Cervical MRI of subacute myelo-optico-neuropathy

Study design: Case study.

Objectives: Subacute myelo-optico-neuropathy (SMON) is a severe neuro-degenerative disorder caused by poisoning due to over-dose and prolonged oral administration of clioquinol; this disorder was more frequent during 1957-1970. It is characterized by axonal degeneration and gliosis in the cervical gracile fasciculus. Recently, copper-deficient myelo-neuropathies presenting similar symptoms (that is, painful dysesthesia/paresthesia in the lower limbs, ataxia, spastic paraplegia, autonomic disorders and visual impairment) were reported. Magnetic resonance imaging (MRI) of these patients detected T2-weighted hyperintensities in the cervical spinal cord. An unbalanced zinc-copper metabolism was suggested as one of the candidate pathogenesis of clioquinol toxicity because of its metal-chelating ability. The aim of this study was to present MRI findings of old SMON patients and to compare them with those of current copper-deficient myelo-neuropathies.

Setting: Japan.

Methods: We conducted and analyzed cervical and brain MRIs of seven old SMON patients who contracted the disorder during the 1960s. Serum iron, magnesium, copper, zinc and ceruloplasmin levels were also measured.

Results: Cervical T2-weighted MRIs showed mild volume loss and faint hyperintensities in the dorsal columns, which might reflect residual gliosis. Brain fast fluid-attenuated inversion-recovery images and tractography were normal. Current levels of serum copper and zinc were within almost normal ranges.

Conclusion: Although fainter, the abnormal T2 MRI signals we observed were similar to and occurred in the same locations as those reported in copper-deficient myelo-neuropathy patients. We suggest that these findings are useful to study the mechanism of clioquinol toxicity before using it to treat neurodegenerative diseases such as Alzheimer's disease.