maple syrup urine disease ( msud ) is a rare inherited autosomal recessive disorder of branched - chain amino acid ( bcaa ) metabolism presenting with life - threatening cerebral edema and dysmyelination in affected individuals .
msud affects approximately 1 out of 180,000 infants and has a much higher prevalence in children of amish , mennonite , and jewish descent .
we present a case report of a baby boy born to consanguineous married parents , who presented on the 8 postnatal day with history of poor feeding , lethargy , and tonic - clonic seizures , since 2 days .
the child was born at term ( 39 weeks ) after an uneventful pregnancy and normal vaginal delivery .
the baby was apparently normal in the first week of postnatal life . on 8 day , clinical systemic examination showed hypotonia and poor neonatal reflexes .
routine biochemical evaluation including serum electrolytes : sodium 138 ( 133 - 145 meq / l ) , potassium 4.2 ( 3.5 - 5.3 meq / l ) , chloride 102 ( 98 - 106 meq / l ) , calcium 8.6 ( 7.6 - 10.4 mg / dl ) , and magnesium levels 1.6 ( 1.40 - 2.55 mg / dl ) were within normal limits .
non - enhanced computed tomography ( nect ) scan of the brain showed bilateral symmetrical white matter hypodensities in the posterior limb of internal capsule , thalami , midbrain , and cerebellar white matter [ figure 1 ] .
nect of the brain , axial images shows bilaterally symmetrical hypodensities in the posterior limb of internal capsule ( blue arrow in figure 1a ) and in the midbrain ( blue arrow in figure 1b ) with compressed ventricles and gyral swelling conventional magnetic resonance imaging ( mri ) showed bilateral symmetric white matter hyperintensites in the posterior limb of internal capsule , thalami , midbrain , corticospinal tracts , and cerebellar white matter on t2-weighted magnetic resonance ( mr ) sequence [ figure 2a and b ] .
dwis with corresponding adc maps demonstrate restricted diffusion in the posterior limbs of the internal capsules ( blue arrows in figure 2a and 2b ) , pons , corticospinal tracts ( blue arrow in figure 2c ) , and cerebellar white matter ( figures 2c and 2d ) diffusion - weighted imaging ( dwi ) showed characteristic pattern of bilateral symmetrical restricted diffusion within the myelinated areas in the posterior limb of the internal capsule , centrum semiovale , corona radiata , corticospinal tract , thalami , posterior aspect of the mid brain , pons , middle cerebellar peduncle , medulla , and cerebellar white matter , attributed to intramyelinic edema [ figure 3a and b ] .
axial t2-weighted mr images shows bilateral symmetrical hyperintensities in posterior limb of internal capsule ( blue arrow in figure 3a ) , central cerebellar white matter , and in the corticospinal tracts ( blue arrow in figure 3b ) multivoxel proton mr spectroscopy showed the presence of bcaas and branched - chain -keto acids resonating at 0.9 - 1.0 ppm , which are seen especially during a metabolic crisis [ figures 4 and 5 ] .
three days later tandem mass spectroscopy revealed increased levels of bcaas ( valine , leucine , and isoleucine ) , confirming the diagnosis of msud .
multivoxel proton mr spectroscopy showed the presence of bcaas and branched - chain -keto acids resonating at 0.9 - 1.0 ppm , which are seen especially during a metabolic crisis [ figures 4 and 5 ] .
three days later tandem mass spectroscopy revealed increased levels of bcaas ( valine , leucine , and isoleucine ) , confirming the diagnosis of msud .
it is a rare autosomal recessive disorder , associated with defects in the branched- chain  ketoacid dehydrogenase complex .
it is divided into four major categories : ( 1 ) classic , ( 2 ) intermediate , ( 3 ) intermittent , and ( 4 ) thiamine responsive , which carry differing symptoms and prognostic factors . the exact cause for brain injury is not clearly understood . according to a study by zinnanti et al . , they suggest two converging mechanisms of brain injury in msud including : ( i ) neurotransmitter deficiencies and growth restriction associated with bcaa accumulation and ( ii ) energy deprivation through krebs cycle disruption associated with branched - chain ketoacid accumulation .
