MRI Brain and Orbits 11/9/2004  

Clinical History:  Neurofibromatosis 1.  Follow up study.

Technique:  MRI of the brain is performed on the 1.5 Tesla scan utilizing sagittal T1, axial TSE T2, axial FLAIR, axial MT, axial diffusion and post-contrast axial T1 images of the brain.  In addition, thin-section images through the orbits were obtained with axial T1, axial and coronal TSE T2, and post-contrast axial and coronal T1 sequences.

Comparison:  MRI brain and orbits 8/26/04

Findings:  compared to the prior study there is a change in the appearance of the large hypothalamic/chiasmatic mass lesion.

There remains a large mass in the region of the hypothalamus and optic chiasm which demonstrates heterogeneous signal.  There is an increase in the size of the nonenhancing cystic/semisolid components within the mass especially posteriorly and along the right lateral margin.  There has been a change in the enhancement pattern also.  Some of the thick, nodular enhancing areas which were noted on the prior study are not visualized on the current study.  The largest AP dimension of this mass is approximately 4.7 cm.  The largest cranio-caudad dimension of this mass is approximately 3.4 cm.  The largest transverse dimension of this mass is approximately 3.3 cm vs 3 cm on the previous study.  There is mild interval increase in the transverse dimension of the mass.  However the overall size of the mass in the AP and craniocaudal dimensions remains almost unchanged.

The large hypothalamic/chiasmatic mass is seen again to displace the carotid arteries slightly laterally and anteriorly, to deviate the A1 segments of the anterior cerebral arteries anteriorly, to widen the interpeduncular cistern, and to push upward on the third ventricle and downward on the pituitary gland.  The chiasm itself cannot be distinguished from this mass.  This mass demonstrates heterogeneous but avid contrast enhancement, including ring enhancement around the central portions (low on T1 and high on T2) of the mass

Stable scattered foci of T2 hyperintensity are noted in the bilateral medial temporal lobes, glovi pallidus and thalami, in keeping with spongiform dysplasia of neurofibromatosis.  There is mild asymmetry noted in the hippocampi with a larger right hippocampus demonstrating mild T2/flair hyperintensity.  The prominent extaaxial CSF spaces/arachnoid cysts seen anterior to the temporal remain unchanged.

There remains moderate expansion of the pons, greater on the left than the right, with increased T2 and decreased T1 weighted signal and extension into the cerebellar and cerebral peduncles bilaterally.  The signal abnormality also extends into the cerebellar hemispheric white matter (more so on the left than on the right), and inferiorly into the medulla.  No significant enhancement is seen in this region.

The lateral ventricles are normal in size and configuration.  As noted, there is mass effect upon the third ventricle, although the aqueduct and fourth ventricle appear normal.  There is no extraaxial fluid collections.  There is no intracranial hemorrhage.

There remains marked expansion and tortuosity of the intraorbital optic nerves, greater on the left than the right.  The left optic nerve demonstrates stable enhancement following gadolinium administration.  There is minimal interval increase in the thickness of the intraorbital portion of the right optic nerve.  

The major intracranial vessels are patent.  New left maxillary sinus mucosal thickening is noted.  The remainder of the paranasal sinuses and mastoid air cells are grossly unremarkable.  

Impression:   

1. Interval increase in size of the large hypothalamic/chiasmatic mass, especially in the transverse dimension, and change in the morphology and enhancement patter, as detailed.
2. Spongiform changes of neurofibromatosis are seen within the bilateral medial temporal lobes, globi pallidus, thalami, midbrain, pons and the cerebellum, stable.  The pons remains prominently asymmetric and therefore closer follow-up is recommended to exclude the possibility of a low grade glioma.
3. Minimal interval increase in the thickness of the intraorbital portion of the right optic nerve.  Stable change of NF 1 in the left optic nerve.