Nasal region, nasal mucosa and nasal sinuses

In the examination of the nasal region the following structures and details are noted: (a) nostrils and the surrounding tissues; (b) move­ments of the nostrils; (c) respiratory sounds; (d) expired air; (e) nasal discharge; (/) mucous membrane; and (g) paranasal sinuses.

Tissues Surrounding the Nostrils

The changes that may occur in the skin of the nasal region include swelling of the alae nasi (purpura haemorrhagica, neoplasia, actinobacillosis), vesicles, pustules and scabs (contagious pustular dermatitis; see Fig. 53 p. 54); absces­ses, depigmented streak (chronic persistent nasal discharge), etc. Such changes may either origi­nate in the skin and then spread to involve the mucous membrane, or they may be secondary to diseases of the mucosa.

The nose of the dog, the muzzle of the ox and the snout of the pig are normally moist and cool because of continuous secretion of a watery fluid. Occasionally it may occur that the nose of a healthy dog or pig is dry and warm, e.g. in animals that have recently been digging or root­ing in the ground.

Movement of the Nostrils

Distension of the external nares, involving movements of the alae nasi, is to a large extent voluntary in healthy animals. The thick rigid nostrils in the ox prohibit movement altogether. The large, flexible nostrils of the horse permit considerable movement, which is also noted in the rabbit. Inspiratory dyspnoea causes a par­ticularly distinct, involuntary dilatation of the nostril (again most prominently in the horse) which coincides with the inspiratory phase of the cycle; during expiration the nostrils collapse to the normal position and size. This sequence of events is observed in advanced pulmonary emphysema, bronchitis, pneumonia, rupture of the diaphragm, oedema of the larynx, etc.

Respiratory Sounds

In certain diseases, respiration is accompanied by audible, abnormal sounds (stridors). When these arise from constriction of the respiratory passages they are known as stenotic sounds. They may be inspiratory or expiratory, and originate in the nasal cavities, pharynx, larynx or trachea. Stenosis of the respiratory passages may be caused by swelling of the mucous membrane, the presence of excessive mucus, inflammatory oedema, neoplasia, paralysis of the nostrils (facial nerve paralysis in the horse), enlargement of retropharyngeal lymph nodes, paralysis of the larynx, etc. Stenotic sounds are manifested by whistling, roaring or stertorous tones, and are usually louder during inspiration than at expira­tion. In paralysis of the larynx the abnormal sounds only occur during inspiration, whereas in paralysis of the soft palate they occur only at expiration. The sounds caused by the presence of nasal tumours, distortion of the nasal struc­tures (atrophic rhinitis, osteomalacia), fracture of nasal bones, etc., are audible during both inspiration and expiration. Snoring (stertorous) respiratory sounds are normal in brachycephalic breeds of dogs such as the bulldog, boxer, Pekingese, etc. Some such cases are due to a congenitally elongated uvula. In other animals, sounds of this type are usually heard in lym­phadenitis (actinobacillosis, tuberculosis, abscessation caused by Corynebacterium pyogenes) or neoplastic involvement of the pharyngeal lymph nodes, and in laryngitis, arising from vibration of the enlarged lymph nodes in the former two conditions, and of the relaxed soft palate in the latter. Snuffling, bubbling, or rattling sounds are heard when there is an accu­mulation of secretion, or discharge, in the nasal cavities, larynx or trachea. In many cases the stenotic sounds are audible when the animal is resting, whereas in others they develop after gentle, or in some instances only after strenuous, exercise, and disappear, sometimes very soon, after exercise is terminated (e.g. in paralysis of the larynx or of the soft plate in the horse).

The place of origin of the stenotic sounds can often be discovered by listening carefully with the unaided ear; in other cases a more thorough investigation is necessary, comprising palpation, auscultation and other methods of examination (endoscopic, radiological) of the nasal cavities, larynx or trachea. If the lesion causing the ab­normal sound is unilaterally situated in a nasal cavity, the sound will disappear on occluding the nostril of that side, and will be accentuated by occluding the nostril of the normal side. Stenotic sounds originating in the larynx become tem­porarily softer on occluding one nostril because of the reduction in airflow volume.

A sneeze is a sudden, noisy expiration pro­duced reflexly by irritation of the nasal mucous membrane stimulating the sensory nerve endings of the olfactory and facial nerves, e.g. by foreign bodies or parasites (Oestrus ovis in sheep, Linguatula rhinaria in the dog), irritant odours or gases or inflammation of the nasal mucosa. It is preceded by a deep inspiration, with closure of the oropharynx and contraction of the vocal cords; during the early phase of the subsequent forceful expiration movement, the glottis is closed and pressure is elevated so that when it is finally opened the expiration is explosive having as its objective the removal of foreign material from the nasal cavity (Fig. 90).

