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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Neurology

Advanced Diagnosis and Precision Imaging

At a Glance

Diagnosing Chiari malformation often requires advanced imaging beyond a standard MRI. Upright MRIs, Cine-MRIs, and precise measurements like the Clivo-Axial Angle help doctors evaluate cerebrospinal fluid flow, detect spinal cord cavities (syrinx), and identify hidden instability.

Diagnosing Chiari Malformation and its related conditions requires more than just measuring how far your brain tissue has shifted. Because Chiari often overlaps with hypermobility and fluid flow issues, doctors must use specific imaging techniques and measurements to understand the full picture [1][2].

The Role of Advanced Imaging

Standard MRIs are usually performed while you are lying flat (supine). However, for many patients—especially those with Ehlers-Danlos Syndrome (EDS)—this may not tell the whole story.

  • Upright or Dynamic MRI: When you stand up, gravity pulls on your brain and spine. In people with ligament laxity, the skull can “settle” onto the spine, pushing the cerebellar tonsils further down [3][4]. An upright MRI or a dynamic MRI (where you move your neck into flexion and extension) can reveal cranial settling or craniocervical instability (CCI) that disappears when you are lying flat [3][5].
  • Cine-MRI (Phase-Contrast MRI): This is a specialized scan that creates a “movie” of your cerebrospinal fluid (CSF) as it pulses with your heartbeat [6][7]. It is essential for determining if the herniated tonsils are actually blocking fluid flow, which is a key factor in deciding if surgery is necessary [8][6].

Critical Radiographic Measurements

To determine if your brainstem is being compressed, specialists look for specific measurements on your MRI:

  • Clivo-Axial Angle (CXA): This measures the angle between the base of your skull (clivus) and your spine (axis) [9]. A narrow angle (typically less than 135∘135^{\circ}) can indicate that the brainstem is being “kinked” or compressed [10].
  • pB-C2 (Grabb-Oakes Line): This is a measurement of how much the spine is pressing into the space where the brainstem sits [9]. A measurement of 9 mm or more is often associated with ventral (front-side) brainstem compression [9][10].
  • Harris Measurements (BDI/BAI): These help identify if the skull is properly aligned with the first two vertebrae of the neck [9].

Confirming Related Conditions

Diagnosis also involves looking for the “ripples” Chiari causes in other systems:

Syringomyelia (Syrinx)

Doctors use T2-weighted MRI scans to look for a syrinx (a fluid-filled cavity) [11]. They may also look for a presyrinx state, where the spinal cord shows swelling (edema) but hasn’t yet formed a full cavity [12]. Identifying a syrinx is critical because it often suggests that CSF flow is significantly obstructed [11][8].

Dysautonomia and POTS

If you experience a racing heart or dizziness, your doctor may order an Autonomic Profile [13]. The “gold standard” test for Postural Orthostatic Tachycardia Syndrome (POTS) is the Tilt Table Test (TTT) [14].

During a TTT, you are strapped to a table that tilted upright while your heart rate and blood pressure are monitored [14][15]. Clinicians are looking for a sustained heart rate increase of at least 30 beats per minute (40 bpm for teenagers) within 10 minutes of standing or tilting, without a significant drop in blood pressure [14]. Other tests may include the Valsalva maneuver to check heart rate response and the QSART to measure your sweat response [16][13].

By combining these structural measurements with functional tests, your care team can differentiate between a “simple” Chiari and a more complex presentation involving instability or systemic dysfunction [17][18].

Common questions in this guide

What is a Cine-MRI and why is it used for Chiari malformation?
A Cine-MRI is a specialized scan that creates a movie of your cerebrospinal fluid pulsing with your heartbeat. It helps doctors determine if the herniated brain tissue is blocking fluid flow, which is a key factor in deciding if surgery is needed.
Why might I need an upright or dynamic MRI instead of a standard one?
Standard MRIs are performed lying down, but gravity pulls on your brain when you stand. An upright or dynamic MRI can reveal issues like cranial settling or craniocervical instability that disappear when you are lying flat, which is especially important for patients with hypermobility.
What are the Clivo-Axial Angle (CXA) and Grabb-Oakes measurements?
These are specific radiographic measurements doctors use to check if your brainstem is being compressed. A narrow CXA or a high Grabb-Oakes measurement indicates that the spine may be pushing into the space where the brainstem sits.
What is a syrinx or presyrinx in Chiari malformation?
A syrinx is a fluid-filled cavity within the spinal cord, while a presyrinx is swelling that hasn't yet formed a full cavity. Identifying these on an MRI is critical because they suggest that cerebrospinal fluid flow is significantly obstructed.
How are POTS or dysautonomia diagnosed with Chiari?
Doctors use a Tilt Table Test or an Autonomic Profile to evaluate dysautonomia symptoms like a racing heart or dizziness upon standing. During this test, you are tilted upright while your heart rate and blood pressure are monitored to check for abnormal changes.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my MRI show a 'true' syrinx or a 'presyrinx' state with medullary edema?
  2. 2.What are my specific CXA and Grabb-Oakes (pB-C2) measurements, and do they fall within the range associated with brainstem compression?
  3. 3.Should I have a cine-MRI to check the pulsatile flow of CSF at my craniocervical junction?
  4. 4.Would an upright or dynamic (flexion/extension) MRI be more appropriate given my symptoms and potential hypermobility?
  5. 5.Do you recommend a Tilt Table Test or a formal Autonomic Profile to investigate my POTS-like symptoms?
  6. 6.Are there signs of 'acquired tonsillar herniation' that might suggest my Chiari symptoms are driven by instability rather than being congenital?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
  1. 1

    The Role of Arachnoid Veils in Chiari Malformation Associated with Syringomyelia.

