Neurologic Disorders in Dogs (NAVLE Notes)
Neurologic disorders in dogs cover a broad range of conditions that vary in presentation, prognosis, and treatment approaches. Here is a breakdown of several key conditions commonly seen in canine neurology.
Intervertebral Disc Disease (IVDD)
- Classic Case:
- Signs: Severe pain in the neck or back, often seen as an arched back or head held down.
- Neurologic Symptoms: Ataxia, paraparesis, paraplegia, or tetraparesis.
- Breeds: Chondrodystrophic breeds (e.g., Dachshunds) are at higher risk.
- Diagnosis:
- Imaging:
- MRI: Best quality, non-invasive.
- CT: Safer and faster, but lower resolution than MRI.
- Myelography: Invasive; may cause seizures during recovery.
- Treatment:
- If pain only (no neurologic deficits): Strict cage rest and analgesia (opiates or NSAIDs).
- Nonambulatory or unresponsive cases: Surgical decompression.
- Hemilaminectomy for thoracolumbar disks.
- Ventral slot for cervical disks.
- Note: Steroids are less favored due to adverse effects; NSAIDs preferred.
- Key Points:
- Hansen Type I occurs in chondrodystrophic breeds, involving extrusion of the nucleus pulposus.
- Hansen Type II involves annulus hypertrophy or bulging in non-chondrodystrophic breeds.
Epilepsy
- Classic Case: 1- to 5-year-old dog with a history of seizures but normal between episodes.
- Diagnosis:
- Rule out other causes: CBC, biochemistry profile, bile acids, lead levels, MRI, and CSF analysis.
- Treatment:
- Anticonvulsants (e.g., phenobarbital, levetiracetam, zonisamide) to prevent or reduce seizures.
- Spaying females is advised.
- Key Points:
- Monitor anticonvulsant levels, especially with phenobarbital, which requires bile acid monitoring for liver health.
Traumatic CNS Injury
- Classic Case: History of trauma (e.g., contusions, lacerations) leading to neurologic deficits like paraparesis, paraplegia, tetraparesis, pain, altered consciousness, or seizures.
- Diagnosis:
- Imaging: Survey spinal radiographs, CT, +/- MRI.
- Treatment:
- Stabilize airway, breathing, and circulation.
- Administer fluids and oxygen.
- Surgical decompression and/or stabilization if indicated.
- Cage rest and external splinting.
- Key Points:
- Steroids are controversial for traumatic brain injuries, with concerns over efficacy and side effects.
Brain Tumor
- Classic Case: >5-year-old dog with signs based on tumor location:
- Signs: Seizures, altered consciousness, head pressing, ataxia, nystagmus, facial paralysis, head tilt.
- Diagnosis:
- Imaging:
- MRI: Best quality.
- CT: Safe and efficient.
- CSF Analysis: May show elevated protein; tumor cells rarely found.
- Treatment:
- Definitive: Surgical resection, radiation, or chemotherapy.
- Supportive: Prednisolone, anticonvulsants.
- Key Points:
- Meningiomas are more common in dolichocephalic breeds; gliomas are more frequent in brachycephalic breeds.
- Brain tumors are a leading cause of seizures in dogs over 5 years.
Geriatric Vestibular Disease
- Classic Case: Older dog with acute onset of head tilt, horizontal nystagmus, ataxia, circling, and normal mentation.
- Diagnosis: Rule out other causes of vestibular disease with thyroid testing, otoscopy, MRI/CT, +/- CSF analysis.
- Treatment:
- Nursing care (well-padded bedding, physical therapy).
- Sedatives if flailing.
- Key Points:
- Excellent prognosis, often resolves within days to weeks, though a residual head tilt may persist. Relapses can occur.
NAVLE-Style Practice Questions on Neurologic Disorders
Question 1
A 4-year-old Dachshund presents with severe back pain, an arched back, and reluctance to move. The owner reports that the dog’s pain has not improved despite 2 days of NSAID therapy. What is the most appropriate next step in management?
- A) Continue NSAIDs and monitor
- B) Start corticosteroids
- C) Schedule MRI and refer for surgical decompression
- D) Switch to acetaminophen
Correct Answer: C
Explanation: This Dachshund, a high-risk breed, presents with severe pain unresponsive to NSAIDs, suggesting intervertebral disc disease requiring advanced imaging and possible surgical decompression.
Question 2
A 3-year-old mixed-breed dog with a history of seizures presents for evaluation. Between episodes, the dog appears healthy, and diagnostic tests are within normal limits. What is the most likely diagnosis?
- A) Epilepsy
- B) Brain tumor
- C) Geriatric vestibular disease
- D) Hepatic encephalopathy
Correct Answer: A
Explanation: This young dog with a normal presentation and intermittent seizures is most consistent with idiopathic epilepsy, which typically presents between 1-5 years of age.
Question 3
A 6-year-old Boxer presents with head pressing, pacing, and circling to the left. Physical exam reveals mild ataxia and nystagmus. MRI shows a mass in the left temporal lobe. What is the likely diagnosis?
- A) Geriatric vestibular disease
- B) Brain tumor
- C) Intervertebral disc disease
- D) Idiopathic epilepsy
Correct Answer: B
Explanation: The neurologic signs, age, breed predisposition, and MRI findings of a mass suggest a brain tumor, which is common in older dogs, especially brachycephalic breeds like Boxers.
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