Schizas morphological grading of lumbar central canal stenosis

{
  "categories": [
    {
      "outcome_code": "A1",
      "broad_grade": "A_no_or_minor_stenosis",
      "CSF": "clearly_visible",
      "rootlets": "dorsal_and_occupy_less_than_half_of_dural_sac_area"
    },
    {
      "outcome_code": "A2",
      "broad_grade": "A_no_or_minor_stenosis",
      "CSF": "clearly_visible",
      "rootlets": "dorsal_in_contact_with_dura_in_horseshoe_configuration"
    },
    {
      "outcome_code": "A3",
      "broad_grade": "A_no_or_minor_stenosis",
      "CSF": "clearly_visible",
      "rootlets": "dorsal_and_occupy_more_than_half_of_dural_sac_area"
    },
    {
      "outcome_code": "A4",
      "broad_grade": "A_no_or_minor_stenosis",
      "CSF": "clearly_visible",
      "rootlets": "central_and_occupy_majority_of_dural_sac_area"
    },
    {
      "outcome_code": "B",
      "broad_grade": "moderate_stenosis",
      "CSF": "some_visible_grainy_appearance",
      "rootlets": "occupy_entire_dural_sac_but_remain_individually_recognizable"
    },
    {
      "outcome_code": "C",
      "broad_grade": "severe_stenosis",
      "CSF": "not_visible",
      "rootlets": "not_individually_recognizable",
      "posterior_epidural_fat": "present"
    },
    {
      "outcome_code": "D",
      "broad_grade": "extreme_stenosis",
      "CSF": "not_visible",
      "rootlets": "not_individually_recognizable",
      "posterior_epidural_fat": "not_visible"
    }
  ],
  "applicability": {
    "use_for": "Qualitative morphology grading of degenerative lumbar central canal stenosis on axial T2-weighted MRI.",
    "classification_unit": "one_named_lumbar_level_at_the_most_stenotic_representative_axial_slice",
    "required_inputs": [
      "lumbar_level",
      "diagnostic_axial_T2_images",
      "CSF_visibility_and_distribution",
      "rootlet_position_occupancy_and_individualization",
      "posterior_epidural_fat_visibility",
      "stenosis_cause_and_other_compartments",
      "symptoms_and_neurologic_status_for_clinical_interpretation"
    ],
    "outside_scope": [
      "foraminal_stenosis_grade",
      "lateral_recess_grade",
      "cervical_or_thoracic_canal_grade",
      "tumor_infection_fracture_or_epidural_lipomatosis_without_explicit_adaptation",
      "postoperative_canal_without_supported_interpretation",
      "clinical_diagnosis_or_treatment_selection_from_MRI_alone"
    ]
  },
  "acquisition_and_quality_gate": {
    "reference_method": "Supine axial T2-weighted MRI; the original study used 3.0-T imaging, 3.0-mm sections and a 0.3-mm gap, but those acquisition values describe the study rather than a universal eligibility threshold.",
    "plane_rule": "Review an axial plane as close as possible to perpendicular to the lumbar canal and through the narrowest part of each evaluated level; obliquity and partial-volume averaging can change rootlet and posterior-fat appearance.",
    "image_requirements": [
      "adequate_T2_CSF_contrast",
      "motion_not_obscuring_rootlets",
      "complete_level_coverage",
      "level_localized_from_sagittal_images",
      "review_of_adjacent_slices_to_avoid_single_slice_artifact"
    ],
    "failure_rule": "If CSF, individual rootlets or posterior epidural fat cannot be assessed because of technique or artifact, return ungradable at that level and describe the observed narrowing rather than assigning a fabricated grade."
