J Neurosurg (Pediatrics 5) 100:530–531, 2004
Bone growth causing ventriculoperitoneal shunt malfunction in a patient with osteopetrosis Case report RACHEL GROSSMAN, M.D., AND ZEEV FELDMAN, M.D. Division of Pediatric Neurosurgery, The Chaim Sheba Medical Center, Tel Hashomer, Israel Osteopetrosis is an inherited skeletal condition of defective osteoclastic resorption of bone resulting in increased bone density. Osseous changes occur most severely at the base of the skull. Important clinical symptoms include cranial nerve palsies due to uni- or bilateral obliteration of cranial nerve foramina including deafness, facial paralysis, and optic nerve compression. Thickening of the skull and progressive diminution of the cranial capacity may lead to elevation of intracranial pressure, papilledema, and hydrocephalus. The authors present an unusual case of a patient with osteopetrosis in whom a ventriculoperitoneal shunt became obstructed at its exit from the skull by the developing bone mass. To the best of their knowledge, this has not been described.
KEY WORDS • osteopetrosis • hydrocephalus • ventriculoperitoneal shunt • pediatric neurosurgery
STEOPETROSIS, also known as marble bone disease, is an inherited skeletal condition of defective osteoclastic resorption of bone resulting in increased bone density. There are three clinical groups: infantile– malignant autosomal recessive, which is fatal within the first few years of life in the absence of effective therapy; intermediate autosomal recessive, which appears during the first decade of life but does not follow a malignant course; and autosomal dominant, with a full life expectancy but associated with many orthopedic problems.3 Bone changes occur most severely at the skull base. Important clinical symptoms are cranial nerve palsies due to uni- or bilateral obliteration of the cranial nerve foramina.1 In many cases deafness early in infancy occurs when the progressive bone mass encroaches on the middle ear cavities and auditory nerve canals.2 Transient facial nerve palsy occurs somewhat later, and bilateral facial paralysis is usually permanent in adulthood.1 Optic nerve compression causes acute and chronic visual loss, and visual field defects usually develop later in the course of the disease. Other ocular symptoms are strabismus, nystagmus, and exophthalmos. Thickening of the skull and progressive diminution of the cranial capacity may lead to elevation of ICP, papilledema, hydrocephalus, convulsions, and mental retardation. We present an unusual case in which a VP shunt was obstructed at its exit from the skull by the devel-
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Abbreviations used in this paper: CT = computerized tomography; ICP = intracranial pressure; VP = ventriculoperitoneal.
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oping bone mass in a patient with osteopetrosis. To the best of our knowledge, this has not been previously described. Case Report History. This 9-year-old boy with osteopetrosis was referred to the emergency room after experiencing gradually worsening headaches and vomiting for several hours. He suffered from blindness, deafness, and bilateral facial nerve paralysis. A VP shunt had been inserted 19 months earlier to treat gradual visual impairment related to increased ICP and obliteration of the optic nerve foramina by a cranial mass. The opening pressure during the procedure was more than 40 cm H2O, and a Sophysa valve (Sophysa, Costa Mesa, CA) was inserted. Six months later he underwent a rescue operation to decompress the optic canal when he experienced a rapid loss of vision; however, the procedure failed to save his vision. Examination. The patient had a large head, a broad flat nasal bridge, and hypertelorism. He was blind, suffered bilateral facial nerve paralysis, and almost complete bilateral hearing loss was exhibited. The shunt reservoir was umbilicated, and the valve was found to be set for a high pressure. Noncontrast CT scanning (Fig. 1 left) revealed diffuse hyperostosis with thickened calvaria that measured up to 3.8 cm in some areas. All foramina were significantly narrowed and occlusion of the shunt catheter was observed (Fig. 1 center). The bone area around the valve notch and the previous burr hole were noted to be J. Neurosurg: Pediatrics / Volume 100 / May, 2004
Osteopetrosis and VP shunt malfunction
FIG. 1. Preoperative CT scans. Left: The skull bones have thickened, and the size of the frontal horns of the lateral ventricles has increased. Center: Bone window scan revealing bone overgrowth and occlusion of the shunt catheter. Right: Bone window scan demonstrating thickening of bone area around the valve (arrow).
very thick, and the notch was hardly seen (Fig. 1 right). Compared with his last CT scan, which had been acquired a few months earlier, there was a significant increase in the size of the frontal horns of the lateral ventricles. Treatment, Operation, and Clinical Course. After resetting the valve to a low pressure and initiating acetazolamide therapy, the patient felt better for a few hours and stopped vomiting; however, the symptoms recurred, and he was taken to the operating room for revision of the shunt. The bone compressed the shunt valve and the proximal catheter; it had grown over the valve and truncated the proximal part of the ventricular catheter, causing the obstruction. The thick bone around the valve and the ventricular catheter was drilled off. After releasing the ventricular catheter, an opening pressure of 45 cm H2O was measured. After shunt revision, the patient improved, and postoperative CT scanning demonstrated drained ventricles. He was discharged from the hospital 2 days later. Discussion Patients with osteopetrosis can present with variable degrees of neurological deficits due to cranial nerve compression including deafness, visual loss, and facial nerve paralysis. Cerebrovascular complications include intracerebral hemorrhage, subdural hematoma, cerebral venous thrombosis, and subarachnoid hemorrhage, which have been attributed to a narrowed carotid canal or vertebral canal, or even occlusion of the middle cerebral artery.4 Chronic headache, convulsions, and mental retardation, as well as optic neuropathy, are occasionally present. They are considered to be a result of increased ICP
J. Neurosurg: Pediatrics / Volume 100 / May, 2004
due to progressive diminution of the cranial capacity. We found no report involving patients with osteopetrosis who were treated with a VP shunt. In this case the shunt valve and the proximal part of the ventricular catheter were compressed by the developing bone mass, causing its obstruction. Because bone formation is continuous, it is clear to us that at some point in the future proximal shunt obstruction will recur; however, we do not believe that we will be able mechanically to eliminate the compression of the shunt components by the growing bone because we cannot change the course of cranial nerve compression by the obliteration of their respective foramina. References 1. Fujiwara S, Tsurumi Y, Kodama N: [Sibling case of osteosclerosis with cranial nerve symptoms.] No Shinkei Geka 10: 1217–1222, 1982 (Jpn) 2. Miyamoto RT, House WF, Brackmann DE: Neurotologic manifestations of the osteopetroses. Arch Otolaryngol 106: 210–214, 1980 3. Shapiro F: Osteopetrosis. Current clinical considerations. Clin Orthop 294:34–44, 1993 4. Tasdemir HA, Dagdemir A, Celenk C, et al: Middle cerebral arterial occlusion in a child with osteopetrosis major. Eur Radiol 11:145–147, 2001
Manuscript received June 27, 2003. Accepted in final form October 17, 2003. Address reprint requests to: Zeev Feldman, M.D., Department of Neurosurgery, The Chaim Sheba Medical Center, Tel Hashomer 52621, Israel. email:
[email protected].
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