NEURORADIOLOGY


Case 39 :
A 4-year old boy presented with delayed mental growth, speech disturbances and abnormal size of head. Physical examination revealed macrocephaly. There was incomplete achievement of mental milestones. History did not reveal any evidence of accidental or non-accidental head injury.
What is the diagnosis?
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Discussion

Computed tomographic (CT) scan of brain revealed bilateral frontotemporal atrophy, bilateral enlarged sylvian fissures and few hypodensities in the lentiform nuclei.
Biochemical investigations clinched the diagnosis of Glutaric aciduria type 1 (GA-1).
GA - 1 is an autosomal recessive inborn error of lysine, hydroxylysine and tryptophan metabolism that results from a deficiency of glutaryl-CoA dehydrogenase. The diagnosis of GA-1 is made by the presence of increased urinary glutaric acid and 3-hydroxyglutaric acid and is confirmed by a deficiency or absence of glutaryl-CoA dehydrogenase in cultured fibroblasts. Because the levels of urine glutaric acid and 3-hydroxyglutaric acid may be normal or only slightly elevated especially when the patient is clinically stable, glutaryl-CoA dehydrogenase should be measured whenever GA-1 is strongly suspected from clinical and/or radiological findings.
Common features on neuroimaging include increased spaces anterior to the frontotemporal lobes (vs. frontotemporal atrophy) wide sylvian fissures, (giving a "bat-wing" formation) and prominent interhemispheric fissures (1). There may be diffuse hypodensity of the basal ganglia. A prominent clinical feature of infants and children with glutaric aciduria type 1 is macrocephaly (3) .
The fact that the radiographic findings are present 3 months before the onset of clinical symptoms indicates that the metabolic defect can affect the brain before the onset of clinical symptoms.
Metabolic disorders are often considered as a differential diagnosis in abusive head trauma. Glutaric aciduria type 1, in particular, is mentioned because of the presence of subdural effusions on imaging in this disorder (4).


References

1. Brismar J, Ozand PT. CT and MR of the brain in glutaric acidemia type 1: a review of 59 published cases and a report of 5 new patients. AJNR 1995;16:675-683.
2. Hartley LM, Khwaja OS, Verity CM. Gluteric aciduria type 1 and nonaccidental head injury. Pediatrics 2001;105 :174-176.
3. Drigo P, Piovan S, Battistella PA, et al. Macrocephaly, subarachnoid fluid collection, and glutaric aciduria type 1. J Child Neurol 1996;11:414-417.
4. Morris AAM, Hoffmann GF, Naughten ER, et al. Gluteric aciduria and suspected child abuse. Arch Dis Child. 1999;80:404-405.


Contribution :

Dr Santosh Rai, Consultant Radiologist, Manipal Hospital, Mangalore