Evidence

Checked November 3, 2026; accuracy-audit fixes added November 4, 2026. Mirrors the “Evidence” tab of the planning doc.

Opened means the source page itself was opened and read during the November 4 accuracy checks (CLAUDE.md rule 1a, check 1), not just a search summary. Quotes for opened sources are in the audit reports in docs/audits/.

Every medical sentence on the site and every shape in the 3D model is listed here with the source it rests on. Nothing medical ships without a row in this file. The exact site wording lives in docs/COPY.md.

Verdict	Meaning
Verified	An authoritative source states it directly
Partly supported	True with a qualifier; the site wording carries that qualifier
Simplified	Accurate in substance but drawn or worded simply for patients; the simplification is named on the site
Removed	Not supported; taken off the site

Preferred sources, in order: NIH/NINDS and NLM, peer-reviewed research, major medical centers, then patient organizations for their own details.

Medical claims

#	Topic	Site wording (summary)	Verdict	Sources
1	What Chiari is	The lowest part of the cerebellum (the tonsils) extends below the foramen magnum. The cerebellum helps control balance and coordination. Often linked to a smaller or differently shaped lower back of the skull, which crowds the brain; less often it develops later in life	Verified	NINDS fact sheet PDF, StatPearls, Radiopaedia, Cleveland Clinic
2	Who has it	Most people are born with the skull differences that lead to it; some never have symptoms, others first notice them as teens or adults (Make your own, Nov 5: “Most people with Chiari malformation are born with…”, same meaning, subject made explicit)	Verified	Cleveland Clinic (opened Nov 5: “Nearly all CM cases are present at birth (congenital)”; “Differences in skull structure often cause Chiari malformations”), NINDS (opened Nov 5: “part of the skull is smaller than normal or misshapen”), Mayo Clinic (not opened Nov 5: access denied)
3	How it’s found	Usually an MRI plus a doctor’s exam; sometimes by chance. “A doctor looks at the scan together with your symptoms” (changed Nov 4 from naming a neurologist or neurosurgeon, which no opened source says)	Verified	NINDS, Mayo Clinic, Cleveland Clinic (opened: “your healthcare provider will ask about your symptoms”), PMC12888059 (opened: “clinical decision-making must integrate both imaging and patient-reported symptoms”)
4	Classic headache	Back of the head, after coughing, sneezing or straining. On a Make your own graphic it is followed by row 20’s “Not everyone with Chiari gets these headaches.”	Verified	NINDS PDF (opened Nov 5: “Headache is the hallmark sign of Chiari malformation, especially after sudden coughing, sneezing, or straining”); “back of the head” from Cleveland Clinic (opened Nov 5: “pain in the back of your head or neck that get worse after coughing or sneezing”) and PMC12888059 (saved copy); Mayo Clinic and StatPearls not opened Nov 5 (blocked)
5	Other symptoms	Neck pain; dizziness and balance trouble; numbness or tingling in hands and feet; weakness or trouble with fine hand movements; trouble swallowing or speaking (changed Nov 4 from “voice changes”: NINDS says “Trouble swallowing, breathing, or speaking”); breathing or sleep problems such as sleep apnea; ringing in the ears; blurry or double vision; a curve in the spine (scoliosis), especially in children. (Changed Nov 4: vision moved into the main list as “blurry or double”, since Cleveland Clinic lists “Double or blurred vision” with no “less often” group; scoliosis added: NINDS “A bend in the spine (scoliosis)”, MedlinePlus “Scoliosis (in children)”)	Verified	NINDS (opened), Cleveland Clinic (opened), NINDS: syringomyelia (opened: “Curvature of the spine (scoliosis); may be the only symptom in children”), PMC12888059 (opened: “In pediatric and adolescent patients, scoliosis may be a presenting feature”), MedlinePlus: syringomyelia (opened; this is the syringomyelia page, not a Chiari page), Mayo Clinic (care-network copy), Cleveland Clinic, StatPearls
6	No symptoms	Many people with Type I have no symptoms at all	Verified	NINDS PDF (opened Nov 5: “Many people with Chiari malformations have no symptoms”), Cleveland Clinic (opened Nov 5, Type 1: “Many people don’t have symptoms.”); Mayo Clinic and StatPearls not opened Nov 5 (blocked)
7	The 5 mm measurement	About 5 mm is the traditional cutoff. How far the tonsils extend doesn’t always match how someone feels; some with clear descent have no symptoms and some under 5 mm do. Doctors also look at tonsil shape, fluid flow and whether a syrinx is present. (Changed Nov 4: “lower tonsils make symptoms somewhat more likely” removed; studies disagree, and the opened sources say only that descent “does not always correlate with symptom burden” and “is not sufficient to identify symptomatic patients”)	Verified	Review, PMC12888059 (opened), Polish J Radiol, PMC9834072 (opened), Massimi et al. 2022, Sekula et al. 2005, Radiopaedia, StatPearls
8	Brainstem	Connects the brain to the spinal cord; runs automatic functions such as breathing, heart rate and swallowing	Verified	Cleveland Clinic
9	Spinal fluid	Cushions the brain and spinal cord; with each heartbeat it pulses back and forth between the skull and the spinal canal	Verified (simplified)	Cleveland Clinic, Takizawa et al. 2017 (PMC5615451, opened: “a fast movement synchronized with the heartbeat”; breathing also moves it, so the card is simplified)