Other abnormal respiratory sounds which may be heard include coughing and grunting (see p. 36).

Expired Air

The stream of expired air is examined by holding the back of the hand in front of both nostrils. In the normal animal the flow of air from the left and right sides is equal in strength. If there is an obstruction in the nasal passage (neoplasm, fracture, exostosis), the airflow is weaker on the affected side. Variations in airflow volume between nostrils can be further assessed by occluding the nostrils one at a time. When there is significant obstruction of one nasal cavity, severe respiratory embarrassment is pro­duced by temporary occlusion of the other nos­tril. When respiration is so shallow that there is doubt as to whether the animal is breathing, holding a previously cooled hand-mirror close to the nostrils may prove of assistance; condensa­tion on the surface of the mirror will occur as the result of expiration.

In certain diseases of the nasal cavities and neighbouring structures, or of other respiratory organs, the expired air has a very offensive odour, which can be perceived some distance away from the animal. This odour is usually produced by putrefaction of the tissues, e.g. gangrenous pneumonia, necrosis of the turbinate bones, pus in the paranasal sinus, accumulation of nasal exudate. If the origin of the odour is unilateral, it can be detected on one side only; otherwise if it originates distal to the pharynx it can be detected at both nostrils. There is usually a sweet, sickly odour from the exhaled air in cattle with ketosis. Putrefactive conditions in the mouth, arising from deposits on the teeth, decaying teeth or necrosis and ulceration of the mucous membrane may also impart an offensive odour to the air exhaled through the nostrils, but in this case the odour from the mouth is more obvious and it can also be detec­ted in the saliva. Odours originating in the res­piratory tract are usually detectable with each expiration.

Nasal Discharge

This may be unilateral or bilateral (when nasal discharge is observed both nostrils should always be examined), continuous or intermittent, scanty or copious, and may be serous, mucoid, mucopurulent, purulent, sanious, or haemorrhagic in character. If it has been in existence for several months it may have caused an area of derma­titis, or a depigmented streak.

The nasal discharge usually originates in the nasal cavities or pharynx, but it may also arise in a paranasal sinus, the trachea, bronchi, bron­chioles, lungs, mouth, oesophagus or stomach (the guttural pouch is an important source in the horse). Excretions from the conjunctival sacs may also appear in small amounts as apparent nasal discharge (via the lacrimal ducts).

A unilateral nasal discharge occurs in uni­lateral disease of a nasal cavity (necrosis of turbinate bone, Oestrus ovis infestation in sheep, Linguatula rhinaria infestation in the dog, neoplasia), in diseases of the paranasal sinuses (pyogenic infection, defective drainage) and in some cases of empyema of the guttural pouch in the horse. A bilateral nasal discharge occurs in in­flammatory affections of the nasal cavities and in diseases involving the parts of the respiratory tract beyond the posterior nares (allergic rhinitis, atrophic rhinitis, strangles, equine viral arteritis, equine viral rhinopneumonitis, glanders, malig­nant catarrhal fever, mucosal disease, infectious bovine rhinotracheitis, bluetongue, feline viral rhinopneumonitis, infective pneumonias when there is an accompanying inflammation of the upper respiratory tract or the exudate in the bronchioles is copious, etc.).

A nasal discharge may be constantly present or appear only intermittently when the head is lowered (empyema of the paranasal sinuses), or spontaneously (rupture of abscesses in the nasal cavities, pharynx or lungs). The discharge may contain bubbles giving it a frothy appearance; the bubbles are usually of large size when they originate in the pharynx or nasal cavities, and are small in those cases where the origin is the lower respiratory tract.

Bleeding of varying severity from the nostrils (epistaxis) is not uncommon in young race­horses during exertion. Nasal haemorrhage some­times results from local trauma caused by passage of a stomach tube, entry of a foreign body into the nostril or accidental injury to the facial bones. The quantity of blood which escapes varies considerably, it is mainly unclotted and not ad­mixed with exudate or any other solid material. Haemorrhage from the nasal cavities, pharynx or guttural pouches (horse) may originate from lesions of the mucous membrane, e.g. ulceration (glanders), aspergillosis of the guttural pouch, neoplasia or granulomas. Small quantities of blood may escape from the nostrils in purpura haemorrhagica, warfarin or sweet clover intoxi­cation and bracken fern poisoning. In haemor­rhage from the nose or pharynx the escaping blood is dark red (venous). In acute pulmonary congestion, equine infectious pneumonia, equine infectious anaemia and congestive heart failure, small amounts of rusty-coloured serous fluid are not infrequently observed in the nostrils. In acute pulmonary oedema the discharge from the nostrils consists of greyish-white or bright-red froth which contains innumerable small bubbles; the quantity of the discharge is often considerable and its passage is often accompanied by cough­ing and severe dyspnoea.

