Reversible Splenial Lesion Syndrome with Some Novel Causes and Clinical Manifestations

Cytotoxic lesions of the corpus callosum: a systematic review

OBJECTIVES

Cytotoxic lesions of the corpus callosum (CLOCC) are a common magnetic resonance imaging (MRI) finding associated with various systemic diseases including COVID-19. Although an increasing number of such cases is reported in the literature, there is a lack of systematic evidence summarizing the etiology and neuroimaging findings of these lesions. Thus, the aim of this systematic review was to synthesize the applied nomenclature, neuroimaging and clinical features, and differential diagnoses as well as associated disease entities of CLOCC.

MATERIALS AND METHODS

A comprehensive literature search in three biomedical databases identified 441 references, out of which 324 were eligible for a narrative summary including a total of 1353 patients.

RESULTS

Our PRISMA-conform systematic review identifies a broad panel of disease entities which are associated with CLOCC, among them toxic/drug-treatment-associated, infectious (viral, bacterial), vascular, metabolic, traumatic, and neoplastic entities in both adult and pediatric individuals. On MRI, CLOCC show typical high T2 signal, low T1 signal, restricted diffusion, and lack of contrast enhancement. The majority of the lesions were reversible within the follow-up period (median follow-up 3 weeks). Interestingly, even though CLOCC were mostly associated with symptoms of the underlying disease, in exceptional cases, CLOCC were associated with callosal neurological symptoms. Of note, employed nomenclature for CLOCC was highly inconsistent.

CONCLUSIONS

Our study provides high-level evidence for clinical and imaging features of CLOCC as well as associated disease entities.

CLINICAL RELEVANCE STATEMENT

Our study provides high-level evidence on MRI features of CLOCC as well as a comprehensive list of disease entities potentially associated with CLOCC. Together, this will facilitate rigorous diagnostic workup of suspected CLOCC cases.

KEY POINTS

• Cytotoxic lesions of the corpus callosum (CLOCC) are a frequent MRI feature associated with various systemic diseases. • Cytotoxic lesions of the corpus callosum show a highly homogenous MRI presentation and temporal dynamics. • This comprehensive overview will benefit (neuro)radiologists during diagnostic workup.

Deciphering seizure semiology in corpus callosum injuries: A comprehensive systematic review with machine learning insights

INTRODUCTION

Seizure disorders have often been found to be associated with corpus callosum injuries, but in most cases, they remain undiagnosed. Understanding the clinical, electrographic, and neuroradiological alternations can be crucial in delineating this entity.

OBJECTIVE

This systematic review aims to analyze the effects of corpus callosum injuries on seizure semiology, providing insights into the neuroscientific and clinical implications of such injuries.

METHODS

Adhering to the PRISMA guidelines, a comprehensive search across multiple databases, including PubMed/Medline, NIH, Embase, Cochrane Library, and Cross-ref, was conducted until September 25, 2023. Studies on seizures associated with corpus callosum injuries, excluding other cortical or sub-cortical involvements, were included. Machine learning (Random Forest) and deep learning (1D-CNN) algorithms were employed for data classification.

RESULTS

Initially, 1250 articles were identified from the mentioned databases, and additional 350 were found through other relevant sources. Out of all these articles, 41 studies met the inclusion criteria, collectively encompassing 56 patients The most frequent clinical manifestations included generalized tonic-clonic seizures, complex partial seizures, and focal seizures. The most common callosal injuries were related to reversible splenial lesion syndrome and cytotoxic lesions. Machine learning and deep learning analyses revealed significant correlations between seizure types, semiological parameters, and callosal injury locations. Complete recovery was reported in the majority of patients post-treatment.

CONCLUSION

Corpus callosum injuries have diverse impacts on seizure semiology. This review highlights the importance of understanding the role of the corpus callosum in seizure propagation and manifestation. The findings emphasize the need for targeted diagnostic and therapeutic strategies in managing seizures associated with callosal injuries. Future research should focus on expanding the data pool and exploring the underlying mechanisms in greater detail.

