Answer of July 2009

Clinical History:

A 10 year old boy presented to the Accident and Emergency department for poor eye vision. He was first noted by teacher that he cannot see the blackboard clearly and very slow in response. Occasionally he walks unsteadily but he can still attend the physical education lesson.

                        Fig 1 CT axial image                                            Fig 2 T1 weighted image

                    Fig 3 T2 weighted image                                   Fig 4 Diffusion weighted image

                             Fig 5 FLAIR image

Diagnosis:

Adrenoleukodystrophy

Discussion:

Leukodystrophies are inborn errors of metabolism that cause a defect in the production or maintenance of myelin as their primary manifestation. Among those, the "classic" form of adrenoleukodystrophy is an X-linked disease with a clinical onset between 5 and 7 years old, which includes behavioral problem, followed by progressive neurological deterioration and death within the ensuing 5 to 8 years.

The typical appearance on CT and MRI shows predominate posterior involvement of periventricular deep white matter, which appears symmetric and over time progress from posterior to anterior into the frontal lobes and from the deep white matter to the peripheral subcortical white matter.

MR spectroscopy shows abnormal spectra within both regions of abnormal signal and normal-appearing white matter of neurologically asymptomatic patients, which is characterized by slightly elevated concentrations of composite choline compounds. The increase of choline and myo-inositol reflects the onset of demyelination, whereas markedly elevated choline, myo-inositol, and glutamine in affected white matter are suggestive of active demyelination and glial proliferation. There is good correlation between MR spectroscopy metabolite ratios and a patient's clinical status. The more severe metabolic disturbances correspond to progressive demyelination, neuroaxonal loss, and gliosis leading to clinical deterioration and eventually death. There is also a very strong association between the presence of contrast enhancement on T1-weighted MR images and disease progression. The detection of MRS abnormalities before the onset of neurologic symptoms may help in the selection of patients for bone marrow transplantation and stem cell transplant. The spectral profiles can be used to monitor disease evolution and the effects of therapies.