Keros classification of olfactory fossa depth

{
  "categories": [
    {
      "outcome_code": "I",
      "olfactory_fossa_depth_mm": "less_than_or_equal_to_3",
      "lateral_lamella": "short_depth_component",
      "traditional_label": "shallow"
    },
    {
      "outcome_code": "II",
      "olfactory_fossa_depth_mm": "greater_than_3_and_less_than_or_equal_to_7",
      "lateral_lamella": "intermediate_depth_component",
      "traditional_label": "intermediate"
    },
    {
      "outcome_code": "III",
      "olfactory_fossa_depth_mm": "greater_than_7",
      "original_reported_range_mm": "8_to_16",
      "lateral_lamella": "long_depth_component",
      "traditional_label": "deep"
    }
  ],
  "applicability": {
    "use_for": "Anatomic description of each olfactory fossa on high-resolution coronal reformatted CT, especially during preoperative evaluation for endoscopic sinus or skull-base surgery.",
    "classification_unit": "one_side_at_one_anterior_posterior_location_with_right_and_left_reported_separately",
    "required_inputs": [
      "thin_section_bone_algorithm_CT",
      "true_coronal_or_high_quality_coronal_reformation",
      "side",
      "vertical_cribriform_plate_level",
      "ethmoid_roof_level",
      "continuous_depth_mm",
      "measurement_location",
      "skull_base_symmetry",
      "lateral_lamella_length_and_angle_when_relevant",
      "anterior_ethmoid_artery_course",
      "adjacent_dehiscence_or_postoperative_distortion"
    ],
    "outside_scope": [
      "sinus_inflammatory_burden",
      "diagnosis_of_chronic_rhinosinusitis",
      "complete_FESS_risk_prediction",
      "automatic_operability_or_navigation_decision",
      "grading_olfactory_function",
      "applying_population_prevalence_to_an_individual"
    ]
  },
  "measurement_protocol": {
    "definition": "Measure the vertical difference between the cribriform plate and the ethmoid roof, represented by the height of the lateral lamella, on a coronal bone-window image.",
    "side_rule": "Measure and classify right and left independently. Do not average bilateral depths or report only the deeper or shallower side.",
    "location_rule": "Depth and lateral-lamella angle can vary from anterior to posterior; retain the measured location and do not assume one mid-coronal value describes the entire skull base.",
    "boundaries": [
      {
        "if": "depth_mm_less_than_or_equal_to_3",
        "output_code": "I"
      },
      {
        "if": "depth_mm_greater_than_3_and_less_than_or_equal_to_7",
        "output_code": "II"
      },
      {
        "if": "depth_mm_greater_than_7",
        "output_code": "III"
      }
    ],
    "precision_rule": "Return the measured millimeters with the type so borderline values and rounding remain auditable.",
    "technical_failure_rule": "If the cribriform plate or ethmoid roof is obscured, dehiscent, distorted by prior surgery, fracture or mass, or the reconstruction is oblique or too thick, report the limitation and avoid a false precise type."
  },
  "laterality_and_skull_base_context": {
    "asymmetry": "State right-left depth and level asymmetry explicitly; different Keros types can coexist in the same patient and asymmetry itself matters for operative orientation.",
    "low_side_guard": "The side with the more inferiorly positioned skull base can be hazardous even when its numeric Keros type is lower.",
    "additional_features": [
      "lateral_lamella_length",
      "lateral_lamella_horizontal_angle",
      "fovea_ethmoidalis_height_and_slope",
      "cribriform_or_lateral_lamella_dehiscence",
      "anterior_ethmoid_artery_course_and_bony_coverage",
      "lamina_papyracea_integrity",
      "Onodi_cells_and_optic_canal_relationship",
      "sphenoid_pneumatization_and_carotid_or_optic_canal_dehiscence"
    ],
    "CLOSE_mnemonic": {
      "C": "cribriform_plate_and_anterior_skull_base",
      "L": "lamina_papyracea",
      "O": "Onodi_cell",
      "S": "sphenoid_sinus_pneumatization",
      "E": "anterior_ethmoidal_artery"
    }
  },
  "risk_interpretation": {
    "traditional_type_III_signal": "A deep type III fossa has a longer exposed lateral lamella and is traditionally associated with greater vulnerability to penetration and cerebrospinal-fluid leak during endoscopic surgery.",
    "no_safe_type": "Type I is not synonymous with a safe skull base. Long or acutely angled lateral lamellae, a low or reverse-sloping roof, asymmetry, dehiscence and artery exposure can create substantial hazard in any type.",
    "no_probability": "Keros type does not provide a calibrated probability of surgical injury, cerebrospinal-fluid leak, anosmia, meningitis or another complication for an individual.",
    "anatomy_not_outcome": "Observed population frequencies by sex, side or ancestry are descriptive cohorts and must not be used to infer an individual type or outcome without measurement."
  },
  "management_boundary": {
    "appropriate_use": "Communicate the side-specific measurement, type and coexisting skull-base variants to the operating team for preoperative planning and intraoperative orientation.",
    "no_type_specific_order": "No type alone mandates or prohibits surgery, selects the surgical corridor, requires navigation, changes consent or prescribes a technique; those decisions belong to the surgeon and full clinical-anatomic plan.",
    "urgency_guard": "A Keros type on an otherwise routine CT is not an emergency finding. Actual dehiscence, fracture, meningoencephalocele, cerebrospinal-fluid leak or invasive disease is reported separately and can change urgency."
  },
  "agent_output_contract": [
    "Return CT technique, bone reconstruction adequacy and whether anatomy is native, postoperative or distorted.",
    "Return right and left continuous depths, exact measurement locations and separate Keros types.",
    "Return asymmetry, the lower skull-base side, lateral-lamella length or angle when assessable and relevant anterior-posterior variation.",
    "Return the other CLOSE landmarks and any dehiscence, fracture, encephalocele or anterior ethmoid artery exposure separately.",
    "Describe traditional relative hazard without calling type I safe or attaching an individual complication percentage.",
    "Never convert Keros type into Lund-Mackay inflammatory burden or a surgical order."
  ],
  "missing_input_behavior": [
    "If only one side is measurable, report that side and leave the other unclassified rather than assuming symmetry.",
    "If a rounded value lies near 3 or 7 mm, preserve the underlying measurement precision and flag the boundary.",
    "If the image plane is oblique or the roof is incompletely covered, request diagnostic coronal reformations before classification.",
    "If prior surgery, fracture or tumor has altered landmarks, describe the anatomy directly and do not force the native Keros framework.",
    "If only the Keros type is supplied, do not infer the exact depth, side, artery course, dehiscence or total operative risk."
  ],
  "supporting_sources": [
    {
      "role": "original_ranges_reproduced_in_large_CT_series",
      "citation": "Souza et al. Indian J Otolaryngol Head Neck Surg. 2018",
      "pmcid": "PMC6319094"
    },
    {
      "role": "preoperative_CT_reporting_checklist",
      "citation": "O'Brien et al. Radiology. 2016;281:10-21",
      "doi": "10.1148/radiol.2016152230"
    },
    {
      "role": "single_metric_safety_limitation",
      "citation": "Hamour et al. J Neurol Surg B Skull Base. 2020;83:53-58",
      "doi": "10.1055/s-0040-1716690",
      "pmcid": "PMC8824605"
    }
  ]
}