  },
  "assignment_algorithm": [
    {
      "priority": 1,
      "if": "CSF_clearly_visible_AND_rootlets_dorsal_AND_occupy_less_than_half_of_dural_sac",
      "output_code": "A1"
    },
    {
      "priority": 2,
      "if": "CSF_clearly_visible_AND_rootlets_dorsal_touch_dura_in_horseshoe_configuration",
      "output_code": "A2"
    },
    {
      "priority": 3,
      "if": "CSF_clearly_visible_AND_rootlets_dorsal_AND_occupy_more_than_half_of_dural_sac",
      "output_code": "A3"
    },
    {
      "priority": 4,
      "if": "CSF_clearly_visible_AND_rootlets_central_AND_occupy_majority_of_dural_sac",
      "output_code": "A4"
    },
    {
      "priority": 5,
      "if": "some_CSF_remains_with_grainy_sac_appearance_AND_rootlets_fill_sac_but_are_still_individually_recognizable",
      "output_code": "B"
    },
    {
      "priority": 6,
      "if": "no_visible_CSF_AND_no_individual_rootlets_AND_posterior_epidural_fat_remains_visible",
      "output_code": "C"
    },
    {
      "priority": 7,
      "if": "no_visible_CSF_AND_no_individual_rootlets_AND_no_visible_posterior_epidural_fat",
      "output_code": "D"
    }
  ],
  "boundary_and_conflict_rules": {
    "A_family_rule": "All A1-A4 states retain clearly visible CSF and belong to the original no-or-minor-stenosis family. Their rootlet configurations should not be converted into distinct treatment levels or patient-risk percentages.",
    "A1_A3_boundary": "Use rootlet occupancy below versus above one half only after confirming a dorsal configuration; retain the measured estimate and adjacent-grade uncertainty near one half.",
    "A2_rule": "A2 is defined by dorsal rootlets touching the dura in a horseshoe arrangement, not merely by an intermediate rootlet percentage.",
    "A4_rule": "A4 requires a predominantly central rootlet arrangement with visible CSF; central aggregation with no visible CSF belongs in the B-C assessment rather than automatic A4.",
    "B_C_boundary": "Individual rootlets and some grainy CSF support B. Loss of both visible CSF and recognizable individual rootlets supports C or D.",
    "C_D_boundary": "Posterior epidural fat is the C-versus-D discriminator after no CSF and no individual rootlets are established. Do not infer D from a small dural-sac area alone.",
    "mixed_slice_rule": "Grade the most stenotic reproducible slice at the named level and retain the slice location. If adjacent slices differ because of obliquity, report the range and technical limitation."
  },
  "per_level_and_patient_synthesis": {
    "per_level_rule": "Assign and report a separate grade at every clinically relevant lumbar level. Do not average multilevel grades.",
    "patient_summary": "A patient-level summary may name the most severe level only when every evaluated level and the selection rule remain available.",
    "causal_morphology": "Report disc bulge or herniation, facet hypertrophy, ligamentum flavum thickening, spondylolisthesis, congenital narrowing and other contributors separately.",
    "other_compartments": "Report lateral recess, foraminal and extraforaminal narrowing separately using an appropriate descriptive or validated framework; Schizas central grade does not cover them."
  },
  "quantitative_and_variant_boundaries": {
    "DSCA": "Dural-sac cross-sectional area and Schizas morphology are related but not interchangeable. The original study found broad area overlap and both over- and underclassification when surface thresholds were substituted for morphology.",
    "Lee_system": "The Lee central-canal system uses ventral CSF obliteration and cauda-equina aggregation in a four-grade framework. Do not translate Lee grades into Schizas codes without separately applying the Schizas features.",
    "sedimentation_sign": "The nerve-root sedimentation sign is a separate binary or modified sign and cannot replace the seven-grade morphology.",
    "dynamic_stenosis": "Supine conventional MRI can underrepresent posture-dependent narrowing. Dynamic symptoms or instability require clinical and, when indicated, additional positional or radiographic assessment."
  },
  "clinical_and_management_context": {
    "diagnostic_rule": "Lumbar spinal stenosis is a clinical-imaging syndrome. Symptoms and examination take priority; imaging narrowing alone can occur in asymptomatic people.",
    "management_rule": "No Schizas grade independently orders conservative care, injection, decompression or fusion. Decisions require symptom pattern, neurologic examination, responsible-level concordance, instability, comorbidity and patient goals.",
    "emergency_rule": "New bladder or bowel dysfunction, saddle anesthesia, rapidly progressive weakness or another cauda-equina concern requires urgent clinical escalation independent of the stored grade.",
    "surgical_planning_rule": "The grade can describe central morphology and help localize narrowing, but it does not identify the symptomatic level or determine whether fusion is needed."
