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Neurodegeneration With Brain Iron Accumulation (NBIA)


KEY FACTS

Terminology

  • Group of neurodegenerative disorders characterized by dystonia, parkinsonism, and spasticity

    • Caused by mutations in L-ferritin gene FTL

    • All characterized by abnormal Fe accumulation in basal ganglia

      • –

        Lewy bodies, axonal swellings, hyperphosphorylated tau in some subtypes

    • Includes (among others)

      • –

        Pantothenate kinase-associated neurodegeneration (PKAN)

      • –

        Infantile neuroaxonal dystrophy (INAD)

      • –

        Aceruloplasminemia

Imaging

  • Globus pallidus (GP) T2 hypointensity with central hyperintensity of GP: Eye of the tiger sign

    • Specific to classic PKAN ( PANK2 mutations)

    • May also be seen in neuroferritinopathy

  • GP ± substantia nigra, dentate nucleus, cortex, striatum, & thalamus T2 dark without eye of the tiger sign = other NBIA

  • Caution: GP normally hypointense on T2 at 3T or above

Pathology

  • Iron directly causes or facilitates cellular injury or is consequence of axonal disruption

Clinical Issues

  • PKAN

    • Classic < 6 years, atypical during teenage years

  • INAD

    • Classic < 2 years, atypical at 4-6 years

  • Aceruloplasminemia and neuroferritinopathy

    • Mean age 40 years

Diagnostic Checklist

  • Look for: T2 hypointensity of GP in patient with movement disorder

  • Consider: T2* (gradient echo) or SWI in patients with movement disorders

Axial T2WI FS MR shows classic imaging of PKAN (Hallervorden-Spatz syndrome), which is within the spectrum of NBIA. Note the globus pallidi hypointensity
related to iron deposition with central hyperintensity
, consistent with the eye of the tiger sign, highly specific for the PANK2 mutation.

Axial T2WI MR shows symmetric hypointensity within the globus pallidi
. The eye of the tiger sign is absent; therefore, this is not PKAN. These findings are characteristic of NBIA.

Axial T2* GRE MR shows marked hypointensity related to iron deposition in the dentate nuclei
of the cerebellum in this patient with aceruloplasminemia. Aceruloplasminemia and neuroferritinopathy occur in adults and have a similar imaging appearance.

Axial T2* SWI MR in the same patient shows diffuse linear hypointensity in the cortex
with marked “blooming” in the basal ganglia and thalami
related to iron deposition. Substantia nigra involvement is also typical.

TERMINOLOGY

Abbreviations

  • Pantothenate kinase-associated neurodegeneration (PKAN)

  • Infantile neuroaxonal dystrophy (INAD)

  • Neurodegeneration with brain iron accumulation (NBIA)

Definitions

  • Group of neurodegenerative disorders characterized by dystonia, parkinsonism, and spasticity

    • Caused by mutations in L-ferritin gene FTL1

    • All characterized by abnormal Fe accumulation in basal ganglia

    • Includes PKAN, INAD, aceruloplasminemia, etc.

      • –

        Lewy bodies, axonal swellings, hyperphosphorylated tau in some subtypes

IMAGING

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