Pure Cystic Lesions of the Conus Medullaris: A British Single Centre Study

Pure cystic lesions at the conus medullaris comprising ependymal cyst of ventriculus terminalis (ECVT), intramedullary arachnoid cyst (IMAC) and neurenteric cyst (NEC) are rare benign cysts. Compared to IMAC and NEC often requiring surgery, ECVT is a normal anatomic phenomenon rarely needing more than MRI surveillance. However, the literature predominantly reports surgical cases. We present our experience and discuss management strategies.

A retrospective review was conducted identifying adults ≥16 years with ECVT, IMAC and NEC at the National Hospital for Neurology and Neurosurgery, London, United Kingdom (2012-2026). Presenting symptoms using the de Moura Batista/Ganau classification were recorded. Patients with previous trauma or radiological evidence of tumour tissue, Chiari malformations or spinal dysraphism were excluded. Non-parametric Mann-Whitney U or Kruskal-Wallis H tests were used.

Twenty-two patients were included. An associative trend was observed between the cyst size and the symptoms, P=0.221. Eight patients underwent cyst fenestration ± cysto-subarachnoid shunt placement. Histology was available for six patients revealing NEC in three, IMAC in one and inconclusive in two. Six patients experienced radiological recurrences where two with previously diagnosed NEC underwent surgical re-exploration. Partial recovery was observed in four patients. Another four experienced worsening neurology especially patients with recurrent NEC, P=0.220. Fourteen patients underwent MRI surveillance and all but one remained stable with a median follow-up of 33 months.

Pure cystic lesions rarely require surgery, especially the radiologically presumed ECVTs. Unless the cyst causes clinical symptoms by exerting pressure on the neural tissue, a conservative management should be chosen.