Skip to content
Epomedicine
Epomedicine

Mnemonics, Simplified Concepts & Thoughts

  • Medical Students
  • Bedside Clinics
  • Case Reports
  • Emergency Medicine
  • Blog
  • Surgical Skills
  • Medical Mnemonics
Epomedicine

Mnemonics, Simplified Concepts & Thoughts

Radiological Lines for assessing Basilar Invagination : Mnemonic

Epomedicine, Nov 24, 2024Feb 21, 2025

Last updated on February 21, 2025

Mnemonic: Imagine a letter “Z“.
a. McRae’s line has “R” and is at Roof.
b. Chamberlain’s line starts with “C” and is at Center.
c. McGregor’s line has “G” and is at Ground.

basal skull lines

a. McRae’s line (foramen magnum line): drawn from anterior margin of foramen (basion) to posterior margin of foramen (opisthion)

  • Normal: Tip of dens should not cross this line

b. Chamberlain’s line: drawn from posterior end of hard palate to posterior margin of foramen (opisthion)

  • Normal: Tip of dens is no more than 3 mm above this line

c. McGregor’s line: drawn from posterior end of hard palate to posterior occiput curve

  • Normal: Tip of dens is no more than 4.5 mm above this line

Other lines

ranawat and redlund line

a. Wackenheim’s line (Clivus canal line): Line drawn along clivus into cervical canal

  • Normal: Tip of dens is ventral and tangential to this line

b. Ranawat’s line: A perpendicular line drawn from center of C2 pedicle towards a line from center of anterior to posterior arch of C1

  • Abnormal: <13 mm

c. Redlund-Johnell’s method: Measure distance between midpoint of C2 body inferior margin and McGregor’s line

  • Abnormal: <28 mm
  • Facebook
  • Twitter
PGMEE, MRCS, USMLE, MBBS, MD/MS Nervous systemOrthopedicsRadiology

Post navigation

Previous post
Next post

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Epomedicine. Radiological Lines for assessing Basilar Invagination : Mnemonic [Internet]. Epomedicine; 2024 Nov 24 [cited 2025 May 9]. Available from: https://epomedicine.com/medical-students/radiological-lines-for-assessing-basilar-invagination-mnemonic/.

Pre-clinical (Basic Sciences)

Anatomy

Biochemistry

Community medicine (PSM)

Embryology

Microbiology

Pathology

Pharmacology

Physiology

Clinical Sciences

Anesthesia

Dermatology

Emergency medicine

Forensic

Internal medicine

Gynecology & Obstetrics

Oncology

Ophthalmology

Orthopedics

Otorhinolaryngology (ENT)

Pediatrics

Psychiatry

Radiology

Surgery

RSS Ask Epomedicine

  • What to study for Clinical examination in Orthopedics?
  • What is the mechanism of AVNRT?

Epomedicine weekly

  • About Epomedicine
  • Contact Us
  • Author Guidelines
  • Submit Article
  • Editorial Board
  • USMLE
  • MRCS
  • Thesis
©2025 Epomedicine . All rights reserved.