10	Fluid flow in Chiari	In many people, not all, flow is reduced or blocked at the foramen magnum; a cine MRI can show it	Verified	NINDS, surgical series, PMID 16823310 (81% abnormal flow), Radsource
11	Treatment	No symptoms: usually monitored. Symptoms: surgery often recommended; it improves or stabilizes symptoms in most people, damage already done may not fully reverse, some need more than one operation; a syrinx can be a reason for surgery even without symptoms	Verified	NINDS, StatPearls, Mayo Clinic, pediatric consensus
12	Awareness Month	September, widely recognized through state and city proclamations (not federal)	Verified	Michigan 2026, Virginia, Bobby Jones CSF
13	How common	Not on the site. If ever used: roughly 1% to 4% of people having brain MRIs, depending on age; not a general-population figure	Not used	Strahle et al. 2011, Meadows et al. 2000
14	Cine MRI	A fluid-flow MRI (used in the visit-prep question)	Verified	Cleveland Clinic
15	How far the tonsils extend in Chiari I	“In one study of 160 people with Chiari I, the average was about 12 mm, but it ranged from 5 to 25 mm, and the number alone doesn’t decide who needs surgery.” (Replaces “in people who need surgery it’s often around 10 to 12 mm”, which had no row and implied the number decides surgery)	Verified	Polish J Radiol, PMC9834072 (opened): 160 patients, tonsillar herniation 12.4 ± 3.7 mm, range 5.0 to 25.4; “the presence of cerebellar tonsillar herniation is not sufficient to identify symptomatic patients or patients who require surgical treatment”
16	Symptoms vary and often show few outward signs	“Symptoms can come and go, and there are often few outward signs.” (Explain It “How you can help”; the 280-character starter note uses the shorter “Symptoms can come and go, often with few outward signs.”; Awareness kit: “Chiari symptoms often have few outward signs.”, changed Nov 5 from “often don’t show” after the check-up audit, closer to the source’s “paucity of physical findings”) Changed Nov 5 from “…and are often invisible” after the independent check: closer to the source, and doesn’t suggest Chiari can’t be seen on MRI	Simplified	Baisden 2012, “Controversies in Chiari I malformations”, Surg Neurol Int 3:S232 (opened Nov 5): “patients’ clinical complaints vary and fluctuate, and are often accompanied by a paucity of physical findings.” Saved copy: docs/audits/sources/2026-11-05-symptoms/
17	Crowded fluid space and symptoms	“This can crowd the space where spinal fluid flows, which can cause headaches and other symptoms.” (Explain It: the starter note and “What you’re looking at”; changed Nov 5 from “That crowds the space where spinal fluid normally flows…”, stated as always true, after the check-up audit). Tour and side by side: the tonsils “often crowd the space where fluid should pass” (was “fill the space”), matching rows 10 and “Cisterna magna”	Simplified	Baisden 2012 (opened Nov 5): “as the cerebellar tonsils encroach on the brain stem at the craniocervical junction, CSF flow is decreased and diverted along alternate pathways. This change in CSF flow dynamics contributes to the various clinical complaints characteristic for CMI”; surgeons operate “when they are truly symptomatic, e.g. contributing to impaired cerebrospinal fluid (CSF) circulation by crowding the foramen magnum.” Row 10 (in many people, not all). Saved copy: docs/audits/sources/2026-11-05-symptoms/
18	What a cough does to spinal fluid	“A cough briefly raises the pressure in your chest, which pushes some spinal fluid up from the spine into the head. Normally it then flows back down.” (3D Explorer, “Why can coughing bring on a headache?”; approved Nov 5 after the independent audit docs/audits/2026-11-05-new-features-audit.md; was “straight back down”)	Simplified (the sources say the chest pressure swells the veins around the cord, which pushes the fluid; the site leaves out the veins; a real-time MRI study saw no clear return peak, so “normally”, not “straight back”)	Bezuidenhout 2018, PMC7655446 (opened Nov 5); Vandenbulcke 2024, PMC11148133 (opened Nov 5); Bhadelia 2016, PMC7960326 (opened Nov 5). Saved copies: docs/audits/sources/2026-11-05-new-features/
19	One explanation for what happens after a cough in Chiari I	“One explanation is that, in some people with Chiari I, the low tonsils get in the way as the fluid flows back, so just after a cough they are pushed further down into the opening.”	Partly supported (stated as one explanation, for some people; the studies included only people with symptoms; the tonsil movement is inferred, not measured, so the animation does not show it; a 2025 preprint, not peer reviewed and not opened, disputes the related finding that flow drops)	Bhadelia 2016 (opened Nov 5): coughing “pushes the already herniated tonsils downward and further narrows the foramen magnum”, “immediately after coughing”; Bezuidenhout 2018 (opened Nov 5); medRxiv 10.1101/2025.05.01.25326708 (not opened: blocks automated readers)
20	Whether this explains the headache	“Researchers don’t all agree on how this works, or whether it’s why coughing can bring on the classic headache. Not everyone with Chiari gets these headaches.”	Verified (the disagreement is stated, as in the sources)	Bhadelia 2011, PMC7965870 (opened Nov 5): “there is a difference of opinion as to the exact mechanism responsible for CAH”; Vandenbulcke 2024 (opened Nov 5): “not well understood”, about one-third of patients; rows 4 and 6
