Glossary
The clinical scales, surgical concepts and modeling methods behind the tools, each defined in plain language and linked to the tools that use it.
Vascular
- Aneurysm recanalization after coilingRecanalization is the reappearance of blood flow into a coiled aneurysm over time, from coil compaction, aneurysm growth or thrombus resolution. Major recanalization often prompts retreatment.
- Cerebral revascularization (EC-IC bypass)Cerebral bypass routes blood from an extracranial donor artery (or a graft) to an intracranial artery, so that a complex aneurysm and its parent vessel can be clipped, trapped or occluded safely.
- Coil packing densityCoil packing density is the volume of the coils placed in an aneurysm divided by the aneurysm's volume, expressed as a percentage. Denser packing is associated with lower recanalization.
- Giant intracranial aneurysmA giant intracranial aneurysm has a maximum diameter of 25 mm or more. They can present with hemorrhage or mass effect and often need bypass or parent artery occlusion.
- Modified Rankin Scale (mRS)The modified Rankin Scale grades disability after stroke or neurosurgery from 0 (no symptoms) to 6 (death). Scores of 0 to 2 or 0 to 3 are commonly used as a good outcome.
- Raymond-Roy classificationThe Raymond-Roy classification grades how completely a coiled intracranial aneurysm is occluded on angiography: class 1 complete, class 2 residual neck, class 3 residual aneurysm.
- Stent-assisted coilingStent-assisted coiling places a stent across an aneurysm's neck to hold coils inside the sac, allowing endovascular treatment of wide-neck aneurysms. It requires antiplatelet therapy.
- Wide-neck aneurysmAn intracranial aneurysm is usually called wide-necked when its neck is 4 mm or wider, or its dome-to-neck ratio is under 2. Wide necks make simple coiling harder.
- Woven EndoBridge (WEB) deviceThe Woven EndoBridge (WEB) is an intrasaccular flow disruptor: a braided nitinol device placed inside a wide-neck bifurcation aneurysm to disrupt flow at the neck and promote thrombosis.
Skull base
- CraniopharyngiomaCraniopharyngioma is a benign but locally aggressive sellar and suprasellar tumor arising from Rathke pouch remnants. Surgery risks pituitary and hypothalamic injury; recurrence is common.
- Diabetes insipidus after sellar surgeryCentral diabetes insipidus after sellar surgery is a deficiency of vasopressin that causes large volumes of dilute urine. It can be transient, triphasic or permanent.
- Endoscopic endonasal approachThe endoscopic endonasal approach reaches the skull base through the nose and sphenoid sinus using an endoscope, avoiding brain retraction but carrying a risk of CSF leak.
- Extent of resectionExtent of resection describes how much tumor was removed: gross-total (no visible residual), near-total (a small remnant) or subtotal (a larger remnant). It trades tumor control against surgical risk.
- Tuberculum sellae meningiomaA tuberculum sellae meningioma arises just in front of the pituitary fossa and typically compresses the optic nerves and chiasm, presenting with progressive visual loss.
Spine
- Adjacent segment disease (ASD)Adjacent segment disease is symptomatic degeneration at the spinal level next to a fusion. It is distinguished from adjacent segment degeneration, which is seen on imaging without symptoms.
- PI-LL mismatchPI-LL mismatch is pelvic incidence minus lumbar lordosis. A mismatch over about 10 degrees indicates sagittal malalignment and is linked to worse outcomes after lumbar fusion.
Pediatric
- Frailty index (deficit accumulation)A frailty index counts health deficits a person has out of those assessed, giving a score from 0 to 1. Higher scores predict worse outcomes; values near 0.7 approach a practical ceiling.
- Open spina bifida (myelomeningocele)Open spina bifida, most often myelomeningocele, is a neural tube defect in which the spinal cord is exposed at birth. Most affected children need lifelong care, often including a CSF shunt.
Intraoperative
- Brain shiftBrain shift is the movement and deformation of the brain during surgery, from CSF loss, gravity, swelling and tumor removal. It makes preoperative neuronavigation progressively less accurate.
- Intraoperative ultrasound (iUS)Intraoperative ultrasound images the brain in real time during surgery. It is fast and inexpensive, and paired before-and-after sweeps can measure and correct brain shift.
Maternal
- Levels of maternal careACOG and SMFM define four levels of maternal care, from basic (Level I) to regional perinatal health care centers (Level IV), so that each pregnant patient delivers where her risks can be managed.
- Maternity care desertA maternity care desert is a county with no hospital providing obstetric care, no birth center and no obstetric clinicians, a definition popularized by the March of Dimes.
Medicolegal
Methods
- Calibration of a prediction modelA calibrated model's predicted risks match observed rates: of patients given a 20% risk, about 20% have the event. Calibration matters as much as discrimination for clinical use.
- Concordance index (C-index)The C-index measures how well a model ranks patients by risk: the chance that, of two patients, the one predicted at higher risk has the event first. 0.5 is chance, 1.0 is perfect.
- Double machine learning (DoubleML)Double machine learning estimates a causal effect from observational data by using machine learning to remove the influence of confounders, with cross-fitting to avoid overfitting bias.
- Graph neural network (GraphSAGE)A graph neural network learns from data arranged as a network. GraphSAGE builds each node's representation from its own features and a sample of its neighbors' features.
- Membership inference attackA membership inference attack tries to tell whether a specific person's record was used to train a model. It is a standard privacy test for synthetic data.
- Nash bargaining solutionThe Nash bargaining solution picks the option that maximizes the product of each party's gain. In surgery it can balance competing goals such as tumor control and safety.
- SHAP (Shapley additive explanations)SHAP explains an individual prediction by splitting it into contributions from each input feature, based on Shapley values from game theory.
- Survival analysis (time-to-event modeling)Survival analysis models how long until an event happens, while correctly handling patients whose follow-up ends before the event (censoring).
- Synthetic EHR dataSynthetic EHR data are artificial patient records generated by a model trained on real records. They aim to keep the statistical patterns of the original data while protecting privacy.
- TSTR (train on synthetic, test on real)TSTR measures the usefulness of synthetic data: train a model on synthetic records, test it on real ones, and compare with a model trained on real data (TRTR).