Natural history of the cervical high-intensity intramedullary lesion in achondroplasia.

STUDY DESIGN Retrospective cohort study. OBJECTIVE The cervical high-intensity intramedullary (CHII) lesion is a recognised finding in achondroplasia, manifesting as a focal area of increased T2W signal intensity in the upper cervical cord in the absence of cervical cord compression. The aim of this study is to determine the natural history of this abnormality. SETTING Tertiary referral spinal and orthopaedic hospital, UK. METHODS A retrospective review was undertaken of all patients with achondroplasia who had undergone at least one MRI study which included the cervical spine. Patient age at presentation was recorded and presence of the CHII lesion was determined on the sagittal T2W FSE sequence. For patients who had follow-up studies, presence of the CHII lesion was assessed for any change in morphology (resolution, partial resolution or enlargement). The development of new CHII lesions and presence of associated cord atrophy was also recorded. RESULTS The study group consisted of 40 patients (20 males, 20 females: mean age at first MRI of 32.6 years (range 7-66 years). The CHII lesion was identified in 19 (47.5%) cases and was associated with focal cord atrophy in 17 (85%) cases. There was no change or resolution of these lesions nor any associated cord compression. No new CHII lesions developed but progressive cord atrophy was evident. CONCLUSION The CHII lesion is seen in 47.5% of cases of achondroplasia. It appears to be a stable abnormality which does not progress or change its morphology. However, it does appear to be associated with progressive cord atrophy.