It's Tuesday afternoon and you have an emergency case coming that is reported to be unable to walk. Your staff tells you that you will be seeing a 5 year old Labrador that was found unable to walk in the back legs today. You square your shoulders and remind yourself of the common neuroanatomic lesion localizations for the spinal cord, and enter the room. After performing a thorough neurologic exam (self high five!) you conclude the following findings:
Mentation: BAR
Cranial nerves: reduced blink reflex bilaterally with normal corneal reflex, menace response, PLR, physiologic nystagmus and gag reflex.
Gait: Non-ambulatory tetraparesis
Reflexes: absent withdrawal reflex in both pelvic limbs, absent patellar reflexes bilaterally, absent panniculus reflex bilaterally, and reduced withdrawal reflexes more right thoracic limb than left, but both affected.
Postural reactions: When supported, paw replacement is absent in all four limbs
Palpation: non-painful, normal cervical range of motion
You make a hasty exit from the room and search for the number to your closest neurologist. Just kidding! You take a deep breath and realize that due to the multiple reduced reflexes in multiple limbs and cranial nerves, this must be neuromuscular, not spinal and not brain. Great job! What does neuromuscular actually mean?
Neuromuscular Neuroanatomic Lesion Localization:
Neuropathy - reflexes are reduced to absent, paresis without ataxia.
Junctionopathy - reflexes are typically absent however Myasthenia gravis is a junctionopathy and reflexes can be normal for this disease. Again, paresis or plegia without ataxia.
Myopathy - reflexes are normal, dogs are just paretic and are not ataxia
This dog could be a neuropathy or a junctionopathy.
What are my top 5 differentials for a dog with acute, progressive, junctionopathy?
1. Tick paralysis
2. Polyradiculoneuritis (Coonhound paralysis)
3. Botulism
4. Coral snake envenomation (not common in the Midwest)
5. Organophosphate/carbamate intoxication
Stay tuned for next week's TidBit Tuesday to discuss how we might diagnose and manage these unique cases!
Thanks for reading - have a great week and stay safe.