Nico – Narcolepsy
Nico, an 8-month-old Rottweiler presented to Southeast Veterinary Neurology (SEVN) for inability to stand and walk. He had a brief anesthetic procedure at the referring veterinarian’s office to remove a skin growth. Anesthesia was uneventful and he went home that afternoon.
That evening, the owner noted that Nico was sleepier than normal and seemed wobbly when he was walking, but attributed it to Nico’s anesthesia.
The following day, Nico re-presented to his regular veterinarian; however, at this point, he was unable to stand and walk. He was referred to SEVN. On examination, Nico was laterally recumbent. He did not respond to stimuli. He had ventral strabismus.
The remainder of cranial nerves were normal. When supported, he was flaccid in all four legs. Spinal reflexes were absent in the thoracic limbs and were normal in the pelvic limbs. Postural reactions were absent. He did not seem painful. Two days later, he was more alert but seemed excessively sleepy during the day. He would have episodes such as this one.
Note that this episode looks similar to a seizure – he seems unconscious, vocalizes, has involuntary facial twitches, and paddles. However, note that the episode can be stopped by distracting him.
The following day, he was more alert but seemed unable to move any of his legs.
At this point, I was suspicious of a particular disease but wanted to see what his response to food would be.
Nico's Final Diagnosis
Nico has narcolepsy/cataplexy. Narcolepsy is a syndrome characterized by abnormalities in the sleep-wake cycle. Excessive sleepiness is manifested as drowsiness and “sleep attacks”. Cataplexy is a brief episode of flaccid paralysis usually brought on by excitement.
There are two forms of narcolepsy in dogs. A genetic basis has been found in Labrador Retrievers and Doberman Pinschers and is due to a mutation involving the hypocretin receptor 2. Sporadic cases can happen in any breed and is caused by a loss of hypocretin 1-producing neurons in the hypothalamus.
Diagnosis in dogs is based on finding appropriate clinical signs (collapse or even falling asleep due to excitement). The source is often food but may include other sources of excitement. It is important to differentiate narcolepsy/cataplexy from other diseases that may cause collapse such as seizures, syncope, myasthenia gravis, myotonia or other diseases.
Treatment involves medications. Nico was treated with imipramine, a tricyclic antidepressant that acts via blocking cellular norepinephrine and serotonin reuptake in the central nervous system (CNS).
Here is a video of Nico after treatment on the day of discharge.