Atlanto-Occipital Fusion, Basilar Impression, and Block Vertebrae Associated with Intraspinal Neurofibroma, Meningocele, and von Recklinghausen's Disease

The object of this paper is to present an unusual case in which a serious congenital skeletal deformity at the base of the skull was associated with an intraspinal cervical neurofibroma and meningocele at the same site, in a patient with von Recklinghausen's disease. Error in embryological segmentation of the cervical spine is not characteristically associated with either intraspinal neurofibroma or meningocele, nor is intraspinal neurofibroma a common feature of von Recklinghausen’disease (neurofibromatosis of peripheral nerves remote from the central nervous system). von Recklinghausen's disease is, however, a congenital condition, often hereditary and sometimes familial. Penfield (10) made a distinction between multiple neurofibromatosis of von Recklinghausen and the solitary neurofibromas which occur on the nerve roots within the spinal canal and cranial vault. Grinker (3), on the other hand, points out that there is frequent association of acoustic neuromas, particularly, with peripheral neurofibromatosis. Among other less common sites of associated central nervous system neuromas he mentions the vagus, trigeminal, and hypoglossal cranial nerves. Furthermore, as Grinker mentions, gliomatous tumors of the spinal cord or brain, especially of the optic chiasm and tracts, may be associated with generalized neurofibromatosis. If as a result of congenital bony dysplasia the bony arch surrounding the spinal canal remains partially open, the exposed meninges and cord become attached to superficial tissues and meningocele develops. This may occur at any level. In the case presented below the roentgen features were typical of segmental deformity, i.e., atlanto-occipital fusion with basilar impression and block vertebrae. Roentgenologic recognition and neurological examination were followed by surgical correction of the deformed bony arch, excision of an intraspinal neurofibroma, and drainage of the meningocele. The principal roentgen features which may be observed in atlanto-occipital fusion are as follows : 1. Fusion of the atlas to the base of the skull. The neural arches and articular condyles are fused to the occipital bone although a vestigial or “remnant” joint may persist. 2. Distortion and constriction of the foramen magnum. Accessory eminences and ossicles may encroach upon and distort the foramen. 3. Lateral or forward dislocation of the atlas on the axis. 4. Nonsegmentation below the fused atlas. This is of common occurrence, and torticollis may be present if the block vertebrae are asymmetrical. 5. Basilar impression (elevation of the floor of the posterior fossa around the foramen magnum because of a funnel-shaped deformity.) This is frequently present. The neuropathological features associated with the above abnormalities are: 1. Compression and destruction of the spinal cord secondary to bony impingement upon and constriction of the foramen magnum. 2. Impaired vascular supply to the spinal cord. 3. Adhesions.