A 10-day-old neonate presented with vomiting and irritability. Diffusion-weighted imaging showed abnormal signal intensities, including characteristic involvement of the optic pathway (Figure, A and B). Maple syrup urine disease (MSUD) was suspected. Blood tests confirmed elevated levels of branched-chain amino acids (BCAAs)—leucine, isoleucine, and valine.
(A) Diffusion-weighted MRIs and (B) corresponding ADC images demonstrating diffusion restriction with corresponding reduced ADC in bilateral optic tracts (curved arrows), lateral geniculate bodies (long arrows), optic radiations (short arrows), bilateral perirolandic white matter (arrowheads), brainstem (open arrows), and cerebellar white matter (asterisks). ADC = apparent diffusion coefficient; MSUD = maple syrup urine disease.
Optic pathway signal abnormalities occur in 26.3% of patients with MSUD and may cause cortical visual impairment and transient blindness.1 These abnormalities are caused by a deficiency of alpha-ketoacid dehydrogenase, elevated BCAAs, and reduced (Na+/K+ATPase) pump function resulting in water accumulation between the myelin layers (intramyelinic edema); however, they are reversible with treatment and over time.2
Study Funding
The authors report no targeted funding.
Disclosure
The authors report no disclosures relevant to the manuscript. Go to Neurology.org/N for full disclosures.
Appendix Authors
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Submitted and externally peer reviewed. The handling editor was Roy Strowd III, MD, MEd, MS.
Teaching slides links.lww.com/WNL/C318
- Received March 25, 2022.
- Accepted in final form August 10, 2022.
- © 2022 American Academy of Neurology
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