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Between 1975 and 1994, 52 hemispherectomies, of which two were anatomical and 50 hemidecortications, were performed at Johns Hopkins Medical Institutions. Eighteen patients were 2 years old or less. There were three perioperative mortalities and one patient died 9 months later from causes not related to surgery. One patient developed hydrocephalus 6 years postsurgery and has been treated effectively. Seizure control and the functional status of each patient were measured as outcome variables. Forty-six (96%) of the surviving patients were seizure free or had reduced seizures as of their last follow-up examination. Twenty-one individuals (44%) were participating in age-appropriate classes or working independently, 18 were classified as semiindependent, and nine children will likely depend on a lifetime of assisted living. The relationships between the outcome variables and the patient's age at surgery, the interval to surgery, and the etiology of the disease were compared. The authors' clinical experiences strongly suggest the importance of a multidisciplinary approach to patient selection and follow-up care. Moreover, anesthetic management of infant surgery is a major component of success.

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Nickel is an essential component of all H2-uptake hydrogenases. A (7) but also affects hydrogenase synthesis in wild-type strains of the bacterium (8). From use of inhibitors of 63Ni uptake in B. japonicum JH, it has been suggested that the bulk of nickel is transported via a magnesium transport system (9). A nickel metabolism locus has been identified within the hydrogenase gene cluster of B. japonicum (10). A mutation within this locus resulted in strains that require higher levels of nickel than the wild type for hydrogenase activity, and that produce an (apo)hydrogenase deficient in nickel content (10,11). The mutant strain is not deficient in nickel transport (10). In this study, we have isolated a fragment of DNA which complements the nickelmetabolism locus-deleted mutant strain. Here we report the cloning, sequence,t and characterization of the role of these nickel-metabolism genes from B. japonicum. Complementation and mutant analyses indicate that each ofthe three genes (hupNOP) is needed for complete nickel incorporation into the hydrogenase enzyme. hupO and hupP lack homology to known genes. Of particular comparison interest is the product of hupN, which has a predicted 56% identity to the previously described HoxN (high-affinity nickel-specific transport protein) of A. eutrophus (3). MATERIALS AND METHODS

Cerebral revascularization is often required for the surgical treatment of complex intracranial aneurysms. In certain anatomical locations, vascular anatomy and redundancy make in situ bypass possible. The authors present four patients who underwent revascularization performed using the rarely reported posterior inferior cerebellar artery (PICA)-PICA in situ bypass after their aneurysms had been trapped. At Barrow Neurological Institute, between 1991 and the present, four male patients underwent PICA-PICA by-passes to treat aneurysms involving the vertebral artery, the PICA, or both. The mean age of these patients was 34 years (range 5-49 years). Follow-up studies revealed patent bypasses and no evidence of infarction. Patient outcomes were excellent or good. Multiple surgical techniques have been described for revascularization of at-risk cerebral territories. Often, the blood supply must be derived from extracranial sources through a mobilized pedicle or interposited graft. Certain anatomical locations such as the vertebrobasilar junction, the anterior circle of Willis, and the middle cerebral artery bifurcation are amenable to in situ bypass because there is vessel redundancy or proximity to the contralateral analogous vessel. The advantages of an in situ bypass include one suture line, a short bypass distance, and a close match with the caliber of the recipient graft. Although technically challenging, this technique can be successful and should be considered for appropriate candidates.

We conclude that the current diagnostic yield (20%) of brain biopsy for progressive neurodegenerative disorders is lower than that of earlier reports and that the therapeutic benefits of the procedure are limited.

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