Study Links Rare Disease to Brain Fluid Clearance Failure

Researchers have identified convergent evidence suggesting that Skogholt’s disease, a rare maternally inherited neurodegenerative syndrome, is driven primarily by a failure in the brain’s fluid clearance system rather than direct neuronal degeneration. Published in Fluids and Barriers of the CNS, the study presents multimodal data from a cohort of 40 individuals, including 16 affected patients and 24 controls, to test whether primary dysfunction of the choroid plexus can reshape cerebrospinal fluid dynamics and biomarker profiles independently of overt brain tissue loss. The findings indicate that the condition may represent a prototype for disorders defined by primary clearance failure, offering a new perspective on how solute transport mechanisms influence neurodegenerative biomarkers.

The study focused on the choroid plexus, a structure within the brain responsible for producing cerebrospinal fluid and regulating the transport of solutes between the blood and the central nervous system. Previous proposals suggested that dysfunction in this area could reduce fluid production and impair the clearance of brain solutes, but the in vivo consequences of such failure remained poorly defined. By examining Skogholt’s disease as a natural human model, the team aimed to determine if sustained clearance failure could alter biomarker profiles without the typical signs of widespread neurodegeneration.

The assessment involved a multimodal evaluation of the 40 participants, who had a mean age of 57.8 years. The researchers utilized dynamic contrast-enhanced MRI to perform a model-free analysis of contrast washout from the choroid plexus, providing a direct measure of clearance dynamics. Additionally, diffusion MRI was employed to evaluate tissue properties, while the team analyzed relationships between cerebrospinal fluid and plasma biomarkers.

The results revealed a distinct choroid plexus-centred clearance defect in the affected individuals. Patients exhibited markedly reduced choroid plexus volume, with a Cohen’s d effect size of 2.64, indicating a substantial difference from the control group. Furthermore, the time taken for contrast to wash out of the choroid plexus was significantly prolonged, with a time-above-half-peak effect size of 4.9. Crucially, these changes occurred without disruption of the cerebral parenchymal blood–brain barrier, suggesting that the defect was localized to the fluid production and transport mechanisms rather than a general breakdown of vascular integrity.

Diffusion MRI findings provided further insight into the nature of the tissue changes. The study observed widespread reductions in mean diffusivity, with effect sizes of approximately 1.0 in white matter and between 0.85 and 0.89 in the cortex. This pattern suggests that the brain tissue in Skogholt’s disease patients remains structurally intact, reinforcing the conclusion that the primary pathology lies in the clearance system rather than in the neurons themselves.

Biomarker analysis highlighted a marked dissociation between cerebrospinal fluid and plasma levels. In the affected individuals, cerebrospinal fluid concentrations of tau, amyloid beta species, beta-trace, neurofilament light, and glial fibrillary acidic protein were elevated by up to 12-fold. In contrast, plasma levels of these markers were either normal or reduced. This divergence indicates that the elevated cerebrospinal fluid levels most parsimoniously reflect impaired clearance of these solutes from the brain to the blood, rather than an increase in their production. The findings underscore the importance of considering clearance capacity when interpreting biomarker profiles in neurodegenerative contexts.

Genetic analysis provided a potential molecular basis for the observed phenotype. Mitochondrial genome sequencing identified a rare homoplasmic variant in the MT-RNR2 gene, specifically the m.1681G > A mutation. This variant segregates with the disease in the studied population and is absent as a homoplasmic variant in public mitochondrial reference datasets. The mutation localizes to a highly conserved structural element of the mitochondrial 16S ribosomal RNA, supporting its candidacy as a pathogenic variant. Directional shifts in trace metals further suggested impaired ATP-dependent transport, aligning with the hypothesis of mitochondrial dysfunction affecting energy-dependent clearance processes.

The study concludes that these findings provide in vivo evidence for choroid plexus dysfunction in a maternally inherited disorder, with convergent data supporting a mitochondrial etiology. The associated reduction in cerebrospinal fluid production and impaired blood–cerebrospinal fluid barrier transport substantially alters biomarker profiles in the absence of cortical atrophy or blood–brain barrier disruption. The authors suggest that dynamic contrast-enhanced MRI washout and cerebrospinal fluid–plasma coupling could serve as complementary in vivo markers of clearance capacity. While the variant requires further functional validation, the study offers a compelling model for understanding how primary clearance failures can drive neurodegenerative-like biomarker signatures without direct neuronal degeneration.

Subject of Research: Multimodal evidence for choroid plexus-centred clearance failure in Skogholt’s disease

Article Title: Skogholt’s disease: multimodal evidence for choroid plexus–centred clearance failure

Article References: Selnes, P., Jarholm, J., Vila-Sanjurjo, A., Aaseth, J., Gonzalez-Ortiz, F., MacIntosh, B., Grimstad, K., Sørensen, H., Utnes, E., Bjørnerud, A., Geier, O., Holmøy, T., Fladby, T., Viñas, N. O., Hudson, G., & Taylor, R. W. (2026). Skogholt’s disease: multimodal evidence for choroid plexus–centred clearance failure. Fluids and Barriers of the CNS. https://doi.org/10.1186/s12987-026-00853-y

Image Credits: AI Generated

DOI: 10.1186/s12987-026-00853-y

Keywords: Skogholt’s disease, Choroid plexus, Cerebrospinal fluid, Brain clearance, Neurodegeneration, Biomarkers, Mitochondrial DNA, MRI, Blood-brain barrier, Genetics, Skogholt, disease