Main MRI patterns of leukodystrophies
Magnetic resonance imaging allows leukodystrophies to be differentiated based on which white matter regions are involved in the early stages.
- Adrenoleukodystrophy (ALD): Characterized by symmetric involvement of the posterior white matter (peritrigonal zones, splenium of the corpus callosum). T2-weighted imaging shows hyperintense signals and increased diffusion. A specific marker of active inflammation and blood-brain barrier breakdown is the peripheral contrast enhancement along the anterior edge of the abnormal signal zone.
- Alexander disease (Alexander disease): Unlike ALD, the pathological process starts in the frontal lobes and spreads to the periventricular white matter. Patients present with macrocephaly. A characteristic feature is the «garland appearance» (garland appearance) — contrast enhancement along the ventricular ependyma. In the early stages on T1-weighted images, cavities are not detected, and the picture corresponds to edema.
- L-2-hydroxyglutaric aciduria: Predominantly affects subcortical U-fibers, internal and external capsules. An important differential diagnostic sign: the corpus callosum and periventricular tracts remain intact.
- Krabbe disease (Krabbe disease): Belongs to lysosomal storage disorders. Changes predominate in the posterior and central tracts. A highly specific MRI sign is a dark (hypointense) signal in the thalami on T2-weighted images.
- Maple syrup urine disease (MSUD): Associated with the accumulation of leucine, isoleucine, and valine. In the acute stage, massive edema of the white matter tracts is observed (especially the corticospinal tracts in the internal capsules) and the brainstem.
Mitochondrial and peroxisomal disorders
These groups of disorders disrupt the functions of cellular organelles: mitochondria (energy metabolism) and peroxisomes (catabolism).
- Leigh disease (Leigh disease): A mitochondrial disorder. MRI reveals bilateral symmetric lesions in the brainstem and basal ganglia. A classic sign is the «panda face» (panda face) sign in the midbrain due to involvement of the substantia nigra and tegmentum.
- MELAS syndrome: Manifests as stroke-like episodes. Infarct lesions develop in non-vascular territories (not corresponding to the blood supply zones of specific arteries). Calcification of the basal ganglia is frequently detected.
- Zellweger syndrome (Zellweger syndrome): A peroxisomal disorder. The MRI picture is considered pathognomonic: a combination of severe delayed myelination, periventricular germinolytic cysts, and cortical formation disorders (perisylvian polymicrogyria, gray matter heterotopia).
Heavy metal metabolism disorders
Disruptions in the transport of copper, molybdenum, and other trace elements cause severe toxic encephalopathies.
- Wilson's disease (Wilson disease): A defect in extracellular copper transport. MRI shows T1 shortening (bright signal) in the basal ganglia, which is also seen in other hepatic encephalopathies. On T2-weighted images, the signal is increased in the basal ganglia, pons, and thalami.
- Menkes disease (Menkes disease): An X-linked disorder of transcellular copper metabolism. Characterized by severe vasculopathy (vessels become tortuous and prone to dissection) and progressive brain atrophy.
- Molybdenum cofactor deficiency: A cause of neonatal encephalopathy. In the acute stage, it causes total edema similar to hypoxic-ischemic injury, but has a specific feature — focal changes in the globus pallidus and subthalamic nuclei.
Differential diagnosis: globus pallidus involvement
Bilateral symmetric signal changes in the globus pallidus (globus pallidus) occur in several metabolic conditions:
| Abnormal | MRI findings |
|---|---|
| Methylmalonic acidemia | Isolated involvement of the globus pallidus, thalami and cortex are intact |
| Kernicterus (Kernicterus) | Bilirubin encephalopathy with involvement of the basal ganglia |
| Kearns-Sayre syndrome | Involvement of the globus pallidus combined with involvement of the thalami, caudate and dentate nuclei |
Briefly: answers to topical questions
What clinical symptoms are characteristic of MELAS syndrome besides stroke-like episodes?
The clinical presentation of MELAS syndrome includes encephalopathy, seizures, and myopathy. In addition, comorbidities in this condition include cardiomyopathy and endocrinopathies.
Which toxic and metabolic conditions cause bilateral symmetric involvement of the globus pallidus on MRI?
Bilateral symmetric involvement of the globus pallidus on MRI is caused by the following toxic and metabolic conditions:
- Methylmalonic acidemia (Methylmalonic acidaemia) — an inherited metabolic disorder.
- Guanidinoacetate methyltransferase deficiency (GAMT) — a metabolic condition.
- Kearns-Sayre syndrome (Kearns–Sayre syndrome) — a mitochondrial disorder.
- Kernicterus (kernicterus) — bilirubin encephalopathy.
- Carbon monoxide poisoning (Carbon Monoxide Intoxication) — a toxic condition.
Mutations in which genes lead to impaired copper metabolism in Wilson's disease and Menkes disease?
In Wilson's disease, impaired copper metabolism is associated with mutations in the ATP7B gene. For Menkes disease, the specific gene is not specified in the cited sources; only X-linked inheritance is indicated.
To avoid confusing the onset of demyelination on MRI, remember: Alexander disease "hits the front" (starts in the frontal lobes), while adrenoleukodystrophy (ALD) "creeps from behind" (the splenium of the corpus callosum and parieto-occipital regions are affected first).
Class and exam questions
How to differentiate Menkes disease from shaken baby syndrome (non-accidental trauma)?
In Menkes disease, due to marked brain atrophy, cerebrospinal fluid often accumulates in the subdural space, which can mimic traumatic subdural hematomas. The key distinguishing feature is the presence of severe vessel tortuosity and T1 shortening in the basal ganglia.
Which condition is characterized by the «panda face» sign?
This sign is detected on MRI in Leigh disease (a mitochondrial disorder) and is caused by symmetric signal changes in the midbrain with involvement of the substantia nigra and tegmentum.
How do infarcts in MELAS syndrome differ from conventional ischemic strokes?
In MELAS syndrome, lesion zones occur in non-vascular territories, meaning they do not correspond to the anatomical blood supply zones of major cerebral arteries.
What else to study on this topic
- Craniosynostosis: classification, radiographic, and CT signs (sagittal, coronal, metopic synostoses).
- Acute neonatal encephalopathy: evaluation of DWI and ADC maps in total brain edema.
- Pelizaeus-Merzbacher disease: paradoxical myelination pattern on T1-weighted and T2-weighted images.
- Conditions with macrocephaly: Alexander disease, L-2-hydroxyglutaric aciduria, and megalencephalic leukoencephalopathy with subcortical cysts (MLC).
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