Patterns of brain injury in inborn errors of metabolism

Abstract

Many inborn errors of metabolism (IEMs) are associated with irreversible brain injury. For many, it is unclear how metabolite intoxication or substrate depletion accounts for the specific neurologic findings observed. IEM-associated brain injury patterns are characterized by whether the process involves gray matter, white matter, or both, and beyond that, whether subcortical or cortical gray matter nuclei are involved. Despite global insults, IEMs may result in selective injury to deep gray matter nuclei or white matter. This manuscript reviews the neuro-imaging patterns of neural injury in selected disorders of metabolism involving small molecule and macromolecular disorders (ie, Phenylketonuria, urea cycle disorders, and maple syrup urine disease) and discusses the contribution of diet and nutrition to the prevention or exacerbation of injury in selected inborn metabolic disorders. Where known, a review of the roles of individual differences in blood-brain permeability and transport mechanisms in the etiology of these disorders will be discussed.

Figure 1

UCD pathway.

Figure 2

¹H MRS showing elevations of glutamine and lowered myoinositol in a patient with OTCD relative to a control subject.

Figure 3

Brain swelling in MSUD.