Townsend-2017-diagnostic-evaluation-for-sinus-pathology

Anatomy of Equine Paranasal Sinuses

• Pairs of Paranasal Sinuses: Horses have seven pairs, which include:

  • Frontal and dorsal conchal sinuses (collectively termed the concho-frontal sinus, CFS)

  • Caudal maxillary sinus (CMS)

  • Ethmoidal sinus

  • Sphenopalatine sinus

• Rostral Maxillary Sinus (RMS) and Ventral Conchal Sinus (VCS):

  • RMS and VCS communicate and drain through the RMS sino-nasal aperture into the sinus drainage angle.

  • Recent CT studies show variable drainage patterns, affecting diagnosis of sinus conditions.

  • Significant Features:

    • All or part of maxillary 08 and all maxillary 09 alveoli situated within the RMS.

    • RMS is smaller than CMS, separated by an angulated bony septum.

  • VCS Location: Medial compartment of the RMS, extending into CMS above the infra-orbital canal, forming the maxillary septal bulla.

• Caudal Maxillary Sinus (CMS):

  • Largest paranasal sinus, located medial to maxillary, lacrimal, and zygomatic bones, caudal to the RMS.

  • Normally contains alveoli of maxillary 10 and 11 cheek teeth.

  • Maxillary septal bulla occupies the caudal aspect of the CMS.

Diagnostic Evaluation for Sinus Pathology

• Common Conditions: Paranasal sinusitis usually results in unilateral nasal discharge.

• Clinical Signs: Nasal discharge, lymphadenopathy, which may complicate diagnosis between primary and secondary sinusitis.

• Diagnostic Techniques:

  • Upper Respiratory Endoscopy: Eliminates other causes of unilateral nasal discharge, like guttural pouch empyema.

  • Oral Examination: Detect occlusal dental issues contributing to sinusitis.

  • Radiography: Assesses sinus involvement and dental issues.

  • Advanced Imaging: CT is especially useful for definitive diagnosis and anatomical insight.

  • Direct Sinus Endoscopy: Used for diagnosis and therapeutic lavage.

Aetiopathogenesis of Sinus Disease

• Prevalence: Most commonly occurs unilaterally, with bilateral sinusitis being rare.

• Clinical Signs:

  • Unilateral nasal discharge and sometimes submandibular lymphadenopathy.

  • Implications of various conditions leading to sinusitis:

    • Primary Sinusitis: Mucosal infection/inflammation reducing drainage ostia size and mucociliary action, leading to mucus retention.

    • Secondary Sinusitis Causes:

      • Dental sinusitis (e.g., apical pulpitis)

      • Oro-sinus fistulas

      • Mycotic factors

      • Sinus cysts

      • Intra-sinus ethmoidal haematoma

      • Traumatic injuries

      • Neoplastic disorders

Diagnostic Methodology

• Clinical Examination: Key observations include unilateral nasal discharge, lymphadenopathy, and facial swellings.

• Nasal Endoscopy: Critical for identifying infection and anatomical abnormalities, including potential sino-nasal fistulas.

• Oral Examination:

  • Requires sedation and dental tools (e.g., endoscope).

  • Examine maxillary cheek teeth for signs of dental infections or structural damage.

  • Check for signs of deep diastema indicating oro-sinus fistula formation.

Radiographic Techniques for Sinus Disease

• Radiographic Projections:

  • Lateral radiographs show fluid or soft-tissue opacity within sinuses.

  • Oblique projections evaluate maxillary cheek teeth for dental issues.

  • Dorso-ventral views help assess the ventral conchal sinus status.

• Computed Tomography (CT):

  • Offers high sensitivity and specificity for diagnosing apical dental pathology and defines pathology deeply.

Advanced Imaging Techniques

• Scintigraphy: Useful for diagnosing dental conditions, though lacking in anatomical clarity.

• Magnetic Resonance Imaging (MRI): Limited studies; occasionally effective where visible pulp appears blurred and of lower signal intensity.

• CT Scanning: Preferred for assessing sinusitis, providing detailed anatomical views of sinus structures.

Sinus Trephination and Direct Endoscopy

• Direct sinus endoscopy helps identify intra-sinus pathologies effectively, including exudate and masses.

• Proper trephination techniques facilitate diagnostic acquisition and therapeutic interventions.

Conclusion & Key Points

• The equine paranasal anatomy is complex, requiring a comprehensive approach to diagnostics.

• Essential diagnostic tests include clinical examinations, endoscopy, oral checks, and radiography.

• When initial efforts fail to yield conclusive diagnoses, advanced imaging methods (e.g., CT or MRI) and sinus trephination may be necessary for thorough evaluation and treatment.

• Key points to remember:

  • Sinuses divided into caudal and rostral groups by drainage pathway.

  • CFS and associated structures significantly influence overall respiratory health.

  • Effective diagnosis combines multiple techniques informed by clinical presentation.