MRI in Late-Onset Rasmussen Encephalitis: A Long-Term Follow-Up Study

Abstract

Late-onset Rasmussen encephalitis (LoRE) is a rare unihemispheric progressive inflammatory disorder causing neurological deficits and epilepsy. The long-term radiological evolution has never been fully described. We retrospectively analyzed the MR images of 13 LoRE patients from a total of 136 studies, and searched for focal areas of volume loss or signal intensity abnormality in grey matter or white matter. Each subject had a median of nine MRI studies (IQR 7-13). Frontal and temporal lobes were the most affected regions (13/13 and 8/13, respectively) and showed the greatest worsening over time in terms of atrophic changes (9/13 and 5/8, respectively). A milder cortical atrophy was found in the insular and parietal lobes. The caudate nucleus was affected in seven patients. Hyperintensities of grey matter and white matter on T2-WI and FLAIR images were observed in all patients, and transiently in eight patients. In two cases out of the latter patients, these transient alterations evolved into atrophy of the same region. Disease duration was significantly associated with signal abnormalities in the grey matter at last follow-up. LoRE MRI alterations are milder, and their progression is markedly slower compared to radiological findings described in the childhood form.

Keywords: MRI; Rasmussen encephalitis; epilepsy; late-onset.

Figure 1

Atrophy progression timeline for each patient. Patients’ age (years) increases from left to right. The shades of blue represent MRI controls and worsening of the degree of atrophy (according to numerical values deriving from the sum of the scores of different areas, as mentioned in Table 2). Yellow line represents clinical onset; red squares represent patients’ last clinical evaluation and red stars the surgical intervention. Patient 10 and 13 died after last follow-up due to non-neurological disease. F = frontal lobe; Ca = Caudate nucleus; T-I = temporoinsular lobes; P = parietal lobe; O = occipital lobe.

Figure 2

Atrophy and signal intensity changes in gray and white matter in relation to disease duration for 13 patients. Dashed lines represent linear regression for atrophy, GM SI changes and WM SI changes.

Figure 3

Patient 1, progression of the disease in 21 years. Axial (a–f) T2-weighted images at (a,b) 2 years, (c,d) 12 years and (d,e) 21 years from clinical onset. The disease slowly progressed over time, involving mainly frontobasal, insular, perisylvian and temporal left structures. At first MRI scan, only subtle atrophic changes could be seen in the perisylvian region (b).

Figure 4

Patient 2, progression of the disease in 21 years. Axial (a,b,d,e) T2-weighted images, coronal T1-inversion recovery (c) and T1-weighted image (f) at (a–c) 5 years (first MRI scan) and (d–f) 21 years from clinical onset (last MRI scan). The disease showed mild progression over time, involving left perisylvian region (including frontal, insular and temporal structures, arrowhead). Clinical symptoms progressed from seizures at onset to seizures, focal deficits, EPC, cognitive and behavioral disorders.

Figure 5

Patient 3, progression of the disease in 17 years. Axial (a,c,e,g) and coronal (d) T2-weighted images, coronal FLAIR (b,f,h) at (a,b) 2 years, (c,d) 5 years, (e,f) 10 years and (g,h) 17 years from clinical onset. In the first MRI (a,b), only subtle dilatation of left ventricle (arrowhead) and enlargement of frontal sulci could be seen. In (d), WM hyperintensity preceded the later atrophic change. Surgical treatment was performed at 6 years from onset, between (c,d) and (e,f); after surgery, EPC was controlled. At last follow-up, seizures and cognitive and behavioral disorders were present.

Figure 6

Patient 8, hyperintense signal intensities that preceded focal atrophy. Coronal FLAIR images at (a) 3 years, (b) 4 years, (c) 8 years and (d) 18 years from clinical onset. Focal atrophy limited to right perisylvian and insular region at the first MRI scan was followed by hyperintense alteration both of GM and WM in insula and frontal lobe (b,c, arrowhead). These alterations preceded worsening of the atrophic changes in the same areas.

Figure 7

Patient 13, with stable atrophy changes during 12 years of MRI controls. Axial FLAIR images (a–c) and coronal T2-weighted image (d) at a single timepoint, showing frontal, insular and temporal atrophy with SI involving subcortical WM and cortical GM. The patient has a 25 years of disease duration with clinical onset with focal deficits, seizures and cognitive disorders; at last follow-up, EPC and behavioral disorders are present.

Figure 8

Patient 1, cerebellar diaschisis. (a) Coronal T2-weighted image and (b) axial T1-weighted image, showing right cerebellar atrophy contralateral to the affected cerebral hemisphere.