Nerve Root Enhancement and Elevated Cerebrospinal Fluid Protein in Four Patients With SOD1-Linked Amyotrophic Lateral Sclerosis

Introduction: The superoxide dismutase type 1 (SOD1) gene has been implicated in both sporadic and familial forms of amyotrophic lateral sclerosis (ALS). We report four ALS cases carrying pathogenic or likely pathogenic SOD1 variants, characterized by albuminocytologic dissociation and nerve root enhancement. Methods: We present the results of the diagnostic work-up, including lumbosacral magnetic resonance imaging (MRI) with gadolinium, electromyography (EMG), and cerebrospinal fluid (CSF) analysis. We also assessed the relationship between the albumin quotient (Q-Alb)—an index of blood–brain barrier (BBB) dysfunction—and the disease progression rate (DPR) in 12 SOD1-linked ALS patients (including the four described above) and in a cohort of 137 non-genetic ALS (NgALS) cases. Results: The four patients presented with spinal onset (progressive lower limb weakness). The EMG ultimately showed diffuse subacute neurogenic changes, while CSF analysis revealed albuminocytologic dissociation. Lumbosacral MRI demonstrated contrast enhancement of the cauda equina roots. Immunomodulatory treatment was administered due to suspected immune-mediated neuropathy, but all patients continued to deteriorate. Genetic testing revealed pathogenic or likely pathogenic variants in the SOD1 gene, confirming the diagnosis of ALS. CSF Q-Alb and protein levels were similarly distributed between SOD1-linked and NgALS patients. Q-Alb and CSF protein levels showed a positive correlation with DPR in SOD1-linked patients (Rho = 0.625, p = 0.03; Rho = 0.755, p = 0.005), but not in NgALS patients. Conclusion: Albuminocytologic dissociation and nerve root enhancement may occur in SOD1-related ALS, expanding the spectrum of atypical ALS phenotypes.