Michael G. Muhonen

Pathogenesis and treatment of growing skull fractures

BACKGROUND Growing skull fractures are poorly understood complications of pediatric skull fractures. METHODS A retrospective review of skull fractures at our institution from 1980-1993 revealed 10 patients with growing skull fractures. The age at injury ranged from 1-144 months, with 9 of 10 patients being under one year of age. The etiology of these fractures included falls, motor vehicle accidents, and child abuse. On average, growth of the fracture was diagnosed 14 months after the initial injury. RESULTS Six patients have had magnetic resonance imaging (MRI) with one demonstrating leptomeningeal cyst herniation, two having brain herniation, and three having both brain parenchyma and leptomeningeal cyst herniation. All patients had malacic cortex underlying the fracture, but there was no evidence of intracranial hypertension. Nine patients have undergone craniotomy with excision of granulation tissue and gliotic brain, dural repair, and cranioplasty using surrounding normal skull. There were no surgical complications or recurrences. CONCLUSIONS Brain/leptomeningeal cyst herniation through a dural rent, without MRI evidence of increased intracranial pressure, implicates physiologic growth and brain cerebrospinal fluid (CSF) pulsations as the cause of fracture enlargement.

Cerebral aneurysms associated with neurofibromatosis

An uncommonly recognized complication of neurofibromatosis (NF) is an angiopathy of the intracranial and extracranial arteries. Most of the previously reported cases have presented as an occlusive process similar to Moyamoya disease. We present our experience over the past 3 years involving three patients with five cerebral aneurysms and associated NF. Four of the aneurysms were intracranial, two being fusiform in nature. Treatment was surgical occlusion and included Selverstone clamping, balloon occlusion, and direct clipping. There appears to be an association between the development of cerebral artery aneurysms and NF, but the pathophysiology of these vascular changes is not fully understood.

Aneurysmal bone cyst of the temporal bone presenting as hearing loss in a child

We present an unusual case of a temporal bone and skull base tumor in a ten-year-old child. The patient presented with unilateral hearing loss and headaches. Radiologic, surgical, and histologic findings were consistent with an aneurysmal bone cyst. This is the first report on this rare entity to document its appearance in the temporal bone and skull base using magnetic resonance imaging. Treatment consisted of surgical removal, cranioplasty, and reconstruction of the external auditory canal.

Vault reduction cranioplasty for extreme hydrocephalic macrocephaly

Due to early diagnosis and treatment of hydrocephalus, neurosurgeons rarely are called upon to treat patients with extreme hydrocephalic macrocephaly. Macrocephaly can limit mobility and hygiene. The critical evaluation and surgical correction of the morphological problem of macrocephaly secondary to hydrocephalus is complex. Various techniques such as quadrantal, picket fence, crossbar, and modified rr techniques have been used to reduce the size of the cranial vault to decrease cranial volume while achieving good cosmesis. Limitations of vault reduction cranioplasty include the inability to alter the anteroposterior and lateral diameters of the skull base, the inability to shorten the superior sagittal sinus, and the need to avoid infolding of the brain due to the risk of venous infarcts. Reduction cranioplasty is indicated in the occasional patient whose large head size represents a mechanical or cosmetic problem of sufficient magnitude to seriously interfere with motor development and functioning, with resultant development of pressure sores and difficulties with nursing care. Reduction cranioplasty should be avoided in patients under the age of 3 years.

Hydroxyapatite cement resistant to fragmentation following full cerebrospinal fluid bathing.

Prolonged cerebrospinal fluid bathing of cranioplasty cement frequently results in breakdown of the cement implants. A 5-year-old boy with a history of severe head trauma at 2 weeks of age presented with marked protrusion of the entire superior temporal bone and inferior parietal bone. The defect was elevated by more than 1 cm and was associated with a 4.5 × 3-cm skull defect located above and behind the right ear. There also was pulsatile tissue at the depths of the defect. A computed tomographic scan taken of the head revealed an expanding skull fracture from a dural defect with underlying brain herniation. The cranial lesion was repaired with OsteoVation hydroxyapatite cement. Within 8 weeks, the fluid encased the cranioplasty site. This resolved following implantation of a shunting device. At 2 and 12 months after the repair, the implant was still palpably solid without breakdown and did not fragment despite the prolonged bathing in cerebrospinal fluid.