Cerebral spinal fluid flow, venous drainage and spinal cord compression inachondroplastic children: impact of magnetic resonance findings for decompressive surgery at the cranio-cervical junction

In order to investigate the diagnostic properties of MRI of the brain and s pine in achondroplastic children with regard to decompressive surgery, 25 p atients were examined by conventional morphological and by "functional" ima ging of CSF flow and magnetic resonance angiography (MRA) of the veins and sinuses at the cranial base following a special protocol. The results were compared to those from age-matched controls and were correlated with each o ther and retrospectively with the neurological findings. Measurements of di stances and angulations at the cranio-cervical junction (CCJ) from MR scans showed similar values to those from conventional radiographs and CTs and t hus can be used without correction for spatial distorsion. Signs of cervica l medullary compression, myelomalacia and intramedullary cyst formation wer e found in six, seven and three children respectively. These alterations co rrelated significantly with each other (P < 0.05). Semiquantitative evaluat ion of CSF flow demonstrated interruption of CSF pathways at the CCJ, which correlated with CCJ narrowing (P < 0.05). MRA showed a significant narrowi ng of the jugular foramina with a variable compensatory enlargement of the emissary veins and a significant reduction of the total outflow area (P < 0 .01). There were no significant correlations between these MR changes and n eurological deficits. Conclusion Due to this unexpectedly poor correlation between magnetic reson ance and clinical findings in achondroplastic children, the present role of magnetic resonance in the clinical setting is limited to the demonstration of spinal cord compression in individual cases. In three of our patients w ith prominent neurological abnormalities, the severe changes demonstrated b y magnetic resonance imaging strongly supported the indication for surgical decompression.