Acute Metabolic Crisis in Maple Syrup Urine Disease, a Rare but Life-Threatening Neurocritical Care Emergency: Case Report

Technical Summary: Acute Metabolic Crisis in Maple Syrup Urine Disease

Problem Statement
Maple Syrup Urine Disease (MSUD) is a rare, autosomal recessive disorder caused by a deficiency in the branched-chain alpha-keto acid dehydrogenase enzyme complex. This deficiency prevents the metabolism of branched-chain amino acids (BCAAs)—leucine, isoleucine, and valine—leading to toxic accumulations during periods of stress, illness, or dietary changes. While MSUD is typically managed in neonates, acute metabolic crises in adults are rare and poorly characterized. The authors highlight a critical gap in the literature regarding the management of severe adult MSUD crises, particularly those involving life-threatening neurological complications such as cerebral edema, seizures, and coma. Furthermore, existing management guidelines for adults are heterogeneous, and the efficacy of Continuous Renal Replacement Therapy (CRRT) in this specific adult demographic remains under-documented.

Methodology
This study presents a single case report of a 49-year-old male with a history of MSUD (diagnosed via newborn screening) who was admitted with metabolic encephalopathy, agitation, and poor oral intake. The patient's condition deteriorated following the initiation of Lamotrigine and a concurrent respiratory infection, leading to sepsis (Staphylococcus epidermidis bacteremia) and an acute MSUD crisis.

The management approach was multidisciplinary, involving neurocritical care, genetics, metabolism, nutrition, nephrology, and pharmacy teams. Key interventions included:

• Diagnostic Monitoring: Continuous EEG (cEEG) to detect non-convulsive seizures; Head CT and MRI to assess cerebral edema and diffusion restriction; daily monitoring of BCAA levels.
• Therapeutic Interventions:
  • Metabolic Control: Initial attempts at dietary modification (BCAA-restricted high-protein diet with IV lipids) were discontinued due to aspiration risk. The patient was subsequently placed on a blended metabolic formula via tube feeding, supplemented with specific BCAAs (valine and isoleucine) to prevent deficiency while managing total load.
  • Seizure Management: Focal seizures detected on cEEG were treated with midazolam infusion, followed by Keppra and propofol sedation.
  • Cerebral Edema Management: Hyperosmolar therapy (3% hypertonic saline) was utilized.
  • Metabolic Clearance: Continuous Renal Replacement Therapy (CRRT) was initiated and titrated specifically to lower elevated BCAA levels that were refractory to dietary management.
  • Infection Control: Antibiotic therapy was tailored based on culture results (ESBL E. coli and S. epidermidis), utilizing agents such as linezolid, Zosyn, daptomycin, and ertapenem.
  • Supportive Care: The patient underwent tracheostomy and PEG tube placement due to prolonged intubation and airway protection needs. Sedation was carefully downtitrated to manage autonomic storming.

Key Results

• Neurological Imaging: MRI revealed extensive diffuse restricted diffusion (DWI hyperintensity) with an ADC correlate throughout the bilateral cerebral cortices, caudate, putamen, and thalami. These findings were initially concerning for irreversible neurologic injury.
• Metabolic Response: CRRT effectively reduced BCAA levels, which had remained elevated despite dietary modifications.
• Clinical Outcome: Despite the profound MRI findings and a 25-day ICU stay, the patient regained consciousness, demonstrated motor responses, and eventually returned to his pre-admission neurological baseline. He was decannulated and discharged home, walking independently.
• Seizure Control: Seizures were successfully suppressed, and the patient was weaned from sedation without recurrent seizure activity.

Significance and Claims
The authors claim this case report offers several critical insights for the management of adult MSUD:

1. CRRT Efficacy: This is presented as the first case involving hyperosmolar and CRRT management for a severe CNS MSUD crisis in an adult. The authors assert that CRRT is a safe and effective method for correcting metabolic disturbances in adults when dietary measures fail.
2. Prognostic Caution: The case challenges the prognostic utility of severe MRI findings in MSUD crises. The authors emphasize that extensive diffusion restriction, while alarming, does not necessarily predict poor neurologic recovery and should not be misclassified as anoxic injury.
3. Multidisciplinary Necessity: The successful outcome is attributed to intense collaboration among diverse specialists to manage complex drug interactions, amino acid intake, and metabolic fluctuations.
4. Neurological Complications: The report underscores the severity of neurological complications in MSUD crises, including non-convulsive seizures, respiratory failure, and cerebral edema, necessitating neurocritical care expertise.

The paper concludes that while adult MSUD crisis management remains challenging due to a lack of standardized guidelines, a coordinated, multidisciplinary approach utilizing CRRT can lead to full neurological recovery even in the presence of severe radiographic abnormalities.