PubMed · 13944735
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E FERGUSON. 1963. Ten-second radiography.. https://pubmed.ncbi.nlm.nih.gov/13944735/
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It is well known that in patients with communicating hydrocephalus or normal pressure hydrocephalus, ventricular volume decreases following implantation of differential pressure valved shunts. Hydrostatic valves (Miethke dual-switch valves) were implanted in 60 normal pressure hydrocephalus patients at Unfallkrankenhaus Berlin between September 1997 and September 2001. One year postoperatively, these patients underwent CT scan, and their ventricular size was ascertained using the Evans index. Although 77% of these patients showed no postoperative change in ventricular volume, 65% nonetheless showed good to excellent clinical improvement, 13% satisfactory improvement and 22% no improvement. A moderate reduction in ventricular size was observed in 17% of the patients in our cohort. 40% of these patients showed good to excellent clinical improvement, 20% satisfactory improvement, and 40% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of our patients. Of these latter patients, 50% showed good to excellent outcomes, while 50% had unsatisfactory outcomes. The favorable outcomes following implantation of a hydrostatic shunt in patients with normal pressure hydrocephalus did not correlate with decreased ventricular volume one year after operation. Better clinical outcomes were observed in patients with little or no alteration in ventricular size than in patients with a marked decrease in ventricular size. Postoperative change in ventricular volume should be assessed differently for patients with normal pressure hydrocephalus than in patients with hypertensive hydrocephalus.
The techniques of targeting the subthalamic nucleus (STN) and the ventralis intermedius nucleus (Vim) are similar, only the coordinates are different. Targeting ideally consists of gathering all data about a target and positioning the electrode correctly within that target. The electrode should be positioned within a statistical range of coordinates, where the neuronal firing fits a given pattern and responds to external stimuli, particularly to proprioceptive inputs, in a somatotopically organized manner. Moreover, final placement should provide the best clinical improvement of symptoms under the stimulation parameters expected to be used in the long term. This latter criterion is by far the most important, because intraoperative findings indicate the functional benefit for the patient, which is the ultimate purpose of this surgery. A variety of radiological modalities are available to provide data for electrode placement, but each type has its drawbacks. Ventriculography, although safe when performed accordingly to strict technical procedure, is the most precise method but provides more indirect targeting and is more invasive than magnetic resonance imaging (MRI). MRI is the best method for visualizing the STN and, to some extent, for discerning the Vim, but it is plagued with unpredictable and nonreproducible deformations that induce a systematic distortion. These shortcomings no doubt will be corrected in the near future, and the technologies will better assist us in the proper placement of electrodes, which will provide the patient with the highest possible benefit.