Radiological anatomy of Frontal sinus Balasubramanian Thiagarajan drtbalu's otolaryngology online

drtbalu's otolaryngology online Introduction Highly complex and variable anatomy Variations – impact on drainage Efficiency of muco-ciliary clearance – relationship to morphology of frontal sinus drtbalu's otolaryngology online

drtbalu's otolaryngology online Embryology drtbalu's otolaryngology online

drtbalu's otolaryngology online Embryology - contd Continuation of embryonic infundibulum, frontal recess superiorly Upward migration of anterior ethmoid air cells Penetration via inferior aspect of frontal bone between the two tables Pneumatization 2-9 years Complete – 9 years drtbalu's otolaryngology online

Frontal sinus drainage Expands into the diploic space of frontal bone from frontal sinus ostium Each sinus grows independently of the other Growth is dependent on ventilation, drainage, growth of surrounding sinuses and skull base Drainage is hence highly variable drtbalu's otolaryngology online

Frontal sinus drainage - contd Inferomedially into funnel shaped area (frontal sinus ostium) Anterior wall of drainage channel is bounded by nasal beak Ostium is oriented perpendicular to the posterior wall of the sinus at the skull base level drtbalu's otolaryngology online

drtbalu's otolaryngology online Frontal beak drtbalu's otolaryngology online

Frontal sinus drainage pathway compartments Drainage pathway is divided into superior and inferior compartments Superior compartment is formed by union of adjacent air cells at the antero inferior portion of ethmoid bone Size and shape of this component varies with the varying anatomy for fronto ethmoidal air cells Superior compartment communicates with the inferior compartment drtbalu's otolaryngology online

drtbalu's otolaryngology online Inferior component This passage is really narrow This compartment is formed by ethmoidal infundibulum / middle meatus This is dependent on the attachment of uncinate process drtbalu's otolaryngology online

drtbalu's otolaryngology online Inferior compartment Inferior portion - infundibulum Inferior portion - infundibulum drtbalu's otolaryngology online

drtbalu's otolaryngology online Attachment to lamina papyracea – inferior component formed by middle meatus drtbalu's otolaryngology online

Inferior compartment formed by infundibulum drtbalu's otolaryngology online

drtbalu's otolaryngology online

Frontal beak Frontal beak forms the floor of frontal sinus drtbalu's otolaryngology online

drtbalu's otolaryngology online Frontal recess Antero superior portion of ethmoidal air cell system This is where the frontal bone pneumatization begins Lateral wall is formed by lamina papyracea Medial wall is formed by vertical attachment of middle turbinate Posterior wall is variable ? Bulla if it manages to reach up to skull base drtbalu's otolaryngology online

drtbalu's otolaryngology online Frontal recess drtbalu's otolaryngology online

drtbalu's otolaryngology online Agger nasi drtbalu's otolaryngology online

drtbalu's otolaryngology online Large bulla Can obstruct frontal sinus outflow This area should be critically studied during imaging Causes obstruction from behind drtbalu's otolaryngology online

drtbalu's otolaryngology online Bulla drtbalu's otolaryngology online

Uncinate vs frontal sinus drainage Uncinate – skull base attachment causes frontal sinus to drain into superior portion of ethmoidal infundibulum Uncinate – attached to middle turbinate causes frontal sinus to drain into ethmoidal infundibulum Uncinate – attached to lamina papyracea causes frontal to drain into superior aspect of middle meatus. Ethmoidal infundibulum ends in terminal recess drtbalu's otolaryngology online

Ethmoidal infundibulum 3 – d space Lateral – LP Anteromedial – Uncinate Posterior - Bulla drtbalu's otolaryngology online

drtbalu's otolaryngology online Frontal recess block Large agger cell causing narrowing of frontal recess drtbalu's otolaryngology online

drtbalu's otolaryngology online

drtbalu's otolaryngology online uncinate process attached to skull base. The frontal recess is seen between the agger nasi and uncinate process drtbalu's otolaryngology online

drtbalu's otolaryngology online Scan showing uncinate process being attached to lamina papyracea. This causes terminal recess to form. Frontal sinus drains directly into middle meatus drtbalu's otolaryngology online

drtbalu's otolaryngology online scan shows the uncinate process being attached to the middle turbinate. Note the presence of infundibulum between the bulla and the uncinate process. Frontal sinus is seen opening into the infundibulum drtbalu's otolaryngology online

Bent's classification of frontal cell variants Type I: Single frontal recess cell above the agger Type II: Tier of air cells above agger projecting into the frontal recess Type III: Single massive air cell above agger expanding in superior direction Type IV: Single isolated cell within frontal sinus. Difficult to visualize due to thin walls drtbalu's otolaryngology online

drtbalu's otolaryngology online Type I & II frontal cell drtbalu's otolaryngology online

drtbalu's otolaryngology online Type III drtbalu's otolaryngology online

drtbalu's otolaryngology online Type IV drtbalu's otolaryngology online

Supraorbital air cells Pneumatization of orbital plate of frontal bone Posterior to frontal recess & lateral to frontal sinus Sometimes can reach high up mimicking frontal sinus drtbalu's otolaryngology online

drtbalu's otolaryngology online Thank you drtbalu's otolaryngology online