Answer for BIR CoW 22 Oct 2023
Boomerang sign
Findings
T2/FLAIR hyperintensity noted extending throughout the splenium of corpus callosum with restricted diffusion.
Discussion
The boomerang sign is a radiological term used to describe a boomerang-shaped region of cytotoxic edema in the splenium of the corpus callosum. This phenomenon is typically observed in cytotoxic lesions of the corpus callosum (CLOCCs). It's associated with a variety of terms, including "transient lesions of the splenium of the corpus callosum," "mild encephalitis/encephalopathy with a reversible isolated SCC lesion (MERS)," "reversible splenial lesions," and "reversible splenial lesion syndrome (RESLES)." The term "cytotoxic lesions of the corpus callosum (CLOCCs)" is a more recent and precise description of this phenomenon. There are numerous potential causes associated with CLOCCs, including: 1. Seizures 2. Sudden withdrawal of antiepileptic medications 3. Metabolic disturbances such as electrolyte imbalances 4. Conditions like haemolytic-uremic syndrome, hepatic encephalopathy, hypoglycaemia, Marchiafava-Bignami disease 5. Osmotic demyelination 6. Malignancies 7. Infections 8. Central nervous system (CNS) malignancies 9. Drugs or toxins 10. Subarachnoid haemorrhage MRI findings These lesions demonstrate the expected features of cytotoxic edema: T1: hypointense T2: hyperintense DWI/ADC: restricted diffusion (ADC typically 300–500 x 10-6 mm2/s) T1 C+ (Gd): no enhancement In the context mentioned, the patient was found to be positive for Dengue IgM, indicating a Dengue virus infection. Dengue is traditionally considered a nonneurotropic virus, which means it is not known to directly infect the brain parenchyma or the meninges. However, there have been reports, such as the one by Mathew et al., that have drawn attention to transient splenial hyperintensities (TSH) as a feature of dengue encephalitis. This suggests that Dengue may have neurological implications. The key factors responsible for TSH in dengue encephalopathy are thought to involve a breach of the blood-brain barrier, osmotic and inflammatory injury, leading to intramyelinic edema or microvascular leak. Overall, the recognition of the boomerang sign and related radiological patterns can provide valuable insights into the underlying pathology and guide clinical decision-making in cases of Dengue virus-associated neurological complications.
References:
1. Sureshbabu S, Khanna L, Peter S, Patras E, Mittal GK. The brightening splenium: An imaging hallmark of dengue encephalopathy? Ann Indian Acad Neurol. 2016 Oct-Dec;19(4):516-517. doi: 10.4103/0972-2327.192385. PMID: 27994366; PMCID: PMC5144478. 2. Trivedi, S., Chakravarty, A. Neurological Complications of Dengue Fever. Curr Neurol Neurosci Rep 22, 515–529 (2022). https://doi.org/10.1007/s11910-022-01213-7
Findings
T2/FLAIR hyperintensity noted extending throughout the splenium of corpus callosum with restricted diffusion.
Discussion
The boomerang sign is a radiological term used to describe a boomerang-shaped region of cytotoxic edema in the splenium of the corpus callosum. This phenomenon is typically observed in cytotoxic lesions of the corpus callosum (CLOCCs). It's associated with a variety of terms, including "transient lesions of the splenium of the corpus callosum," "mild encephalitis/encephalopathy with a reversible isolated SCC lesion (MERS)," "reversible splenial lesions," and "reversible splenial lesion syndrome (RESLES)." The term "cytotoxic lesions of the corpus callosum (CLOCCs)" is a more recent and precise description of this phenomenon. There are numerous potential causes associated with CLOCCs, including: 1. Seizures 2. Sudden withdrawal of antiepileptic medications 3. Metabolic disturbances such as electrolyte imbalances 4. Conditions like haemolytic-uremic syndrome, hepatic encephalopathy, hypoglycaemia, Marchiafava-Bignami disease 5. Osmotic demyelination 6. Malignancies 7. Infections 8. Central nervous system (CNS) malignancies 9. Drugs or toxins 10. Subarachnoid haemorrhage MRI findings These lesions demonstrate the expected features of cytotoxic edema: T1: hypointense T2: hyperintense DWI/ADC: restricted diffusion (ADC typically 300–500 x 10-6 mm2/s) T1 C+ (Gd): no enhancement In the context mentioned, the patient was found to be positive for Dengue IgM, indicating a Dengue virus infection. Dengue is traditionally considered a nonneurotropic virus, which means it is not known to directly infect the brain parenchyma or the meninges. However, there have been reports, such as the one by Mathew et al., that have drawn attention to transient splenial hyperintensities (TSH) as a feature of dengue encephalitis. This suggests that Dengue may have neurological implications. The key factors responsible for TSH in dengue encephalopathy are thought to involve a breach of the blood-brain barrier, osmotic and inflammatory injury, leading to intramyelinic edema or microvascular leak. Overall, the recognition of the boomerang sign and related radiological patterns can provide valuable insights into the underlying pathology and guide clinical decision-making in cases of Dengue virus-associated neurological complications.
References:
1. Sureshbabu S, Khanna L, Peter S, Patras E, Mittal GK. The brightening splenium: An imaging hallmark of dengue encephalopathy? Ann Indian Acad Neurol. 2016 Oct-Dec;19(4):516-517. doi: 10.4103/0972-2327.192385. PMID: 27994366; PMCID: PMC5144478. 2. Trivedi, S., Chakravarty, A. Neurological Complications of Dengue Fever. Curr Neurol Neurosci Rep 22, 515–529 (2022). https://doi.org/10.1007/s11910-022-01213-7
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!