Sagittal T1 MRI of a 24-year-old woman with occipital headaches worsened by coughing and Valsalva manoeuvre shows peg-like cerebellar tonsils extending 8 mm below the foramen magnum with effacement of CSF at the craniocervical junction and a cervical syrinx. The most likely diagnosis is:

• A Chiari type I malformation ✓
• B Chiari type II malformation
• C Dandy-Walker malformation
• D Arachnoiditis of the posterior fossa

Explanation

Tonsillar descent exceeding 5 mm below the foramen magnum with a pointed peg-like configuration, crowding of the craniocervical junction, and an associated syringomyelia defines Chiari I malformation, which typically presents in young adults with cough headache. Chiari II involves caudal displacement of the vermis, brainstem and fourth ventricle and is almost always associated with myelomeningocele.

Reference: Osborn's Brain, 2nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.