Sub-types of adrenoleukodystrophy:
Childhood-onset adrenoleukodystrophy (ALD) – Characterized by early onset (i.e. between ages 5 and 8) progressive cerebral inflammatory demyelination with or without prior adrenal insufficiency, and rapid neurologic deterioration leading to death
Adulthood-onset adrenomyeloneuropathy (AMN, adult version of ALD) – Characterized by spinal cord and peripheral nerve involvement out of proportion to cerebral disease
Locations to assess:
Supratentorial white matter – periventricular, central, and subcortical regions of:
- Parietooccipital (including posterior temporal white matter)
- Anterior temporal
- Frontal regions
Corpus callosum
- Genu
- Body
- Splenium
Visual pathway
- Optic radiations
- Lateral geniculate body
- Meyer’s loop
Auditory pathway
- Medial geniculate body
- Brachium to the inferior colliculus
- Lateral lemniscus
- Pons (trapezoid bodies)
Frontopontine-corticospinal projection fibers
- Internal capsule
- Brain stem
Additional regions of interest
- Basal ganglia
- Cerebellum
- Anterior thalamus
Patterns of disease observed in MRI:
(Type 1) Posterior white matter pattern (approximately 80%)
Note: Abnormalities progress from central to peripheral, and posterior to anterior cerebral white matter involvement with subsequent development of focal and global atrophy
- Parietooccipital white matter
- Splenium of corpus callosum
- Frequent visual and auditory pathway
- Occasional corticospinal tract
(Type 2) Anterior white matter pattern (approximately 15%)
- Frontal white matter
- Genu of corpus callosum
- Frontopontine tract
- Occasional cerebellar
(Type 3) Isolated (approximately 5%)
- Projection fiber abnormalities
Areas to observe for focal atrophy:
- Parietooccipital, anterior temporal, and frontal white matter
- Genu and splenium of the corpus collosum
- Cerebellum
- Brain stem
Scoring is based on:
- Age
- Segmentation
- Third ventricular width, or
- Bifrontal horn-to-inner table ratio
How to score:
Note: This scoring method is not sufficient to compare patients with different disease patterns
Qualitatively
Assess for definite loss of brain parenchyma
Quantitatively
Measure the ratio between maximum bifrontal horn diameter and distance connecting the inner tables of the skull at the same level:
1 point = Third ventricular diameter between 5 and 10mm
2 points = Third ventricular greater than 10mm
1 point = Bifrontal horn-to-inner table ratio greater than 40%
2 points = Bifrontal horn-to-inner table ratio greater than 50%
For global atrophy:
1 point = mild
2 points = moderate
3 points = severe
Reference:
1. Loes DJ, et. al., Adrenoleukodystrophy: A Scoring Method for Brain MR Observations, American Journal of Neuroradiology, (1994) 15:1761-1766.
