Difference between revisions of "Diseases of the nasal cavity and sinuses"

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==Functional anatomy==
 
==Functional anatomy==
*Mucosa
+
===Mucosa===
 
**Mucosal epithelium
 
**Mucosal epithelium
 
***Nares and epiglottis- stratified squamous
 
***Nares and epiglottis- stratified squamous
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***Lymphoid tissue
 
***Lymphoid tissue
 
**Blood vessels, lymphatics and nerves
 
**Blood vessels, lymphatics and nerves
***Very rich blood supply to nasal mucosa
+
***Very rich blood supply to nasal mucosa===
*Nasal chambers and turbinates
+
===Nasal chambers and turbinates
 
**Scrolls of turbinate bone
 
**Scrolls of turbinate bone
 
**Arrangements vary with species
 
**Arrangements vary with species
*Nasal septum
+
===Nasal septum===
 
**Full length of nasal chamber in horses
 
**Full length of nasal chamber in horses
 
***2 openings into pharynx
 
***2 openings into pharynx
 
**Partial length in other species
 
**Partial length in other species
 
***Single opening into pharynx
 
***Single opening into pharynx
*Sinuses
+
===Sinuses===
 
**Size, arrangement and number vary with species
 
**Size, arrangement and number vary with species
 
**Poorly developed in carnivores
 
**Poorly developed in carnivores
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***Cheek teeth embedded within the maxillary sinuses
 
***Cheek teeth embedded within the maxillary sinuses
 
***Maxillary sinusitis secondary to tooth root abscesses
 
***Maxillary sinusitis secondary to tooth root abscesses
*Guttural pouch
+
===Guttural pouch===
 
**Horses
 
**Horses
 
***Diverticulum of the eustachian tube with a thin slit-like opening at the rostroventral aspect into the pharynx.
 
***Diverticulum of the eustachian tube with a thin slit-like opening at the rostroventral aspect into the pharynx.

Revision as of 21:16, 29 November 2006

Clinical signs and locations of sinonasal pathology

Nasal discharge

    • Bilateral discharge:
      • Lesion is caudal to nasal septum eg: pharyngeal lesion; LRT lesion in horses
      • Lesion has resulted in nasal septum destruction
        • Neoplasia
        • Fungal infection
    • Unilateral discharge:
      • Lesion is cranial to nasal septum eg: nasal or sinus lesion; pharyngeal or guttaral pouch lesion in horses

Type of discharge

    • Serous
    • Catarrhal
    • Purrulent
    • Haemorrhage

Clinical signs

    • Sneezing - nasal
    • Facial swelling - nasal, pharyngeal
    • Pain - any location
    • Coughing - pharynx, larynx, trachea
    • Dyspnoea/altered air flow
    • Respiratory noise

Functional anatomy

Mucosa

    • Mucosal epithelium
      • Nares and epiglottis- stratified squamous
      • Nasal cavity, paranasal sinuses, larynx, trachea - pseudostratified, columnar, cilliated
    • Submucosa
      • Submucosal glands
      • Lymphoid tissue
    • Blood vessels, lymphatics and nerves
      • Very rich blood supply to nasal mucosa===

===Nasal chambers and turbinates

    • Scrolls of turbinate bone
    • Arrangements vary with species

Nasal septum

    • Full length of nasal chamber in horses
      • 2 openings into pharynx
    • Partial length in other species
      • Single opening into pharynx

Sinuses

    • Size, arrangement and number vary with species
    • Poorly developed in carnivores
      • Poor communication of frontal sinus in cats with nasal cavity
        • Predisposed to frontal sinus bacterial infections
      • Maxillary sinus opening very large - 'maxillary recess'
        • Maxillary sinus infections very uncommon in carnivores
      • Highly developed in horses
      • Slit-like, high openings in horses
      • Predisposed to bacterial infections
      • Cheek teeth embedded within the maxillary sinuses
      • Maxillary sinusitis secondary to tooth root abscesses

Guttural pouch

    • Horses
      • Diverticulum of the eustachian tube with a thin slit-like opening at the rostroventral aspect into the pharynx.
      • Mucous secretions drain out of the pouch when the horse lowers its head
      • Lined by respiratory epithelium
      • Bordered by glossopharyngeal, vagus, accessory and hypoglossal nerves; sympathetic trunk; internal and external carotid arteries
    • Pathology
      • Mycotic infections eg: Aspergillus fumigatus
        • Bacterial infections eg: Streptococcus equi var. equi ('Strangles') or S.equi var zooepidemicus
      • Tympany - associated with dysfunction of the pharyngotubal opening resulting from thickening (oedema, inflammation) or obstruction by a mucosal fold (eg: foals)

