This 10-year-old male has a history of encephalitis.
Q1 – The most likely diagnosis is:
(a) Herpes encephalitis
(c) Acute disseminated encephalomyelitis
(d) Acyl-CoA oxidase deficiency
(e) Metachromatic leukodystrophy
A1 – (b) Adrenoleukodystrophy
Adrenoleukodystrophy (ALD) is an X-linked disorder affecting young males due to the accumulation of very long chain fatty acids from a genetic deficiency in perioxisomal oxidation related to ALDP gene mutation. Carrier females can be symptomatic. MRI appearance includes relative sparing of subcortical U fibers, posterior distribution, central areas of scarring, and an active leading edge of demyelination. There are childhood, adolescent and adult forms as well as spinal (adrenomyeloneuropathy) manifestations and forms limited to Addison’s disease.
Herpes encephalitis is more temporal and hemorrhagic. It also has a more acute, rather than chronic, progressive presentation. Meningeal enhancement is common.
Acyl-CoA oxidase deficiency (pseudo ALD) can have a similar appearance, but is rare and seen in neonates. The disease is progressive unlike acute disseminated encephalomyelitis, which is monophasic.
Arylsulfatase A is decreased in metachromatic leukodystrophy (MLD). It does not have a parieto-occipito-callosal predilection on MRI.
Besides X-linked ALD (symmetric), not very many diseases affect the splenium of the corpus callosum, especially symmetrically. Some include:
- Lymphoma (mass effect)
- Glioblastoma (mass effect)
- Posterior reversible encephalopathy syndrome (PRES)
- Marchiafava-Bignami disease (alcohol-related non-masslike)
- Multiple sclerosis (patchy)
- Infective [e.g. Influenza (reversible), rotavirus, mumps, adnovirus, and E. coli]
- Hyperosmolar hyperglycemia (reversible)
- Legionnaires’ disease (reversible)
- Glufosinate Ammonium Poisoning (non-masslike)
- Krabbes disease (non-masslike, symmetric)
- Dai-Diffuse axonal injury (trauma, hemorrhage, siderosis)
- Infarct (usually hypoxic type)
- Post-shunt decompression
- Venous thrombosis (internal cerebral veins and straight sinus)
- Others: AIDs dementia complex; antiepileptic drugs; mild encephalopathy with reversible splenial lesion (MERS); hemolytic uremic syndrome (HUS)
*For a proposed scoring method on adrenoleukodystrophy (ALD), see the referenced article by Daniel J. Loes.
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1. Loes DJ, et. al., Adrenoleukodystrophy: A Scoring Method for Brain MR Observations, American Journal of Neuroradiology, (1994) 15:1761-1766.