Case report: Reversible splenial lesion syndrome caused by diquat poisoning

Diquat (DQ), chemically known as 1,1 '-ethylene-2,2' -bipyridine, is a non-selective herbicide for leaf removal and drying. It has toxic effects on central nervous system cells, and toxic neurological lesions include axonal degeneration and pontine myelolysis. At the same time, DQ can also affect the activity of dopaminergic nerve cells through oxidative stress, causing degeneration and reducing dopamine uptake. With the increasing application of DQ in agricultural production, the clinical reports of neurotoxicity caused by acute DQ poisoning are also increasing. At present, DQ rapid-phase-related toxic encephalopathy mainly involves the pons, midbrain, basal ganglia, thalamus and other brain regions. However, this case is unusual in that the lesion mainly involved the splenium of the corpus callosum. It is also the first time to be reported.

Transient splenial lesion syndrome in bipolar-II disorder: a case report highlighting reversible brain changes during hypomanic episodes

Background

Reversible splenial lesion syndrome (RESLES) is a rare neurological condition characterized by temporary abnormalities in the splenium of the corpus callosum, which has been reported in mental disorders. Previous studies on bipolar disorder (BD) primarily focused on aspects such as brain structure and function, neurochemical changes, and genetics. However, there have been no studies reporting the occurrence of this syndrome during hypomanic episodes and its disappearance during the remission phase in bipolar disorder type 2 (BD-II).

Case presentation

We present a case report of a 30 years-old female patient with BD-II who exhibited symptoms of RESLES during a hypomanic episode. The patient, with a 12 years psychiatric history, has experienced recurrent depressive episodes initially, with the first hypomanic episode occurring 8 years ago. During this period, this patient made several visits to the outpatient clinic to have her medications adjusted due to repeated suicide attempts. This time, she was admitted to our hospital with a second hypomanic episode due to drug withdrawal during pregnancy. The RESLES was observed on her brain magnetic resonance image, and it was alleviated after treatment with lithium carbonate and quetiapine until achieving remission.

Conclusion

We present the first report of identifying RESLES in BD-II with hypomanic episodes, which subsequently disappears during the remission phase. Our case report highlights a potential association between BD and RESLES, emphasizing the need for future studies to explore the underlying mechanisms connecting these two conditions in greater depth.

Reversible splenial lesion after surgery for distant arteriovenous malformation: a case report

Isolated lesions of the corpus callosum are rare and may represent permanent but also transient responses to various pathology termed "reversible splenial lesion syndrome" (RESLES) when in light of relevant clinical presentation. We present the first case of the RESLES after elective surgery for distant arteriovenous malformation (AVM), followed by a slight speech disturbance and MRI verified small, oval, well-circumscribed area of apparent cytotoxic edema in the center of the corpus callosum splenium, which completely resolved within 15 days. Surgery for AVM is followed by the complex adaptation to a new vascular pattern, RESLES might develop, and should be suspected.

Cytotoxic lesions of the corpus callosum during the course of ketotic hyperglycemia revealing type I diabetes: A case report

Cytotoxic lesions of the corpus callosum are lesions secondary to different medical conditions. Radiologically, lesions are identified on magnetic resonance imaging as a hyperintense signal on diffusion-weighted imaging and decreased apparent diffusion coefficient values of the splenium of corpus callosum. Signal changes are reversible in almost totality of the cases. Previous cases of cytotoxic lesions of the corpus callosums have been associated with several metabolic disturbances, but ketotic hyperglycemia has never been reported. We here discussed the case of 28-year-old patient with complex visual hallucinations presenting with cytotoxic lesions of the corpus callosums and type I diabetes. Treatment of hyperglycemia was followed by full clinical recovery and complete regression of the radiological abnormalities at 3-month follow-up. Elevated levels of circulating pro-inflammatory mediators associated with ketotic hyperglycemia in type I diabetes support an implication of cytokines in the pathophysiology of the cytotoxic lesions of the corpus callosums.