21	The cough animation	One press: the spinal fluid marks move up through the opening into the head, the same in the Typical and Chiari I views, then ease back to the heartbeat pulse. Nothing else moves (no tonsil movement, no pressure wave, no numbers). Caption: “Animation simplified.” with the usual captions. Calm mode: still frames	Simplified (drawn to be easy to see, not measured)	Rows 18 to 20; the audit’s animation findings (docs/audits/2026-11-05-new-features-audit.md, items 1 and 6)
22	Real-world size of the measurement	“The usual cutoff, about 5 mm, is half a centimeter, about the height of 3 stacked quarters. The model shows about 12 mm, a little over 1 centimeter, about the height of 7 stacked quarters. How far the tonsils extend doesn’t always match how someone feels.” (3D Explorer, Chiari I and syrinx views with Measure on)	Verified (unit conversion and the quarter’s thickness: 3 × 1.75 = 5.25 mm, 7 × 1.75 = 12.25 mm; the numbers and the last sentence are rows 7 and 15)	Rows 7 and 15; the model’s own measurement (12.4 mm, npm run model:check); the U.S. Mint’s quarter specifications (Non-medical claims). Stacked quarters chosen by Matthew Nov 5 (option A)
23	Surgery questions (Visit prep: “Before surgery”, “Before going home from the hospital”, “Follow-up after surgery”)	Questions only; none states a fact. Worded so none assumes something true for everyone (“For example…”, “are likely to”, “or my syrinx if I have one”)	Verified (questions only)	Connecticut Children’s, MedlinePlus “Brain surgery - discharge”, Stanford Children’s (all opened Nov 5); sentence-by-sentence table in docs/drafts/2026-11-05-surgery-and-children.md; audit docs/audits/2026-11-05-surgery-and-children-audit.md; saved copies docs/audits/sources/2026-11-05-surgery-and-children/
24	Packing for a hospital stay (Visit prep)	Practical list, led by “Your hospital may send its own list. Follow theirs first.”; medicines: “ask the hospital which to bring” (hospitals differ)	Verified	SickKids “What to Pack for the Hospital” and “How to prepare for surgery based on your child’s age” (opened Nov 5); docs/drafts/2026-11-05-surgery-and-children.md; docs/audits/2026-11-05-surgery-and-children-audit.md
25	Getting a child ready (Helping your child, parent tips)	Eleven tips: honest words; why; “special sleep” (avoid “put to sleep”); don’t promise no pain or needles; “I don’t know”; feelings; delays; comfort item; play and draw; child life specialist (“Ask if the hospital has…”); look after yourself	Verified (adapted, credited on the page: “Adapted from SickKids AboutKidsHealth and Nemours KidsHealth.”)	SickKids “How to talk to your child about surgery”, “How to prepare… by age”; KidsHealth “Helping Kids Get Ready for Surgery” (opened Nov 5); docs/drafts/2026-11-05-surgery-and-children.md; docs/audits/2026-11-05-surgery-and-children-audit.md
26	Picture story for children (Helping your child)	Six pages: cerebellum helps balance; cushioned by a clear liquid; in Chiari the bottom of the cerebellum reaches down through the opening; “You didn’t do anything to cause it.”; special sleep; bone at the back of the head and often a little from the top of the neck; “Many times” a patch; sore afterward, medicine helps; stay “until your doctors say you’re ready to go home” (no length given); rest at home before school	Simplified (child level; no timeline or promise)	Rows 1 and 9; approved After decompression wording; KidsHealth “Chiari Malformation” (doctors don’t know the exact cause; born with it or develops early); Stanford Children’s; SickKids; docs/drafts/2026-11-05-surgery-and-children.md; docs/audits/2026-11-05-surgery-and-children-audit.md (two sentences changed on its advice)
27	School sheet (Helping your child)	“In Chiari I, the lowest part of the back of the brain extends below the opening at the base of the skull. The surgery makes more room there.” Time away, limits and “call me right away if” are blanks for the care team’s own answers	Verified	Row 1; KidsHealth “Chiari Malformation” (“This surgery makes more space for the cerebellum”); docs/drafts/2026-11-05-surgery-and-children.md; docs/audits/2026-11-05-surgery-and-children-audit.md
28	What happens in surgery, step by step (3D Explorer)	Intro: “Surgeons don’t all do the same operation. Some remove bone only, some also open the brain’s covering and add a patch, and some also shrink the tonsils. This shows one common version…”; five steps: before surgery; the incision (asleep under anesthesia; cut down the middle of the back of the head and upper neck; muscles moved aside); bone removed (and often the back of the first neck bone); the patch (often; “like letting out a waistband”; muscles and skin closed); afterward (“On scans after surgery, the fluid space behind the cerebellum is often larger, and the tonsils often rise only partly”). Caption: “Animation simplified. The incision line is approximate; its length varies.”	Simplified (one common version, named as such)	Mayfield Clinic “Chiari decompression surgery” (opened Nov 5); PMC4821417 (opened Nov 5); PMC10549945 (opened Nov 5); Stanford Children’s; the After decompression table; docs/drafts/2026-11-05-surgery-steps-and-communities.md; audit docs/audits/2026-11-05-surgery-steps-and-communities-audit.md; saved copies docs/audits/sources/2026-11-05-surgery-steps/

