Transient lesions of the splenium (also known as mild encephalitis / encephalopathy with a reversible isolated SCC lesion (MERS)) are occasionally encountered and may be due to a number of underlying aetiologies.
Transient lesions of splenium are only really appreciable on MRI where they have two distinct patterns 4:
- well circumscribed, small, oval lesions in the midline within the substance of the corpus callosum
- more extensive ill defined irregular lesions extending throughout the splenium and into the adjacent hemispheres (boomerang sign)
The smaller well circumscribed lesions is the typical lesion seen in the setting of seizures / cessation of anitepileptic medication, whereas the larger lesion is more typical of other aetiologies.
Aeitiologies include 1-5:
- antiepileptic drug usage and sudden cessation
- posterior reversible encephalopathy syndrome (PRES)
- Marchiafava-Bignami disease
- diffuse axonal injury (DAI)
- AIDS dementia complex
- hemolytic-uremic syndrome with encephalopathy
Unlike other causes of splenial lesions, the small transient lesions of the splenium seen in epiliepsy and antiepileptic drug cessation / use do not demonstrate convincing signs or symptoms of hemispheric disconnection, such as pseudo-neglect, alien hand syndrome, apraxia of the left hand, agraphia, alexia, visual apraxias etc...) 4.
These lesions tend to demonstrate the following signal characteristics 4:
- T1: hypointense
- T2: hyperintense
- DWI / ADC: restricted diffusion
- T1 C+: no enhancement
Treatment and prognosis
The prognosis generally depends on the underlying cause, but in the setting of eplilepsy or antiepilepic drug related lesions it is very good.
- 1. Takanashi J, Barkovich AJ, Shiihara T et-al. Widening spectrum of a reversible splenial lesion with transiently reduced diffusion. AJNR Am J Neuroradiol. 2006;27 (4): 836-8. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 2. Bulakbasi N, Kocaoglu M, Tayfun C et-al. Transient splenial lesion of the corpus callosum in clinically mild influenza-associated encephalitis/encephalopathy. AJNR Am J Neuroradiol. 2006;27 (9): 1983-6. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Singh P, Gogoi D, Vyas S et-al. Transient splenial lesion: Further experience with two cases. Indian J Radiol Imaging. 2010;20 (4): 254-7. doi:10.4103/0971-3026.73531 - Free text at pubmed - Pubmed citation
- 4. Malhotra HS, Garg RK, Vidhate MR et-al. Boomerang sign: Clinical significance of transient lesion in splenium of corpus callosum. Ann Indian Acad Neurol. 2012;15 (2): 151-7. doi:10.4103/0972-2327.95005 - Free text at pubmed - Pubmed citation
- 5. Cho JS, Ha SW, Han YS et-al. Mild encephalopathy with reversible lesion in the splenium of the corpus callosum and bilateral frontal white matter. J Clin Neurol. 2007;3 (1): 53-6. doi:10.3988/jcn.2007.3.1.53 - Free text at pubmed - Pubmed citation
- 6. Kimura. International Journal of Clinical Pediatrics. 2012; . doi:10.4021/ijcp51w
- 7. Tada H, Takanashi J, Barkovich A et-al. Neurology. 2004;63 (10): . doi:10.1212/01.WNL.0000144274.12174.CB
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Mild encephalitis / encephalopathy with a reversible isolated SCC lesion (MERS)||✗|
|Transient lesions of the splenium||✗|
|Mild encephalitis / encephalopathy with a reversible isolated SCC lesion||✗|