Defense mechanisms

  • Particle deposition
    • Coiled nature of turbinates promotes turbulent airflow and impaction of large particles >10 μm in diameter onto the nasal mucosa
  • Mucociliary escalator
    • Cilia on the respiratory epithelium beat in a co-ordinated manner
      • Cilia beat in a caudal direction in nasal cavity
      • Cilia beat in a cranial direction in trachea and lower airways
      • Mucus is swallowed when it reaches the nasopharynx
      • Constant movement reduces chances that pathogens can adhere to the respiratory epithelium
    • Mucus
      • Produced by the goblet cells of the respiratory epithelium and the submucosal glands with contribution from lacrimal glands draining into the nose
      • Traps particles for transportation away and subsequent swallowing
      • Physical barrier against mucosal damage
      • Prevents dessication of the mucosal epithelium
      • Contains antimicrobial substances
      • Immunoglobulin - IgA
        • IgA produced by mucosal plasma cells
        • IgA can attach to specific pathogen antigens (viruses, bacteria) trapping them in the mucus for clearance
      • Lysosyme
        • Direct action on bacterial cell walls
        • Lactoferrin
          • Inhibits bacterial growth as sequesters iron, an essential co-factor for many bacteria
  • Commensal bacteria
      • The normal bacterial flora of the nasal cavity, pharynx, larynx and proximal portion of the trachea compete with potentially pathogenic bacteria and help to prevent their colonisation (competitive exclusion).
      • The airway environment distal to the mid-portion of the trachea is effectively sterile.
  • Reflexes
      • Sneezing
      • Coughing

