INTRODUCTION Granulomatous inflammation is a distinctive ...

Figure 20. Sarcoidosis axial T2W and gadoliniumenhanced
T1W brain images with multiple, extensive
white-matter periventricular and subcortical enhancing
lesions, some of which are large (arrowed). ( Zajicek et
al., 1999)
White matter lesions can mimic lesions seen in multiple sclerosis (Smith et al., 1989). In contrast to
multiple sclerosis, linear enhancement along blood vessels in the region of white matter changes is
seen in neurosarcoidosis. These signal changes along the Virchow-Robin spaces suggest that
lesions infiltrate the brain through perivascular Virchow-Robin spaces, and are believed to be the
result of infarctions caused by granulomatous vasculitis (Corse and Stem, 1990).
Non inhancing brain parenchmal lesions is best seen on the MRI T2 and FLAIR studies and is
seen as confluent or nonconfluent hyperintense patches, that do not show contrast enhancement
and have no mass effect. These lesions tend to occur in the periventricular white matter but may
also occur in the brain stem and basal ganglia and the corticomedullary junction. Periventricular
lesions are nonspecific and can occur in association with multiple sclerosis, hypertension, and
vasculitis. Theoretically, they can result from periventricular granulomas or from small areas of
infarction caused by granulomatous angiopathy. The exact nature of these lesions has not been
identified in the literature. Symptomatic improvement usually did not correspond to improvement
on MR imaging studies. This behavior differed from that of enhancing brain lesions for which
symptoms often correlated with imaging findings and symptomatic improvement correlated with
regression on MR images. These facts also imply that the nonenhancing brain parenchymal
lesions and the enhancing lesions have different pathophysiologic mechanisms (Greg et al., 1999).
Involvement of cranial nerves have been described in association with sarcoidosis. Most
frequently, the facial nerve is involved clinically. Imaging, however, revealed that the optic nerve
and/or chiasma are the most frequently affected cranial nerves (Zajicek et al., 1999).
Spinal Cord and Nerve Root Involvement manifest as cord swelling, with increased signal
intensity on T2-weighted images and a pattern of enhancement on T1-weighted contrast-enhanced
images (Figure 21), that predominates in the periphery of the cord but includes patchy multifocal
enhancement of the cord. Imaging findings are thus nonspecific and can mimic multiple sclerosis,
cord tumor, vacuolar myelopathy, TB, or fungal infection (Gideon and Mannino, 1996).