Explorer structure cards

Card	Site wording	Verdict	Sources (all opened Nov 4)
Cerebrum	The largest part of the brain, responsible for thinking, movement and the senses	Verified (simplified)	Cleveland Clinic: cerebrum: “the largest part of your brain and handles conscious thoughts and actions”; “muscle movements, language, processing what your senses pick up”
Corpus callosum	A thick band of nerve fibers connecting the left and right halves of the brain	Verified	Cleveland Clinic: corpus callosum: “a bundle of nerve fibers that allow your brain’s left and right hemispheres to communicate”
Cerebellum	The back part of the brain that helps control balance and coordination	Verified	Row 1; Cleveland Clinic: cerebellum
Fourth ventricle	A small fluid-filled space between the brainstem and cerebellum, where spinal fluid passes through	Verified	Cleveland Clinic: hydromyelia: “This hollow space is in the lower part of your brain, near your brainstem. It’s filled with cerebrospinal fluid”; PMC10485575: floor formed by the brainstem, roof partly by the cerebellum, fluid leaves through the median aperture “into the cisterna magna”
Brainstem	Row 8	Verified	Row 8
Foramen magnum	The opening at the base of the skull where the brainstem becomes the spinal cord	Verified	Cleveland Clinic: medulla oblongata: “connecting to your spinal cord through the foramen magnum, an opening at the bottom of your skull”
Spinal cord	Carries signals between the brain and the rest of the body	Verified	Cleveland Clinic: spinal cord: “carries nerve signals from your brain to the rest of your body and back”
C2 vertebra	The second bone of the neck. Its upward peg, the dens, sits just in front of the spinal cord	Verified	Cleveland Clinic: cervical spine: “Your second vertebra (C2), also called the axis”; PMC7549867: the odontoid process is “a superior projection of the axial vertebral body”, and the transverse ligament “bounds and constrains the dens posteriorly and prevents it from folding into the brainstem”
Syrinx (part 11)	Uses the approved syrinx definition (Syrinx table)	Verified	NINDS, Merck
Bone removed (part 11)	Uses the approved After decompression wording	Verified	After decompression table

