Austin Veterinary Emergency & Specialty (AVES)

History

Signalment: 4-year-old spayed female Yorkshire Terrier

Acute onset cervical pain that progressed to collapsing when attempting to walk.

Difficulty eating and drinking; trouble holding head up.

Vaccination history: Up to date

Travel history: None

Concurrent medical conditions: Historical mild ALT elevation; IVDD

Medications prior to presentation: Rimadyl (carprofen), methocarbamol, gabapentin (started 2 days prior for cervical pain); historical Denamarin for elevated ALT.

Physical Examination

Temperature: 101.1°F

Pulse: 132 bpm

Respiration: Panting

Weight: 3.26 kg

No significant abnormalities noted.

Neurologic Examination

• Mentation: Appropriate

• Gait/Posture: Initially ambulatory with abrupt collapse episodes consistent with cataplexy; progressed to nonambulatory flaccid tetraparesis

• Cranial Nerves: Absent gag reflex (CN IX, X); abnormal tongue movement (CN XII)

• Postural Reactions: Normal to subtly reduced in all limbs

• Spinal Reflexes: Intact/normal

• Epaxial Palpation: No pain

• Nociception: Not tested

Neurolocalization

Brainstem localization based on:

• Cataplexy (sleep center involvement)

• Absent gag reflex (CN IX, X)

• Abnormal tongue movement (CN XII)

Differential Diagnoses

• Immune-mediated disease

• Infectious disease

• Neoplasia (less likely)

Diagnostics

• CBC: Hematocrit 64%

• Chemistry: ALT 286 U/L; ALP 15 U/L; AST 61 U/L

• MRI: Atlanto-occipital overlap; otherwise unremarkable

• CSF: Not performed due to craniocervical junction abnormalities

• Infectious disease testing: Negative

Treatment

Acquired narcolepsy/cataplexy secondary to immune-mediated disease was suspected.

• Imipramine initiated in hospital; mild improvement within 24 hours (returned to ambulatory status with intermittent collapse episodes).

• Prednisone started after 3-day washout from carprofen.

Outcome

Two-week recheck: Neurologically normal.

Prednisone tapered gradually over 4 months.

Imipramine continued until completion of prednisone taper, then discontinued.

No relapse of clinical signs reported.