Maple Syrup Urine Disease (MSUD) is associated with an inability to metabolize branched chain amino acids. Cerebral edema is a complication that can be fatal.
During periods of metabolic decompensation there is a release of toxic metabolites that:
(1) can lead to a metabolic encephalopathy
(2) can cause the kidneys to excrete sodium and retain water (due to increased vasopressin) resulting in a concentrated urine and hypo-osmolar plasma
Administration of intravenous fluids can worsen fluid overload especially if the infused fluid is hypotonic.
As the osmolarity of the plasma decreases there is an increase in cerebral edema. With severe edema there is increased intracranial pressure which can lead to fatal herniation.
The metabolic encephalopathy may result in an altered level of consciousness, intermittent apnea, seizures, opisthotonus and central respiratory failure.
Signs of impending cerebral herniation:
(1) hyperactive gag reflex
(2) asymmetrical pupils
(3) ophthalmoplegia
(4) decorticate posturing
Venovenous hemofiltration is effective in removing the toxic metabolites and reducing the cerebral edema.
