Sherman C. Stein and Stewart Apfel
✓ A method of measuring flow rate through cerebrospinal fluid (CSF) shunts is reported. It consists of two thermistors in series applied to the skin over the shunt tubing. The thermistors respond by a drop in measured temperature following application of an ice cube placed on the skin overlying the proximal shunt tube. The time required for the thermal response to travel between the two thermistors is related to the velocity of flow through the shunt tubing. Flow rate can then be calculated using the internal diameter of the tubing. A series of animal experiments employing a constant infusion of mock CSF through subcutaneously implanted shunt tubing showed excellent correlation between calculated flow rates and actual infusion rates. The device is noninvasive and easily adapted to use in patients. The measurements are readily repeatable.
Predicting the results of cerebrospinal fluid shunting
Sherman C. Stein and Thomas W. Langfitt
✓ After shunting, 43 patients with normal-pressure hydrocephalus were followed for 6 to 30 months. All patients had complete preoperative clinical evaluations, pneumoencephalograms, and isotope cisternography; in addition, 21 had saline infusion studies, and 15 had biopsies. Of the 10 patients in whom the etiology of the hydrocephalus was known eight (80%) were significantly improved. Of the other 33 patients, 21 (64%) showed some improvement; this was substantial and sustained in only eight (24%). The whole series of patients with idiopathic normal pressure hydrocephalus was divided into two groups on the basis of shunt response and the relative predictive values of preoperative tests. No significant association was found between the results of shunting and preoperative clinical factors, pneumoencephalography, isotope cisternography, saline infusion tests, or various combinations of clinical and laboratory abnormalities. The significance of these findings is discussed.
Sherman C. Stein and Steven E. Ross
✓ The purpose of this study is to determine the initial treatment of patients who appear to have sustained moderate head injuries when first evaluated. The authors reviewed the records of 341 patients whose initial Glasgow Coma Scale (GCS) scores ranged from 9 to 12, as well as another 106 patients with GCS scores of 13. All patients underwent cranial computerized tomography (CT) at the time of admission.
In 40.3% of these patients the CT scans were abnormal (30.6% had intracranial lesions), and 8.1 % required neurosurgical intervention (craniotomies for hematoma in 12, elevation of depressed fractures in five, and insertion of intracranial pressure monitors in 19). Four patients died of their intracranial injuries. A similar incidence of lesions found on CT and at surgery suggests that an initial GCS score of 13 be classified with the moderate head injury group. Skull fractures were found to be poor indicators of intracranial abnormalities.
These results suggest that all patients with head injury thought to be moderate on initial examination be admitted to the hospital and undergo urgent CT scanning. Patients with intracranial lesions require immediate neurosurgical consultation, surgery as needed, and admission to a critical-care unit. Scans should be repeated in patients whose recovery is less rapid than expected and in all patients with evidence of clinical deterioration; this was necessary in almost half of the patients in this group, and 32% were found to have progression of radiological abnormalities on serial CT scans.
Joseph H. Piatt Jr.
Sherman C. Stein and Wensheng Guo
The object of this study was to mathematically model the prognosis of a newly inserted shunt in pediatric or adult patients with hydrocephalus.
A structured search was performed of the English-language literature for case series reporting shunt failure, patient mortality, and shunt removal rates after shunt insertion. A metaanalytic model was constructed to pool data from multiple studies and to predict the outcome of a shunt after insertion. Separate models were used to predict shunt survival rates for children (patients < 17 years old) and adults.
Shunt survival rates in children and adults were calculated for 1 year (64.2 and 80.1%, respectively), 5 years (49.4 and 60.2%, respectively), and the median (4.9 and 7.3 years, respectively). The longer-term rates predicted by the model agree closely with those reported in the literature.
This model gives a comprehensive view of the fate of a shunt for hydrocephalus after insertion. The advantages of this model compared with Kaplan–Meier survival curves are discussed. The model used in this study may provide useful prognostic information and aid in the early evaluation of new shunt designs and techniques.
Mark G. Burnett, Sherman C. Stein and M. Sean Grady
Object. The goal of this study was to create a searchable database of research manuscripts authored by members of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons (AANS/CNS) to describe the nature and character of the research currently being undertaken by neurosurgeons.
Methods. Manuscripts published by all physician members listed in the 2001 AANS/CNS Membership Directory (6921 physicians) were gathered into a database through individual literature searches of the author name for the calendar year 2001. Duplicate publications were purged and the database was reviewed for accuracy. An internal verification of the database revealed a 4% underreporting rate. Statistics from the database were compiled and displayed with information about AANS/CNS members and their clinical activities.
The AANS/CNS members published a total of 2748 research the manuscripts in 479 different journals during 2001. Thirty-eight percent of the manuscripts (1042 of 2748) were authored by US members and 62% (1706 of 2748) by non-US members. The focus of the majority of manuscripts included the areas of brain tumor (26%; 707 of 2748), vascular disease (20%; 558 of 2748), spine (10%; 282 of 2748), and trauma (8%; 233 of 2748). Sixty-nine percent of manuscripts (1897 of 2748) were retrospective and technical clinical studies, and of these 39% (744 of 1897) were case reports. Laboratory investigations made up 15% (414 of 2748) of all manuscripts, whereas prospective randomized clinical trials represented 1% (34 of 2748).
Conclusions. The majority of AANS/CNS member manuscripts are authored by non—US members despite their small AANS/CNS representation. Most research is clinical, based on retrospective data, and includes a large number of case reports. A disparity exists between what neurosurgeons do clinically and both the quantity and subject of their research.
Sherman C. Stein, Mark G. Burnett and Seema S. Sonnad
The average 65-year-old patient with moderate dementia can look forward to only 1.4 quality-adjusted life years (QALYs), that is, longevity times quality of life. Some of these patients suffer from normal-pressure hydrocephalus (NPH) and respond dramatically to shunt insertion. Currently, however, NPH cannot be diagnosed with certainty. The authors constructed a Markov decision analysis model to predict the outcome in patients with NPH treated with and without shunts.
Transition probabilities and health utilities were obtained from a review of the literature. A sensitivity analysis and Monte Carlo simulation were applied to test outcomes over a wide range of parameters. Using shunt response and complication rates from the literature, the average patient receiving a shunt would gain an additional 1.7 QALYs as a result of automatic shunt insertion. Even if 50% of patients receiving a shunt have complications, the shunt response rate would need to be less than 5% for empirical shunt insertion to do more harm than good. Authors of most studies have reported far better statistics.
In summary, many more patients with suspected NPH should be considered for shunt insertion.
Sherman C. Stein, Xiao-Han Chen, Grant P. Sinson and Douglas H. Smith
Object. The goal of this study was to determine the frequency with which cerebral intravascular coagulation (IC) complicates traumatic brain injury (TBI). The authors also investigated the incidence of IC in relation to varying mechanisms, time courses, and severities of TBI and in different species.
Methods. Tissue was sampled from surgical specimens of human cerebral contusions, from rats with lateral fluid-percussion injuries, and from pigs with head rotational acceleration injuries. Immunohistochemical fluorescent staining for antithrombin III was performed to detect cerebral intravascular microthrombi. Abundant IC was found in all specimens, and microthrombi had formed in arterioles and venules of all sizes, ranging from 10 to 600 µm. Although it was more pronounced in focal lesions and more severe injuries, considerable IC was also observed in mild and diffuse injuries. The authors found a strong association between the severity of coagulopathy and the density of IC.
Conclusions. These results strongly support the contention that IC is a universal response to TBI and an important secondary cerebral insult.