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Neurologic Complications Of Osteogenesis Imperfecta.
Gérard Mohr, M.D., FRCS(C), Martin Black, M.D., FRCS(C), Max Aebi, M.D, FRCS(C). Divisions of Neurosurgery, Otolaryngology and Orthopedic Surgery, Sir Mortimer B. Davis Jewish General Hospital, Montreal, P.Q., Canada |
INTRODUCTION : Osteogenesis imperfecta (OI), a variant of osteochondrodysplasia, is characterized by severe bone fragility leading to frequent vertebral body fractures and malleable bones with progressive skeleton deformities, resulting in spinal stenosis, kyphoscoliosis, lumbo-sacral spondyolysis and cranial settling from progressive basilar invagination. NEUROLOGIC MANIFESTATIONS : The most devastating neurologic manifestation of OI consists in cranio-cervical instability from ligamental laxity at the C1-C2 level associated with progressive upward migration of the dens of the axis into the foramen magnum (basilar invagination), resulting in compression of the lower medulla-upper cervical cord with progressive tetraparesis and respiratory disturbances. Platybasia (flattening of the skull base) also occurs and produces stretching of the lower cranial nerves with hearing loss, swallowing disturbances, ataxia. In extreme cases the invaginated dens of C2 may compress the midbrain and produce hydrocephalus. SURGICAL MANAGEMENT : Operative treatment is usually restricted to the most severe cases and is extremely difficult since it requires a combination of posterior stabilization of the cranio-vertebral junction, as well as anterior decompression of the invaginated vertebral bone elements, mostly via transoral approaches. A representative case of a 49 year old patient with severe basilar invagination, cranial deformity and platybasia who developed severe tetraparesis, apneic spells and lower cranial nerve deficits is presented : treatment consisted in posterior fusion using plates and screw fixations from occiput to C6 followed ten days later by a transoral odontoidectomy (removal of the odontoid process of C2). Postoperatively the patient's neurologic condition improved to useful function of her upper limbs but she remained with inability to walk. CONCLUSIONS : Basilar invagination is responsible for the most severe neurologic complication of OI and its treatment remains challenging, requiring extensive procedures with multidisciplinary team approach aiming at anterior transoral decompression of the brainstem and posterior fusion to reduce cranial settling, which will inevitably progress. Adequate and timely surgical treatment will at least improve the quality of life of these severely affected patients. Reference: Proceedings of the 7th International Conference on Osteogenesis Imperfecta. Montreal, Canada, 1999. |