Trigeminal neuralgia protocol (MRI)

MRI protocol for trigeminal neuralgia assessment is a group of MRI sequences put together to best approach a possible cause for this condition.

The diagnosis of trigeminal neuralgia is based on patient's history, and an imaging study is usually indicated when alert signs are noted. Imaging can help diagnosing an enlarged looping artery or vein pressing on the trigeminal nerve at the cerebellopontine angle, multiple sclerosis and cerebellopontine angle tumors.

A recent evidence-based review did not find evidence to support or refute the usefulness of MRI for detecting vascular contact with the trigeminal nerve .

Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and referrer's preference, institutional protocols, patient factors (e.g. allergy) and time constraints.

Sequences

• T1

  • sequence: whole brain axial and sagittal (volumetric when possible)
  • purpose: anatomical, brain screen
• T2
  • sequence: axial, limited to posterior fossa (medulla to the upper pons) with thin slices (e.g. 3D CISS and FIESTA)
  • purpose: assess the trigeminal nerves from their origin at the mid pons anteriorly, through the prepontine cistern until the Meckel's cave (trigeminal ganglion)
    • the most common cause of trigeminal neuralgia is an enlarged looping artery (most commonly the superior cerebellar artery) or vein pressing on the trigeminal nerve at the cerebellopontine angle, which is best depicted by this sequence
• FLAIR
  • sequence: whole brain axial
  • purpose: white matter signal abnormality such as in multiple sclerosis
• T1 C+ (Gd)
  • sequence: axial and coronal
  • T1 C+ (Gd) fat sat considered in at least one plane
    • Gadolinium-based contrast agents (GBCAs) for CNS :
      • gadoterate meglumine (Dotarem®)
      • gadobutrol (Gadavist®)
      • gadopentetate dimeglumine (Magnevist®)
      • gadobenate dimeglumine (MultiHance®)
      • gadodiamide (Omniscan®)
      • gadoversetamide (OptiMARK®)
      • gadoteridol (ProHance®)
    • all these GBCAs are approved by FDA at identical administered total doses of 0.1mmol/kg body weight