Is Chiari I malformation in the aged initiated by mechanical factors? Report of three cases.

Three cases in which the signs and symptoms of Chiari I malformation were induced and worsened after the occurrence of supratentorial mass lesions are reported. The symptoms improved markedly after removal of the supratentorial lesions in these cases. In the first case, a meningioma in the right parietal region coexisted with Chiari I malformation. Although the cerebellar ataxia and nystagmus disappeared after tumor removal, decompressive surgery for the malformation was performed because of upper cervical nerve symptoms and the patient recovered completely. In the second case, the symptoms first occurred after a car accident, and a computed tomographic scan revealed not only a subdural hematoma, but also tonsillar herniation due to Chiari I malformation. After evacuation of the hematoma and decompressive surgery on the craniospinal junction, the symptoms disappeared. In the third case, the symptoms of malformation developed gradually with depression and gait disturbance. A meningioma in the left frontal region coexisted with Chiari I malformation. Although the symptoms improved remarkably after tumor removal, decompressive surgery on the craniospinal junction was performed because of upper cervical nerve symptoms, and the patient recovered completely. These clinical findings indicate that a supratentorial mass lesion may provoke the symptoms of Chiari I malformation in the aged.