neonates will be normal at birth , presents after disease - free interval , usually within the 4 - 7 days of life with poor feeding , vomiting , poor weight gain , and increasing lethargy . in crisis ,
patient 's urine smells like maple syrup , secondary to the large accumulation of isoleucine .
classic appearing msud edema involving : cerebellar white matter , brain stem , globus pallidus , thalamus , cerebral peduncles , and corticospinal tracts .
dwi shows marked restriction and decreased apparent diffusion coefficient ( adc ) which indicates msud edema is an intracellular oedema ( cytotoxic oedema ) .
dwi is more sensitive than conventional mri in detecting msud brain alterations and it can become a useful tool for early diagnosis and follow - up of metabolic diseases in neonates .
kilicarlsan et al . , reported six cases with dwi in which the changes in all patients were reversed with treatment without evidence of volume loss or persistent tissue damage .
acute  metabolic rescue  to reverse cerebral edema may require hemodialysis during acute crisis to limit neurotoxicity / damage .
metabolically appropriate diet ( protein - modified ) minimizes severity and prevent deficiencies of essential amino acids .
if treated with low - bcaa diet and peritoneal dialysis within a few days from the onset of the symptoms , most patients survive and develop only minimal or no neurological deficits .
the changes in cell osmolarity and metabolism can reverse completely after metabolic correction in metabolic decompensated msud with clinical neurological improvement .
it is a rare autosomal recessive disorder , associated with defects in the branched- chain  ketoacid dehydrogenase complex .
it is divided into four major categories : ( 1 ) classic , ( 2 ) intermediate , ( 3 ) intermittent , and ( 4 ) thiamine responsive , which carry differing symptoms and prognostic factors . the exact cause for brain injury is not clearly understood . according to a study by zinnanti et al . , they suggest two converging mechanisms of brain injury in msud including : ( i ) neurotransmitter deficiencies and growth restriction associated with bcaa accumulation and ( ii ) energy deprivation through krebs cycle disruption associated with branched - chain ketoacid accumulation .
neonates will be normal at birth , presents after disease - free interval , usually within the 4 - 7 days of life with poor feeding , vomiting , poor weight gain , and increasing lethargy . in crisis ,
patient 's urine smells like maple syrup , secondary to the large accumulation of isoleucine .
classic appearing msud edema involving : cerebellar white matter , brain stem , globus pallidus , thalamus , cerebral peduncles , and corticospinal tracts .
dwi shows marked restriction and decreased apparent diffusion coefficient ( adc ) which indicates msud edema is an intracellular oedema ( cytotoxic oedema ) .
dwi is more sensitive than conventional mri in detecting msud brain alterations and it can become a useful tool for early diagnosis and follow - up of metabolic diseases in neonates .
kilicarlsan et al . , reported six cases with dwi in which the changes in all patients were reversed with treatment without evidence of volume loss or persistent tissue damage .
acute  metabolic rescue  to reverse cerebral edema may require hemodialysis during acute crisis to limit neurotoxicity / damage .
metabolically appropriate diet ( protein - modified ) minimizes severity and prevent deficiencies of essential amino acids .
if treated with low - bcaa diet and peritoneal dialysis within a few days from the onset of the symptoms , most patients survive and develop only minimal or no neurological deficits .
the changes in cell osmolarity and metabolism can reverse completely after metabolic correction in metabolic decompensated msud with clinical neurological improvement .
early imaging diagnosis of this condition can prevent the progress of neurological deficits and help in appropriate management of the disease .
 maple syrup urine disease ( msud ) is a rare autosomal recessive disorder of branched - chain amino acid metabolism . 
 the condition gets its name from the distinctive sweet odour of affected infants urine . 
 msud is caused by a deficiency of the branched - chain -ketoacid dehydrogenase enzyme complex , leading to accumulation of the branched - chain amino acids ( leucine , isoleucine , and valine ) and their toxic by - products ( ketoacids ) in the blood and urine . 
 imaging is characterestized by msud oedema affecting the myelinated white matter . 
 we present a neonate with classic type of msud and its imaging features on computed tomography , conventional magnetic resonance imaging , diffusion - weighted imaging , and magnetic resonance spectroscopy . 