Cochlear implant electrode array insertion monitoring with intra-operative 3D rotational X-ray.

During cochlear implantation surgery, we use a mobile C-arm with 3D functionality to acquire per-operative 3D X-ray images. Scanning the multielectrode array is performed once before removal of the stylet and once after full insertion. When dissatisfied with the position of the multielectrode a repositioning is considered which happened occasionally. The major advantage is the extra certainty of the multielectrode array position in the cochlea with low-dose and little extra time. All cochlear implantations are now routinely scanned during surgery.

Molecular clips based on propanediurea: exceptionally high binding affinities for resorcinol guests.

A series of new receptor molecules derived from 2,4,6,8-tetraazabicyclo[3.3.1]nonane-3,7-dione (propanediurea) is described. These molecules possess a cavity which is defined by two nearly parallel aromatic side walls positioned on top of a bis-urea framework. The resulting "U-shaped" clip molecules are ideal hosts for the complexation of flat aromatic guest molecules. The affinity of these new propanediurea based molecular clips for dihydroxybenzene derivatives is exceptionally high, with association constants up to K(a) = 2 400 000 L mol(-)(1). Comparison of the binding mechanism of a variety of clip and half clip hosts, in conjunction with NMR, IR, and X-ray studies, has enabled the reason for this high binding to be elucidated. It is shown that subtle sub-angstrom changes in the geometry of the clip molecules have a great impact on their binding properties.

Biochemical hallmarks of tyrosine hydroxylase deficiency.

We report the biochemical hallmarks of tyrosine hydroxylase deficiency with emphasis on reliable diagnostic strategies of four new cases of an inborn error of tyrosine hydroxylase (TH). Three of our patients from different parts of the Netherlands were found homozygous for a mutation in exon 6 (G698A) of the TH gene, and one patient was found compound heterozygous for the same mutation and an additional mutation in exon 3. The first clinical symptoms of hypokinesia, rigidity of arms and legs and axial hypotonia, developed between 3 and 7 months of age. Cerebrospinal fluid investigations revealed a characteristic metabolite constellation in every case: low homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylethyleneglycol concentrations in the presence of normal reference range 5-hydroxyindolacetic acid concentrations. Strict adherence to a standardized lumbar puncture protocol and adequate age-related reference values are essential for diagnosis of this "new" treatable neurometabolic disorder. Urinary measurements of HVA, vanillylmandelic acid, and catecholamines can lead to false-negative conclusions. All patients showed a remarkable clinical improvement on a low dose of L-dihydroxyphenylalanine/ (S)-2-(3,4-dihydroxybenzyl)-2-hydrazinpropionic acid. During treatment, cerebrospinal fluid HVA, and 3-methoxy-4-hydroxy-phenylethyleneglycol increased substantially.