In pharyngitis, paralysis of the pharynx, oesophageal obstruction or occlusion and oesophageal spasm, the nasal discharge may contain recognizable, masticated food particles (regurgi­tation) mixed with saliva, and which may impart a characteristic green colour (chlorophyll from fresh vegetable matter). Vomiting, particularly in the horse, is associated with discharge of food material from the nostrils. The vomitus contains partially digested food particles and has a sour odour; free hydrochloric acid is usually demon­strable.

Regurgitation

In dysphagia (difficulty in swallowing), the masticated food is returned from the pharyngeal region via the nasal cavities and mouth, and water that is drunk runs out through both nos­trils. This is regurgitation. It is observed chiefly in the horse and dog, and occurs when, as a result of inflammatory swelling of the pharyngeal mucosa, paralysis of the upper part of the pharynx, neoplasia in the pharynx, foreign body in the pharynx, etc., contact of the soft palate with Passavant's cushion in the posterior wall of the pharynx is not sufficiently intimate to shut off the cavity of the pharynx from the nasal cavities, and so food escapes through the aper­ture into the posterior nares. Regurgitation, re­sulting from dysphagia, is also associated with structural or functional obstruction of the oeso­phagus. In these circumstances repeated, vigo­rous swallowing movements may have been noted to precede regurgitation. Regurgitated material is usually slightly alkaline in reaction.

Nasal Mucous Membrane

This can be adequately inspected only in equine species, because in these animals the nostrils are wide and flexible, so that the anterior third of the nasal cavities are accessible to direct visual examination (Fig. 91); this is not the case in other species of domestic animals. On the floor of the nasal fossae, at the junction between the skin and the mucous membrane, lie the openings of the lacrimal ducts, one at each side, which are fairly large and clearly visible in equine species. A nasal discharge, in whole or part only, may therefore have originated in the conjunctival sac. In equine species the nasal diverticulum ('false nostril') is readily examined by inserting the finger into the nostril at the upper commissure; if necessary an endoscopic examination can be performed. Sebaceous cysts occasionally develop at this site.

The short ducts of the mucous glands opening on to the surface give the nasal mucosa a finely punctate appearance, which is accentuated in inflammatory conditions causing hyperfunctioning of the glands. The proximal part of the nasal mucosa is somewhat pinkish in colour; the more distally situated parts of the mucous mem­brane have a bluish-red colour on account of the numerous venous blood vessels and spaces occurring there. When infiltrated by exudate, the nasal mucous membrane has a velvety appearance and is slightly spongy on palpation.

The more important changes affecting the nasal mucosa include pallor, injection, petechia-tion, erosion, ulceration or proliferation. Recog­nizing and correctly interpreting the significance of any change may be important. Pallidness occurs in anaemic states and in shock. Injection arises from simple hyperaemia which is noted in allergic rhinitis. Petechiation is a feature of the early stages of purpura haemorrhagica in the horse and of dicoumarol poisoning. Necrosis succeeded by erosive and ulcerative lesions of the nasal mucosa are a typical feature of rinderpest, malignant catarrhal fever and mucosal disease. The ulcerative lesions of glanders, melioidosis and epizootic lymphangitis are characteristic and have important diagnostic merit. Proliferative lesions in the form of small nodules (0-5-20 cm in diameter) develop on the mucosa of the an­terior third of the nasal cavity in rhinosporidiosis (nasal granuloma) in cattle.

In good light the anterior part of the nasal cavity of the horse can be inspected directly, otherwise an electric torch or illuminated specu­lum is used to project light into the cavity. In the horse and ox, the use of a suitable rhino-laryngoscope (see Fig. 110, p. 105) permits adequate visual examination of those parts of the nasal cavities that cannot be inspected directly or by means of an illuminated speculum.

With the aid of the rhinolaryngoscope, or a suitable sound, the patency of the nasal passages and the presence of any constriction (stenosis) can be established. Care is essential when insert­ing the instrument into the nasal cavity in order to avoid injury to the mucosa and, in the case of restless or excitable animals, sedation is usually desirable. Further information about the state of the nasal cavities may be obtained by radiological examination.