Avoid: the “300,000 Americans” figure in some proclamations; it isn’t from peer-reviewed research.

3D model shapes

McRae line: from the front edge of the foramen magnum (basion) to the back edge (opisthion). Tonsillar descent is the perpendicular distance from that line to the lowest tonsil tip, measured on the midline MRI image or the adjacent one where the tonsils sit lowest (Barkovich 1986, Radiopaedia).

Feature	Typical	Chiari I	Sources
Tonsil tip	About 1 mm above the line (meta-analysis mean +1.13 mm; reference interval about 7 mm above to 5 mm below, from +6.93 to −4.67 mm; Barkovich 1986 found 8 mm above to 5 mm below in 200 people; lower in children, rises with age)	At least about 5 mm below by definition; model uses about 12 mm, the average in a study of 160 people with Chiari I (12.4 ± 3.7 mm, range 5.0 to 25.4; PMC9834072, opened); often reaches the C1 back arch	Meta-analysis, PubMed 41081848 (abstract seen in search only; the “3,940 people” count is not confirmed), Barkovich 1986 (PubMed 3096099, abstract via search), Polish J Radiol, SNI review
Tonsil shape	Rounded	Often pointed or peg-shaped	PMC11371388 (opened: “Cerebellar peg-like rather than rounded tonsils … are more common in patients with TH > 5 mm”), Radsource, Radiopaedia: peg-like tonsil
Fluid space behind the cerebellum (cisterna magna)	Open	Often crowded or narrowed	Milhorat 1999, Radsource
Posterior fossa	Normal	Smaller and crowded; brain size normal. The Simple model shows the same skull in both (see the clivus row)	Milhorat 1999
Clivus	About 39 to 47 mm, depending on the study (controls 38.99 ± 2.67 mm in PMC9834072, opened). Simple model: 43.7 mm. Since 2026-11-04 its skull, skull base, brain and head above the foramen magnum are traced from the Z-Anatomy atlas (real proportions; Matthew’s decision), checked by npm run model:check	Several millimeters shorter (2 to 9 mm across studies; 32.63 ± 3.97 mm in PMC9834072). Not shown in either model (Matthew, 2026-11-04): both keep one skull for all four views so the change you see is the tonsils	Polish J Radiol, Can J Neurol Sci, Acta Neurochir
Tentorium	Normal angle	Steeper. Not shown in the Simple model. Note: Sekula 2005 studied people with little or no tonsillar descent, so this needs a Chiari I source before the realistic model shows it	Sekula et al. 2005
Brainstem, fourth ventricle	Normal	Normal position (fourth ventricle may be elongated). A low brainstem is a different category, “Chiari 1.5,” not shown	Radsource, Radiologica, Radiopaedia: Chiari 1.5
Foramen magnum, front to back	About 33 to 36 mm (Simple model 35.3 mm). Realistic model: 38.4 mm, as in the Z-Anatomy atlas; within normal variation (36.2 ± 3.3 mm in controls, PMC9834072, opened), so left as is	Same	Polish J Radiol, JNRP morphometry
Spinal cord, upper neck	About 9 mm front to back (8.8 mm at C2, 8.7 mm at C4, 7.4 mm at C7). The MRI first look measured about 8 to 9 mm on the MNI152 template	Same	PMC8334714 (opened): “from 8.8 mm x 12.4 mm at C2 to 8.7 mm x 14 mm at C4 to 7.4 mm x 11.4 mm at C7”; docs/audits/2026-11-04-mri-first-look.md
Spinal canal, neck (front to back, bone to bone)	About 13 to 15 mm below C2 (normal range in a study of 295 adults); roomier at C1 and the foramen magnum. Closed at the back by the laminae. Simple model: 14.5 mm (checked by npm run model:check); vertebral bodies about 15 mm tall, discs about 4.5 mm	Same	PMC2899662 (opened): “subjects with a normal canal, diameter of 13–15 mm” (C3 to C7)
Fluid pathway	Continuous: from the fourth ventricle outlet into the cisterna magna, around the tonsils, through the foramen magnum and down behind the cord	Tonsils plug the pathway at the foramen magnum	PMC10485575 (opened), Milhorat 1999 (“obliteration of the retrocerebellar cerebrospinal fluid spaces”, abstract)
Dens of C2	Upright, tip below the basion, in front of the cord	Same in the basic view; tilted dens and basilar invagination are related variants, not shown	Polish J Radiol, Milhorat 1999

