Lowered cerebral glucose utilization in amyotrophic lateral sclerosis

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease.
• Understanding the underlying pathophysiology of ALS is crucial for developing effective treatments.
• Positron emission tomography (PET) offers insights into brain metabolism.

Purpose of the Study:

• To investigate regional cerebral metabolic rates for glucose (rCMRGlc) in patients with ALS using PET.
• To differentiate metabolic patterns between ALS subtypes and other motor neuron diseases.
• To explore the relationship between metabolic changes, clinical presentation, and disease progression.

Main Methods:

• Analysis of 19 studies involving 12 ALS patients and 11 age-matched controls.
• Utilized [18F]2-fluoro-2-deoxy-D-glucose PET scans to measure rCMRGlc.
• Correlated metabolic data with clinical signs, disease duration, and follow-up scans.

Main Results:

• Significantly lower cortical rCMRGlc observed in ALS patients with upper motor neuron signs compared to controls (p < 0.01).
• Hypometabolism correlated with disease duration, affecting cortex and basal ganglia, but not cerebellum.
• ALS patients with lower motor neuron disease or prior poliomyelitis showed normal rCMRGlc.
• Repeat PET scans in 3 of 4 patients showed decreased rCMRGlc correlating with clinical worsening.

Conclusions:

• Generalized cortical hypometabolism in ALS with upper motor neuron signs suggests neuronal nonfunction, not just cell death.
• ALS with upper motor neuron involvement exhibits distinct cortical functional deficits compared to lower motor neuron-predominant ALS or other motor neuron disorders.
• These findings highlight the complexity of anatomoclinical correlations in ALS and suggest broader cortical involvement than previously recognized.