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David W. Roberts, John W. Strohbehn, John F. Hatch, William Murray and Hans Kettenberger

✓ A computer-based system has been developed for the integration and display of computerized tomography (CT) image data in the operating microscope in the correct perspective without requiring a stereotaxic frame. Spatial registration of the CT image data is accomplished by determination of the position of the operating microscope as its focal point is brought to each of three CT-imaged fiducial markers on the scalp. Monitoring of subsequent microscope positions allows appropriate reformatting of CT data into a common coordinate system. The position of the freely moveable microscope is determined by a non-imaging ultrasonic range-finder consisting of three spark gaps attached to the microscope and three microphones on a rigid support in the operating room. Measurement of the acoustic impulse transit times from the spark gaps to the microphones enables calculation of those distances and unique determination of the microscope position. The CT data are reformatted into a plane and orientation corresponding to the microscope's focal plane or to a deeper parallel plane if required. This reformatted information is then projected into the optics of the operating microscope using a miniature cathode ray tube and a beam splitter. The operating surgeon sees the CT information (such as a tumor boundary) superimposed upon the operating field in proper position, orientation, and scale.

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Gerald J. Riccardello Jr., Luke K. Barr and Luigi Bassani

The authors report the case of 14-year-old girl with a history of myelomeningocele and previously shunt-treated hydrocephalus who presented with right-sided abdominal pain and subcutaneous emphysema that developed over a 1-week period. A CT scan of the patient's abdomen revealed a retained distal ventriculoperitoneal (VP) catheter with air tracking from the catheter to the upper chest wall. Given the high suspicion of the catheter being intraluminal, an exploratory laparotomy was performed and revealed multiple jejunal perforations. The patient required a partial small-bowel resection and reanastomosis for complete removal of the retained catheter. Six other similar cases of bowel perforation occurring in patients with abandoned VP and subdural-peritoneal shunts have been reported. The authors analyzed these cases with regard to age of presentation, symptomatic presentation, management, morbidity, and mortality. While there was 0% mortality associated with bowel perforation secondary to a retained distal VP catheter, the morbidity was significantly high and included peritonitis and small bowel resection.

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Ray H. Kinnaird and Richard K. Jelsma

✓ A lightweight and completely self-contained traction device is described. It has been used to immobilize the cervical spine during radiographic evaluation and treatment of patients with cervical fracture, and for therapeutic traction in patients with a ruptured disc. Other applications are possible, but have not yet been investigated

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Christian Sainte-Rose, Michael D. Hooven and Jean-François Hirsch

✓ To date, most patients suffering from hydrocephalus have been treated by insertion of differential-pressure valves that have fairly constant resistance. Since intracranial pressure (ICP) is a variable parameter (depending on such factors as patient's position and rapid eye movement sleep) and since cerebrospinal fluid (CSF) secretion is almost constant, it may be assumed that some shunt complications are related to too much or too little CSF drainage. The authors suggest a new approach to treating hydrocephalus, the aim of which is to provide CSF drainage at or below the CSF secretion rate within a physiological ICP range. This concept has led the authors to develop a three-stage valve system. The first stage consists of a medium-pressure low-resistance valve that operates as a conventional differential-pressure valve until the flow through the shunt reaches a mean value of 20 ml/hr. A second stage consists of a variable-resistance flow regulator that maintains flow between 20 and 30 ml/hr at differential pressures of 80 to 350 mm H2O. The third stage is a safety device that operates at differential pressures above 350 mm H2O (inducing a rapid increase in CSF flow rate) and therefore prevents hyper-elevated ICP. An in vitro study is described that demonstrates the capability of this system to maintain flow rates close to CSF production under a range of pressures similar to those observed under various human physiological and postural conditions. Promising clinical results in 19 patients shunted with this valve are summarized.

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Robert F. Spetzler and Alfred A. Iversen

✓ A malleable microsurgical suction device is presented which allows continuous drainage of cerebrospinal fluid or blood from an operative site. A malleable wire incorporated into the plastic tubing allows placement and readjustment of the suction tip to keep it where desired.

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Marc N. Pilipuf, John C. Goble and Neal F. Kassell

✓ The authors have developed a noninvasive head immobilization system for use in neuroimaging (magnetic resonance imaging, computerized tomography, single photon emission computerized tomography, and projection angiography), neurosurgical planning, and neurosurgery. These diagnostic and surgical procedures require patient immobilization, reproducible patient positioning, and anatomical localization. The thermoplastic system described in this technical note addresses each of these requirements with a high degree of accuracy and with no bone fixation. The reproducibility of positioning and effectiveness of immobilization were evaluated using nine healthy volunteers during repeated sessions of magnetic resonance imaging. The mean axial displacement for repeated positioning was 0.6 mm (variance 0.1 mm); the mean displacement during robust patient motion in the axial direction was 1.8 mm (variance 0.9 mm).

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Dhananjaya I. Bhat, B. Indira Devi, Komal Bharti and Rajanikant Panda

OBJECTIVE

The authors aimed to understand the alterations of brain resting-state networks (RSNs) in patients with pan–brachial plexus injury (BPI) before and after surgery, which might provide insight into cortical plasticity after peripheral nerve injury and regeneration.

METHODS

Thirty-five patients with left pan-BPI before surgery, 30 patients after surgery, and 25 healthy controls underwent resting-state functional MRI (rs-fMRI). The 30 postoperative patients were subdivided into 2 groups: 14 patients with improvement in muscle power and 16 patients with no improvement in muscle power after surgery. RSNs were extracted using independent component analysis to evaluate connectivity at a significance level of p < 0.05 (familywise error corrected).

RESULTS

The patients with BPI had lower connectivity in their sensorimotor network (SMN) and salience network (SN) and greater connectivity in their default mode network (DMN) before surgery than the controls. Connectivity of the left supplementary motor cortex in the SMN and medial frontal gyrus and in the anterior cingulate cortex in the SN increased in patients whose muscle power had improved after surgery, whereas no significant changes were noted in the unimproved patients. There was a trend toward reduction in DMN connectivity in all the patients after surgery compared with that in the preoperative patients; however, this result was not statistically significant.

CONCLUSIONS

The results of this study highlight the fact that peripheral nerve injury, its management, and successful treatment cause dynamic changes within the brain's RSNs, which includes not only the obvious SMN but also the higher cognitive networks such as the SN and DMN, which indicates brain plasticity and compensatory mechanisms at work.

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George T. Tindall, Charles P. McGraw, Hans O. Wendenburg and Herbert H. Peel

✓ A simple practical method for monitoring intracranial pressure has been developed; it is based on a diaphragm-type, full-bridge, absolute-pressure gauge that is stable. The transducer is calibrated to absolute pressure at body temperature. It is placed in a trephine opening where it is in contact with the subdural space. The transducer is contained in a self-threading case that will fit in a 14 mm trephine opening. Its use in 30 patients with acute head injury is reported.