Reversible Splenial Lesion Syndrome as a Challenging Casuistry

The corpus callosum plays a vital role in brain function. In particular, in the trunk of the corpus callosum, in the course of various diseases, there may be temporary, reversible changes (reversible splenial lesion syndrome (RESLES)), as well as partially reversible and irreversible changes. This article discusses the differentiation of RESLES and other conditions with changes in the corpus callosum lobe, as well as the accompanying clinical symptoms. Moreover, a case report of a patient in whom the above changes appeared in the nuclear magnetic resonance (NMR) image is presented. A 20-year-old patient with the diagnosis of Ehlers-Danlos syndrome type VI was admitted to the psychiatric ward in an emergency because of psychomotor agitation, refusal to take food and fluids, delusional statements with a message, grandeur, and auditory hallucinations. In the performed magnetic resonance imaging (MRI) of the brain, the corpus callosum non-characteristic in T2-weighted images revealed a hyperintensive area, which was significantly hyperintensive in diffusion magnetic resonance (DWI) sequences and in apparent diffusion coefficient (ADC) sequences with reduced signal intensity and no signs of bleeding. The hypothesis of subacute ischemic stroke of the corpus callosum was presented. In the control MRI of the brain, changes in the corpus callosum completely regressed, thus excluding an ischemic etiology and favoring the diagnosis of RESLES. During hospitalization, the patient experienced significant fluctuations in mental status, with the dominant symptoms typical of the paranoid syndrome in the form of disturbances in the course and structure of thinking and perception, and a clear and stable improvement was obtained after the administration of long-acting intramuscular olanzapine. Taking into account the clinical and radiological picture, the age of the episode, the rapidity of the disease development, the persistence of its clinical symptoms after the withdrawal of radiological changes in the brain NMR image, as well as the significant improvement in the clinical condition after the introduction of antipsychotic drugs, the final diagnosis was made of schizophrenia.

An Equivocal SCC Lesion—Antiepileptic-Induced CLOCC

We present a case of a woman who reported to the emergency unit due to recurrent episodes of severe headache and collapse. MRI examination revealed no relevant findings apart from small meningioma of the right parietal region. The patient was diagnosed with epilepsy and received outpatient treatment, which was changed due to poor toleration. A follow-up MRI was performed which revealed an isolated, focal lesion of the splenium of the corpus callosum. The patient underwent extensive laboratory testing and antiseizure medications were started again. Another MRI indicated substantial regression of the splenium of the corpus callosum (SCC) lesion. Both the complete clinical image and results of the diagnostic evaluation spoke in favor of cytotoxicity of the corpus callosum associated with anti-epileptic drug treatment. Pathologies involving the corpus callosum include congenital, demyelination, infection, neoplasm, trauma and vascular changes. Isolated, non-specific lesions of the splenium of corpus callosum usually indicate multiple sclerosis; however, other pathologies should be considered. Anti-epileptic drugs may evoke cytotoxic lesions of the corpus callosum (CLOCCs).

Transient blindness associated with mild encephalitis/encephalopathy with a reversible splenial lesion (MERS): a case report and review of literature

Background

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a clinical-radiological syndrome that can be related to infectious and non-infectious conditions. The most prominent neurological symptoms are disturbance of consciousness, abnormal speech, delirious behavior, seizures, muscle weakness, ophthalmoplegia, facial nerve paralysis and headache. Here we report the case of a child with MERS presenting with the unusual symptom of bilateral transient blindness.

Case presentation

A 4-year-old female patient, with a history of fever, abdominal pain, loss of appetite and cough lasted for a few days, experienced 3 episodes of transient bilateral loss of vision with difficulty in walking. Her physical examination showed absence of focal neurological and meningeal irritation signs, although responsiveness was slightly impaired. The ophthalmologic evaluation, including a fundus oculi examination, was negative.

The electroencephalogram showed slow activity in the temporo-occipital regions, more evident in the right hemisphere. A lumbar puncture was performed and cerebrospinal fluid analysis revealed normal glycorrhachia, cell counts, protein levels and IgG index.

Magnetic resonance imaging of the brain showed a signal alteration in the splenium of the corpus callosum, without contrast enhancement. This finding was suggestive of a reversible cytotoxic lesion. Empiric antiviral treatment with acyclovir and intravenous dexamethasone was initiated. Polymerase chain reaction search for neurotropic viral nucleic acid sequences in the cerebrospinal fluid was negative, while a low number of HHV-6 DNA copies was detected in the blood.

Electroencephalograms were repeated in the following days, showing a progressive normalization of the pattern. The child was discharged without symptoms after 10 days of treatment with oral corticosteroids. After 40 days, brain magnetic resonance imaging showed a complete normalization of the signal alteration in the splenium of the corpus callosum.

Conclusion

Transient blindness was reported as an initial symptom of MERS in a few children. To date, there is no evidence of effective treatment methods. Nonetheless, MERS diagnosis provides pediatricians with valuable prognostic information in order to reassure patients and their families about the good outcome of this disease.