    Ciappetta P, Signorelli F, Visocchi M

    Acta neurochirurgica. Supplement 2019; (125()):97-99 doi:10.1007/978-3-319-62515-7_14.

    PMID: 30610308
  2. 2

    Prevalence and Impact of Underlying Diagnosis and Comorbidities on Chiari 1 Malformation.

    Sadler B, Kuensting T, Strahle J, et al.

    Pediatric neurology 2020; (106()):32-37 doi:10.1016/j.pediatrneurol.2019.12.005.

    PMID: 32113729
  3. 3

    Ehlers-Danlos Syndrome-Hypermobility Type: A Much Neglected Multisystemic Disorder.

    Gazit Y, Jacob G, Grahame R

    Rambam Maimonides medical journal 2016; (7(4)) doi:10.5041/RMMJ.10261.

    PMID: 27824552
  4. 4

    Report of two cases with omovertebral bone and Klippel-Feil syndrome with craniovertebral junction instability.

    Shah A, Hawaldar A, Lunawat A, et al.

    Journal of craniovertebral junction & spine 2021; (12(1)):95-98 doi:10.4103/jcvjs.JCVJS_7_21.

    PMID: 33850390
  5. 5

    Reference values of four measures of craniocervical stability using upright dynamic magnetic resonance imaging.

    Nicholson LL, Rao PJ, Lee M, et al.

    La Radiologia medica 2023; (128(3)):330-339 doi:10.1007/s11547-023-01588-8.

    PMID: 36715785
  6. 6

    Syringomyelia secondary to "occult" dorsal arachnoid webs: Report of two cases with review of literature.

    Sayal PP, Zafar A, Carroll TA

    Journal of craniovertebral junction & spine 2016; (7(2)):101-4 doi:10.4103/0974-8237.181862.

    PMID: 27217656
  7. 7

    Surgical management of syringomyelia unrelated to Chiari malformation or spinal cord injury.

    Talacchi A, Meneghelli P, Borghesi I, Locatelli F

    European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2016; (25(6)):1836-46 doi:10.1007/s00586-015-4262-x.

    PMID: 26441259
  8. 8

    Evaluation and Treatment of Patients with Small Posterior Cranial Fossa and Chiari Malformation, Types 0 and 1.

    Bogdanov EI, Heiss JD

    Advances and technical standards in neurosurgery 2024; (50()):307-334 doi:10.1007/978-3-031-53578-9_11.

    PMID: 38592536
  9. 9

    Optimizing Alignment Parameters During Craniocervical Stabilization and Fusion: A Technical Note.

    Henderson F, Rosenbaum R, Narayanan M, et al.

    Cureus 2020; (12(3)):e7160 doi:10.7759/cureus.7160.

    PMID: 32257703
  10. 10

    Increase in clivo-axial angle is associated with clinical improvement in children undergoing occipitocervical fusion for complex Chiari malformation: patient series.

    Marianayagam NJ, Chae JK, Hussain I, et al.

    Journal of neurosurgery. Case lessons 2021; (2(23)):CASE21433 doi:10.3171/CASE21433.

    PMID: 36061080
  11. 11

    How Should Syringomyelia be Defined and Diagnosed?

    Klekamp J

    World neurosurgery 2018; (111()):e729-e745 doi:10.1016/j.wneu.2017.12.156.

    PMID: 29317358
  12. 12

    Development of pre-syrinx state and syringomyelia following a minor injury: a case report.

    Kleindienst A, Engelhorn T, Roeckelein V, Buchfelder M

    Journal of medical case reports 2020; (14(1)):223 doi:10.1186/s13256-020-02568-6.

    PMID: 33203466
  13. 13

    Dysautonomia in the Ehlers-Danlos syndromes and hypermobility spectrum disorders-With a focus on the postural tachycardia syndrome.

    Mathias CJ, Owens A, Iodice V, Hakim A

    American journal of medical genetics. Part C, Seminars in medical genetics 2021; (187(4)):510-519 doi:10.1002/ajmg.c.31951.

    PMID: 34766441
  14. 14

    A Cross-Sectional Study of Cardiovascular Autonomic Reactivity in Ehlers-Danlos Syndrome.

    Alauddin W, Alam S, Mishra M, et al.

    Cureus 2024; (16(7)):e64542 doi:10.7759/cureus.64542.

    PMID: 39144845
  15. 15

    COVID-19 Induced Postural Orthostatic Tachycardia Syndrome (POTS): A Review.

    Mallick D, Goyal L, Chourasia P, et al.

    Cureus 2023; (15(3)):e36955 doi:10.7759/cureus.36955.

    PMID: 37009342
  16. 16

    Dysautonomia: a common comorbidity of systemic disease.

    Blitshteyn S

    Immunologic research 2025; (73(1)):105 doi:10.1007/s12026-025-09661-2.

    PMID: 40624434
  17. 17

    Is Cervical Stabilization for All Cases of Chiari-I Malformation an Overkill? Evidence Speaks Louder Than Words!

    Deora H, Behari S, Sardhara J, et al.

    Neurospine 2019; (16(2)):195-206 doi:10.14245/ns.1938192.096.

    PMID: 31261453
  18. 18

    Compromised Cranio-Spinal Suspension in Chiari Malformation Type 1: A Potential Role as Secondary Pathophysiology.

    Shao B, Poggi JA, Amaral-Nieves N, et al.

    Journal of clinical medicine 2022; (11(24)) doi:10.3390/jcm11247437.

    PMID: 36556053

This page explains diagnostic imaging for Chiari malformation for educational purposes. Your neurosurgeon or neurologist is the best source for interpreting your specific MRI scans and measurements.

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