Midline simplification (Simplified): the tonsils sit just to either side of the midline and often descend unevenly. The model shows them at their lowest point on the midline view, as MRI measures them. The figure caption, the printed visit-prep sheet and the tonsil info card say so (PMC11371388, opened: “In adult CM1 patients with syringomyelia, most (91%) tonsillar herniations were asymmetrical”; Tubbs, via springermedizin).

Mockup figure vs built model: the mockup figure is illustrative, not to scale. Since 2026-11-04 the Simple figure and model take the head, skull, skull base and brain above the foramen magnum from midline cross-sections of the Z-Anatomy atlas (model/simple/reference/), and apply the numbers above at and below the foramen magnum (McRae line, tonsils, cord, canal, vertebrae). The realistic model (Phase 2) uses Z-Anatomy throughout.

Surgery, step by step (the incision line): in the “What happens in surgery” play-through, stages 1 to 3 draw the skin incision as a dark red line on the back skin outline. It runs from the level of the inion (where the model’s tentorium meets the back of the skull, figure y 382) down to the level of the C2 spinous process (y 522): about 7 cm top to bottom and about 8 cm along the skin. Sources: PMC4821417 (opened): “A midline incision is made from the inion to the spinous process of C2”; Mayfield Clinic: “The skin incision is about 3 inches long”. Labeled approximate on the site (“its length varies”). The other stages reuse the approved Chiari I and After decompression shapes. Code: surgeryStage in src/lib/anatomy-figure.ts and STAGE_PARTS in src/explorer/viewer3d.ts. Audit: docs/audits/2026-11-05-surgery-steps-and-communities-audit.md.

Syrinx

Feature	What the model shows	Sources
How often	Shown only as “often.” Studies range from about 20% to 85% depending on who was studied	StatPearls, AJNR 2016, Strahle 2011
Location	Most often in the neck part of the cord; one study found the top end most often around C6, though it can start as high as C1	AJNR 2016, NINDS: syringomyelia, Radsource
Shape	Long, spindle-shaped or beaded cavity near the center of the cord; about 5 vertebrae long on average	AJNR 2016, Merck Manual
Definition	“A fluid-filled cavity inside the spinal cord. It often develops alongside Chiari.”	NINDS, Merck, Mayo Clinic

After decompression

The McRae line is still drawn after surgery. It marks where the edges of the opening were before the bone was removed, which is how tonsil position is measured on follow-up scans.

