Extensive neuroimaging of a transient lesion in the splenium of the corpus callosum

Abstract

Transiently high intensities in the splenium of the corpus callosum (SCC) on T2-weighted magnetic resonance imaging (MRI) are increasingly reported [1]; however, their pathophysiology remains unknown. Here, we report various neuroimaging findings to clarify their pathophysiology. Case reportA 23-year-old man had fever of 5 daysÕ duration. He was hospitalized because of visual hallucinations (VH) and delirium. There was no previous history of neurological diseases, alcoholism or malnutrition. Chest X-ray and laboratory tests revealed left bronchopneumonia. A blood vitamin B1 level was normal. The serum arginine vasopressin (AVP) level was elevated (4.9 pg/ml) with normal osmolarity (307 mOsm/l) on admission but was normal (1.5 pg/ml) on day 5. Serum autoantibodies were negative. Routine cerebrospinal fluid (CSF) findings were normal, with normal myelin basic protein level and negative oligoclonal immunoglobulin G (IgG) bands. Infection of mycoplasma and various viruses including herpes simplex virus was excluded by serum and/or CSF antibody titers or polymerase chain reaction (PCR). We performed various neuroimaging analyses on day 2. T2-weighted MRI revealed a high intensity in the SCC, which showed negative enhancement with a single dose of gadolinium-DTPA, decreased water diffusivity on diffusion weighted MRI, and normal fractional anisotropy (FA) on tensor MRI (Fig. 1). Magnetic resonance spectroscopy (MRS) showed normal N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios in the voxel mainly containing the SCC. Perfusion MRI and single photon emission computed tomography (SPECT) showed hypoperfusion in both occipital lobes with normal T2-wieghted and fluid attenuated inversion recovery (FLAIR) imaging, suggesting the diminished metabolic status. Electroencephalogram (EEG) revealed no epileptic discharges. The SCC lesions completely disappeared after 3 months. DiscussionThis is the first report to describe in detail neuroimaging findings of a transient SCC lesion. Diffusion tensor MRI permits the use of FA to evaluate the intrinsic directionality of water diffusion within fibrous structures of myelinated neural axons; ex. decreased FA mostly indicates neuroaxonal degeneration [2]. Normal FA in our patient may reflect intramyelinic edema, non-degenerative intercellular edema speculated previously [3], since the diffusion directionality of water trapped between myelin layers may not differ from that within fibers. The lesion reversibility also supports intramyelinic (intercellular) edema despite showing decreased water diffusion revealed by apparent diffusion coefficient (ADC) maps, which normally indicates frequently irreversible cytotoxic (intracellular) edema [4]. MRS revealed normal NAA/Cr and Cho/Cr ratios, reflecting no neuroaxonal damage and demyelination, respectively. By contrast, low NAA/Cr ratios are seen in ischemia and high Cho/Cr ratios in tumors and demyelinating diseases [5]. All of these findings support a non-degenerative change.Our SPECT and perfusion MRI findings indicated a tran...

Mild Encephalitis/Encephalopathy With a Reversible Splenial Lesion: Evaluation by Diffusion Tensor Imaging -Three Case Reports-

“…7,8) In some cases, including our Cases 2 and 3, reversible lesions detected with diffusion-weighted imaging extended into the entire corpus callosum and deep white matter as well as the splenium of the corpus callosum. 5,12) Moreover, in Case 2, the initial MR imaging showed lesions in the whole corpus callosum and symmetric centrum semiovale lesions, and MR imaging on day 4 revealed lesions only in the splenium, as previously mentioned in a similar case.…”

“…3,5,8,[10][11][12][13] MERS is defined as a radiologically reversible lesion in the corpus callosum involving at least the splenium. Patients with MERS have reversible symptoms such as impermanent conscious disturbance and seizures, and generally recover completely within a week.…”

“…3,5,8,10,12,13) The findings in the early phase disappear mostly within a few days with the resolution of symptoms. 3,5,8,10,12,13) MERS has been increasingly reported, but only one case of MERS has involved decrease in size of the splenial lesion over 5 months in T 2 -weighted imaging. 2) In contrast, most hyperintense lesions on diffusion-weighted imaging with decreased ADC values, including cerebral infarction and contusional lesions due to trauma, are irreversible.…”

“…Diffusion tensor imaging findings for MERS have been reported previously, but detailed data of the early and delay phases were not included. 5,8) The present study evaluated diffusion tensor imaging in three cases of MERS to better understand the etiology of the disease.…”

Splenial and White Matter Lesions Showing Transiently-reduced Diffusion in Mild Encephalopathy Monitored with MR Spectroscopy and Imaging

“…2 MR spectroscopy (MRS) of MERS measured simultaneously following the initial MR imaging examination has been reported. 3,4 Here, we report follow-up MR imaging and spectroscopy of clinically mild encephalopathy with lesions with transiently reduced diffusion in the splenium and white matter in which initial MRS appeared normal subsequent MR imaging and MRS showed abnormality for 90 days, and neurological symptoms did not reappear after 5 years.…”