iNPH Radscale

The iNPH Radscale is a reproducible semiquantified grading scale for the imaging findings of normal pressure hydrocephalus (NPH).

Scale

The iNPH Radscale uses the following imaging findings on both CT and MRI ^1,4:

• Evans index

  • ≤0.25: 0 points

  • 0.26-0.3: 1 point

  • >0.3: 2 points

• narrow parietal high-convexity and medial parafalcine sulci: assessed in the most superior axial and coronal planes

  • normal: 0 points

  • parafalcine: 1 point

  • vertex: 2 points

• Sylvian fissures: compared to adjacent sulci in the coronal plane

  • normal: 0 points

  • enlarged: 1 point

• focally enlarged sulci compared to surrounding sulci

  • not present: 0 points

  • present: 1 point

• temporal horns: measured in the axial plane

  • <4 mm: 0 points

  • 4-5.9 mm: 1 point

  • ≥6 mm: 2 points

• callosal angle

  • >90°: 0 points

  • 90-59.9°: 1 point

  • ≤60°: 2 points

• periventricular white matter change

  • not present (Fazekas grade 0): 0 points

  • frontal horn caps (Fazekas grade 1): 1 point

  • confluent areas (Fazekas grade 2-3): 2 points

Interpretation

iNPH Radscale scores of >8 have been shown to have high sensitivity (>90%) for NPH in patients with clinical symptoms ^2,3 although iNPH Radscale scores alone may not predict response to shunt surgery ⁵.