Feature	What the model shows	Sources
Skull bone removed	A piece a few centimeters across at the back of the foramen magnum, sized to each patient; the model uses about 30 × 25 mm (exact size not stated on the site). (Changed Nov 4 from “about 3×3 to 3×4 cm”, which the Hu 2023 citation could not be confirmed for)	PMC11912941 (opened): “a 2.5 × 3 cm bone window”; PMC10478704 (opened): “suboccipital craniectomy with 3 cm in diameter around the foramen magnum”; PMC4584091 (opened)
C1	Back arch removed, the middle part, about 25 mm (in some techniques only partly). Site text says “often” (changed Nov 4 from “usually”; NINDS: “and sometimes the top of the spine”; PMC12888059: “A C1 laminectomy is commonly performed”)	PMC11912941 (opened): “Approximately 2.5 cm of the middle part of the posterior arch of the atlas was removed”; PMC10478704 (opened): “C1 posterior arch was removed”; PMC4584091 (opened), Balasa et al. 2022
Dural patch	Often; some surgeons remove bone only	Balasa 2022, Khalsa 2017
Fluid space	Re-formed behind the cerebellum and joined to the fluid behind the cord	PMC10549945 (opened): fluid space behind the cerebellum enlarged after surgery; Balasa 2022, Khalsa 2017
Tonsils	Often rise only partly (about 2 mm on average in one study) and may stay below the line. (Changed Nov 4 from “about 4 mm”, which could not be found in the cited sources)	PMC10549945 (opened): “The cerebellar tonsillar position inferior to the McRae line decreased 2 mm 3–6 months after surgery … and 0.8 mm more in following years”
Syrinx after surgery	Smaller in most people, rarely gone; symptoms can improve even when it doesn’t shrink	StatPearls, NINDS
Outcomes	“Results vary, and surgery isn’t right for everyone.” Reported improvement ranges widely across studies	MedlinePlus: syringomyelia (the syringomyelia page), StatPearls, NINDS, Park-Reeves consortium

Organizations (Support page)

Organization	Site wording	Donate link
Bobby Jones Chiari & Syringomyelia Foundation	Maintains an international patient registry (new enrollment currently paused), hosts a yearly research colloquium, and funds Chiari research grants and fellowships	bobbyjonescsf.org/donate-online
Conquer Chiari	Funds Chiari research, publishes patient education materials, and supported the Chiari1000 patient registry (now closed)	conquerchiari.org/donate
ASAP: American Syringomyelia & Chiari Alliance Project	Supports patients and families, publishes a newsletter, and has helped fund research into the genetics of Chiari	asap.org/donate

The Washington University study “Redefining Chiari Malformations Type I” is NIH-funded and enrolling (study page).

Connect with others (Support page)

Links only; Open Chiari adds no social features. Each description comes from the community’s own page, opened Nov 5 (saved copies docs/audits/sources/2026-11-05-communities/; audit docs/audits/2026-11-05-surgery-steps-and-communities-audit.md).

Community	Site wording	Opened source
Chiari Support (Ben’s Friends)	A support forum for patients, families and friends, part of Ben’s Friends, a network of patient communities for rare diseases. Members can be as young as 12.	chiarisupport.org; forum.chiarisupport.org
Bobby Jones CSF Support Community (on Inspire)	…“Bobby Jones CSF says you choose how anonymous you are.”	bobbyjonescsf.org (Inspire’s own page refused automated access; the link is the address Bobby Jones CSF gives)
ASAP support groups	Monthly support groups over Zoom, monthly phone support groups, and help finding a local group that meets in person.	asap.org/find-support
FEMACPA (Spain)	The Spanish federation of Chiari patient associations. It offers support after diagnosis.	femacpa.com/quienes-somos

Left out: ChySPA (its address now shows unrelated casino advertising), Brain & Spine Foundation UK (refused automated access; Facebook groups), Facebook and Reddit groups in general.

Research studies summaries

Plain summaries of individual studies are kept in src/data/study-summaries.json. Each entry records:

• the date Matthew approved it;
• the listing’s last-update date it was checked against;
• its audit report.

Each summary is written from the full ClinicalTrials.gov listing (saved copies are in docs/audits/sources/) and checked by a fresh agent before approval. A summary only describes the study; it makes no claim about Chiari itself. When a listing changes after its check, the daily refresh’s issue lists the study again. (Rule added Nov 5, 2026.)

Study	Listing checked	Audit	Approved
NCT06502431	Last updated 2026-09-08 (opened 2026-11-05)	docs/audits/2026-11-05-study-summaries-audit.md	2026-11-05
NCT06724029	Last updated 2026-03-30 (opened 2026-11-05)	docs/audits/2026-11-05-study-summaries-audit.md	2026-11-05

