Intramedullary inflammatory mass dorsal to the Klippel–Feil deformity: error in development or response to an abnormal motion segment?

Study design: Case study on a 45-year-old female with progressive weakness and paresthesias in her lower extremities and a magnetic resonance image of an intramedullary mass at the level of C5–6 and a Klippel–Feil (KF) deformity ventral to the lesion. Objective: Present an interesting case of an intramedullary mass coexisting with a ventral KF deformity with review of the medical literature on intramedullary masses and cervical spine biomechanics. Setting: New York city, New York, USA. Methods: Case study with discussion of neurosurgical and neuropathological findings and review of the literature. Results: The patient underwent open neurosurgical excisional biopsy of the intramedullary mass which revealed a non-neoplastic inflammatory mass that slowly resolved with medical management. Conclusions: While no definitive etiology was found in this case we offer two interesting mechanisms: (1) maldevelopment of the cervical spine or (2) this inflammatory mass is in response to an abnormal motion at the level of the Klippel–Feil.