The Subarachnoid Fluid Space in Achondroplastic Spinal Stenosis: The Surgical Implication

Abstract

The tragic outcome of decompressive laminectomy in patients with achondroplastic spinal stenosis has been reported (1, 2, 3, 4). Our experience at the Johns Hopkins Medical Institutions supports the observations in the literature. The poor outcome is caused mainly by the extremely stenotic canal, which makes adequate decompression difficult (5, 6, 7, 8, 9, 10, 11). Furthermore, the degree and extent of the spinal stenosis were frequently not clearly delineated by conventional myelography. However, intrathecal enhanced CT provides not only superb bony detail but also delineation of the soft-tissue content of the spinal canal (12). The relationships between the spinal cord and its surrounding subarachnoid space are also well demonstrated. This paper reports the depth of the subarachnoid fluid space surrounding the spinal cord at the cervical and thoracic levels, measured from the intrathecal enhanced axial CT images of 11 adult achondroplastic patients. It describes a modified decompressive laminectomy technique devised by the authors (S.U.) that has been applied in over 20 cases of achondroplastic spinal stenosis. It has helped to prevent the infliction of undue trauma on the neural tissue during the surgical manoeuvers.