Non-medical claims

Claim	Verdict	Sources
A U.S. quarter is 24.26 mm across and 1.75 mm thick	Verified	U.S. Mint, Coin Specifications (opened by Matthew Nov 5, 2026; the Mint blocks automated readers): Diameter 0.955 in, 24.26 mm; Thickness 0.069 in, 1.75 mm. Screenshot: docs/audits/sources/2026-11-05-new-features/usmint-quarter-specifications-screenshot.png (cropped to the specifications table, which has no coin name; Matthew took it from the Mint’s Quarter specifications, and the figures match the Mint’s published quarter size)
Pronunciation (Home, “How do you say it?”): Chiari “key-AR-ee”; Chiari malformation “key-AR-ee mal-fore-MAY-shun”	Verified	Mayfield Clinic (opened Nov 5): “Chiari (pronounced key-AR-ee)”; Nemours KidsHealth (opened Nov 5): “(key-AR-ee mal-fore-MAY-shun)”; Merriam-Webster Medical (opened Nov 5). Saved copies: docs/audits/sources/2026-11-05-new-features/
Pronunciation: syringomyelia “suh-ring-go-my-EE-lee-uh”; syrinx “SEER-inks”	Verified (plain respellings of the dictionary symbols, one main stress; other published versions: KidsHealth “ser-in-go-my-ILL-ee-uh”, Mayfield “sir-RING-o-my-elia”)	Merriam-Webster Medical: syringomyelia (opened Nov 5): “sə-ˌriŋ-gō-mī-ˈē-lē-ə”; syrinx (opened Nov 5): “ˈsir-iŋ(k)s”; M-W Guide to Pronunciation (opened Nov 5)
“Hans Chiari first described Chiari malformations at the end of the 1800s.”	Verified	Bezuidenhout 2018, PMC7655446 (opened Nov 5)
Browsers don’t send the part of a link after # to the server	Verified (scripts on the page can still read it, so analytics must be configured not to record it)	RFC 3986 §3.5
Cloudflare Web Analytics uses no cookies and doesn’t build a profile; collects page, referrer, country, browser and device, page-load timing	Verified; re-check cookies in the browser before launch	Cloudflare FAQ, Cloudflare blog
ClinicalTrials.gov is the U.S. government’s registry, run by the National Library of Medicine	Verified; terms ask for source credit, processed date and a note that summaries are changed	Terms
Z-Anatomy is CC BY-SA 4.0; BodyParts3D is CC BY-SA 2.1 Japan	Verified	Z-Anatomy, BodyParts3D license
WCAG 2.2 AA is the current W3C standard; U.S. ADA Title II rules cite WCAG 2.1 AA	Verified	Section508.gov

Review history

1. First research pass: four parallel research tracks (basics and symptoms, imaging and anatomy, syrinx and surgery, organizations). 14 corrections.
2. Independent fact check: 16 final statements re-checked from scratch. 9 passed, 7 tightened, none wrong.
3. Second pass, four fresh reviewers: about 115 English sentences on all screens (6 tightened); the anatomy figure (8 drawing fixes, re-rendered and checked); the Spanish page (16 fixes, missing sections added); non-medical claims (9 fixes, including the BodyParts3D credit and accessibility wording).

Still open (only people can close these)

• Done: A person with medical training looks at each finished 3D view once. Matthew decided on 2026-11-04 not to use a medical reviewer. Replaced by the accuracy checks in CLAUDE.md rule 1a; reports in docs/audits/.
• Done: Open the blocked medical sources directly. Done Nov 4 for NINDS, Cleveland Clinic, MedlinePlus and PubMed Central (rows marked “opened”).
• Still open: Still not openable from this environment: StatPearls (bot check), Mayo Clinic and Radiopaedia (refuse automated readers), PubMed abstracts, Frontiers, AJNR, QxMD, Manipal. Nothing on the site now rests on these alone; rows citing them also cite an opened source or are marked.
• Still open: A medical translator signs off on the Spanish.
• Still open: Confirm each organization’s description and links on the Support page with the organization (the public “[Before launch…]” note was taken off the page on Nov 5; this stays open here).
• Still open: Confirm the Bobby Jones CSF registry status with them (their page says paused, last updated 2024).
• Still open: Before Explain It launches: confirm in the browser network tab that analytics requests don’t contain the note.
• Done: “Symptoms can come and go and are often invisible” (Explain It) had no source row. Row 16 added Nov 5 (Baisden 2012, opened; NINDS and StatPearls block automated readers). Independent check: pass with notes (docs/audits/2026-11-05-symptoms-source-audit.md); a second source (NINDS or StatPearls) should be added when someone can open one by hand.
• Still open: Open mayoclinic.org by hand once to confirm the care-network copy matches.

Sources not opened

The NINDS Chiari imaging standards file (Word format) and two PubMed Central articles could not be opened. Nothing on the site rests on them alone.