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Metachromatic Leukodystrophy (MLD)


KEY FACTS

Terminology

  • Lysosomal storage disorder

    • Caused by ↓ arylsulfatase A

    • Results in CNS, PNS demyelination

  • 3 clinical forms

    • Late infantile (most common), juvenile, adult

Imaging

  • Best diagnostic clue: Confluent butterfly-shaped ↑ T2 signal in deep cerebral hemispheric white matter (WM)

    • Early: Spares subcortical U fibers

      • –

        Corpus callosum splenium, parietooccipital WM initially

      • –

        Rapid centrifugal spread to frontal, temporal WM

    • Late: Involves subcortical U fibers

  • Sparing of perivenular myelin = tigroid or leopard pattern

  • No WM enhancement

    • Reports cranial nerve, cauda equina enhancement

Top Differential Diagnoses

  • Pelizaeus-Merzbacher disease

  • TORCH

  • Pseudo-TORCH

  • Periventricular leukomalacia

  • Sneddon syndrome (arylsulfatase A pseudodeficiency)

  • Krabbe disease

  • Megalencephaly with leukoencephalopathy and cysts

Clinical Issues

  • Clinical profile: Toddler with visuomotor impairment and abdominal pain

Diagnostic Checklist

  • Adult patients presenting with cryptic spasticity of legs should be screened for X-linked adrenoleukodystrophy/adrenomyeloneuropathy, lysosomal disorders (e.g., MLD)

Axial T2WI MR shows typical butterfly-shaped pattern of white matter (WM) involvement in metachromatic leukodystrophy (MLD). Note the sparing of internal/external capsules and subcortical U fibers
, typical of early disease.

Axial T2WI MR shows confluent, symmetric WM hyperintensity with sparing of subcortical U fibers. Perivenular myelin sparing causes the hypointense lines and dots within the WM
, the characteristic tigroid or leopard pattern of MLD.

Axial FLAIR MR demonstrates the characteristic confluent, symmetric, central WM involvement of MLD. The tigroid or leopard pattern of lines
and dots within the cerebral hemispheric WM is evident.

Axial ADC map in the same patient shows high signal intensity within the affected WM
consistent with increased diffusivity and probable interstitial edema. Reduced diffusivity (cytotoxic edema) is sometimes seen in areas of active demyelination.

TERMINOLOGY

Abbreviations

  • Metachromatic leukodystrophy (MLD)

Synonyms

  • Sulfatide lipoidosis

Definitions

  • Lysosomal storage disorder

    • Caused by ↓ arylsulfatase A (ARSA)

    • Results in CNS, PNS demyelination

  • 3 clinical forms: Late infantile (most common), juvenile, adult

IMAGING

General Features

  • Best diagnostic clue: Confluent butterfly-shaped ↑ T2 signal in deep cerebral hemispheric white matter (WM)

  • Location: Deep cerebral hemispheric WM

    • Early: Spares subcortical U-fibers

      • –

        Corpus callosum, parietooccipital WM initially

      • –

        Rapid centrifugal spread to frontal, temporal WM

    • Late: Involves subcortical U-fibers

  • Morphology: Symmetric, confluent periventricular (PV) and deep WM high T2 signal

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