Radioisotope (RI) cisternography is a frequently performed diagnostic tool for neurological diseases such as meningitis, normal pressure hydrocephalus, and intracranial hypotension. RI cisternography is known as a very safe procedure, but should be performed with caution because lumbar puncture and injection of RI are invasive. Several reports have described complications following RI cisternography, such as post-puncture headache and aseptic meningitis. Conus medullaris syndrome (CMS) is a clinical neurological syndrome caused by various etiologies.2 Common symptoms of CMS include lower back pain, sensory loss in the leg and perineal region, paraparesis, voiding difficulty, and bowel and sexual dysfunction. Conus medullaris syndrome as a complication of RI cisternography has not yet been reported. We encountered four patients who developed CMS following RI cisternography. The clinical features and possible mechanisms of CMS caused by RI cisternography are discussed in this report. ABSTRACT:Objective: Conus medullaris syndrome (CMS) is a clinical neurologic syndrome caused by a conus medullaris lesion. CMS is a heterogeneous entity with various etiologies such as trauma or a space-occupying lesion. Multiple cases of CMS following spinal anesthesia have been reported, but CMS after radioisotope (RI) cisternography has not yet been reported. Methods: We present four patients who developed CMS after RI cisternography. Results: All experienced neurological deficits such as paraparesis, sensory loss, and urinary incontinence three to four days after RI cisternography. Two showed abnormalities on lumbar magnetic resonance imaging, and three had complete symptom resolution within ten weeks. Conclusions: The pathomechanism of the CMS is unclear, but we hypothesize that RI neurotoxicity might be responsible. It is possible that the use of low-dose 99m Tc-DTPA or an alternative diagnostic tool such as magnetic resonance cisternography could help to prevent this complication.RÉSUMÉ: Le syndrome du cône médullaire comme complication de la cisternographie isotopique. Objectif : Le syndrome du cône médullaire (SCM) est un syndrome neurologique causé par une lésion du cône médullaire. Le SCM est une entité hétérogène à étiologie variable, dont un traumatisme ou une lésion envahissante. Bien que de nombreux cas de SCM suite à une anesthésie rachidienne aient été rapportés, aucun cas de SCM n'a été rapporté après une cisternographie isotopique. Méthode : Nous rapportons les observations cliniques de quatre patients qui ont présenté une SCM après une cisternographie isotopique. Résultats : Tous ont présenté des déficits neurologiques tels une paraparésie, une perte sensitive et de l'incontinence urinaire trois à quatre jours après la cisternographie isotopique. Deux avaient des anomalies à la résonance magnétique lombaire et les symptômes avaient complètement disparu dix semaines plus tard. Conclusions : Le mécanisme de la SCM n'est pas connu. Nous émettons l'hypothèse que la neurotoxicité radioisotopique pourrait en être respons...

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