Laryngeal paralysis is a mechanical failure, not an allergy: the arytenoid cartilages stop opening on inhale, so the airway narrows exactly when the cat needs it widest. Three signs carry most of the diagnosis — an inspiratory stridor heard from 1 to 2 m away, a voice that turned hoarse over 2 to 6 weeks, and heat intolerance starting at 22 to 24 C. All 3 plus a resting rate above 40 breaths per minute means a scope within 24 hours, not a 2 week inhaler trial.
The 3 signs, in the order owners notice them
Stridor comes first: inspiratory, low pitched, loudest with the neck extended, and clear enough on a phone recording from 1 m for triage. Cats compensate, breathing 24 to 32 per minute asleep and 50 to 70 when stressed, so one calm reading can look normal. Count 30 seconds while the cat sleeps, double it, repeat on 3 nights.
The voice change is the sign owners dismiss. A meow that went from 2 syllables to a rasp, or a silent meow appearing over 3 to 6 weeks, means air no longer drives the vocal folds cleanly. Record it weekly on the same phone at 30 cm; 4 clips over 4 weeks beat memory.
Exercise and heat intolerance come third. A cat that sprinted 3 m for a toy now stops at 1 m, or pants 60 to 90 seconds after 2 minutes of play. Open mouth breathing at rest is never normal in a cat: the nasal route has failed and the reserve is gone.
Why the airway fails on the inhale
The glottis of a 4 kg cat is 5 to 7 mm across when fully open. Inhale drops pressure inside the trachea, and that negative pressure pulls the arytenoids inward; when the abductor muscle is weak on one or both sides, the cartilage folds into the airstream. Resistance scales with 1 over radius to the fourth power, so losing 1 mm of a 6 mm opening costs over 3 times the work of breathing, and 3 mm costs about 16 times.
The larynx is also a heat exchanger. Air crossing a 6 mm gap at 60 breaths per minute dries and cools the mucosa, which is why 20 to 22 C and 40 to 60% humidity are measurable, not decorative. The diaphragm pays the extra work too: a cat that compensated for 6 to 10 weeks can decompensate in 30 minutes when the room warms 5 C.
What each sign costs you in time
| Sign | What you measure | Typical reading | Act within | Scope needed |
|---|---|---|---|---|
| Inspiratory stridor | Audible distance at rest | 1 to 2 m | 24 to 72 hours | Yes, first visit |
| Voice change | Weeks since onset | 2 to 6 weeks | 2 weeks | Yes, same exam |
| Heat intolerance | Room temperature at first pant | 22 to 24 C | 48 hours | Yes |
| Resting respiratory rate | Breaths in 30 seconds, doubled | 40 to 60 per minute | 12 to 24 hours | Yes, urgent |
| Open mouth breathing | Gum refill time | Over 2 seconds | 0 to 2 hours | Emergency |
Two numbers decide the night: 40 breaths per minute at rest, and 22 C. Below both, plan a weekday scope. Above both, the cat is one hot afternoon from a crisis.
The endoscopy window: 60 seconds at a light plane
The exam is a 30 to 60 second look and the result depends on depth. At a light plane with spontaneous breathing the arytenoids abduct on each inhale and asymmetry is obvious; at a surgical plane the muscles relax and normal cats can look paralyzed. Ask for 3 things: a rate counted for 60 seconds before any drug, video before topical spray, and a second look after 60 seconds of gentle play. A larynx that opens first and fails after play has dynamic collapse.
Grades run 1 to 4: 1 opens fully, 2 is asymmetric with one side lagging, 3 shows minimal movement on the affected side, 4 shows none. Grade 3 or 4 with clinical signs justifies a surgical referral. Have the vet record the grade, the side, and whether collapse was inspiratory only, because those 3 facts separate tie back surgery from a heat and weight plan.
Look alikes that change the plan
Asthma answers a bronchodilator in 5 to 15 minutes and gives an expiratory wheeze; a cat that improves across a 7 to 10 day steroid trial likely never had laryngeal disease. A nasopharyngeal polyp appears at 4 to 18 months with a muffled voice and one sided discharge, cured by a 10 minute pull. Tracheal collapse honks at 1 to 2 cm of neck pressure, which is why a collar is wrong hardware here. Obesity alone adds 20 to 30% to the work of breathing.
The causes worth screening for
In cats most acquired cases are secondary: thyroid surgery in the past 3 to 12 months, a mediastinal mass pressing the recurrent laryngeal nerve, or a generalized neuropathy. Start with a blood count, chemistry, T4, and 2 view chest films; add an acetylcholine receptor antibody test if the cat regurgitates. Laryngeal paralysis plus regurgitation is 2 problems, and the regurgitation kills quietly through aspiration.
What to change at home tonight
- Swap the collar for a Y front harness: 2 to 3 cm of neck pressure narrows a 6 mm glottis.
- Hold the room at 20 to 22 C and 40 to 60% humidity; a 5 C rise shortens exercise tolerance.
- Feed 3 to 4 small meals instead of 1, with the bowl raised 8 to 10 cm.
- Weigh weekly: 1 kg over ideal adds about 10% to the work of breathing.
- Keep aerosols and dusty litter 2 m from the sleeping spot.
What surgery buys, and what it does not
Unilateral arytenoid lateralization opens one side permanently, the usual answer for grade 3 to 4 disease. Most cats breathe quieter within 24 to 48 hours and need 2 weeks without jumping above 30 cm. The trade is aspiration, seen in roughly 1 in 10 cases, so a cat with existing regurgitation is a poor candidate. The voice stays hoarse in most cats and some lose the meow.
Go now, not tomorrow
Blue gums, a gum refill over 2 seconds, open mouth breathing at rest, a rate above 60 per minute, a temperature above 40 C, or any collapse means emergency. Two of those 5 findings make it hours, not days. Call ahead so oxygen is ready and the cat skips a 10 minute wait in a 26 C car.
A cat in respiratory distress often stops urinating too, and 12 hours with no urine is a second emergency running in parallel; the early signs sit in urinary blockage signs. Scope, anesthesia, and surgery prices vary by a factor of 2 to 3 between cities, so run cost estimates before you book.
Terms mentioned in this article
Frequently asked
Can a cat with laryngeal paralysis live without surgery?
Some can, if the grade is 1 or 2 and the triggers are controllable. That means a room held at 20 to 22 C, a harness instead of a collar, 3 to 4 small meals, and a weight 1 kg closer to ideal. The cat is then rechecked every 3 to 6 months with a resting respiratory rate log. Any cat that starts open mouth breathing at rest, or whose rate climbs above 40 per minute asleep, has moved past what management alone can hold.
How is a laryngeal scope done without hurting the cat?
It is a 30 to 60 second look under a light plane of anesthesia with the cat breathing on its own, often after a short acting sedative. The vet watches the arytenoids open on each inhale, films it, then repeats the view after 60 seconds of gentle play to catch dynamic collapse. Deep anesthesia relaxes the muscles and can make a normal larynx look paralyzed, so depth matters more than equipment.
Is the stridor always laryngeal paralysis?
No. Asthma gives an expiratory wheeze that responds to a bronchodilator in 5 to 15 minutes, a nasopharyngeal polyp gives a muffled voice in a cat aged 4 to 18 months, and obesity alone can add 20 to 30% to the work of breathing. That is why the scope, not the sound, makes the diagnosis, and why 2 view chest films belong in the same workup.