  },
  "evidence_and_risk_interpretation": {
    "original_cohort": "In the original 95-subject study, C-D morphology was associated with failure of conservative treatment in a selected symptomatic cohort, but baseline disability and surgical outcome did not correlate with grade.",
    "reliability": "Original average intraobserver agreement was substantial and interobserver agreement moderate, with higher agreement in the originating unit and a learning effect. Later trained-reader studies reported higher agreement.",
    "current_limit": "A 2023 comparative cohort found only weak or absent correlations between morphology, symptoms and postoperative outcomes. Do not convert the grade into an individualized prognosis or surgical-benefit estimate.",
    "no_probability_rule": "The scale supplies no validated per-grade probability of pain, disability, neurologic decline, conservative-treatment failure or surgical success."
  },
  "output_contract": [
    "Schizas_2010_grade_for_each_named_lumbar_level",
    "MRI_plane_sequence_quality_and_slice_location",
    "CSF_visibility_rootlet_configuration_and_posterior_epidural_fat",
    "most_severe_level_without_discarding_other_levels",
    "central_stenosis_causes_and_separate_lateral_recess_and_foraminal_findings",
    "clinical_concordance_and_neurologic_red_flags_when_provided",
    "adjacent_grade_or_ungradable_state_when_features_are_uncertain",
    "no_imaging_only_diagnosis_treatment_or_prognostic_probability"
  ],
  "missing_input_behavior": [
    "If axial T2 quality or plane is inadequate, return ungradable for that level instead of inferring the grade from sagittal narrowing alone.",
    "If CSF is visible but rootlet configuration cannot be distinguished, return broad Grade A morphology with the unresolved A1-A4 subtype rather than guessing.",
    "If no CSF is visible but posterior epidural fat cannot be evaluated, return C-versus-D uncertainty.",
    "If symptoms or examination are absent, report an imaging morphology only and withhold symptomatic-lumbar-stenosis and treatment conclusions.",
    "If the narrowing is foraminal or lateral recess without central sac compression, do not assign a Schizas grade to that compartment."
  ],
  "interpretation_limits": [
    "The original study was small and treatment groups were selected clinically before the grading system was established, creating spectrum and selection limitations.",
    "Supine MRI is static and morphologic; it does not directly measure walking tolerance, dynamic narrowing, nerve physiology or pain generation.",
    "The scale is most defensible for degenerative lumbar central stenosis on adequate axial T2 images and should not be generalized silently to other diseases, regions or modalities."
  ],
  "supporting_sources": [
    {
      "role": "primary_classification",
      "citation": "Schizas et al. Spine. 2010;35:1919-1924",
      "doi": "10.1097/BRS.0b013e3181d359bd",
      "pmid": "20671589"
    },
    {
      "role": "trained_reader_validation",
      "citation": "Ko et al. PLoS One. 2020;15:e0233633",
      "doi": "10.1371/journal.pone.0233633",
      "pmcid": "PMC7252624"
    },
    {
      "role": "clinical_and_outcome_limit",
      "citation": "Yang et al. BMC Musculoskelet Disord. 2023;24:225",
      "doi": "10.1186/s12891-023-06353-6",
      "pmcid": "PMC10039594"
    },
    {
      "role": "current_clinical_context",
      "citation": "Kawakami et al. J Orthop Sci. 2023;28:46-91",
      "doi": "10.1016/j.jos.2022.03.013",
      "pmid": "35597732"
    }
  ],
  "source_locator": "Schizas et al. 2010, DOI 10.1097/BRS.0b013e3181d359bd, Methods pp. 1919-1921 and Figure 1 for acquisition, seven definitions and per-level morphology; Results and Discussion pp. 1921-1923 for agreement, DSCA overlap and limited clinical correlations; Ko et al. 2020, PMC7252624, MRI grading systems and reliability tables; Yang et al. 2023, PMC10039594, abstract and results for weak symptom and outcome correlations; JOA lumbar stenosis guideline 2021 secondary publication for imaging-only diagnostic limits."
}