbs.
2. Traumatic disk herniation is sometimes called a “Type III” disk herniation. This occurs when there is extrusion of a small volume of nucleus pulposus at a high velocity leading to severe spinal cord injury. It is thought that the disk material dissipates in the spinal canal leaving no residual spinal cord compression.
3. MRI Interpretation: The presence of hypointensity on all imaging sequences, especially the T2*HEMO images, is suggestive of either hemorrhage or mineralized material in the spinal cord. It’s possible that this was hemorrhage secondary to spinal cord contusion or other hemorrhagic condition, or could be due to mineralized disk material tearing through the meninges into the spinal cord.
4. CSF interpretation: The large numbers of RBCs along with erythrophagocytosis was thought to be due to peracute hemorrhage into the subarachnoid space from either damage to the vertebral venous sinus or meningeal blood vessels.

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