# Keros — Keros classification of olfactory fossa depth

> Side-specific CT classification of olfactory-fossa depth from the vertical height of the lateral lamella of the cribriform plate: type I up to 3 mm, type II over 3 through 7 mm and type III over 7 mm. Return the continuous measurement and all other skull-base hazards; Keros is one anatomic descriptor, not a complete surgical-risk score or a treatment rule.

**Situação:** vigente · **Órgão:** Skull base · **Órgão emissor:** Keros / sinonasal and skull-base imaging literature · **Versão:** 1962 depth framework; preoperative CT limitations reviewed through 2020 · **Ano:** 1962

## Procedência e vigência
- Família: léxico
- Tipo de lógica: flat
- Modalidade: CT
- Fonte primária: Keros P; reproduction by Souza SA, Souza MMA, et al.. Olfactory fossa depth classification (Keros), reproduced in a CT analysis of 1200 patients (1962) — https://pmc.ncbi.nlm.nih.gov/articles/PMC6319094/
- Última verificação: 2026-07-24
- Última checagem: 2026-08-12

## Lógica de decisão
Return one measurement and type per side, plus asymmetry and the remaining skull-base hazards. Keros describes depth only: type III is the traditional deep-fossa warning, but no type is intrinsically safe and no type alone determines surgery.

## Categorias

| Código | Rótulo | Critérios | Conduta | Risco | Localizador | Verificado |
| --- | --- | --- | --- | --- | --- | --- |
| I | Type I, olfactory fossa depth up to 3 mm | Keros type I: side-specific olfactory-fossa depth up to 3 mm, measured on coronal bone-window CT as the vertical difference between the cribriform plate and ethmoid roof represented by the lateral-lamella height. Return the continuous value, side and measurement location. | For preoperative planning, report the side-specific type and depth together with asymmetry, low skull-base side, lateral-lamella length and angle, dehiscence and the remaining CLOSE landmarks. Type I does not waive careful review or select a surgical technique. | Traditionally the shallowest group, but not a safe-skull-base label. Type-I patients can have a long or acutely angled lateral lamella, a low or reverse-sloping roof, asymmetry or dehiscence; Keros alone supplies no individual injury probability. | Souza et al., PMC6319094, Keros type I depth definition and measurement method; O'Brien et al. 2016, DOI 10.1148/radiol.2016152230, Figures 8-9 and CLOSE checklist; Hamour et al. 2020, DOI 10.1055/s-0040-1716690, type-I safety limitation. | ✓ |
| II | Type II, depth over 3 through 7 mm | Keros type II: side-specific olfactory-fossa depth greater than 3 mm and up to 7 mm, measured as the vertical cribriform-plate-to-ethmoid-roof difference on a true or high-quality coronal CT reformation. Preserve millimeters rather than only the ordinal type. | Communicate the measured right and left anatomy and all coexisting skull-base hazards to the operating team. The intermediate depth is one planning input and does not by itself require navigation, alter the operative corridor or mandate or prohibit surgery. | Intermediate depth exposes a longer lateral-lamella component than type I in the classic model, but complication risk also depends on side asymmetry, roof height and slope, lamellar angle and length, artery course, dehiscence and procedure. No calibrated risk percentage follows from type II. | Souza et al., PMC6319094, type II 4-7 mm description and bilateral measurements; O'Brien et al. 2016, DOI 10.1148/radiol.2016152230, coronal measurement and operative-hazard checklist; Hamour et al. 2020, PMC8824605, multidimensional limits. | ✓ |
| III | Type III, depth over 7 mm (classically 8-16 mm) | Keros type III: side-specific olfactory-fossa depth greater than 7 mm, classically reported as 8-16 mm, with a deep fossa and long vertical lateral-lamella component. Report the exact depth and side and inspect for anterior-posterior variation. | Explicitly highlight the deep side and associated skull-base anatomy for preoperative planning, while separately reporting dehiscence, asymmetry and CLOSE landmarks. The type increases anatomic caution but does not alone cancel surgery, choose instrumentation or prescribe an approach. | The classic deep-fossa warning is associated with greater vulnerability to lateral-lamella penetration and cerebrospinal-fluid leak during endoscopic surgery. It is an anatomic association rather than a personal complication probability, and other hazards can dominate in any Keros type. | Souza et al., PMC6319094, type III 8-16 mm and dangerous-ethmoid discussion; O'Brien et al. 2016, DOI 10.1148/radiol.2016152230, Keros and asymmetry figures; Hamour et al. 2020, DOI 10.1055/s-0040-1716690, warning against single-metric risk assessment. | ✓ |

### Citações por categoria
- **I**: Keros P; reproduction by Souza SA, Souza MMA, et al.. Olfactory fossa depth classification (Keros), reproduced in a CT analysis of 1200 patients (1962) — https://pmc.ncbi.nlm.nih.gov/articles/PMC6319094/ · Souza et al., PMC6319094, Keros type I depth definition and measurement method; O'Brien et al. 2016, DOI 10.1148/radiol.2016152230, Figures 8-9 and CLOSE checklist; Hamour et al. 2020, DOI 10.1055/s-0040-1716690, type-I safety limitation.
- **II**: Keros P; reproduction by Souza SA, Souza MMA, et al.. Olfactory fossa depth classification (Keros), reproduced in a CT analysis of 1200 patients (1962) — https://pmc.ncbi.nlm.nih.gov/articles/PMC6319094/ · Souza et al., PMC6319094, type II 4-7 mm description and bilateral measurements; O'Brien et al. 2016, DOI 10.1148/radiol.2016152230, coronal measurement and operative-hazard checklist; Hamour et al. 2020, PMC8824605, multidimensional limits.
- **III**: Keros P; reproduction by Souza SA, Souza MMA, et al.. Olfactory fossa depth classification (Keros), reproduced in a CT analysis of 1200 patients (1962) — https://pmc.ncbi.nlm.nih.gov/articles/PMC6319094/ · Souza et al., PMC6319094, type III 8-16 mm and dangerous-ethmoid discussion; O'Brien et al. 2016, DOI 10.1148/radiol.2016152230, Keros and asymmetry figures; Hamour et al. 2020, DOI 10.1055/s-0040-1716690, warning against single-metric risk assessment.

## Referências cruzadas
- _fronteira compartilhada_ → [Lund-Mackay — Lund-Mackay CT staging of chronic rhinosinusitis](https://radcommons.laudos.ai/systems/lund-mackay.md) — Both can be reported on sinus CT, but Lund-Mackay scores inflammatory opacification while Keros measures side-specific olfactory-fossa depth. Neither value can be derived from the other.

## Histórico de versões

| Data | Evento | Detalhe | Situação |
| --- | --- | --- | --- |
| 2020-09-10 | revised | A multidimensional skull-base analysis showed that Keros type alone can mislabel hazardous type-I anatomy as safe; length, angle, slope, artery course and anterior-posterior variation remain separate observations. | confirmed |
| 2016-10-01 | revised | The RSNA CLOSE review embedded cribriform depth within a broader preoperative sinus-CT checklist and emphasized side asymmetry and adjacent surgical landmarks; it did not alter the three thresholds. | confirmed |
| 1962-01-01 | published | Keros described three olfactory-fossa depth groups based on the vertical height of the lateral lamella; the original ranges are retained as an anatomic classification. | confirmed |


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> Conteúdo de referência reescrito. Confira a publicação primária vigente. Não é dispositivo médico nem substitui o julgamento clínico. O radiologista responsável pelo laudo permanece o autor e o responsável.

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