Parkinsonism and midbrain dysfunction after shunt placement for obstructive hydrocephalus.

We report a patient in whom placement of a ventriculoperitoneal shunt for obstructive hydrocephalus secondary to non-neoplastic aqueductal stenosis was complicated by progressive parkinsonism and midbrain dysfunction. These sequelae were refractory to treatment, including shunt revision and levodopa therapy. These findings contradict the opinion from the literature that this type of parkinsonism is a reversible condition and levodopa therapy is effective for managing the symptoms.

Odontoid compression of the brainstem without basilar impression-- "odontoid invagination".

We report five patients with odontoid invagination, in which the odontoid process bulges upward into the foramen magnum and compresses the brainstem without deformity of the occipital bone. Two patients had a craniovertebral abnormality associated with Chiari malformation without instability of the craniovertebral junction (stable odontoid invagination). The other three patients had dislocation of the craniovertebral junction due to iatrogenic destruction of the occipital condyle, rheumatoid arthritis or an anomaly of C2 (unstable odontoid invagination).

Surgical experience of syringomyelia with reference to the findings of magnetic resonance imaging.

We present our surgical experience of 20 patients with syringomyelia, who were divided into two groups based on the findings of magnetic resonance (MR) imaging: a "non-visible cisterna magna" group, in which MR imaging did not reveal cerebrospinal fluid (CSF) in the cisterna magna, and a "visible cisterna magna" group. Patients with non-visible cisterna magna were associated with Chiari malformation (14 patients) or tight cisterna magna (4 patients) and underwent craniocervical decompression. Intradural exploration was performed when CSF movement in the cisterna magna or CSF outflow from the fourth ventricle appeared to be insufficient.

Syringomyelia without hindbrain herniation: tight cisterna magna. Report of four cases and a review of the literature.

Idiopathic syringomyelia, which is not associated with any definite pathogenic lesions, has been treated mainly by shunting of the syrinx and rarely by craniocervical decompression. The authors report four cases of syringomyelia thought to be idiopathic syringomyelia but treated by craniocervical decompression with favorable results. Syringomyelia was present without hindbrain herniation.