Paranasal Sinuses

Anatomically the paranasal sinuses connect directly, or indirectly, with the nasal cavity, of which they are diverticula; there are four pairs, viz. maxillary, frontal, sphenopalatine and ethmoidal.

The maxillary sinus lies approximately in the area between the eye and the zygomatic ridge, and the frontal sinus above the level of a line joining the eyes (the position of the sphenoidal sinus and the guttural pouch in the horse will be discussed later).

The first part of the examination of the sinuses consists in observing whether there is any ab­normal bony prominence (Fig. 92) or depression, and then, by palpation, determining whether there is rarefaction or fracture of bone, or local elevation of temperature. Percussing with the fingers (Fig. 93), or with a percussion hammer, determines the character of the sound elicited. In normal animals the sound is clear and loud, but if the sinus is filled with exudate, neoplastic tissue or a cyst, the percussion note is dull. These examinations are always carried out by comparing the findings on one side of the head with those observed on the contralateral side. Only distinctive differences in the features revealed are of diagnostic value. If in a completely darkened room, a very powerful, protected elec­tric torch is introduced into the mouth, the sinuses are transilluminated and appear as clear areas (diaphanoscopy) when normal. This pro­cedure is particularly useful in determining the condition of the maxillary sinuses in the dog. The most common cause of sinusitis in the dog is infection of the medial root of the fourth upper molar tooth (carnassial). The inflammatory exu­date and pus within the sinus may, under pressure, erode the maxillary bone and break through the skin and give rise to a chronic fistula on the face below and in front of the eye (Fig. 94). Prior to the formation of a fistula, a swelling may develop on this part of the face. In cattle, apart from very occasional cases of actinomycosis or neoplasia of the maxillary sinus, it is the frontal sinus that is mainly involved in disease. Frontal sinusitis occurs as an extension of infec­tion from the nasal cavity in malignant catarrhal fever, allergic rhinitis, injuries to horns, contu­sions and fractures in the area, and most commonly as a sequel of dehorning. Horn core tumours, particularly when malignant, invariably extend to involve the frontal sinus. Radiographic examination may be of diagnostic value in cer­tain instances when the existence or nature of a sinus disease is in doubt. Exploratory puncture (trephining) of a sinus might also be undertaken when other methods fail to indicate its state.

A nasal discharge originating in a paranasal sinus is unilateral, persistent, sometimes foetid, and occurs intermittently as a result of the head being lowered. Diseases of the air sinuses may affect adjacent structures as a result of either inflammation (escape of lacrimal secretion from the corresponding conjunctival sac, erosion of the maxillary bone in the dog producing a dental fistula) or swelling (strabismus, stenotic sounds in the affected nasal cavity, bulging of the hard palate interfering with mastication).

Microscopical Examination of Nasal Discharge

Besides examination for various bacteria, in­cluding Streptococcus equi, Strep. zooepidemicus, other streptococci, Actinobacillus mallei, Mycobacterium tuberculosis and fungi, e.g. Aspergillus spp., etc., nasal discharges are occasionally examined microscopically for the presence of virus inclusion bodies or of parasite ova. Virus inclusion bodies occur in the cells of the nasal mucosa in inclusion body rhinitis in pigs, also in infectious bovine rhinotracheitis for a few days only, and in feline viral rhinotracheitis. Identify­ing the inclusion bodies in smears of nasal discharge requires specialized experience. The parasite ova may originate in the nasal cavity (Linguatula rhinaria which produce oval, thick-shelled, double contoured ova), in the trachea and bronchi (Capillaria aerophila, Crenosoma vulpis, Filaroides osleri) or in the lungs (Metastrongylus spp.; see Fig. 160b, p. 205).

If gangrene of the lung is suspected (it occurs in some cases of aspiration pneumonia and causes the expired air to have a foetid odour), the nasal discharge can be examined for the presence of elastic fibres. These are recognizable as slender, wavy, colourless, refractile threads, which are distinguished from fibrin and connective tissue by being soluble in potassium hydroxide solu­tion. Examination of unstained preparations is satisfactory.

Parasite ova can be recognized at a low magnification; elastic fibres require higher mag­nification. In fungus infections of the nasal structures (epizootic lymphangitis of horses, rhinosporidiosis of cattle and chronic granulomatous rhinitis of dogs and cats caused by Histoplasma farciminosum, Rhinosporidium seeberi and Histoplasma neoformans, respectively) or lungs (aspergillosis), the causal organism can some­times be demonstrated in the nasal discharge. Specific identification would, in most cases, re­quire cultural techniques.