Specific Imaging Findings

MR findings in glutaric aciduria type 1 (GA-1) in addition to macrocephaly include characteristic bilateral small anterior poles of temporal lobes with poor opercularization and widened sylvian fissure, subdural collections, and basal ganglia lesions. Central gray matter abnormalities variably include symmetric T2 hyperintensities and volume loss of the basal ganglia and dentate nucleus, with thalamus occasionally involved. In acutely affected areas there may be reduced diffusivity and MRS reveals elevated lactate with decreased levels of NAA. Abnormalities are often seen within the midbrain with involvement of white matter structures, tegmentum and substantia nigra and sparing of red nuclei, producing the “giant panda face” sign. The white matter may be primarily involved in GA-1, characteristically in the periven-tricular regions with sparing of the U-fibers and optic radiations. Diffusion may be persistently reduced with decreased ADC values within the lesions. Additional findings include subependymal nodules and pseudocysts.

Pertinent Clinical Information

The disease has a variable clinical presentation and severity. Patients may remain asymptomatic or mildly affected, with macrocephaly only, or they may present with encephalopathic crises in infancy or childhood after an initially normal development. These episodic crises typically occur following a trigger event (infection, immunization, surgery) and are characterized by hypotonia, spasticity, dystonia, rigidity, orofacial dyskinesia, seizures, opisthotonic posturing, decreased consciousness, and coma. Recovery is slow and often incomplete.