Keros classification of olfactory fossa
The Keros classification is a method of classifying the depth of the olfactory fossa.
The ethmoid labyrinth is covered by the fovea ethmoidalis of the frontal bone and separates the ethmoidal cells from the anterior cranial fossa.
The very thin, horizontal cribriform plate (lamina cribrosa) of the ethmoid bone is bounded laterally by the vertical lateral lamella. The lateral lamella joins the cribriform plate to the fovea ethmoidalis.
In adults, the olfactory recess is a variable depression in the cribriform plate that medially is bounded by the perpendicular plate and laterally by the lateral lamella. It contains olfactory nerves and a small artery.
The depth of the olfactory fossa is determined by the height of the lateral lamella of the cribriform plate, which can be classified into three categories:
- type 1: has a depth of 1-3 mm (26.3% of population)
- type 2: has a depth of 4-7 mm (73.3% of population)
- type 3: has a depth of 8-16 mm (0.5% of population)
The type 3 essentially exposes more of the very thin cribriform plate to potential damage from trauma, tumor erosion, CSF erosion (in benign intracranial hypertension) and local nasal surgery/orbital decompression 2.
Thin bone in the skull base, especially the cribriform plate, is susceptible to erosion, encephalomeningocele herniation and CSF leaks
The most common sites of erosion or defects in the skull base are
- cribriform plate (51%)
- sphenoid lateral pterygoid recess (31%)
- ethmoid roof (8%)
- perisella
- inferolateral or pterygoid recesses
History and etymology
This classification was described in 1962 1 by Predrag Keros (1933-2018) 3, a Croatian physician and later Professor of Medicine at the University of Zagreb.
See also
Related Radiopaedia articles
Anatomy: Head and neck
- skeleton of the head and neck
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cranial vault
- scalp (mnemonic)
- fontanelle
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sutures
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- facial
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- frontomaxillary suture
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- zygomaticomaxillary suture
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- occipitotemporal suture (occipitomastoid suture)
- sphenofrontal suture
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facial bones
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cranial vault
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muscles of facial expression
- occipitalis muscle
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- levator labii superioris alaeque nasalis muscle
- levator labii superioris muscle
- zygomaticus major muscle
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- malaris muscle
- levator anguli oris muscle
- risorius muscle
- depressors, retractors and evertors of the lower lip
- depressor labii inferioris muscle
- depressor anguli oris muscle
- mentalis muscle
- compound sphincter
- orbicularis oris muscle
- incisivus superior muscle
- incisivus inferior muscle
- muscle of mastication:
- elevators, retractors and evertors of the upper lip
- muscles of the middle ear
- orbital muscles
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arterial supply
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cranial nerves
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trigeminal nerve (CN V) (mnemonic)
- trigeminal ganglion
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- facial nerve (CN VII)
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vestibulocochlear nerve (CN VIII)
- vestibular ganglion (Scarpa's ganglion)
- glossopharyngeal nerve (CN IX)
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vagus nerve (CN X)
- superior laryngeal nerve
- recurrent laryngeal nerve (inferior laryngeal nerve)
- (spinal) accessory nerve (CN XI)
- hypoglossal nerve (CN XII)
- parasympathetic ganglia of the head and neck
- greater occipital nerve
- third occipital nerve
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cervical plexus
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ansa cervicalis
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- cutaneous branches
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cranial nerves
- lymphatic drainage of the head and neck
- embryological development of the head and neck
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