Norwich Terrier Upper Airway Syndrome (NTUAS)

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Introduction

Breeders and owners of Norwich Terriers have known for a long time that “snort and snuffle” and “raspy” breathing noises are common.  In recent years, evidence has slowly emerged, pointing to an underlying respiratory condition that is quite variable, ranging from noisy breathing to severe distress with heat and exercise intolerance.

Norwich Terrier Upper Airway Syndrome (NTUAS) affects the larynx (voicebox), a complex anatomical structure that controls the amount of air that enters into the trachea (windpipe) and lungs. If the larynx is obstructed in any way, respiratory distress will ensue. One cannot assume that all upper airway sounds are due to NTUAS. Cysts, tumors, pieces of grass, twigs, etc. can cause upper airway obstruction in any dogs. It is important, therefore, that all dogs being evaluated for NTUAS undergo a full upper airway examination concurrently.

The true prevalence of the condition is unknown because even dogs with no apparent symptoms may be mildly affected. The condition appears breed-specific and has a wide spectrum of severity. The NTUAS Study Group was formed to clearly characterize the condition and develop a protocol to evaluate and grade the Norwich terrier upper airway.

Resources for owners of Norwich terriers and their veterinarians

This section of our NTCA website presents resources developed for veterinarians to evaluate for NTUAS (Full Upper Airway Examination Form) and compute the NTUAS Score .

Of the 56 variables assessed in the study sample of 149 Norwich terriers, these 5 variables distinguished between dogs clinically-affected with NTUAS and dogs not clinically-affected, where the differences were statistically significant (p<0.05). These 5 variables form the basis of the NTUAS Score:

1. Dorsal pharyngeal wall
2. Supraglottic laryngeal mucosa
3. Cuneiform processes of arytenoid
4. Ventricles
5. Infraglottic lumen

The NTUAS Score can be formulated from the full upper airway examination.

Importance of a FULL upper airway examination:

A full upper airway examination should evaluate the nares, tongue, hard palate, soft palate, tonsils, pharynx (laterally and dorsally), epiglottis, hyoepiglottis and valleculae, cuneiform and corniculate processes, piriform recesses, laryngeal mucosa, vestibular and vocal folds, ventricles, immediate infraglottic lumen.

Presence of phlegm, pharyngeal sensitivity, laryngeal sensitivity and laryngeal function should also be assessed.

Although anatomically not part of the upper airway, it is useful to include the trachea, mainstem bronchi and choanae (retroflexed view) in an airway examination.

The nasal cavity, choanae, nasopharynx and soft palate thickness can be evaluated with computed tomography (CT, CAT scan) using a slung maxilla positioning.

An accurate history and exercise tolerance test are also valuable to the owner and veterinarian to determine how compromised the dog may be.

Resources to View and Download

Click here to view NTUAS Score Sheet
Click here to download PDF version of the NTUAS Score Sheet

Click here to view Visual Guide to the NTUAS Score
Click here to download PDF version of the Visual Guide to the NTUAS Score
Click here to download Powerpoint version of the Visual Guide to the NTUAS Score

Click here to view Full Upper Airway Examination Form
Click here to download PDF version of the Full Upper Airway Examination Form

Click here to view a video of Full Upper Airway Examination (without retroflexed view)
Click here to download a video of Full Upper Airway Examination (without retroflexed view)

Click here to view History Questionnaire
Click here to download PDF version of History Questionnaire

Click here to view the Exercise Tolerance Test
Click here to download PDF version of Exercise Tolerance Test

Click here to view NTUAS Study Vets and Contact Info
Click here to download PDF version of NTUAS Study Vets and Contact Info

How the NTUAS score was developed

The NTUAS Study Group enrolled 154 Norwich terriers. Five dogs were excluded (3 inadequate study exam, 1 large choanal mass, 1 subepiglottic cyst), resulting in 149 cases. Based on a detailed owner questionnaire administered online prior to the study visit and corroborated at time of examination, 79 dogs could be clearly designated as clinically-affected and 70 were clearly not clinically-affected.

The Study Group evaluated 56 variables in the airway examination and computed tomography (CT) of the head and neck. These variables pertained to the following anatomic regions of the airway:

Nares
Nasal cavity
Dental and Periodontal
Tonsils
Tongue
Hard Palate
Soft palate
Choanae
Nasopharynx
Epiglottis and hyoepiglottis
Subglottic thyroid
Subglottic cricoid
Trachea
Mainstem bronchi

Lateral pharyngeal walls
Dorsal pharyngeal wall
Supraglottic laryngeal mucosa
Cuneiform processes of arytenoids
Corniculate processes of arytenoids
Vocal folds
Ventricles
Presence of phlegm

In addition, innervation was tested via:

Laryngeal sensitivity & function
Palatal sensitivity & function