Orphanet Journal of Rare Diseases | Clinical Presentation and Treatment Outcomes of Cerebral Edema in Adult Maple Syrup Urine Disease Patients

Recommend:

This paper reviews the diverse clinical presentations of cerebral edema in adult patients with Maple Syrup Urine Disease (MSUD) and highlights the challenges of early recognition and treatment. It provides detailed imaging and biochemical data from multiple cases, emphasizing the importance of multidisciplinary management, and offering new insights for clinical research and diagnosis of rare diseases.

 

Literature Overview

The article entitled 'Cerebral edema in maple syrup urine disease: spectrum of clinical presentation and treatment outcomes', published in the Orphanet Journal of Rare Diseases, summarizes and reviews the clinical manifestations, treatment, and prognosis of cerebral edema during acute metabolic decompensation in 7 adult patients with MSUD. The study reveals that some patients may develop severe cerebral edema and brain herniation even with low plasma leucine levels, highlighting the complexity of clinical monitoring and intervention.

Background Knowledge

Maple Syrup Urine Disease (MSUD) is an autosomal recessive neurometabolic disorder caused by a deficiency in the branched-chain α-ketoacid dehydrogenase complex (BCKD), leading to the accumulation of branched-chain amino acids (BCAAs) and their ketoacid derivatives in the body, which can cause neurotoxicity. The global incidence of MSUD is approximately 1 in 185,000, but it is significantly higher in populations with consanguineous marriages, such as the Old Order Mennonite population in the United States (1 in 400), and neonatal screening data from Saudi Arabia show an incidence of 1 in 15,816. During acute metabolic decompensation, patients may experience a wide range of neurological symptoms, from irritability and confusion to seizures, coma, and even death. Cerebral edema is a severe complication of MSUD, with pathophysiological mechanisms involving leucine's competitive inhibition of other amino acids entering the brain, disruption of neurotransmitter synthesis, and interference with Na+/K+-ATPase activity, which disturbs brain water homeostasis. Additionally, the accumulation of BCAAs and ketoacids in the brain can lead to redox imbalance, mitochondrial energy metabolism dysfunction, and lactate buildup, further exacerbating cerebral edema. Currently, studies on MSUD-related cerebral edema are primarily focused on pediatric patients, while adult cases often present with more insidious and non-specific symptoms, increasing the difficulty of early detection and intervention. This study fills the gap in the management of acute cerebral edema in adult MSUD patients and highlights the importance of multidisciplinary collaboration, imaging evaluation (particularly MRI), and timely hemopurification therapy.

 

A practical tool for quickly mapping DNA or RNA sequences to the genome.

Learn More

 

Study Methods and Experimental Design

This retrospective study included 7 adult MSUD patients (≥14 years old) who were admitted to a tertiary care center due to encephalopathy symptoms between 2016 and 2023. Clinical manifestations, laboratory data, imaging findings, treatment strategies, and outcomes were collected from medical records. All patients received intravenous dextrose saline and BCAA-free nutritional support, with some undergoing continuous renal replacement therapy (CRRT) or hemodialysis. The study also documented genetic mutations, baseline plasma leucine levels, and neuropsychiatric status.

Key Findings and Insights

• Of 10 episodes of encephalopathy, 9 were accompanied by cerebral edema, with 2 patients developing severe brain herniation and dying even after plasma leucine levels improved
• Some patients remained fully conscious with a GCS score of 15/15 despite having extremely high plasma leucine levels (e.g., patient 1 had plasma leucine of 1938 µmol/L) during the acute phase
• Cerebral edema may develop silently without apparent neurological symptoms, indicating the need for high clinical vigilance
• CT scans may fail to detect cerebral edema in early stages; MRI combined with diffusion-weighted imaging (DWI) is more suitable for early diagnosis and monitoring
• There is no direct correlation between plasma leucine levels and brain leucine concentrations or the severity of cerebral edema, suggesting that plasma amino acid monitoring alone is insufficient for assessing the risk of brain injury
• Adult MSUD patients face greater challenges in maintaining dietary compliance due to psychosocial issues or cognitive impairments, resulting in a higher frequency of metabolic decompensation compared to pediatric patients
• CRRT or hemodialysis can effectively reduce plasma leucine levels, but studies on their application in adults remain limited
• Cerebral edema may persist even after plasma leucine levels decrease, necessitating close imaging follow-up
• Optic nerve edema and visual impairment can be a presentation of acute metabolic decompensation; fundoscopy and OCT are recommended during acute episodes
• Treatment strategies should include hypertonic saline, BCAA-free nutritional support, and, when necessary, neurosurgical decompression procedures

Significance and Future Directions

This study is the first systematic description of the diverse clinical presentations of acute cerebral edema in adult MSUD patients, emphasizing the complementary roles of plasma amino acid monitoring and neuroimaging evaluation. Future research should further explore the molecular mechanisms linking cerebral edema with plasma BCAA levels, develop non-invasive techniques for intracranial pressure monitoring, and optimize multidisciplinary management protocols for adult MSUD patients.

 

Evaluates the pathogenic potential of gene variants and provides a reference for variant functional analysis.

Learn More

 

Conclusion

This study highlights the complexity and insidious nature of cerebral edema in adult MSUD patients, urging clinicians to maintain a high index of suspicion when encountering non-specific neuropsychiatric symptoms such as hallucinations, irritability, and headache. Despite reductions in plasma leucine levels, some patients may still develop severe neurological injury, underscoring the necessity of post-treatment imaging follow-up. The study also identifies current limitations in the management of adult MSUD, such as the lack of adult metabolic specialists and unfamiliarity with the disease among multidisciplinary teams, which often results in treatment delays. Future efforts should focus on improving long-term monitoring strategies, enhancing dietary compliance interventions, and standardizing the use of acute-phase imaging and hemopurification therapies to improve survival and neurological outcomes in adult MSUD patients.

 

Raashda A Sulaiman, Ruqaiah Altassan, Randa Alshammari, Mohamed Al-Owain, and Zuhair Al-Hassnan. Cerebral edema in maple syrup urine disease: spectrum of clinical presentation and treatment outcomes. Orphanet Journal of Rare Diseases.