A 46-year-old woman whose gradually worsening neurological problems defied easy classification has provided nuclear medicine specialists with a striking imaging lesson. Writing in EJNMMI Reports, clinicians report that brain scans in this patient revealed subtle cortical hypometabolism on fluorine-18 fluorodeoxyglucose PET, yet a complete absence of on-target binding on iodine-123 ioflupane SPECT, a pattern pointing to profound degeneration of presynaptic dopaminergic nigrostriatal neurons. Genetic testing subsequently revealed two variants in the SPG7 gene, identifying her condition as spastic paraplegia type 7.
The FDG PET scan showed an unspecific pattern of regional cortical hypometabolism, with more pronounced striatal hypometabolism. The FP-CIT SPECT showed no on-target binding at all, a finding the authors interpret as profound degeneration of the presynaptic dopaminergic nigrostriatal neurons rather than a subtle or partial deficit.
Clinically, the patient presented with frequent falls, a gradually progressive bipyramidal syndrome with gait ataxia, dysphagia, urinary urgency and incontinence, low mood with disturbed emotional regulation, and a mild asymmetric hypokinetic rigid syndrome. She also had blurry vision, asymmetrical ptosis and abnormal vertical saccades.
Nuclear medicine neuroimaging is becoming increasingly important for the diagnosis and differential diagnosis of Parkinson’s disease, atypical parkinsonian syndromes and rarer neurological movement disorders. In this context, the authors argue, the case expands the still limited literature on molecular neuroimaging in SPG7-associated parkinsonism. In this patient, however, no clear structural correlate explaining the clinical presentation was identified on MRI.
The dissociation between the two functional imaging modalities is the technical heart of the report. FP-CIT SPECT, by contrast, revealed a complete absence of binding, a finding the authors interpret as evidence of profound neurodegeneration of the presynaptic nigrostriatal dopaminergic pathway in SPG7.
Treatment response added a further practical observation.
The authors are careful about generalisation. Because this is a single-case report, they state that the observed PET and SPECT abnormalities should not be regarded as disease-specific imaging biomarkers at present. The value of the report lies instead in alerting clinicians that SPG7 can present with a complex parkinsonian phenotype and that molecular imaging may reveal unexpected patterns of nigrostriatal degeneration in such patients.
Subject of Research: Molecular neuroimaging findings in parkinsonism associated with spastic paraplegia type 7
Article Title: Subtle hypometabolism on [18F]FDG-PET, yet absent [123I]FP-CIT SPECT binding in a patient with spastic paraplegia type 7
Article References: Henssen, D., Radder, D. L. M., Snijders, A. H., & Arens, A. I. J. (2026). Subtle hypometabolism on [18F]FDG-PET, yet absent [123I]FP-CIT SPECT binding in a patient with spastic paraplegia type 7. EJNMMI Reports, 10(1), Article 39. https://doi.org/10.1186/s41824-026-00323-6
Image Credits: AI Generated
DOI: 10.1186/s41824-026-00323-6
Keywords: spastic paraplegia type 7, SPG7, FDG PET, FP-CIT SPECT, parkinsonism, dopamine transporter, nigrostriatal degeneration, nuclear medicine, genetic testing, movement disorders, levodopa, case report
News Source: Cassandra Pierce. (October 29, 2026). Rare Genetic Spastic Paraplegia Case Shows Complete Loss of Dopamine Transporter Binding on Brain SPECT. Scienmag.
