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Pantothenate Kinase-Associated Neurodegeneration (PKAN)


KEY FACTS

Terminology

  • Pantothenate kinase-associated neurodegeneration (PKAN)

    • Most common form of neurodegeneration with brain iron accumulation (NBIA)

    • Mutated pantothenate kinase 2 gene ( PANK2 )

    • Formerly known as Hallovorden-Spatz disease

Imaging

  • Best diagnostic clue

    • Highly suggestive of PKAN is eye-of-the-tiger sign

      • –

        Diffuse pallidal T2 hypointensity with medial foci ↑ T2 signal

Top Differential Diagnoses

  • Disorders with ↑ T2 signal globus pallidus

    • Metabolic

      • –

        Methylmalonic acidemia, Kearns-Sayre, L-2-hydroxyglutaric aciduria, Canavan, neuroferritinopathy

    • Ischemic/toxic

      • –

        Anoxic encephalopathy, carbon monoxide/cyanide poisoning, kernicterus

Clinical Issues

  • Classic PKAN

    • Dystonia, dysarthria, rigidity, choreoathetosis in young child

  • Atypical PKAN

    • Psychiatric, speech, pyramidal/extrapyramidal disturbances in older child/teenager

  • Epidemiology

    • Rare; incidence unknown

  • Prognosis

    • Classic PKAN: Fatal; mean disease duration after symptom onset is 11 years

    • Atypical PKAN: Eventual severe impairment/death

  • No curative treatment

Axial T2WI MR in a 5 year old with a diagnosis of cerebral palsy demonstrates an “eye of the tiger” typical of PKAN: Symmetric areas of high T2 signal
within the medial globus pallidus with surrounding pallidal hypointensity
.

Four years later, dystonia prompted repeat imaging in the same patient. Axial T2WI MR shows that the “eyes”
have decreased in size and intensity; the surrounding pallidal hypointensity
is more prominent. Volume loss is now seen, particularly frontal
.

Coronal T2WI MR of the same patient at 9 years of age shows abnormal hypointense signal in the globus pallidus
and substantia nigra
.

Axial T2* GRE MR in the same patient at 9 years of age shows “blooming” of hypointense signal in the globus pallidus secondary to the paramagnetic effect of iron
. The findings in this patient are typical of the evolution of classic PKAN: Diminishing caliber of the “eye,” increasing surrounding pallidal hypointensity, and progressive volume loss.

TERMINOLOGY

Abbreviations

  • Pantothenate kinase-associated neurodegeneration (PKAN)

Synonyms

  • Neurodegeneration with brain iron accumulation type 1 (NBIA-1)

  • Hallervorden-Spatz syndrome

    • PKAN and NBIA-1 = preferred terms

Definitions

  • Neurodegeneration with brain iron accumulation (NBIA) = umbrella term for neurodegenerative disorders characterized by brain iron accumulation

    • Known causes include PKAN (most common), aceruloplasminemia, neuroferritinopathy, and infantile neuroaxonal dystrophy

  • PKAN caused by mutation pantothenate kinase 2 gene ( PANK2 )

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