Asymmetric Iron Deposits in Basal Ganglia May Signal Early Neurodegeneration

Radiologists in Spain have reported a previously undescribed magnetic resonance imaging finding that they believe could act as an early warning sign of neurodegeneration: an asymmetric accumulation of paramagnetic substances, most likely iron, in the basal ganglia on the same side of the brain as a frontal lobe lesion. The observation, described in a Hypothesis and Theory article accepted for publication in Frontiers in Neurology, emerged when the team reviewed susceptibility weighted imaging (SWI) scans of patients with a history of frontal tumors, ischemic damage or previous surgery. The retrospective study covered 35 patients whose scans were re-examined specifically to determine whether this asymmetric deposition was present.

The underlying causes of the frontal pathology were diverse, ranging from tumors to ischemic injury and the effects of prior neurosurgery, with the frontal lobes as the predominant site of the primary lesion. According to the authors, the paramagnetic deposition tended to appear predominantly in the globus pallidus and the substantia nigra, both components of the basal ganglia circuitry, and always on the ipsilateral side relative to the supratentorial lesion. Forty-five percent of the patients presented symptoms that the authors associated with the magnetic resonance findings, although the abstract does not detail which symptoms or how the association was established.

A second observation lends the finding its proposed link to degeneration. Because the basal ganglia receive and modulate cortical output, the authors hypothesize that a frontal lesion can trigger transsynaptic degeneration, a process in which injury propagates across neuronal connections, and that this degeneration is accompanied by iron deposition in the connected basal ganglia nuclei. One detail the authors highlight as particularly suggestive is temporal.

In patients who had undergone surgery, the asymmetric deposition was absent from imaging studies performed before the intervention. That absence indicates the deposits were not a pre-existing feature of the patients' brains but appeared in relation to the acquired frontal pathology, which is consistent with the idea that the deposition develops as a consequence of the lesion rather than preceding it. The authors caution, however, that the entire report is framed as a hypothesis: they propose that the finding could represent an early magnetic resonance sign of transsynaptic degeneration with associated iron accumulation, not that this mechanism has been proven.

If the hypothesis withstands prospective testing, the authors argue the sign could become a biomarker and prognostic factor in patients with frontal cortex pathology, and could deepen understanding of basal ganglia pathophysiology. The evidence base for such claims remains limited by the study's design. The cohort was small, the review was retrospective rather than planned in advance, the etiologies were heterogeneous, and the final formatted version of the article had not yet been published at the time of this report, so the full methods and statistical analyses are not yet available for scrutiny.

The authors themselves note that all claims in the article are their own and do not necessarily represent the views of their affiliated institutions or the publisher. What the report does establish is a concrete, testable imaging observation: on SWI sequences, paramagnetic deposition in the globus pallidus and substantia nigra that is restricted to the side of a frontal lesion, appears after the lesion or its surgical treatment, and in nearly a third of cases coincides with early degeneration of the ipsilateral corticospinal tract.

Subject of Research: Asymmetric paramagnetic deposition in the basal ganglia on SWI MRI as a proposed early sign of neurodegeneration in patients with frontal brain lesions

Article Title: Unilateral deposition of paramagnetic substances in basal ganglia as early sign of neurodegeneration in magnetic resonance imaging

Article References: Saralegui Prieto, I., Ontañón Garcés, J. M., Fernandez-Ruanova, B., Tenorio-Laranga, J., & Vicente Olabarria, I. (2026). Unilateral deposition of paramagnetic substances in basal ganglia as early sign of neurodegeneration in magnetic resonance imaging. Frontiers in Neurology, 17, Article 1917665. https://doi.org/10.3389/fneur.2026.1917665

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1917665

Keywords: basal ganglia, iron deposition, magnetic resonance imaging, susceptibility weighted imaging, transsynaptic degeneration, globus pallidus, substantia nigra, frontal lobe lesions, corticospinal tract, neurodegeneration, biomarker, retrospective study