Pathology of the upper airways

  • Developmental abnormalities
    • Palatoschisis
    • Nasal deviation
    • All brachycephalic dog and cat breeds!
      • Esp. English Bulldogs - stenotic nares, wide/long soft palate, hypoplastic trachea
  • CIrculatory diseases
    • Epistaxis
      • Haemorrhage from the nose
      • Causes
        • Inflammation eg: ulcerative rhinitis
        • Neoplasia eg: infiltrating tumour, haemangioma
        • Trauma
        • Clotting defects
      • Horse:
        • Haemorrhagic nasal polyp
          • 'Ethmoid haematoma', 'Progressive haematoma' - arise from the ethmoid region and can extend to fill the nasal cavity. They can be difficult to control as they can recur after surgery.
          • Histology - multiple areas of acute to chronic haemorrhage within a fibrous tissue stroma.
        • Exercise-induced pulmonary haemorrhage
  • Inflammatory disease
    • Inflammation in the URT can be classified on:
      • Location
        • Nasal cavity - rhinitis
        • Paranasal sinuses - sinusitis
        • Guttural pouch and eustachian tube - eustachitis
        • Pharynx - pharyngitis
    • Type
      • Grossly many inflammatory processes (eg: response to viral or bacterial infection) in the URT will begin as a serous discharge, and then progress to a catarrhal exudate, and then to purulent/pseudomembranous/haemorrhagic as neutrophils are recruited
      • Serous - transparent fluid exudate (acute inflammation)
      • Catarrhal - mucous exudation (acute to subacute inflammation)
      • Pseudomembrnaous - fibrin exudation
      • Purulent - pus
      • Ulcerative
      • Haemorrhagic
      • Granulomatous (chronic inflammation)
      • Polypoid (chronic inflammation)
    • Timecourse
      • Acute, subacute, chronic
    • Causes
      • Infectious agent - viral, bacterial, fungal, parasitic
      • Trauma or foreign body (eg: grass seed)
      • Irritant or allergens
      • Neoplasia
      • Viral infections
        • Herpesviruses
          • Bovine herpesvirus -1
            • Causes Infectious bovine rhinotracheitis (IBR)
            • Highly infectious URT disease of cattle
            • High morbidity, low mortality
            • Aerosol transmission - requires close contact between animals
            • BHV-1 infects the respiratory mucosal epithelial cells (intranuclear inclusion eosinophilic inclusion bodies)from nasal mucosa down to bronchioles
              • leading to neutrophilic inflammation of varying severity.... serous -> catarrhal -> purulent nasal discharge, sneezing, coughing.
              • with secondary bacterial infection (eg: Pasturella spp., Mycoplasma spp., Fusobacterium necrophorum) can lead to fibrinous to necrotizing inflammation; mucosal sloughing, ulceration... pyrexia, dyspnoea ... inhalation pneumonia... death.
            • Clinical signs include coughing, discharge, lacrimation, and increased respiratory rate.
            • Clinical disease most severe in young calves - can develop mucosal ulcerative lesions in the oesophagus and forestomachs and viraemia with multiorgan infection.
            • Cause of abortion >5 months of gestation
          • Cytomegaloviruses
            • Porcine cytomegalovirus
              • Causes Inclusion body rhinitis
              • Disease of suckling piglets 1-5 wks of age
              • Clinical signs: those associated with acute/subacute rhinitis (ie: serous nasal discharge, progressing to catarrhal or purulent discharge with time and secondary bacterial infections; sneezing; pyrexia)
              • Morbitity high, mortality low
              • Histology: large basophilic intranuclear inclusion bodies in the nasal and sinus respiratory epithelium with lymphocytic infiltration of the mucosa.
              • Can develop viraemic stage, with inclusions in other organs eg: renal tubular epithelium. Piglets can die during this phase.
          • Equine herpesvirus - 1, 4
          • Feline herpesvirus -1
            • One of the causes of Feline viral rhinotracheitis
            • Viruses and bacteria are involved in the complex. The most frequent aetiologic agent is FHV-1, and less frequently feline calicivirus and/or Chlamydophia psittaci (NB: previously called Chlamydia psittaci var felis)
            • All three agents infect URT respiratory epithelium, although FHV-1 has the highest affinity for this epithelium
            • Feline calicivirus more frequently infects the oral mucosa -> ulcerative stomatitis
            • C.psittaci more frequently infects the conjunctival epithelium -> chronic conjunctivitis
            • Infection of the respiratory epithelium by FHV-1 results in a typical neutrophilic rhinitis with intraepitheial intranuclear eosinophilic inclusion bodies, with expected clinical signs
            • Resolution of clinical signs usually occurs by 7-14 days.
            • FHV-1 remains latent in the trigeminal ganglion, and can reactivate at times of stress. Can infect the cornea -> ulcerative keratitis.
            • Occasional mortality in kitten or immunocompromised animals usually associated with secondary bacterial infection.
      • Bacterial infections
        • Pasturella multocida
          • Atrophic rhinitis in pigs
          • Pigs aged 4-12 weeks old show clinical signs
          • Catarrhal nasal discharge (due to an acute rhinitis), sneezing, coughing, can progress to dyspnoea and anorexia.
          • Shortening and distortion of snout, secondary to nasal turbinate bone loss (histological evidence of osteolysis)
          • 2 forms of the disease
            • 'Progressive' atrophic rhinitis
              • Due to infection of the nasal turbinates by P.multocida strains carrying the toxA gene that encodes for an osteolytic toxin. P.multocida adheres poorly to mucous membranes, and therefore requires a predisposing nasal insult to assist colonisation eg: co-infection with B.bronchoseptica; or Porcine cytomegalovirus (inclusion body rhinitis)
              • Turbinate bone atrophy is permanent and progressive
            • 'Non-progressive' atrophic rhinitis
              • Due to infection of the nasal turbinates by Bordatella bronchoseptica strains alone, that carry a gene that encodes for a dermonecrotic toxin.
              • Turbinate bone can regenerate by the time of slaughter
          • 'Snuffles' in rabbits
            • Most often P.multocida and/or B.bronchoseptica infection of the nasal mucosa
            • Clinical signs (nasal discharge, sneezing) result from an acute to chronic rhinitis.
        • Streptococcus equi
          • Streptococcus equi subsp. equi
          • Cause of 'Strangles' in horses
          • Infection with Streptococcus equi occurs after contact with contaminated feed, water bowls or an infected carrier horse
          • Organism remains viable in environment for months
          • Possibility of other sources of infection - in pharynx of in-contact dogs?
          • Colonisation of nasopharynx causing:
          • Chronic purulent rhinitis, sinusitis, eustachitis
          • Can progress to development of nodular masses in the guttural pouch consisting of inspissated pus and viable bacteria (guttural pouch empyema) - 'carrier' state
          • Regional suppurative lymphadenitis - can rupture onto skin of neck
          • Bacteraemia with abscess formation in other organs (eg: liver, kidneys) - Bastard Strangles!
        • Streptococcus equi subsp. zooepidemicus
          • Can infect the respiratory tract (nasal cavity, paranasal sinuses, trachea and bronchi/bronchioles)
    • URT infection can be indistinguishable clinically from Strangles, but does not cause suppurative lymphadenitis (cf: S.equi subsp. equi)
    • Fungal infections
    • Filamentous fungal organisms
    • Aspergillus fumigatus
    • Guttural pouch infections in horses - fungal plaques form on the adventitia of the carotid arteries can lead to catastrophic haemorrhage following erosion of carotid arteries!
    • Nasal infection in dogs and cats - plaques develop on the nasal or paranasal sinus epithelium. Result in severe neutrophilic rhinitis/sinusitis. Can occur secondary to areas of mucosal compromise eg: adjacent to a space-occupying lesion.
    • Mucor spp.
    • Yeast-like fungal organisms
    • Cryptococcus neoformans
    • Most commonly in cats and dogs
    • Chronic granulomatous rhinitis
    • Can invade through adjacent structures, eg: through the cribiform plate into the brain! These cases therefore can present as a primary neurological disease.
    • Parasitic infections
    • Insecta
    • Oestrus ovis larvae in the nasal cavity of sheep and goats
    • 'Nasal bots'